GEO-151

1. What are the relationships among Earth's mantle, crust, asthenosphere, and lithosphere? The Earth’s mantle sits on top of the Core. As the mantle stretches up, it is cooled until the point where the crust is formed and sits on top of the upper most part of the mantle. Therefore, the relationship between the crust and the mantle is, the crust encompasses the outside layer of the planet, including the ocean floor, that floats on top of the mantle, which as stated, stretched down to the outer core. The crust is the thinnest under the oceans, as little as merely 5 km thick and can reach a thickness of around 65km in a continental mountain range. The mantle begins where the crust leaves off and extends downward to a depth of around 2900 km deep, where the deeper you go, the hotter it gets. The lithosphere is what makes up the tectonic plates. It consists of the crust and that, relatively, cooler part of the upper mantle and extends downward to a depth of around 80 km. The lithosphere is broken apart in to the plates and float around the planet on the more liquid part of the mantle. This movement is what causes Earthquakes and volcanic eruptions. This more fluid part of the mantle is known as the asthenosphere. The asthenosphere flexes and deforms under the pressure and stresses caused by the core of the planet. This flexing and deforming is what causes the lithosphere to move as it floats on top. This movement the asthenosphere causes is known as plate tectonics. http://www.differencebetween.com/difference-between-lithosphere-and-vs-crust/ 2. By what processes did the planets form from the clouds of gas and dust? What are some of the main differences between the Earth-like planets and the giant outer planets such as Jupiter and Saturn? Cosmic clouds of dust and gasses are what bind to for stars and planets. The planets form from this cloud when the dust particles are drawn towards a young star and begin to rotate around it. As this happens, the dust particles stick together and grow into what is known as planetesimals. These planetesimals continue to grow in size as they revolve around the star and after a while, in planetary terms, they form the core of what will become the planet. Of the eight planets (poor Pluto, I still think of you as a planet) that make up our solar system, the first four are known as terrestrial planets. They are the rocky “solid” planets. The last four (five?) are known as the Jovian planets. They are the gaseous planets that are formed after their icy planetesimals began to collect up massive amount of gasses similar to the way the terrestrial planets planetesimals began collecting up rock and other dust and debris forming their rocky surfaces.

3. Describe the Earth's magnetic field and the magnetic poles.
The Earths geomagnetic field stretches out from the core of the Earth and is generated by the movement of the iron located in the outer core. Similar to a bar magnet, the Earth has a North and a South magnetic pole, not to be confused with the North and South axis poles which indicates the location where the spin axis would pass through the planet. The magnetic poles indicate the north and south ends of the magnetic field. It is the magnetic poles that the needle of a magnetic compass points too. It is important to note that the magnetic poles change. They move around the planet quite simply because the molten iron in the core moves. As the core swirls and changes, it has the same effect on the magnetic field causing it to move and change with it. What this magnetic field actually means to the planet however, or rather us beings that live on the planet, is that this magnetosphere, as it’s called, helps to protect the planet and its inhabitants. It protects us from the solar radiation that is given off by the sun and other radiation producing sources. Without the magnetic field, the solar radiation would burn us and the entire surface of the planet up. http://www.windows2universe.org/earth/Magnetosphere/earth_magnetic_poles.html 4. Differentiate between seamounts, guyots, and aseismic ridges. Seamounts are underwater, volcanic mountains. They usually cone shaped in a traditional mountain form, just underwater. Guyots are very similar to the seamount in that they are also volcanic mountains, and they too are underwater. The difference between seamounts and guyots is that where seamounts are the traditional cone shape mountain, guyots have flat tops instead of a peak. Seamounts can, given enough time, stretch up to the surface to form volcanic islands. Guyots, with their flat tops do not, but it is theorized that their flat tops are a result of them at one point being volcanic islands, but wave action has eroded the tops flat. Aseismic ridges are long mountainous structures that were formed by the process of volcanism, however, what separates these ridges from other undersea ridges, such as the mid-oceanic ridge, is that the aseismic ridges are no longer volcanically active. Farther out from the ridge, volcanism may still occur, but at the ridge itself, it is seismically inactive.

5. How does the age of sea-floor rocks compare with the age of continental rocks? The continental rocks are much, much older than that of the sea floor rocks. The simplest way to explain it is simply the sea floor is younger. The tectonic plates are formed from the mid-oceanic ridges. From these ridges, new sea floor and rock is formed and gets pushed outward towards the continental shelf. On its journey, it gets worn away by ocean currents and other forms of undersea erosion. The continental rock has much less to contend with and erodes much, much slower, although it does erode away.