ES8005 – Chapter 1

A system is any portion of the universe that can be isolated for the purpose of observing & measuring changes
A system must have a boundary that sets it apart from its surroundings

3 basic types of systems

1. Isolated system * Boundary prevents the system from exchanging BOTH matter & energy with its surroundings. * Both matter and energy within the system are fixed & finite because none can enter and none can leave the system. * Imaginary – impossible for any real boundary to be so perfectly insulated that energy can neither enter or escape.

2. Closed system * Boundary permits the exchange of energy, but not matter within its surroundings * Matter within the system is finite but energy is exchangeable in and out of the system

3. Open system * Boundary permits exchange of both energy and matter * Ie. Island. * Open systems are more difficult to study because they have more potential for uncontrolled variation

Box model * A model is a representation of something. * A box model can show the essential features of a system. i. The process by which matter enters & leaves the system and the rates at which they do so ii. The process which matter moves among the various parts of the system internally & the rates at which this happens iii. The amount of matter (or energy) in the system at a given time and its distribution within the system

* The amount of matter (or energy) that is transferred along & the rate that is being transferred is called a flux * Places where energy or matter is stored for a period of time is called a reservoir ie water stored in the atmosphere ; water stored in groundwater. * When the flux of matter into the reservoir matches the flux out – reservoir is at a steady rate * When flux in > flux out = sink / flux out > flux in = source * Some materials have such long residence times in certain reservoirs it is called sequestration * The length of time energy or matter spends in a reservoir is its residence time. * The residence time is determined by the interaction of factors ie physical, chemical, biologic properties of the material itself, properties of reservoirs etc

Earth system Reservoirs Earth is a closed system – the amount of matter is fixed and finite: Mineral resources are limited
Waste materials remain confined within earth
If changes are made in one part of a closed system, the results of those changes eventually will affect other parts of the system.

The place where Earth’s 4 reservoirs interact most intensively is called a life zone ( No wider than 20km apart) * Geosphere, hydrosphere, atmosphere, biosphere. * Conditions favourable for life are created as a result by interactions between the geosphere, hydrosphere, atmosphere & modifield by the BIOSPHERE.

Geosphere – Any naturally formed, non-living mass of solid matter that constitutes part of a planet and regolith (loose blanket of uncemented rock particles) * Surface of the geosphere – where energy that comes into the earth system from outside sources meets energy that comes from within the planet.

Hydrosphere – Totality of Earth’s water/ Provide critically important services along with the atmosphere as they store, purify and continually redistribute water.

Atmosphere – mixture of gases ; very thin layer – protects life from damaging solar radiation. Reservoir for O2 and CO2.
Outer boundary of the Earth’s system.

Biosphere – Includes all of Earth’s organisms as well as any organic matter NOT yet decomposed.

Antroposphere – Humans and their impact on the natural earth system

DYNAMIC INTERACTION AMONG RESERVOIRS
Because energy flows freely in & out of the system, all closed/open system respond to inputs and have outputs.
Feedback – occurs when the output of the system also serves as an input and leads to changes in the state of the system.
Negative feedback – the system’s response is in the opposite direction from the initial input (Self regulating)
Desirable as it is stabilizing & usually leads to a system that remains in a constant condition.
It is self regulating – state of equilibrium. Dynamic equilibrium – constantly responding to small changes and disturbances, in such a manner that it returns to a state of equilibrium.

Positive feedback – an increase in output leads to a further increase in output.
Positive feedback – destabilizing as it amplifies the original disturbance.

Cycles – The constant movement of material from one reservoir to another.
Material and energy flow from one system to another but the system themselves don’t change overall as the different parts balance one another.

Hydrologic cycle – Fluxes of water among the various reservoirs/ composed of pathways and reservoirs.

Energy cycle – Encompasses the external and internal energy sources of the planet.
-Different from other earth cycles as it describes the movement of energy through the system, rather than the movement of materials
-Energy cannot be endlessly recycled – there must be a source of energy coming into the system that replenishes energy on a continuous basis
-Energy may be added to or subtracted from the budget but overall the additions and subtractions and transfers must balance.
-Energy from internal/external sources drives earth processes, then degraded and eventually lost though radiation to outer space.

Rock cycle – Competing internal and external forces that meets at the earth surface, building up, breaking down, transporting and transforming rocks.

Tectonic cycle – where earth’s main geologic features are formed.

Biogeochemical cycle – describes the movement of any chemical element or chemical compound that cycles through the biosphere and plays a role in its stability.

HOW SCIENCE WORKS – ESS advances by the application of the scientific method * Based on observations and the systemic collection of evidence that can be seen and tested by anyone with resources who cares to do so.

1. Scientists start with the observation of a phenomenon & seek to aquire evidence thru management & experimentation 2. Explains their observations by developing a hypothesis – a plausible but yet unproven explaination for the way things happen. 3. Testing the hypothesis through predictions & numerous tests as well as subjecting it to peer review 4. After the hypothesis has been found to make successful predictions and withstand numerous tests, scientists become more confident in its validity and it may become a theory 5. A theory is a generalization about nature – very substantial 6. A theory whose application has been decisively demonstrated may become a law/principle of science 7. A scientific law is a statement that some aspect of nature is ALWAYS observed to happen in the same way & that no deviations from the rule have ever been SEEN.

Role of uncertainity – Uncertainty in science is not a problem ; does NOT imply a lack of scientific knowledge or understanding.

Chapter 2

* Energy is the capacity to do work, to move matter & make things happen * The sum of the different kinds of energy in a system is called the internal energy of the system * Work done on a system – transfer of energy into the system * Work done by a system – energy is transferred out

Potential energy – energy stored in a system 1. Chemical energy * The energy that holds the molecules and compounds of our world together 2. Nuclear energy * The energy that holds atomic nuclei together ; released when a heavy atom is split 3. Stored mechanical energy * ie Energy that resides in a compressed spring 4. Gravitational energy * Energy of position ie water at the top of the waterfall

Kinetic Energy – Energy expressed in the movement of electrons, atoms, molecules, materials and objects

1. Radiant energy – electromagnetic radiation 2. Electrical energy – Movement of electons 3. Thermal energy – heat ; the vibrational movement of atoms & molecules 4. Sound – results when an object is caused to vibrate ; alternating compression and expansion of a material as energy passes through it in the form of sound 5. Motion of objects

FUNDAMENTAL LAWS OF THERMODYNAMICS

Conservation & Transformation 1. In a system of constant mass, energy involved in any physical or chemical change is neither created nor destroyed but merely converted from one form to another * One form of energy can be transformed into another form of energy
Efficiency & Entropy

2. Energy ALWAYS changes from a more useful, more concentrated form to a less useful, less concentrated form * Complete recycling is impossible because whenever work is done, energy is converted to heat * Degradation – the transformation of energy into a form that is less useful & less available for work * Degradation leads to increasing disorganization in the system as energy is dispersed as heat * Measure of this disorganization is called entropy * The more organized energy is, the more it is available to do work ; entropy is at its minimum * Entropy increases because energy is degraded and becomes increasingly dispersed & unavailable as it is used.

Absolute Zero

3. Postulates the existence of the state of absolute zero temperature * Temperature is a measure of heat, the vibrational movement of particles * In a state of absolute zero, all the microscopic molecular motion (vibrational movement) would cease * Entropy of a material at absolute zero would disappear because the material is in a perfectly ordered, perfectly still state * Provides the foundation point for the Kelvin Temperature scale * Kelvin temperature scale is absolute because it is defined on the basis of a fundamental thermodynamic constant – entropy = zero

EXTERNAL ENERGY SOURCES

1. The Sun * BY FAR the main source of energy coming into the Earth System from an external source * The Sun radiates heat as a result of thermonuclear reactions in its core * Nuclear reaction involves the fusion of lightweight chemical elements to form heavier elements like helium & carbon * Energy released by fusion reactions in the Sun is in the form of gamma rays – short, high energy electromagnetic waves * Of the total energy , 2 percent is in the form of neutrinos and 98% in the form of gamma rays * Neutrinos do not play any part in bringing solar energy to Earth

i. Structure of the Sun * The sun consists of 6 concentric layers – 4 inner regions that make up the sphere we see & 2 gaseous outer layers that we cannot see * THE CORE : The site of all nuclear fusion reactions * RADIATIVE LAYER : Surrounds the core BUT not hot enough for fusion to occur * Energy released from the core moves across this layer by radiation (radiation is the process in which energy in the electromagnetic spectrum is transferred from radiating body through a surrounding gas, liquid or vacuum) * Elections in the radiative layer absorb the gamma radiation : This is what makes the escape of energy from the Sun such a slow process * CONVECTIVE LAYER – Across which energy moves via convection (heat content is physically carried from one location to another) * Radiative & Convective layers are kept gassy and prevented from collapsing into the core by the intense pressure created by the gamma radiation attempting to move outward * PHOTOSPHERE – An intensely turbulent zone that emits the light that reaches earth * CHROMOSPHERE – A low-density layer of very hot gas * CORONA – Outermost layer of the Sun, a zone of lower density gas than the chromosphere (Transparent)

The Solar Spectrum

* The radiation energy released in the Sun’s core has a very short wavelength & is extremely energetic * As gamma rays from the core move out through the radiative layer, they are repeatedly absorb and reemitted by electrons * In the process, they are converted to longer-wavelength, lower energy radiation * The energy flux from the Sun varies with wavelength * Blackbody – radiation absorbing properties of a body * The hotter a radiating body, the shorter the wavelength of its radiation peak * The spectrum of electromagnetic radiation emitted by the Sun is not the same as the spectrum of solar radiation that actually reaches the Earth’s surface * Because gases in Earth’s atmosphere selectively absorb some wavelengths from the solar radiation as it passes through on its way

2. Gravity & Tides * Gravity: The mutual physical attraction between the masses of the moon and earth * The source of energy is due to the influence of gravity on the Earth’s rotation * The gravitational pull that the Moon exerts on Earth is balanced by an equal and opposite inertial force created by Earth’s movement * On the side of Earth nearest to the Moon, the magnitude of the gravitational attraction exceeds the inertial force: resulting pull is in the direction of the moon. * On the opposite side, the magnitude of the inertial force exceeds the Moon’s gravitational pull, and the resulting pull is directed away from the Moon * This difference causes a strain in both objects, producing a cyclic distortion called a tide * The Earth is elastic; it has the capacity to deform reversibly * The internal resistance, caused by elastic distortion within the planet is translated to heat – one of the main sources of Earth’s internal heat energy.

INTERNAL ENERGY SOURCES

These geothermal/terrestrial energy sources are much smaller than the solar input

i. Distribution of Terrestrial energy * The increase in temperature along with the increase in the depth of the Earth is called geothermal gradient – it becomes less pronounced with depth * Heat energy that flows out through the solid rock of Earth’s outermost layer does so by conduction (The process by which heat moves directly from one object to an adjacent object with which it is in contact) * Some heat energy reaches Earth’s surface by convection. * Convective heat transfer provides the driving force behind plate tectonics

1. Radiogenic heat – MAIN source of terrestrial energy * Radiogenic heat is produced by the spontaneous breakdown, or decay of radioactive elements * It is a nuclear process: Some mass is lost in the conversion from one form of the element to another * This ‘lost’ mass in converted to energy: released as heat * Some naturally occurring elements take billions of years to decay – providing a steady supply of internal heat

2. Accretionary heat – Internal heat left over from the origins of Earth * When particles collided into one another, accreting to form large planetary bodies * The kinetic energy of those collisions were converted to heat energy

3. Tidal Heating – Gravitational interactions of Earth with the Moon & Sun causes body tides – internal friction from the constant distortion of the planet translated into heat energy

4. Core formation – Gravitational potential energy of the dense material that formed the core converted to heat as it sank to the centre of the planet. * Further heat was released as the innermost material- the part that now constitutes Earth’s solid inner core solidified. * The latent heat released in the course of crystallization ( change from liquid iron to solid) * As the liquid outer core crystalizes, latent heat is still being released today

EARTH’S ENERGY CYCLE

The energy cycle encompasses the inputs & outputs, pathways & reservoirs for the energy that drives all of the other cycles of the Earth system

Energy budget – Energy can be added to or subtracted from the budget and transferred from one storage reservoir to another but overall the additions & subtractions/ transactions must balance

Energy in – Incoming short-wave radiation dominates the flow of energy into Earth’s energy budget
Earth’s internal heat energy drives the tectonic cycle, causing the lithospheric plates to shift & shape the face of the Earth

Energy out – Energy lost in 2 ways : Reflection, degradation & reradiation * About 40% of solar radiation is reflected by the top of the atmosphere, clouds, ocean surface etc * Incoming radiation that is reflected unchanged is called the albedo * A high albedo means a highly reflective surface * Absorbed solar radiation undergoes irreversible degradations in which it is transferred from one reservoir to another and converted from one form to another * Eventually ends up as heat and reradiated back to space * Incoming energy degraded into longer wavelength radiation. * Earth’s outgoing radiation is selectively absorbed by gases in the atmosphere * Greenhouse effect

Pathways & Reservoirs – The energy cycle involves pathways, processes & storage reservoirs
Ie reservoirs – solid ground on a hot day : heat energy / atmosphere holds & transports a significant amount of solar energy.

Energy & society

* Humans tap into energy from Earth’s reservoirs to extract power for transportation, home & office use, industrial use * Energy consumed by the global population is about 3.0 x 10 power 20 joules * 4 energy sources have been extensively developed i. Fossil fuels ii. Biomass energy iii. Hydroelectric energy iv. Nuclear energy * 5 sources of energy have been tested and developed on a limited basis but not yet on a large scale
Solar, wind, waves, tides and geothermal energy (earth’s internal energy) * Drawback of geothermal energy – needs a high temperature gradient (high temperature @ shallow depth) * Unfortunately, all these energy sources have drawbacks & limitations, and all of them too have potential negative impacts on the quality of the environment * We must change our energy consumption patterns & our practices of producing energy

CHAPTER 3 – MATTER

Matter is substance – It has mass and occupies space
3 common states of matter – solid, liquid and gas
Materials that occur in the same state can still differ substantially from one another in properties
Eg : water & lava : Same state but different composition

Change of State vs Change of Phase * Materials in different states can exist together at the same time * Different phases: Homogenous masses of material that can be separated from one another by a definable boundary & different properties * Possible for materials to exist in the same state BUT different phase ie. Oil & water. * Unlike solids & liquids, gases are ALWAYS miscible

Atoms, Elements, Ions & Isotopes * Chemical elements are the most fundamental substances in which matter can be separated by ordinary chemical means * An atom is the smallest individual particle that retains the distinctive properties of a given chemical element * Atoms are made of protons, neutrons & electrons * Protons & neutrons join to form the nucleus of an atom: NUMBER OF PROTONS in an atom is called the ATOMIC NUMBER. * Sum of NEUTRONS & PROTONS = mass number. * Isotopes: atoms with the same atomic number but different mass number * Ion : An atom that has excess positive or negative charge is called an ion

Compounds & Mixtures * Compounds form when one or more kind of anion combine chemically with one or more kind of cation in a specific ratio * A molecule is the smallest unit that retains all properties of a compound. * When 2 or more liquids or several gases blend thoroughly without undergoing a chemical reaction, the result is a mixture – NOT compounds as each of them retain their identities
Organic Compound * Organic : Specifically referred to compounds consisting of carbon atoms bonded together through a covalent bond * Organic usually implies that the compound is biotic * Biotic: Once or presently alive, of biologic origin. * Inorganic compounds are abiotic : Non-living & of nonbiologic origin.

Organic molecules * Tend to occur in long, chainlike structures called polymers * Polymerization : Small molecules link together to form long chains are 3D networks * Polymers that consist of organic compounds are called biopolymers * Protein; Nucleic acid ; Carbohydrate * Lipids are not polymers but still an organic molecule.

Protein * The building blocks of proteins are organic molecules called amino acids * Proteins are long chain like polymers made of amino acids bonded together

Nucleic Acid * Giant polymers built from molecules called nucleotides * Nucleic acid produces proteins * DNA & RNA

Carbohydrates * Molecules are composed of carbon, hydrogen & oxygen * Basis of the food we eat

Lipids
Not polymers but chemically diverse 1. Fats & oils 2. Phospolipids 3. Waxes 4. Steroid

COMPOSITION & INTERNAL STRUCTURE OF THE EARTH

Internal layering of the Earth is due to the chemical differentiation of the partially molten planet
Internal layers can be distinguished from one another on the basis of differences in..

1. Composition 2. Differences in rock strength 3. Differences in the state of matter in the layers

Layers of different composition * The core : Densest of the 3 compositional layer ; A spherical mass composed largely of metallic iron & smaller amount of nickel * Mantle : Less dense than the core but denser than the crust; dense rocky matter * Crust : The core and mantle has near constant thickness but the crust is far from uniform and differs in thickness * Oceanic crust about 8km & continental crust 30-70km * Oceanic crust is typically composed of BASALT (relatively dense rock) * Continental crust more variable in composition & less denser rock * One way to determine composition indirectly is to measure how the densities of the materials change. * The crust is varied in composition, and its composition & density are very different from those of the mantle and the boundary between the two are distinct.

Layers of different rock strength * Earth contains layers with differences in the strength of rock making up each layer. * Strength of solid determined by pressure & temperature. * When a solid is heated, it loses strengths * When a solid is compressed, it gains strength * Mesosphere : Strength of rock is huge due to the intense pressure even though there is much heat (2883-350km) * Upper mantle : Asthenosphere : Where the balance between temperature and pressure is such that rocks have little strength (350-100km) * Lithosphere – Region where temperature is much cooler : Rocks are much cooler, stronger & more rigid

Layers of different physical state (Solid, liquid, gas)

* Solid centre is the inner core : Pressure in this region is so great that iron is solid despite its high temperature. * Surrounding the inner core is a zone (outer core) : Same compostition but just that outer core’s iron is molten and it is a liquid.

Abundant elements * Of the 92 naturally occurring chemical elements, 12 occur in Earth’s outermost layers * Responsible for determining the composition of the common materials of Earth * Crust is dominated by just 2 elements ; OXYGEN & SILICON

Minerals

There are 5 properties of minerals

1. Naturally formed 2. Inorganic 3. Solid 4. Specific chemical composition 5. Characteristic crystal structure – MUST BE A SOLID
(GLASS IS NOT A MINERAL)

Mineral compositions & structures * Most convenient way to classify & study minerals i. Crystal structure ( The way atoms are packed together) ii. composition (major chemical elements that are present & their proportions in the mineral)

Common minerals * As oxygen and silicon make up more than 70% of the continental crust, these 2 elements form the basis of the most common & abundant rock forming mineral. 1. Silicates 2. Oxides * Silicates are the MOST abundant followed by oxides * In many silicates, the anions join together by sharing their oxygen atoms & so they form tetrahedral (chains, sheets, 3D networks etc) * NUMBER 1 DOMINANT VARIETY : Feldspar * 2nd : Quartz * Together they account for 75% of the contental crust * All silicates make up for 95% of the continental crust

Non-silicates : Hematite ; Magnetite ; Goethite

Identifying minerals

1. Crystal form & grow habit * Planar surfaces that bound a crystal are called crystal faces , & the geometric arrangement of faces are called crystal form. * Unique property of crystal is not in the face sizes but the angle between the faces – gives the mineral a distinctive crystal form * Crystals can ONLY form when a mineral can grow freely in open space.

2. Cleavage * A mineral’s tendency to break in preferred directions along bright, reflective planar surfaces * Many minerals have distinctive cleavage planes

3. Lust, Colour & Streak * Quality & intensity of the light reflected from a mineral produce an effect known as luster * Most important luster : Metallic or Non Metallic * Non metallic ( Vitreous ; resinous ; pearly) * Colour of a mineral is not a reliable means of identification – (trace amounts of impurities) * To reduce the error of judgment is to use a streak (think layer of powdered mineral made by rubbing a specimen on a nonglazed porcelain plate. * Powder gives a reliable colour effect.

4. Hardness * Relative resistance of a mineral being scratched * Governed by the crystal structure & strength of the chemical bonds * Measure through the Moh’s Hardness Scale

5. Density & Specific Gravity * Specific gravity is the ratio of the weight of the substance to the weight of an equal volume of pure water * Densities of some minerals are distinctive & can help in their identification ie Gold ; Galena

ROCKS * A rock is any naturally formed, non-living, firm, coherent aggregate mass of solid matter that constitutes part of a planet * Minerals are the most common building blocks of rocks

3 Families of Rocks 1. Igneous * Formed by the cooling and consolidation of magma 2. Sedimentary rock * Formed either by chemical precipitation of material carried in solution in sea, lake or river water, or by the deposition of mineral particles 3. Metamorphic rock * Change of form from igneous/sedimentary as a result of high temperature, high pressure or both.

* Earth’s crust is mainly igneous/ metamorphic

Features of rock (2 main features : Texture & mineral Assemblage)

* Texture : The overall appearance of a rock which results from the size, shape & arrangement of its constituent mineral grains * Mineral assemblage : Kinds & relative amounts of minerals present.

Basic Rock Identification

Igneous rocks * Specific textural feature – Presence of interlocking crystals as a result of their formation through crystallization of magma * Crystalize from magma underground = plutonic rocks * Crystalize from magma above ground = volcanic rocks * Interlocking crystals in volcanic rocks tend to be very small – because they come from lava that cools extremely rapidly when exposed to the cool temperatures of the surface ; very fine grained * In contrast, interlocking crystals in plutonic rocks tend to be large – coarse – takes a long time to solidify = time to form large interlocking crystals

Sedimentary Rocks * Textural evidence : Composed of accumulation of individual particles that have become stuck together * Individual mineral grains held together by cementing minerals.

Metamorphic Rocks * Mineral grains have been rotated & lined up so that they are all orientated in the same direction * Texture of this type are the result of directional stresses that operate on the rock during the metamorphic process.

Regolith * Rocks of all kinds physically broken up & chemically altered throughout the zone where the geosphere and all the spheres meet. * Given sufficient time, the result is conspicuous decomposition & disintegration by the process known as weathering * Product of rock weathering is a layer of broken up, disintegrated rock matter called regolith

Surface Blanket * Regolith contains many types of materials * 3 Categories : Saprolite ; Sediment ; Soil
Saprolite – Rock that has been weathered & broken up but still in the place where it is originally formed
Sediment – Unconsolidated rock & mineral particles that constitute the regolith
Clastic sediment : Broken up solid particles chemical sediment : dissolved material

Soil – Contains organic matter mixed with the mineral environment
- Soil is derived from the decay of dead plants & animals.

CHAPTER 5- THE TECTONIC CYCLE

Tectonics is the study of movement & deformation of lithospheric plates
All major topographic features of the Earth’s surface arise as a direct result of the motion & interacting of lithospheric plates.

Alfred Wagner: Continental Drift theory
Harry Hess: Seafloor Spreading Theory
Arthur Holmes: Continent are carried along by convective movements within the mantle * Suggested that rocks in the earth’s interior was ductile & would be buoyant & rise to the surface, sinking down as they became cooler & denser. * Lithosphere has energy of motion * Source of energy: Earth’s internal heat * 3 forces might play a role in moving the brittle slabs of the lithosphere * 1. Push the plates away from each other * 2. Dragging * 3. Sliding * Sliding : The lithosphere is thinnest near a spreading ridge & grows cooler & thicker away from the ridge; * Consequently, the boundary between the lithosphere & underlying asthenosphere slopes away from the ridge * If the asthenosphere moves, the lithosphere must move too : they are closely bound together.

Relative thickness of oceanic crust : 8km
Relative thickness of continental crust : 45km
Plates that carry continental crust move slowly whereas plates that carry oceanic crust moves rapidly.

Constructive plate boundaries vs Destructive plate boundaries
Destructive plate boundaries : Locations where slabs of lithosphere capped by old oceanic crust are sinking into the asthenosphere in a process called subduction.

Plate Margins * Lithosphere has broken into 9 major plates * Divergent plate margins/spreading centers. * Convergent plate margins * Transform plate margins * ALL CAN HAPPEN IN OCEANIC/CONTINENTAL CRUST.

Divergent Plate margins (constructive margins) * Divergent plate margins start on a CONTINENT * Becomes an ocean * Huge continental masses act as thermal blankets, slowly heating up & expanding * Expands from below, form a broad plateau (elevated piece of rock) * Plateau splits & starts a cycle of spreading.

Constructive plate margin * Where 2 lithospheric plates move towards one another * Oceanic-oceanic : one of the plates will subduct beneath the other * The fact that the lithosphere is cold contributes to a higher density in the subducting plate * Convection drives the downgoing motion of the lithospheric plate. * Oceanic plate subduction depends on the velocity & angle at which the plates approach each other.. * Oceanic/Continental crust – Oceanic crust undergoes subduction * Continental/Continental : Collision * Marks the final disappearance of the ocean basin (continental suture zone) * Result in the crumpling,folding & uplift of continental crust : mountain zones * Entire process : rifting, opening of an ocean basin, maturing into an ocean ; convergence ; recycling of oceanic crust in a subduction zone = Wilson cycle.

Transform Plate Margin * Slide past each other * Neither constructive/destructive – conservative

Topographic Features * Structure & topography of ocean basin can be explained as the result of rifting, seafloor spreading, recycling of oceanic lithosphere in subduction zones & the eventual closure of ocean basin between two continental crust. * Continents do not under go subduction ; ride along the lithosphere.

Topography of ocean basins * Lithosphere swells to form a PLATEAU * Only a thin layer near the top retains the strength because of the rising heat from the asthenosphere to the spreading centre * Tensional stress from the divergence of the plates eventually causes the lithosphere to break * Continental shelf : Flooded margin of a continent * Continental slope : Sharp drop off of the continental shelf * Continental Rise : Base of the continental slope * Continental slope : A region of gently changing slope where the seafloor flattens out & continental crust meets oceanic crust.

* Oceanic Trench : Where oceanic capped lithosphere sinks into the asthenosphere. * True edge of the continent is where oceanic crust meets continental crust. * Benioff zone : Subduction zone. * Island Arc – arc shaped chain of volcanic islands. * Form as a result of melting associated with subduction

Topography of continents & collision zones * Oceanic crust is uniform is composition, density, thickness & other characteristics * Continental crust is NOT * Active continental margins (continental volcanic arc) * Formed when melting occurs & magma rises to the surface & cool, * Some continental margin concide with active edges of tectonic plates * creating volcanoes * Mountain ranges, * Transform faults * Passive continental margins : Edge of continent far away from geologically active plate margins

2 kinds of structural units can be distinguished in continental crust

1. Craton : A stable core of very ancient rock 2. Orogens : Draped around the cratons – Elongated regions of crust that have been intensely bent & fractured during continental collisions * Eroded roots of mountain ranges * ONLY the YOUNGEST orogens are mountain ranges today

* Continental mass that was present by the end of the Hadean Eon continued to grow to the Archean Eon

Isotasy * Where the lithosphere maintains a FLOATATIONAL balance as it rides on top the asthenosphere. * Floatational height of the object depends on its overall mass/density * Cratons have attained isotasy * In a stable floatational state with respect to the underlying asthenosphere & is neither sinking or rising.

Tectonics & How they influence earth system

1. Climate & ecosystem in modern oregons

2. Composition of Ocean Water * Submarine volcanoes is the site of intense chemical reaction between the ocean water & hot rocks of the seafloor. * Some chemical elements are extracted from the seawater into the rocks & others are released from the rocks to the seawater * Determines the composition.

3. Composition of the atmosphere * Volcanoes release vast amounts of gas into the atmosphere * Vigor of volcanic activity is one of the fundamental controls on the concentration of greenhouse gases in the atmosphere * Volcanic gases continue to play an important role in the climate & long term composition of the atmosphere. * Very large eruptions can disrupt the climate

4. Sequestration of carbon * Sediments accumulated in the low lying ocean basins are the most important places in where carbon-rich organic matter is sequestered * Opening & closing of ocean basins is important, influences the sea lvel, rates of weather

CHAPTER 6 : Earthquakes & Volcanoes

Earthquake : Storage of elastic energy in rock masses, followed by the break of rock mass ; slipping of two masses along an earlier break & then sudden release of stored energy

Elastic Rebound hypothesis * Rocks are elastic & within limits : they can be bent * Some fault surfaces are rough, so that rock masses on either side of the fault become locked against one another * If the two rock masses are locked but tectonic forces are still pushing on them, rocks will undergo deformation * By deforming, the rocks store elastic energy : when the fault slips, the deformed rock rebounds to their original shape and the elastic energy is all released at once thru an earthquake * The longer the rocks are locked the more energy it will release

Seismic Wave : Vibrations that carry the elastically stored energy from the focus to other parts.

* Seismic waves spread out spherically. * Seismic waves must be recording while the rock is still vibrating : Rocks do not carry a permanent record of their deformation : they revert back to their orginal shape * 2 types of waves : Body & Surface

Body Waves * Rocks can be deformed in 2 ways – change in volume or shape * Body waves that causes volume changes consist of alternating pulses of compression & expansion * Compession/expansion waves pass early through rocks & they have the GREATEST velocity 6km/s * First to be recorded : PRIMARY WAVES * Body waves that deform materials through a change of shape are called SHEAR WAVES. * Each particle in the rock is displaced perpendicular to the direction of the wave. * Can only be transmitted by SOLIDS * Slower velocity : 3.5km/s * Secondary Waves * Body waves travel outward in all direction from the focus & have the capacity to travel through Earth’s interior.

Surface Waves * Only can travel around Earth rather than through it. * Travel more slowly than body waves ; last to arrive ; last to be detected * Can have very long wavelengths * The greater the amplitude (wave height) , the greater the surface disruption & the deeper the wave motion reaches. * Because they last a long time & have large amplitudes & wavelengths, surface wave can be extremely damaging to buildings & other structures on the surface.

Determining Earthquake Location * The point where energy is first released : Focus * Epicentre : the point on Earth’s surface that lies vertically above the focus. * The farther the waves travel, the more S waves will lag behind P waves. * Determined by triangulation to detect an Earthquake’s location : 3 or MORE seismographs

Measuring Earthquakes * Richter Magnitude : Calculated from the maximum recorded amplitudes of seismic waves * Correction of distance from the same epicenter * Calculate the energy released from an earthquake * Assumes that the focus of an earthquake is at a point

iii. Seismic Moment Magnitude : * Used to determine magnitudes * Takes account of the fact that energy may be released over a large area

iv. Modified Mercalli Intensity * Based on the strength of vibration that people feel & the extent of the damage * No distance correction in the MMI scale, intensity varies with distance from the epicenter.

Earthquake Damange

Effections of 2 primary kinds

i. Primary Effects : Cause direct damage to buildings, infrastructure & landscape due to ground motion & surface disruption ii. Secondary Effects : Cause damage indirectly as a result of processes set in motion by the earthquake.

Primary effects
Ground Motion : Results from the movement of seismic waves esp surface waves : can completely destroy buildings

Surface rupture : When a fault breaks the ground surface, buildings can be split, roads disrupted. Creates an open fissure/fault scarp

Secondary Effects

Fires
Landslides
Liquefaction : Sudden disturbance of water-saturated soil/sediment can turn seemingly solid ground into quicksand
Tsunami

Earthquake prediction * Forecasting means determining the long term likelihood of an earthquake striking in a particular location * Based principally on developing on understanding of the tectonic setting & history of seismic activity in that location * The scientific basis for modern prediction : Observation of odd/unusual occurences that would precede an earthquake * Also based on study of properties that might be expected to change in rocks that are undergoing elastic deformation including rock to magnetism etc. * Studies of recurrence patterns : Identifying seismic gaps (places where earthquakes have not occurred for a long time but in tectonically active areas –deformation is said to be increasing) * Receive a lot of research attention : place most likely experience a large earthquake.

Earthquakes & Earth’s interior

Seismic Waves can be reflected & refracted when they encounter the surfaces/boundaries of materials

Refraction : When the speed of a wave changes as it passes from one medium to another, causing the wave path to bend.

Speed of body waves is determined partly by the density of the rocks they are passing through – the higher the density, the greater the speed.

Body waves are abruptly refracted & reflected at several depths inside Earth * This shows that must be some boundaries separating materials that have distinctively different properties.

Core-Mantle Boundary
P waves are refracted at 2883km

Seismic Discontinuity * Core/mantle boundary & mantle/crust boundary are seismic discontinuities * Where the velocity of the seismic wave changes suddenly * The more ductile a rock, the slower the speed seismic waves passes through. * The more brittle the rock, the more elastic it is – can store more elastic energy

Earthquakes & Plate tectonics * Spreading ridges : Shallow-focus earthquakes of low magnitude * Transform faults : Shallow-focus but sometimes very POWERFUL earthquakes * Continental collions : Shallow to deep focus . very POWERFUL * Subduction zones : Deepest and most powerful Earthquakes : megethrust

Focal Depth * Earthquakes along spreading ridge are hot & too weak to store much elastic energy. * Shallow focus because only rocks nearer to the surface are cold enough & strong enough to behave this way * Crust/mantle boundary very close to the surface under a spreading ridge * In contrast to collision zones (thick crusts) & subduction zones (as long as plate sliding down the mantle remains cold enough & brittle enough, earthquakes can occur no matter how deep)

VOLCANOES

A volcano is a vent from which a combination of melted rock, solid rock debris & gas is erupted.
Under every volcano is a magma chamber * Magma is a mixture of molten rock, suspended mineral grains & dissolved gas.
Rocks begin to melt when heated to 800c -1000c
As pressure increases, melting point of rock increases
The presence of water dramatically reduces its melting temperature

Fractional Melting * When temperature increases enough for part of the material in a rock to melt & part to remain solid, it becomes a fractional melt. * The process of fractional melting can make it possible for a melt of one composition to become separated from residual rock of a different composition. * Leads to a great diversity of magmas & igneous rock times.

Magma * Characterized by a rang of compositions in which SILICA is predominant * Magma has properties of liquid & ability to flow * High temperatures * Principle volcanic gas : water vapor & carbon dioxide : Accounts for 98%. 1. Basaltic Magma : 50% silica ( Little dissolved gas) 2. Andesitic Magma : 60% silica (Moderate) 3. Rhyoltic Magma 70% silica (Highest gas content) * The higher the silica content, the higher its viscosity (resistance to flow) * Due to more linkages among silica in the magma * The higher the temperature, the less the viscosity of the magma & the more readily it flows. * Pahoehoe : Hot runny basaltic magma * Aa : High viscosity/cooler

Volcanic eruptions * Magma is less dense than the solid matter from which it is formed * Because pressure is proportional to depth, it decreases as the magma rises, allowing melting to occur & gas dissolved in it to be released * The process of ascent & characterisitcs of the magma determine the eruptive style of the volcano.

Non-explosive eruptions * Difference between explosive/nonexplosive = viscosity & dissolved gas content * Most commonly basaltic * Higher temperature than andesitic or rhytolic magma * Very fluid initial lava forms thin pahoehoe flows : With increasing viscosity the rate of movement slows and the cooler stickier lava is transformed into a slow-moving aa flow. * Vesicles : When lava finally solidifies to rock, the bubbles that are trapped inside it.

Explosive eruptions

* Andesitic & rhyolitic have high silca content & erupt at lower temperatures than basaltic magma * Combination of silica-rich composition, low temperature, high viscosity & high dissolved gas = explosive eruption * As the gas charged, viscous magma rises, the gas comes out of solution through bubbles but cannot escape * Shatter violently * Pyroclast : A fragment of hot, shattered magma/rock * Deposit of loose pyroclasts : tephra * Pyroclasts cemented or consolidated tgt : Pyroclastic rock * Explosivness of a volcano : Volcanic Explosivity Index * Measures used : Volume of content erupted, height of eruption cloud.

Eruption Columns * Rapid drop in pressure as magma rises cause an increased intensity in bubbling * Eruption column : Hot, turbulent mixture that rises rapidly in the cooler air above the volcano. * Rising column is driving by heat energy released from hot, newly formed pyroclasts * Vesuvian eruption : Column spreading laterally ; density of column = density of atmosphere.

Pyroclastic flows * Hot, highly mobile mass of tephra that is high density than the atmosphere will rush down the flanks

Lateral blasts : Blowing a mixture of pyroclast/hot gases sideways & upwards

Types of volcano
Location/shape.
Shape of the volcano has a lot to do with the kind of magma erupted & the relative proportions of lava & pyroclasts.

1. Shield volcanoes * Broad, rougly dome shape gentle slopes * Characterized by successive eruptions of basaltic lava

2. Tephra cones/stratovolcanoes * Rhyolitic/andesitic : tend to eject a large proportion of pyroclasts & therefore surrounded by layers of tephra. * Steep sided : Slope of cone determined by size of pyroclast * Stratovolcanoes : Steep conical mountains that consist of layers of both lava & tephra

Caldera : Circular steep walled basin after magma chamber has been emptied out
Fissure eruption : Elongate fracture in the crust
Volcanic disasters: Active, dormant (have not erupted in recent memory but got volcanic activity) , extinct

Volcanic Hazards * Kill people * Tephra & hot poisonous gases may bury people or suffocate * Rainwater can loosen tephra piled on a steep volcano slope & start mudflow * Undersea eruptions can cause tsunamis * Wreak havoc on agriculture; cause famine.

Predicting eruption * Long term eruptions based on geologic history & understanding * Common signs of imminent eruption : Swarms of small earthquakes of increasing frequency or intensity * Dramatic change in focal depths of local earthquakes ; sudden changes in the amount or composition of gas emitted. * Signs of magma moving upwards or beginning to emerge from the volcano.

Post eruption * Volcanism renews the land surface * Surface renewal * Fertile volcanic soils * Produce new land * Provide geothermal energy/formation of mineral deposits

Magma underground * Plutons : igneous rocks that solidy underground * Dikes : Cut across layering of intruded rock * Sills : parallel to layering * Laccoliths : sills that cause the intruded rock to bend upwards * Stocks : Intrusive igneous bodies of irregular shape * Batholiths : LARGER.

Midocean ridges : balsaltic magma
Oceanic crust is thin

Lava that is erupted at contental divergent margins tend to be high in silica content because the magma passes through thick continental crust, metling & assimilating silica rich crustal materials.
Rhyolitic magma do not form in the mantle unlike basaltic

Andestic magma : where subduction occurs in oceanic subduction ; partial melting may separate the minerals with higher melting point from melt formed at lower temperature, allowing the minerals to erupt to the surface
Water reduces melting point of rocks.

CHAPTER 7 : THE ROCK CYCLE

Minerals in metamorphic rocks & igneous rocks form at pressures & temperatures much higher than ground surface
Therefore their minerals are chemically unstable at ground surface
Chemical weathering : Principle agent : carbonic acid. Chemical reactions transforms them into new chemical compounds

Joints : Sheetlike fractures as a result of physical weathering
Frost wedging : When water freezes in the joints , volume increases & the pressure is so great that it can wedge the rock aprt
Material dissolved in groundwater can precipitate out to form salts.
Fires can overheat a rock, cause it to expand, fracture & break away
Chemical & Physical weathering works hand in hand to increase surface area of rock.
Surface area always increases when a large unit is divided into sub units

Sediment & Transport
Sediment : regolith that has undergone erosional transport
3 types of sediment : Clastic, chemical & biogenic

i. Clastic Sediment * Bits of broken rock & minerals that are moved as solid particles * Individual fragment : clast * MOST durable during chemical weathering * 4 main classes of clast size from coarsest to finest : Gravel, sand, silt, clay. * Sediment is deposited through gravitational settling because of a drop in energy * Clast size of sediment moved is related to the speed of the agent * During transport, clasts are broken down even faster * When speed fluctuates, clast sorting occurs * Well sorted : clasts are of the same size * Poorly sorted : clasts are of different size

ii. Chemical & Biogenic sediment * Chemical sediment :dissolved substances transported in solution & then precipitated * Precipitation : refers to the chemical separation of a solid from a solution. * Biogenic sediment : As a result of biochemical reactions in the water.

Mass wasting * The downslope movement of regolith under the pull of gravity * The composition and texture of sediment involved, the amount of water & air mixed with the sediment & the steepness of the slope call influence the type & velocity of landslide.

Tectonic environments of sedimentation * Clast Sediment accumulate in low-lying areas as a result of gravity * Largely controlled by PLATE TECTONICS * Chemical & biogenic sedimentation not as affected : occur in open aquatic environments * Erosion proceeds most rapidly where slopes are the steepest * Accretionary wedges : Great thicknesses of sediment that accumulate in subduction trench environment.

From Regolith to rock

Lithification: When sediment turns back into rock
Bedding: Banded appearance that is due to sediment being deposited in distinct layers

Lithification 1. Compaction : Sediment accumulated is subject to high pressure because the pile grows thicker 2. Cementation : Bonded together by a piece of cementing material 3. OR recrystallization : Mineral grains grow to become interlocked

Diagenesis : Various low temperature & low pressure changes that happen to sediment after deposition : ie lithification/chemical reaction

Sedimentary rock * Can learn its source, the weathering process, reveal info about its sediment transport & deposition process. * FOSSILS : diagnostic of sedimentary rock ; the prime indicator

Clastic Sedimentary Rock * 4 classes : conglomerate, sandstone, siltstone, shale. * Conglomerate : ROUNDED clast bigger than 2mm * Matrix : Large clasts surrounded by much finer-grained material * Breccia : Clasts with sharp angles/angular * Sandstone : 0.05mm-2mm ; dominated by quartz * Siltstone : Silt/claysized particles * Shale : Higher proportion of clay-sized particles * Fissile : Splits into sheetlike fragments * Mudstone : Not fissile

Chemical & Biogenic sedimentary rock * Evaporite : Sedimentary rock that forms as a result of evaporation * Limestone : most important rock formed in the lithification of sediment * Monomineral : Consist of just one mineral

Sedimentary Strata * A distinct layer of sediment accumulated at Earth’s surface * Each bed can be distinguished by difference in thickness or some character ie size/shape of the clasts/colour of the rock.

3 principles of Stratigraphy

1. Principle of original horizonality : Sediment deposited in a layer horizontal to the earth surface. 2. Principle of stratigraphic superposition : Sequence of sedimentary strata is that the strata is deposited from bottom to top. Youngest stratum on top/ oldest at the bottom 3. Principle of lateral continuality : Layer of sediment will extend horizontally as far as it was carried – will get thinner and ultimately pinch out at the farthest stages

Cross bedding : Sedimentary beds that are inclined with respect to a thicker stratum within which they occur

Stratigraphic Correlation : Determination of equivalence in age of the succession of strata in 2 or more different areas.

Breaks in stratigraphic records
Conformable : Sequence of strata deposited layer after layer without any interruption.

Unconformity : Substantial breaks or gaps in a pile of strata
3 kinds : Nonconformity : strata overlie igneous/metamorphic rock : Angular unconformity : older strata deformed, uplifted & partially removed by erosion, after which younger sediment deposited on top

: Disconformity : Irregular surface of erosion between parallel strata ; implies that sedimentation ceased for a period of time but with no deformation or tilting of the underlying strata.

Cross-cutting : A stratum MUST be older than any feature that cuts or disrupts it.
A foreign rock (xenolith) that is encased within another rock unit must predate the rock that encloses it.

Metamorphic Rock * Igneous or sedimentary rock that has been changed in mineralogy/texture of both

Metamorphism * Describe changes in mineral assemblage & texture that occur in sedimentary/igneous rock * Must be subjected to temperatures above 150 & pressures in excess of about 300MPa * Metamorphism only applies to changes that happen in SOLID rock. * Low Grade metamorphism : Changes in mineral assemblage & texture 150-550 degrees at low pressure * High grade : High temp/high pressure

Role of fluids * Pores : open spaces between grains in sedimentary rock * Pore fluid plays a vital role in metamorphism * When metamorphism occurs , some of the dissolved constituents move from the pore fluid into the new minerals growing in the metamorphic rock. * Serves as a transporting medium that speeds up chemical reactions * Metasomatism : When very abundant pore fluids are involved in metamorphism that it is fundamentally altered

Temperature, Pressure & Stress

* Stress not uniform in metamorphic rock (differential stress) * The term “stress” is use as it has the connotation of direction * Igenous rocks have textures formed under uniform stress * Most visible effect of metamorphism : Parallel alignment of minerals as opposed to igneous rock (random alignment of mineral grains)

Metamorphic Mineral assemblage * Metamorphism produces new mineral assemblages characteristic of a given range of temperature/pressure

Metamorphic processes

1. Mechanical deformation : Grinding, crushing & development of foliation 2. Chemical recrystallization : Includes all the changes in mineral compostion
- 3 most important kinds of metamorphism

Contact metamorphism * When hot magma intrudes cooler rock, high temperature causes chemical reaction & recrystallization * Contact metamorphism : Temperature driven

Burial Metamorphism * Sediment when buried may attain temperatures in excess of 150 or more * Intitate burial metamorphism * Abundant pore water is present & helps speed up chemical recrystallization & helps new minerals to grow. * Does not tend to be foliated because not much mechanical deformation

Regional metamorphism * Involves differential stress & a lot of mechanical deformation * Tends to be distinctly foliated. * Rock can transmit pressure v quickly but transmits heat very slowly.

Metamorphic rock

i. Shale : Slate -> phyllite -> schist -> gneiss (SPSG) ii. Basalt : Greenschist -> Amphibolite -> Granolite (GAG) iii. Limestone : Marble iv. Sandstone : Quartzite

Because rocks contain many different constituents, melting proceeds over a range of temperatures rather than a single temperature

When the melted portion eventually solidifies, it will form an igneous rock with a very different composition from the unmelted residual rock

Crysalization & Igneous rock

Crystallization : The set of processes whereby crystals of the individual mineral components nucleate & grow in cooling magma.

Extrusive volcanic rock : Formed from the rapid cooling & solidification of lava
Intrusive/plutonic rock : Formed when magma cools & solidifies within the crust or mantle

Felsic : Rocks that contain a lot of silica
Mafic : Rocks that do not contain a lot of silica ; rich in magnesium & iron

Volcanic Rock * Characteristic of volcanic rock : fine grain * Pyroclastic rock : trainsitional between igneous & sedimentarya * 2 ways that tephra can be converted to pyroclastic rock (cementing agent or welding of hot,glassy ash particls) * Welded tuff : Glassy pyroclastic rock * Agglomerate : Tephra bomb sized * Tuff : Smaller pieces : ash sized

Plutonic Rock
Pegmatite : Extremely coarsed grained rock.
Porphyry : Distinctive mixture of large & small grains

Igneous rock diversification * Due to fractional crystallization * Crystallization forms over a range of temperature * Due to various sources * Seperated melt & high temperature crystals will each form diverse types of igneous rocks

The Rock Cycle, Tectonic cycle & Earth’s Landscape
-Denudation : Combined destructive effects of weathering, erosion & mass wasting (downslope movement of regolith)

* Calculation of long-term denudation rates needs knowledge of how much rock debris has been removed from an area during a specified length of time * Rates are high on steep slopes and in areas underlain by soft, erodible highly jointed rock. * Human activity also affects denudation Factors controlling landscape development

1. Process : distinctive landscape elements result from the activity of various surface processes 2. Climate: Determine which processes are active in any area 3. Lithology : Less/more erodible? 4. Relief : Topographic relief 5. Time

* A change in geosphere can lead to environmental changes

CHAPTER 8 : The Hydrologic Cycle

Largest reservoir in the hydrologic cycle : Ocean 97.5% of water

Largest reservoir for fresh water : Polar ice sheets
UNFROZEN fresh water : 98.5% of unfrozen fresh water is groundwater

Water : Evaporation; condensation ; surface runoff ; infiltration into the soil

Water tends to move to downhill in a process called overland flow
Streamflow consist of stormflow – comes from overland flow & base flow (fed by groundwater directly into the channel
Ephemeral: no base flow ; dries up seasonally
Perennial: Base flow do not dry up

Stream’s channel : Efficient conduit for carrying water
Load : Total of all the sediment
Alluvium : sediment load
Drainage basin : total area that contributes water to the stream
Divide: A ridge that separates adjacent drainage basins

Area of any drainage basin is proportional to both the length of the stream that drain the basin & the average annual volume of water that moves through the drainage system

* Several controlling factors affect the size & shape of a stream channel 1. Erodibility of the rock or sediment across which the stream flows 2. Steepest of its descent 3. the average volume of water passing through the channel.

Stream gradient – Vertical distance that a stream channel descends between two points along its course
A local change in gradient may occur when channel passes from resistant rock into more erodible rock or where a landslide or lava flow forms a natural dam across the channel.

Factors that control stream behavior 1. Average width & depth of the channel 2. Channel gradient 3. Average velocity of the water. 4. Discharge : Quantity of water passing a point on a stream bank during a given interval of time 5. Sediment load

The variable factors are interdependent : The erosion continues until the increased discharge can be accommodated by an enlarged channel & faster flow

From Head to Mouth : width & depth of the channel increase ; gradient decreases ; flow velocity increases & discharge increases

* Discharge is low in the headward reaches of a stream * Average velocity is low because of the frictional resistance of the water passing over a very rough seabed * Flow is turbulent ; discharge increases downstream as each tributary introduces more water * Velocity also increases downstream as a result of the progressive increase in discharge & decrease in frictional resistance as the streambed becomes smoother.

Meandering channels * Bend in a stream channel * Occurs most commonly in channels cut into fine-grained alluvium * Looping pattern reflects the way in which a stream minimizes resistance to flow * Dissipates energy as uniformly as possible * On the INSIDE bend velocity is least * OUTSIDE BEND : Velocity is the highest * Inner side of meander : Water is shallow & velocity & energy of flow is lowest. * Sediments therefore deposited there & accumulated to form a point bar * Oxbow-lake

Braided Channels : A stream with many interlacing channels & bars : when a stream that is unable to transport the entire available sediment load tends to deposit the coarsest & densest sediment to form a bar, which locally divides & concentrates the flow in the deeper segments of the either side of the bar.

* Tends to form in a stream that has a highly variable discharge & easily erodible banks, therefore can supply abundant sediment to the system.

Stream load : Sediment normally decreases in coarseness downstream
A stream load consists of 3 parts : Bed load ( coarse particles that move along the stream’s bed) & fine particles (suspended in the water)
Steams carry dissolved substances

i. Bed Load * Amounts to 5-50% of the total sediment load * Move discontinuously by rolling or sliding * Moves short distances by saltation (short,intermittent jumps along arc-shaped paths) * Distribution of bed-load sediment in a stream is generally related to the distribution of water velocity within the channel * Coarse-grained sediment is concentrated where velocity is high and fine grained sediment –velocity low.

ii. Suspended Load * Particles of silt & clay carried in suspension * Derived from fine-grained regolith * Tend to remain in suspension longer than they would due to high velocity that would not let them settle

iii. Dissolved Load * Contains dissolved substances

Running Water & Landscapes * Depositional landforms
Floodplain : A wide valley where streams typically deposit well-sorted layers of coarse & fine particles. * Natural levee : Coarsest part of suspended load * Alluvial fan : Fan-shaped body of alluvium at the base of an upland area. * Delta : When stream water enters standing water of sea,lake, its speed diminishes rapidly, decreasing its ability to transport sediment

Continental Divide : All continents can be divided into large regions from which major through-flowing rivers enter one of the oceans

Surface Water Reservoirs
Lake : Can be formed by tributary alluvial fans damming stream valleys
- Transitory landscape

Wetlands * An area that is permanently/intermittently moist * Eutrophication : infilling of sediment & organic material & shallowing process

Floods * Floods are normal & expected events * Floods transport & deposit abundant sediment, replenishing mineral content of soil in the floodplains * Peak discharge * Crest : The time when the peak flow passes the location where measurements are being made * Recurrence interval : Average time interval between 2 floods

Flood Prevention & Channelization * Channelization : Widening, deepening, straightening or lining of natural channels * Can interfere with natural habitats & ecosystems & aggravate water pollution * Urbanization may contribute to flooding because they allow the runoff from paved areas to reach the river channel more quickly *

Groundwater : Subsurface water
Chemistry of groundwater : The more the water spends in direct contact with the rock, the more mineral constituents will be dissolved from the rock into the water.
Composition of groundwater varies from place to place.

Movement of groundwater * Aerated zone: Open spaces in regolith or bedrock filled mainly with air ; water may be present but it merely wets the mineral grains & does not saturate the ground * Saturated zone : All openings are filled with water * Water table : Upper surface of the saturated zone/ represents the upper limit of all readily usable groundwater * Percolation: Groundwater flow * Percolation of groundwater depends on the nature of the rock or sediment through which it moves

Recharge & Discharge

Recharge – Replenishment of groundwater when rainfall & snowmelt enter the ground

Discharge : Where subsurface water emerges on the ground surface
Groundwater responds to gravity

Aquifers, Wells & Springs

Aquifer – a body of rock sufficiently porous & permeable to store & conduct significant quantities of groundwater
Porous to store water ; permeable to allow water to pass through
Unconfined aquifer : Aquifer that has a water table ; in contact with the atmosphere
Confined aquifer : bounded above & below by bodies of impermeable rock/sediment
Rock/sediment that slows/prohibits the passage of groundwater : aquicide
High porosity does not mean high permeability
Porosity : Open spaces between rocks
A cone of depression may form if the withdrawal > local rate of groundwater flow
High hydrostatic pressure (pressure due to weight of overlying water) : Artesian aquifer

Spring – Flow of groundwater emerging naturally at the ground surface
Dissolution : Chemical weathering involving mineral & rock constituents passing directly into solution

Cave : forms when circulating groundwater slowly dissolves and remove carbonate rock, leaving an underground void.
Cave formations are precipated from materials in groundwater

Sinkhole
Open to the sky
Dissolution
Cover subsidence (covered by deep permeable clay)
Cover collapse (most dangerous ; covered by deep impermeable clay)

Karst : In regions of exceptionally soluble rock, sinkholes and caves are so numerous that they combine to form a distinct topography of smalls basins, ridges, and pinnacles called karst

Water & Society
Crop irrigation accounts for 75% of demand for fresh water (the most)
Water stress : Water shortages (29 countries worldwide)
Interbasin Transfer : Surface water moved from one drainage basin to another
Result in low flow, low sediment load & high salinity
Groundwater mining : If the rate of withdrawal > rate of natural recharge
Compaction of aquifer : When its mineral grains collapse on one another : pore water holding them apart has been removed – permanently damanged

Industrial effluent : Contanminated runoff
Remediation : Cleaning up of contaminated surface water.

Groundwater contanmination * Most common pollutants : Untreated sewage /nitrate from agricultural chemicals * Saline contamination of groundwater * Caused by intrusion of seawater into coastal aquifers.

CHAPTER 10 : The World Ocean

Seawater covers 70.8% of the Earth Surface
Echo sounders used to measure ocean depths

Age & Origin of the Ocean * Carbonaceous chrondites : contain several % of water * MOST likely origin : condensed from steam produced in primordial volcanic eruptions

Salinity of seawater : 33-37 per mil
Principle elements : Sodium & chlorine

Origin of ocean salinity * Due to volcanic eruptions : water vapor/carbon dioxide/chloride/sulfate * Volcanic gas released from submarine volcanism * Dust eroded from desert regions blown to the sea * Gaseous, liquid & solid pollutants from human activity * Salinity controlled because organisms withdraw such elements to build their shells/skeletons * Potassium & sodium are absorbed & removed by clay particles as they settle to the seafloor.

Controls on ocean salinity * Closely related to latitutde * 1. Evaporation * 2 Precipitation of rain * 3. Inflow of fresh water * 4. Freezing of sea ice (when seawater freezes salts are excluded from the ice)

Salinity is high in latitudes where deserts lie because here, evaporation > precipitation
Salinity lower in the tropics : precipitation is high

* Water has a high heat capacity : For a given amount of heat absorbed, it has a lower rise in temperature * Both the range & seasonal changes in ocean temperatures are much less what we observe on land. * Mild climates along the coast.

Vertical Stratification of the Ocean * Seawater becomes denser as it becomes colder & its salinity increases * Colder, saltier water is denser than warmer, fresher water * 3 major depth zones : Surface zone , mix * Thermocline * Halocline * Pycnocline (Increasing salinity/decrease in temperature or both) * Beneath the zone of halocline,pynocline & thermocline – deepzone

Biotic zones * Pelagic zone (uppermost water) * Benthonic zone (bottom, within bottom sediment) * Plant life restricted to the photic zone (200M)

Oceanic Sediment
-Calcareous/siliceous ooze (deep ocean floor mantled with skeletal remains of single planktonic/benthonic animals) >30% of such remains - Found in middle-low latitudes where there is warm water
- Not found in unusually deep water, because deep water contain more carbon dioxide than able to dissolve such carbonate particles.

Lithic sediment (rock fragments derived from continental sources)

Ocean Circulation * Factors that drive currents 1. Radiation from the Sun provides heat energy to the atmosphere 2. Non uniform heating generate winds 3. Winds drive the movement of ocean surface water.

Ultimate source of this motion : The Sun

Movement of deep-ocean water is fundamentally driven by the characteristics of the water itself, principally temperature & salinity

Factors that influence current direction : Corolis Force & Ekman Transport

1. Corolis force : Northern Hemisphere : Deflected right (EAST) 2. Southern hemisphere : Left (WEST) * Maximum influence at the poles & least at the equator

Ekman Transport * Wind affects the uppermost layers of the water column more than it affects the underlying layers * But underlying layers affected by corolis effect * Ekman effect : Combined effect of the wind & corolis force stronger with depth. By 100m the wind has lost its effectiveness * Corolis force doesn’t drive currents but only influence their direction

Upwelling : When net transport of water is away from land, subsurface water replaces

Downwelling : If net Ekman transport is toward the coast, the surface water thickens & sinks : downwelling

Surface current system
Gyre : Large sub-circular current system
5 major ocean gyres : 2 each in the pacific & atlantic ocean and one in indian ocean
Currents in northern hemisphere : clockwise
Currents in Southern hemisphere : Counterclockwise

On either side of the equator, the low latitude ocean regions are dominated by warm, westward-flowing North & South Equatorial currents * Trade winds blow towards the west on either side of the equator * Between the North & South equatorial currents flowing approximately along the equator is the eastward flowing Equatorial countercurrent

Northern Indian Ocean – direction of flow changes seasonally with the monsoon

Largest mass of polar surface water : Antartic Cirumpolar current
North Atlanic Deep Water – flows downwards & spread into the South Atlantic
Antartic Bottom Water : Deepest, densest water flows beneath the North Atlantic deep water

Global Thermohaline Circulation : NADW flows southward & warm water drawn towards north atlantic to compensate : gulf stream.

Reaching the South, NADW enters the Antartic circumpolar current

Ocean Waves * Determined by wind speed, fetch (distance across which it blows) , & length of time in which it blows across. * Diameter of loops at water surface must be exactly equal to the wave height * Tsunami long wave length low wave height high levels of periodicity

Beaches & Other Coastal Deposits * Beach : Wave-washed sediment along a coast, including sediment in the surf zone that is in constant motion * Barrier islands : Long narrow islands parallel to a coast separated by a lagoon

Reefs : Fringing Reef : Attached to the adjacent land
Barrier reef : Reef separated by a lagoon
Atoll : Forms whens a tropical volcano with a fringing reef subsides

Hard Stabilization : Structural responses ie Sea wall jetties
Soft Stabilization : Non structural approach ie beach replenishment
Retreat : abandoned

Changing Sea Levels
Eustatic : Long time intervals in change in sea water * Rise or fall in sea levels that affect the ocean globally * Submergence : Rising sea level * Emergence : lowering of water level. * Melting of SEA ICE does not have a dramatic increase as water is already displaced by their presence * As opposed to ICE SHEETS

CHAPTER 11 : THE ATMOSPHERE

The atmosphere stores moisture & solar energy, transporting it globally in the form of heat etc.etc.

Volcanic gases collected to form Earth’s secondary atmosphere

Chemical Evolution of the atmosphere
Photodissociation : Ultraviolet rays breaking up water into oxygen & hydrogen
Changes in oxygen levels in earth atmosphere recorded in the black/red banded iron formations

Limestone acts as a long-term reservoir for carbon in the carbon cycle
When new ocean basins open up through plate divergence, vast amount of sediment accumulated on the new continental margin, accelerating the burial rate of organic matter
Subduction also subducts limestone into the mantle, isolating carbon further

Composition of Air
Composition varies because aerosols & water vapor varies 1. Aerosols : Extremely tiny liquid droplets/solid particles that are so small they remain in the air 2. Water vapour

5 greenhouse gases : Carbon dioxide, water vapour, methane, ozone & nitrious oxide * Minor gases ; absorbs infrared radiation

Temperature Vs Heat

Heat : Total kinetic energy of atoms in a body
Temperature : Average kinetic energy of the atoms in a body

Insolation * Energy that actually reaches the surface of the Earth * 3 reasons * Atmosphere reflects some of the radiation back to space * Absorb some radiation * Shape of the earth : only sun directly overhead then will be 1370

Profile of the atmosphere from bottom to top : Troposphere, Stratosphere, Mesosphere, Thermosphere

Troposphere : Declining temperature with altitude because reradiated heat is most effectively absorbed at the bottom of the atmosphere where air is most dense.
Air at the bottom is reradiated by the ground & ocean
Endlessly convecting : Cold air sinks & warm air rises
From surface to 10-16km

Stratosphere
Reaches 50km in altitude
Densest cold air at the bottom & warm air on top
Temperature increases with altitude
Most of the ozone resides here. Maximum absorption is found at the top of the stratosphere
As altitude declines, temperature declines, hence the lowering of temperature

Mesosphere * Temperature decreases with increasing altitude * Coldest layer until 85km * Does not contain ozone, hence solar radiation just passes through

Thermosphere * reaches out to 500km * Temperature increases with altitude * Because it is directly exposed to the Sun’s radiation * But very cold because very little gas molecules.

Air Pressure * Amount of molecules contained in a given volume of air * Air pressure is measured with a barometer * Air pressure decreases with altitude

Relative humidity
-Saturation : When the no. of molecules that evaporate = no. of molecules that condenses
- Saturation determines the number of h2o molecules that can reside in the vapor phase at any moment
- Vapour pressure cannot be higher than the saturation but can be lower
- If it is higher, it condense to form water droplets

* Relative humidity : The ratio of the vapor pressure in a sample of air to the saturation vapor pressure at the same temperature expressed as a percentage * Refers to the ratio of water vapor to the maximum amount of water vapor the air can hold * Relative humidity can be changed by the addition of water vapor or a change in temperature
Adiabiatic Lapse Rate * : Processes that occur within the addition or subtraction of heat from an external source * Warm air is less dense than cold air & therefore rises, creating a convection cell. * When air has reach saturation & CONDENSATION begun, the dry adiabiatic lapse rate will then turn to MOIST

Cloud Formation Clouds are minute water droplets, tiny ice crystals or both

4 lifting forces

1. Density Lifting : When warm low density air rises convectively & displaces cooler, denser air 2. Frontal lifting : When 2 flowing air masses of different density meets (fronts) – warm front, warm air rises over & form clouds ; cold front (denser air flows in and displaces warm air by pushing it up) ; occluded front cold front overtakes a warm front 3. Orographic lifting : Air forced up over a terrain 4. Convergence : When 2 air masses meet & flows upwards.

Condensation, Nucleation, Precipitation

Nucleation : Formation of a water droplet
Amount of energy for nucleation is large when there is no surface ie the sky.
Aerosols in the air provide the energy for nucleation
Clouds with temperatures between 0 to -9 only contain supercooled water droplets
-10 to -20 : Ice crystals also nucleate so that cloud becomes a mixture of supercooled water droplets & ice crystals

-20 & below : solely ice crystals
Sleet : Frozen raindrops. When raindrops fall & hits a layer of air that is below 0.

Cloud types : Cumulus, stratus, cirrus

Cumulus : Form when hot humid air rises convectively & reaches a level of condensation where cloud rises again

. Flat based-cauliflower shaped clouds
Stratocumulus : When they combine
Cumulonimbus : When they rise to the top of the troposphere : expand horizontally
Forms at 2-6km : Altocumulus
6-15 : Cirrocumulus

Stratus clouds :Cover the entire sky.
Cloud blanket several km thick : nimbostratus
6-8 : Alto 8-12: Cirrostratus

Cirrus : composed entirely only of ice crystals ; form above 6km in altitude only

CHAPTER 12 – WIND & WEATHER SYSTEMS

5 determinants of weather

1. Temperature 2. Air pressure 3. Humidity 4. Cloudiness 5. Wind Speed & Direction

Weather is short term whereas climate is long term (average weather condition of a place)

Areas of high pressure is where cool air descends & collects near the surface
Areas of low pressure is where hot air rises away from the surface.
Horizontal movement of air is always associated with some vertical movement

Factors affecting Wind speed & direction

1. Pressure gradient force 2. Corolis force 3. Friction

Pressure gradient force
- The stronger the pressure gradient, the stronger will be the resulting flow of air
- Isobars together, the gradient is steep
- Equal air pressure connected by isobars
- Air pressure differences develop both horizontally & vertically
- Horizontal pressure gradients Measurements must be taken at a constant altitude ie mean sea level

Corolis Force : The longer the distance covered, the greater the effect of the corolis force
Friction : Friction diminishes the effect of the corolis force. Most influential for winds that blow within 1km of Earth’s surface

Geostrophic Winds : Winds that result from a balance of pressure-gradient & corolis effect. Friction upsets this balance

Convergent & Divergent Flow
-Northern hemisphere – Inward spiral rotate counter clock wise, outward spiral rotates clockwise
- Southern hemisphere, inward rotates clockwise & outward rotates anti-clockwise.
- Air spiraling inward around a low pressure centre is called a cyclone
- Air spiraling outward is called an anti cyclone
- Inward spiral flow causes convergence : leads to an upward flow of air at the centre of the low. Low pressure centre – air moves upwards : Convergence
- High pressure centre : Air moves downwards inwards. : Divergence

Global Air Circulation

Hadley Cells * Warm air rises in the tropics & creates a low-pressure zone of convergence (ITCZ) * Deflected by the corolis effect & blows east

Monsoons * Seasonally reversing wind system * Caused by the seasonal shift of the ITCZ (low pressure system) * During winter time, ITCZ is in the south * During summer , ITCZ is in the North

El-Nino/ Southern Oscillation * Easterly trade winds slacken, reduces upwelling * Trade winds : High level winds are westerlies, low level are easterlies * Periodic variation in air pressure * Normally high pressure in the east of pacific & low pressure in the west * Difference in air pressure is known as the Southern Oscillation Index * During el nion, the Walker circulation is weak

Local Wind & Weather systems * Sea breeze (In the day, land heats up hotter, low pressure – sea heats up slower, high pressure – flows towards land * Land breeze – reverse

Katabatic & Chinhook Winds * Katabatic winds : Flow of cold, dense air under the influence of gravity * Chinhook Winds : Warm dry winds : Downward flowing air heated adibiatically – caused by anticyclones

Severe Weather * Cyclones i. Wave cyclones : Responsible for most of the everyday weather systems ii. Most intense : Tropical cyclones iii. Cyclones cannot form along the equator because they need the effect of the corolis force iv. Because a hurricane draws its energy from ocean water, its wind speeds will diminish & the hurricane will quickly dissipate once it moves onshore v. Storm surge – flood of ocean water vi. Torrential rain

Thunderstorms * Develop when an updraft of warm, humid air releases a lot of latent heat very quickly & becomes unstable * Released heat causes stronger updrafts, which pull in more warm, moist air which in turn releases more latent heat. * Cumulonimbus clouds form

Tornadoes * Extends down from a cumulonimbus cloud * Develop from large thunderstorm

Droughts & Dust storms
Droughts -> requires below average precipitation
A

Deserts * Most extensive deserts are formed along the 2 circumglobal belts of divergence * 5 types of deserts

Positive feedback – when the change in the system tends to be magnified
Negative feedback – Change in the system tends to be minimized

Threshold- System can handle & respond to changes by returning to its original state but up to a certain point only * If pushed beyond the threshold, system will never be able to return to its earlier state.

CHAPTER 13 – CLIMATE SYSTEM

Climate – A measure of the average weather conditions of any place on Earth over time

ALL but the GEOSPHERE is driven by solar energy * When changes happen, the atmosphere is the system that responds most rapidly – within a month or less * Hydrosphere : Moderate * Geosphere : Millions of year * But the surface of the geosphere can respond rapidly to local changes * Absence of biosphere/vegetation can cause wind erosion * Because of its ability to absorb & retain heat, the ocean serves as a great source of thermal energy that helps moderate climates (little contrast between seasons)

Evidence of Climatic change * ID of climate change must be based on a shift in average conditions over a span of year * Climate is commonly expressed in terms of mean TEMPERATURE & mean PRECIPITATION.

Geologic Record of climate change * Paleoclimates : climates of ancient times * Climate proxy records : Reconstructing paleoclimates by relying on records of natural events that closely mimic climate * Can provide evidence of the year to year variability of weather in a specific location * CPR from different locales can add up to a detailed picture of local, regional & global climatic trends * 2 basic ways to assess climate proxies * i. Look at historical records maintained by people of events & processes that were controlled by climate * ii.Examine natural records of climatic variations recorded by natural processes

Advantage of (i) – Dates are attached so we know when
Advantage of (ii) – Record of climate change but we do not know when

Human record of climate proxies – Doesn’t track the weather directly but a process or event influenced by the weather ie. Quality of wine harvests

Ice Cores & Isotopic studies * Measurements of the ratio of 2 isotopes of oxygen enable scientists to estimate the air temperature when snow was transformed to ice * Lighter isotope evaporate & accumulated on glaciers whereas heavier isotope got left behind * A particularly useful aspect of ice-core analysis is that bubbles of air are trapped in the glacier ice during its transformation from snow to ice * Glacier ice is laid down in annual layers : scientists can count back in time to attach dates to the temperature determinations

Annual Growth Rings * Dendrochronlogy : Establishing a date using tree rings * Trees & corals * Basically any material that equilibrates with its surroundings on a temperature dependent basis & preserves a chronologic sequence can be used for paleoclimate reconstruction.

Sedimentary Evidence * Some lake sediments display a distinctive alternation of parallel layers with different clast sizes * Varve : A pair of layers deposited over the cycle of a single year * Varves are most common in deposits of high latitude or high altitude lakes * Deep sea sediment cores provide the BEST evidence of climatic changes : through abundant sea fossils called foraminera.

Fossil Pollen studies * Climatic conditions outside the great ice sheet during glacial times * Pollen possesses a hard, waxy coating that resists destruction. * Pollen can be identified & assigned to specific plants so pollen fossils from a sediment core can reveal the plant assemblage * When a modern vegetation assemblage can be found similar to the fossil pollen, the precipitation & temperature at the sit of the modern assemblage can be used to estimate climatic conditions represented by the fossil assemblage

EARTH’S PAST CLIMATE

Medieval Warm Period : Episode of relatively mild climate 800 years ago
Little Ice Age : Earth temperature in Western Ep 1-2 lower ; lower : Unusually harsh conditions

Last Glaciation : Started 70,000 years ago, ended 10000 years ago
Pleistocene Epoch

Temperature in the tropics were the same as they were today * At the height of the glacial age , middle latitudes were both windier & dustier than they were today due to katabatic winds * Extent of the ice maxed 24,000 years ago * World sea levels fell 120m exposing continental shelves * Vegetation changes accompanying the advance & retreat of the ice sheets were dynamic & complicated – species were displaced in various directions forming new plant communities * Average length of a glacial – interglacial cycle : 100,000 years * Prior to that time, ice volume on land appears to have been smaller & duration of each cycle averaged about 40,000 years

Ancient Glaciations * 2.4 billion years ago early Proterzoic * Creataceous period : Warmest climate in earth history

Climate Change

Internal factors vs External Factors

External Causes of Climate Change
Climate forcing : Changes in the amount of solar radiation reaching the top of the atmosphere (Positive forcing vs Negative forcing)

i. Solar Variation * Principle cycle of solar variation is the 11 year sunspot cycle : A temporary cool dark spot on the photosphere : affects overall solar luminosity * Fluctuations in the energy output of the Sun result in cooling of Earth’s climate when output is low & warming when output is high

ii. Milankovitch Cycles

1. Axis of rotation : Precession of the Equinoxes complete one full cycle every 23,000 years 2. Tilt of Earth axis varies : Influences the extent to which a given portion of the Earth’s surface points away or tilt towards the sun * Average angle : 23.5 degrees with a 1.5 degrees tilt either side during a cycle of 41,000 years 3. Eccentricity of Earth’s orbit * Point Earth is nearest to the Sun : Perihelion * Point earth is Furthest : Aphelion * Milankovitch Cycles refer to the combined influence of astronomical factors

Internal Causes of climate change 5 Factors

1. Atmospheric filtering * Effectiveness of the atmosphere at filtering solar radiation is dependent on the abundance of greenhouse gases * Radiatively active gases selectively absorb infrared radiation which causes a layer of warmed air to accumulate close to the surface

2. Changes in albedo
- Aerosols increase albedo ; the higher the aerosols the higher the increase in albedo -> leads to the scattering of incoming radiation back to space 3. Volcanic Co2 * Associated with superplumes – vast masses of hot rock that rises from the mantle via convection * Spreading to the lithosphere to warm the earth

4. Shifting continents * Movement of continents – create mountain chains, opening & closing of ocean basins * In process, ocean currents & atmospheric circulation have been altered * Effect results from landmasses & mountain chains standing the way of oceanic & atmospheric circulation * Also due to the fact that masses of water & land store & release heat in different ways

5. Changes in ocean circulation * Warm surface water moving northward to replace south flowing NADW releases heat to the atmosphere via evaporation – maintaining the mild climate * As a result of evaporation, the remaining water becomes more cool & saline, sinking to produce NADW * Changes in the system explains why Earth climate fluctuate * Interglacial (circulation is functional) * Glacial ( circulation shut down) * Heinrich Event : When cold,fresh water enter the ocean through massive release of icebergs