Physical Geography Chapter 1:
The Discipline of Geography
Principles of Geography
Geography is the study of the distributions and interrelationships of earth phenomena. Geography is different from other disciplines in that it doesn't have a particular "thing" it studies. Botanists study plants, while geologists are interested in rocks. Geography is defined by its approach or methodology. Geographers describe their discipline as a spatial science. By "space" we aren't talking about celestial space. Geographers are concerned with answering questions about how and why phenomena vary across the surface of the Earth. For instance, geographers investigate patterns of vegetation as they relate to distributions of climate, soils, and topography.
Geographers recognize the dynamic nature of Earth's physical systems. The physical geography of Earth changes in response to variations in weather and climate, the shifting of continents, and and the sculpting of coastlines by wave action. By recognizing the Earth system is dynamic, geographers take time into consideration when looking at the spatial patterns of Earth phenomena. Therefore, geographers are playing important roles in understanding the effects of climate change on earth systems. The role of geographers in assessing patterns of environmental change is a theme that reoccurs throughout this book.
Figure 1.1 Folded Appalachian Mountains Linear folds of the Appalachian Mountains can be easily seen in this satellite image. (Source: NASA/GSFC/JPL, MISR Team)
Geographers study both the form and processes acting at the surface of the earth, the principal domain of geographic study. Examine the landscape of the Appalachian mountain range in North America in the satellite image illustrated in Figure 1.1 and compare them to Mt. Saint. Helens found in the Cascade Mountain Range. The Appalachian mountains appear as a series of linear folds in the earth surface. The Cascades on the other hand are much taller than the Appalachians and contain many peaks that are conical in shape, as exemplified by Mt. Saint Helens. If both are mountain systems, why do they differ so greatly in form? Their difference arise from the processes that created them. The Appalachian Mountains were created by folding of the earth's crust. The conical shaped peaks of the Cascades are volcanoes. Many of these form where crustal plates collide, causing rock to melt deep beneath the earth, and finally erupting onto the surface to build the mountains we see today.
Figure 1.2 Mt. Saint. Helens, Cascade Mountain Range, USA (Source: USGS)
Think about what information was required to answer the question as to why these two mountain systems are so different. To understand their form we needed to investigate their geologic history to determine the processes that created them. Geographers must rely on information provided by other sciences to help understand the form and distribution of Earth phenomena. This is why geography has been called an "integrative science". It draws on the knowledge of many disciplines to understand the natural patterns within the earth system.
Geographers also study how human activities shape, and are shaped by, the natural environment. Geographers are actively engaged in research about the relationship between agriculture practices, water erosion, and flooding. Others are uncovering the impact of air pollution on ecosystems, and how global warming will affect the physical geography of earth. These studies are a part of the "human-environment" tradition in geography, which was the precursor to modern environmental studies.
Geography as a spatial science
The key question facing most sciences is "how" and thus focus on the process whereby something comes about regardless of time or place. Geography is described as a spatial science because it focuses is on "where" things are and why they occur there. Geographers seek to answer all or more than one of four basic questions when studying our environment. These relate to location, place, spatial pattern, and spatial interaction. Let's look at how a physical geographer answers these questions about a desert.
Figure 1.3 Location of the Sonoran Desert
Courtesy USGS (Source)
Location: Location is defined as "the position in space" of something. Latitude and longitude is a convenient way to locate something's position. The Sonoran Desert is located at a latitude and longitude of 33°40'N, 114°15'W. This defines the Sonoran Desert's absolute location. It actually covers an area of 311,000 square kilometers (120,000 sq mi) between 25° to 33° North and longitude 105° to 118° West. We can also define the Sonoran Desert in relation to a known location, called its relative location. "The Sonoran Desert wraps around the northern end of the Gulf of California, from northeastern Baja California through southeastern California and southwestern Arizona to western Sonora." (Wikipedia)
Place. Geographers describe place as “... the human and natural phenomena that give a location its unique character ...” (Gershmel, 2009). A geographer may want to know how the Sonoran Desert compares to the Sahara desert. To answer this question, a physical geographer will collect data to compare their temperatures and precipitation, and contrast the vegetation, soils and fauna found there.
Spatial Pattern. Geographers are especially interested in the arrangement or patterns of earth phenomena. We might want to know - "What is the distribution of deserts on the Earth?". By examining a map of world climates we find deserts in the dry interiors of the subtropics and midlatitudes.

Figure 1.4 Distribution of Non-Polar Deserts
Courtesy USGS (Source)
Spatial Interaction. Finally, geographers are interested in how elements of the earth system interact with one another to create geographic patterns. A geographer might ask - "How do mountains interact with weather systems to affect the distribution of deserts?" By looking at maps of mountain systems, wind and precipitation patterns and, maps of climate we find that mountains oriented perpendicular to the flow of wind create moist conditions on the windward side and dry conditions on the leeward side. The dry leeward side is described as being in the "rain shadow". In many parts of the world deserts, like the Sonoran Desert of the United States is found in the rain shadow.
Figure 1.5 The Sonoran Desert near Maricopa, Arizona. Courtesy Wikipedia (Source)
Fundamentally, geographers are concerned with where something is at, why it's there, and how it relates to things around it. They address this through defining where their object of inquiry is located, what the place is like, uncovering its distributional pattern, and understanding how it interacts with its environment. Our interest in understanding the geography of earth goes back centuries and will continue to intrigue us far into the future.
The Continuum of Geography
Geography is a wide ranging field that incorporates a number of diverse subject areas. Broadly speaking, geography can be divided into human geography and physical geography. Human geography deals with spatial aspects of human activities and culture. Physical geography, our topic here, focuses on the geographical attributes of the natural environment. The diagram below illustrates the continuum of geography. Though the discipline can be broken down into two separate areas of study, physical geography and human geography, they are actually seen as blending with one another along a geographic continuum (Figure 1.6)

Figure 1.6 The Continuum of Geography
As we move toward the center of the diagram we enter a zone where the subject matter of the two meet and intermingle. At the center is where the synthesis of the physical environment with the human/cultural environment occurs. In so doing we create a holistic view of earth systems. The study of environmental issues like global warming, response of humans to natural hazards, and deforestation requires this kind of synthesis or examination of relationships between society and the natural environment to understand them.
Figure 1.7 Measuring lichen diameter to date glacial moraines. Courtesy Michael Ritter
Borrowing a technique from archeology and paleontology, physical geographers use lichen growth rate and diameters to estimate the age of debris flows, recent moraines, and other rocky deposits.
Each subdiscipline draws on the knowledge provided by a variety of disciplines outside of geography. For instance, to study earth phenomena like the distribution of soils we have to draw on the expertise of such disciplines as soil science, botany, and climatology because soil properties are a function of vegetation, energy, and moisture. Geography, therefore, is a very integrative science.
Physical geography and earth science share much in common. Physical geography places earth science content in a spatial context. This video by the American Geological Institute illustrates why earth science (and by extension physical geography) is important to all of us. Geography and the Scientific MethodThe steps in geographic inquiry are embodied in the "scientific method". The scientific method consists of systematic observation, formulation, testing and revision of hypotheses. If a hypothesis withstands the scrutiny of repeated experimentation and review it may be elevated to a theory. Theories may undergo revision as new data and research methods are improved. Figure 1.8 The Scientific MethodThe scientific method includes: * Observation * Hypothesis Formulation * Choose methods of analysis * Data collection * Analysis: Hypothesis testing * Hypothesis acceptance or rejection * Report results Let's look at a very simple example of how you as a geographer could use the scientific method.Observation. During a trip through the Cascade Range of Oregon you notice that the western slope tends to have more lush vegetation than the eastern slope and wonder why. Our experience tells us that vegetation requires moisture to live, and more lush vegetation is found where precipitation is abundant. Could it be that the western slopes are rainier than the eastern slopes given the spatial variation in vegetation? | Figure 1.9 View of western slope of Cascade Range mountains.
(Source: Flickr) | Figure 1.10 Near Condon, OR, east slope of Cascade Range
(Courtesy NRCS Photo Gallery) | Hypothesis formulation. A hypothesis is referred to as "an educated guess". That is, upon recognizing a particular pattern displayed by earth phenomenon, the geographer offers a "guess" or explanation as to what caused it. Previous research serves as the foundation for constructing hypotheses. Given our initial observation and past experience we suggest that there is a relationship between slope orientation and precipitation. A hypothesis is stated in a clear and concise way so that it can be tested through data collection and analysis.When constructing a hypothesis, scientists actually formulate two hypotheses related to their problem. The null hypothesis is a statement of no relationship. This is the hypothesis we will either reject or not reject. The null hypothesis (Ho) for our problem is: Ho: There is no relationship between slope orientation and precipitation.The alternative hypothesis is a statement of relationship. The alternate hypothesis is:Ha: There is a relationship between slope orientation and precipitation.Determine the methods used to test our hypothesis is the next step. There are a variety of quantitative and qualitative methods to test our hypothesis. One could calculate the average precipitation for the western and eastern slopes and apply a difference of means test (t-test).Data collection. In order to test our hypothesis we must collect a sample of data. For most cases, a sample set of 30 will suffice. Primary data can be collected in the field and analyzed, or secondary data that has already been published can be used. Precipitation data is available from a variety of public and private sources. Figure 1.11 Precipitation in Oregon. Note linear purple areas of of high precipitation along western slopes of the mountains.Analysis: Testing the hypothesis. A geographer often starts their analysis using some way to visualize the spatial pattern of precipitation. A map showing the geographic pattern of precipitation can be created if data from several places have been obtained. Or a graph of precipitation with the y-axis scaled for precipitation and x-axis for distance between locations along a transect. Statistics describing the data are usually calculated. The mean or average of each data set (west side and east side of the mountains) are determined and finally the hypothesis is tested using the difference of means test.Hypothesis Acceptance/Rejection (Explanation). After testing our hypothesis we will either accept or reject our null hypothesis. In reality, we can't prove our hypothesis correct, we can only disprove it based on our analysis. That is, we reject the null hypothesis that there is no difference in precipitation based on the data that we have collected. If new data or better data collection techniques are available in the future, they may lead us to conclude that we cannot reject our null hypothesis. Hence it is hard to prove a hypothesis is correct as new information and understanding may present itself in the future.Report Results. If we can accepted out hypothesis then we can report our results so others can scrutinize our work and test our hypothesis under different circumstances.If our null hypothesis is rejected we can turn to our alternative hypothesis or restate the null hypothesis in a different way. Thus, applying the scientific method can be an iterative process. If our work can be replicated many times under different circumstance the hypothesis can be elevated to a theory. A theory can be a hypothesis or group of hypotheses that has been validated through repeated experiments and coming to the same conclusion. |
Tools of the Geographer
Maps
A map is the fundamental tool of the geographer. With a map, one can illustrate the spatial distribution (i.e., geographic pattern) of almost any kind of phenomena. Maps provide a wealth of information. The information collected to create a map is called spatial data. Any object or characteristic that has a location can be considered spatial data. Maps can depict two kinds of data. Qualitative map data is in the form of a quality and expresses the presence or absence of the subject on a map, like the kind of vegetation present occupying a region. Quantitative map data is expressed as a numerical value, like elevation in meters, or temperature is degrees celsius. There are many different kinds of maps that serve quite different purposes.
Types of Maps
Reference Maps
Reference or navigational maps are created to help you navigate over the earth surface. These kinds of maps show you where particular places are located and can be used to navigate you way to them. A street map or the common highway road map falls into this category.
Thematic Maps
Thematic maps are used to communicate geographic concepts like the distribution of densities, spatial relationships, magnitudes, movements etc. World climate or soils maps are notable examples of thematic maps. There are five common techniques for depicting geography data on a thematic map. The most common is a choropleth map that uses color to show variations in quantity, density, percent, etc. within a defined geographic area. Each color usually depicts a range of values.

Figure 1.12 Palmer Drought Index
Source: NOAA Climate Prediction Center
Defined areal units are colored on the Palmer Drought Index map in Figure 1.12 to show the pattern of dryness across the United States. Using administrative units presents a less realistic picture of the pattern of the distribution of natural phenomena. To overcome this, a variant of the choropleth map, the dasymetric map was created. This type of map employs special statistical methods and extra information to combine areas of similar values to depict geographic patterns on the map. The USDA's Plant Hardiness Zone Map is a dasymetric map.

Figure 1.13 USDA's Plant Hardiness Zone Map
An isarithmic map uses isolines, lines that connect equal values, to illustrate continuous data such as elevation, air pressure, and precipitation. Topographic maps use contour lines to show elevation (height above sea level). Contour lines connect points of equal elevation above a specified reference, usually as sea level. The heavy brown contour lines with the elevation printed on them are called index contours. Intermediate contours are the lighter brown lines between index contours. Sometimes dashed lines called supplemental contours are used in areas of very low relief. Benchmarks are locations where the elevation has been surveyed. Benchmarks are denoted on a map with the letters "BM", "X" or a triangle with the elevation printed beside. Figure 1.14 Sample Topographic map
Source: USGS Monarch Lake
Not only are natural features like mountains, valleys, streams and glaciers portrayed, but cultural features as well, like houses, schools, streets, and urbanized areas. Examine a topographic symbol sheet (pdf file) from the USGS to see how a variety of features are symbolized on a topographic map.

Figure 1.15 Major earthquakes felt in Canada. Source: NAISMap WWW-GIS
Proportional or graduated circle maps are another way of depicting geographic information on a map. Figure 1.15 is a map that shows population density of Canada as colored polygons and the distribution of major earthquakes felt throughout the country. Graduated circles indicate the area over which the earthquakes were felt. This map was created using a geographic information system which has the capability of overlying different kinds of spatial data to show the relationships between them.

Dot maps use dots to illustrate the presence of the phenomenon on a map. A dot may equate to one or several units of measurement. Dot maps are especially useful in visualizing the frequency of occurrence or density of a mapped variable.

Figure 1.16 Dot map of agricultural chemical use (Source: USDA)
Isolines
Isarithmic maps use isolines to depict the geographic pattern of earth phenomena. An isoline is a line that connects points of equal value. For instance, the brown contour lines on a topographic map connect points of equal elevation. Isobars are used to show the distribution of air pressure . Some common isolines encountered in physical geography are: * isotherm: a line connecting points of equal temperature. * isohyet: a line that connects points of equal precipitation * isophene: a line representing points where biological events occur at the same time, such as cops flowering. * isopleth: a line connecting points of equal numerical value, like population * isotach: a line of equal wind speed. * isobath: a line representing points of equal water depth.

Figure 1.17 Isobars on a weather map depicting pressure pattern over United States
(Courtesy NASA)
A few "rules" apply to isolines. First, two different isolines cannot cross each other. If they did, it would mean two different values are at the same location. Second, points on one side of an isoline will have a higher value than ones on the other. Third, isolines cannot branch or fork. Fourth, the interval between isolines is a constant value on any map.
Figure 1.18 The land surface and how its depicted on a topographic map. (Courtesy USGS)
Because the interval between isolines is constant, their spacing gives an visual indication of the change that occurs over a given distance, called a gradient. The more closely spaced the isolines, the larger is the gradient. For example, the spacing of contour lines between A-B on the topographic map shows a much steeper hillslope gradient than does the spacing of the contour lines between points C-D. Map projections
A map projection is a method of portraying the curved surface of the Earth on a flat planar surface of a map. Projections are created to preserve one or several measurements of the following qualities: * Area * Shape * Direction * Bearing * Distance * Scale
Each projection handles the conversion of these metric properties from the curved surface of a globe to the flat surface of map differently.
Figure 1.19 Visualizing a map projection (Courtesy USGS. Source)
The purpose of the map is of primary importance in choosing a projection to illustrate spatial patterns of Earth phenomena. For instance, the Mercator projection was long used for navigation or maps of equatorial regions. The cylindrical Mercator projection mathematically projects the globe onto a cylinder tangent to the Equator. Large areas become distorted which increases toward away from the Equator. Distances are true only along the Equator, special scales are provided for other latitudes for measurement.

Figure 1.20 Cylindrical Mercator projection
(Courtesy USGS - Source)
The Robinson projection uses tabular coordinates rather than mathematical formulas to make earth features look the "right" size and shape. A better balance of size and shape result is a more accurate picture of high-latitude lands like Russia, Soviet and Canada. Greenland is truer to size but compressed.

Figure 1.21 Robinson projection
(Courtesy USGS - Source)
For more on projections see: Map Projections from the United States Geological Survey.
Map Scale
Map scale is the relationship between distance on a map and distance in the real world. There are several ways to specify map scale. Often we find the scale of a map expressed in words like, "one inch equals one mile". You’ve most likely seen map scale depicted with a graphic, like a bar divided up into segments. The length of a segment represents some distance on the earth. We can specify scale as a representative fraction as well. These fractions often appear as follows:
1:24000
The fraction means that one unit of measurement on a map represents 24000 units in the real world. It’s important to remember that the same units of measurement are on either side of the colon. That is, 1 inch represents 24000 inches, or 1 centimeter represents 24000 centimeters. To calculate the distance between two points, one simply measures the map distance and multiplies it by the number of "real world" units. For example, if the measured distance between two points on a map with a scale of 1:62500 is 2.4 inches, then the real world distance is 2.4 times 62500 or 150000 inches. It’s hard to think how far that really is so convert it to miles. To do so simply take 150000 and divide by the number of inches in a mile which is 63360. So, the distance between the two points is about 2.37 miles.
Scale Categories
Map scales are grouped into small, medium and large categories. Large scale maps, such as 1:24000 scale maps show a smaller area in great detail. They are useful for showing the locations of buildings and other features important to engineers and planners. Medium scale maps, (1:62500) are good for agricultural planning where less detail is required. Small scale maps have the least detail but show large areas. These are useful for extensive projects at regional levels of analysis. You can easily see the impact of map scale on the information in figures 1.22a through 1.22c below. Figure 1.22a
Scale 1:24000
1 inch = 2000feet
Area Shown: 1 square mile(Source: U.S.G.S.
Topographic Maps, 1969) | Figure 1.22b
Scale 1:62500
1 inch = nearly 1 mile
Area Shown: 6 3/4 square miles(Source: U.S.G.S
Topographic Maps, 1969.) | Figure 1.22c
Scale 1:250,000
1 inch = nearly 4 miles
Area Shown: 107 square miles(Source: U.S.G.S.
Topographic Maps, 1969) |
Aerial Photographs and Remote Sensing
Aerial Photographs
For years, geographers have used aerial photographs to study the Earth’s surface. In many ways air photographs are better than maps. They provide us with a real world view of the earth’s surface, unlike a map which is a representation of the real world. Aerial photographs can be used to make the same measurements that we make on a map, as they too are a scaled image of the surface.
Figure 1.23 Air photograph of Fair Glacier, Colorado. (Source: USGS)
Figure 1.23 shows the rugged terrain one finds in the Front Range of the Colorado Rocky Mountains. North is at the top of the photograph. Alpine glaciers are found in favorable sites for snow and ice accumulation. Few of these glaciers are very active under present day conditions though. The glacier is easily identified by its white color. Surrounding the glacier on its western, southern, and eastern sides are the walls of a cirque in which it sits. A cirque is a bowl-shaped landscape feature common to mountainous regions which have been glaciated. The glacier formed in the area to the bottom of the picture and extended itself towards the north. The dark triangular - shaped feature to the north of the glacier is Triangle Lake.

Remote Sensing and Satellite Imagery
To get a much larger view of the earth’s surface features, geographers have turned to using remotely sensed data from satellites. Satellite sensors scan the surface and break it down into picture elements or pixels like those displayed on your computer monitor. Each pixel is identified by coordinates known as lines (horizontal rows), and samples (vertical columns). As the satellite scans the ground, it transmits this information to earth-based receivers, the same way a television station broadcasts a signal to your television. The digital data received is processed in a variety of ways: simulated natural color, "false" color, signal filtering, enhanced contrast, etc. Figure 1.24 SIR-C/X-SAR image of the Mississippi River (Source: NASA Jet Propulsion Lab)
Figure 1.21 shows a portion of the Mississippi River that lies north of Vicksburg along the Arkansas-Louisiana-Mississippi state borders. The image was created from data obtained by Spaceborne Imaging Radar – C/X-band Synthetic Aperture imaging system aboard the space shuttle Endeavor. These images help scientists assess flooding potentials and land management along the river. Much of the area in purple is agricultural land. Areas occupied by water appear in black while the bright green areas are forested. The long narrow lakes bordering the river are called oxbow lakes and are created when the river changes course, abandoning the old channel for a new one. NASA has a detailed discussion (optional reading) about imaging radar online. Read how remote sensing is used to evaluate drought, desertification and the effect of war on Mozambique.
Geographic Information Systems
Advanced computer technology has placed new tools in the hands of geographers to not only create maps much more efficiently, but to analyze spatial data in map form as well. A geographic information system is a computer-based technology that enters, analyzes, manipulates, and displays geographic information. It is a marriage between computer-based cartography and database management.

Figure 1.25 GIS layers (Source: The Geographer's Craft, UC-Boulder. GIS: Context, Concepts, and Definitions by Kenneth E. Foote and Margaret Lynch)
A simple way of visualizing a geographic information system is to think of a set of overhead transparencies. On each transparency is a map of a particular set of data. Examine Figure 1.25. The bottom transparency is the most important as it has the coordinate system (latitude and longitude) upon which we can align or register the other layers of information. The second layer is a map of industrial sites, the third shopping centers and so on. By layering the information one on top of the other, a geographer can show the relationship and degree of connectivity between various land uses and transportation routes. Transportation geographers can then plan new routes between population centers found on the census tract map layer and business locations. Geographic Information Systems are being employed to study a number of geographic issues like flood hazard mapping, earthquake hazard studies, economic market area analysis, etc.
Figure 1.26 Earthquakes 1568 - 1996 and population density 2000, the National Atlas. (Courtesy USGS)
Figure 1.26 is a map constructed using a GIS from the online National Atlas of the United States. Layers of data, earthquakes 1568 - 1996 and population density 2000, are turned on and off with digital buttons. The map product from the GIS permits us to visualize those population centers most threatened by earthquake activity.
Models in Geography
A model is simply a representation of a real thing. You have seen and used models in the past, like a globe which is a model of the earth. Geographers construct models to analyze geographic processes because the real object of study may be too large to examine, the processes which created it operate over too long of a time frame, or experimentation might actually harm or destroy it. For instance, physical geographers construct physical models like stream tables to investigate the impact of hydrological processes on the earth. A stream table is more or less like a shallow sink filled with earth material similar to the land surface of interest. Water is applied to the material to see what effect varying amounts of water have on the erosion of the surface. Models may be simple conceptual models such as a box and arrow diagram showing the flows of energy between compartments of an ecosystem. Climate scientists use elaborate mathematical or numerical models. These could be complex numerical statements programmed into a computer model representing the impact of increasing carbon dioxide content of the atmosphere on global temperature.

Figure 1.27 Soil Scientists examine model of plots to investigate soil erosion (Source: Ben Nichols, U.S.D.A. Natural Resources Conservation Service)

Graphs and StatisticsGraphsGraphs are a visual way to portray the relationship between a set of variables. Graphs can easily show the spatial pattern and discern a cause and effect relationship between earth phenomena. The variable plotted on the x-axis is the cause of the variable plotted on the y-axis. A good example of how graphs can be used for the analysis of relationships in physical geography is to plot the change in temperature range across latitudes. The Y-axis of Figure 1.28 has been scaled for temperature range and the X-axis for latitude. Note that temperature range appears to increase with latitude as one travels from the equator (0o) toward the pole (90o). Notice how the points seem to line up in a straight line. From the graph there appears to be a strong relationship between latitude and temperature range. From this graph we can say that (at least) latitude is a causal factor of temperature range. Figure 1.28 Graph of Latitude vs. Temperature RangeStatisticsA statistic is a quantity that is computed from a sample of data. Statistics are used for analyzing and interpreting numerical information. Statistics are all around us and we all use them from time-to-time. Statistical methods refers to "the collection, presentation, analysis and interpretation of numerical data for the purpose of making more correct decisions" (Parl, B., 1967). Statistical methods are generally grouped into two categories descriptive statistics and statistical inference.Descriptive statistics attempt to simplify masses of data into a single number to communicate an existing condition or phenomena in the data. You will encounter two common descriptive statistics in this book. The mean (average) is the sum of the observations divided by the number of observations in the data set. The range is the difference between the highest and lowest value in a set of a data set. Choosing the right statistic, or statistics greatly influences our ability to accurately describe the spatial and temporal patterns of the natural world. Descriptive statistics can be deceiving. Imagine trying to compare the climate of two places to a friend who hasn't visited either. Let's say location A has a summer temperature of 80o F and a winter temp of 20o F. Location B has a summer temperature of 65o F and winter temperature of 45o F. Notice when we average the summer and winter temperatures for each their average temperature for the year is the same, 50o F. There appears to be no difference in climate between the two locations because both have the same average temperature. However, if we compute the seasonal range in temperature, 60o F for location A and 20o F for location B there appears to be a great deal of difference between the two. We should use both the average and temperature range to accurately describe climate. Table 1.1 Comparison of Average and Range | Location ASummer temperature = 80o FWinter temperature = 20o FAverage = 50o FRange = 60o F | Location BSummer temperature = 65o FWinter temperature = 45o FAverage = 50o FRange = 20o F | Statistical inference "is a method concerned with the analysis of a subset of data leading to predictions (or inferences) about an entire set of data" (Goodman, 1996). An inference is an educated guess or estimate. One cannot make a definitive statement of what the correct answer is but couches the conclusion in a degree of uncertainty. Inferential statistics are employed to test the hypotheses we create about the relationship between phenomena.Correlation and regression analysis are two widely used statistical techniques. Correlation analysis attempts to express the degree to which variation in one variable is associated with the variation in another. Developing from correlation, regression enables us to estimate a mathematical statement which describes the relationship between two variables. These techniques are beyond the scope of this book. |
The Global Positioning System (GPS)
The Global Positioning System consists of three parts: 1) Earth orbiting satellites, 2) control and monitoring stations across the Earth, and 3) GPS receivers owned by individuals. A set of 24 satellites orbiting the Earth every 12 hours broadcasting their position and time. A ground-based receiver listens to the signals from four or more satellites, comparing the time transmissions of each with its own clock. Given that signal travels at a known rate of speed, the receiver can calculate the distance between the satellite and receiver. Combining the position of the satellite at the time of transmission with the distance, the receiver is able to determine its location.
Figure 1.29 The constellation of GPS satellites (Courtesy USGS)
Differential GPS uses a base station of an exact known location and a mobile unit to determine position. GPS determines location by computing the difference between the time that a signal is sent by a satellite and the time it is received by a GPS receiver. The base station calculates its position from satellite signals and compares this location to the known location. The base station broadcasts the range errors they're seeing from GPS satellites to the remote receiver. The mobile receiver uses these correction messages, correlated with the satellite signals its receiving, to determine position.
Figure 1.30 GPS ground receiver on the flank of Augustine Volcano (Cook Inlet, Alaska) Courtesy USGS
GPS is being employed in a variety of ways. GPS is widely used for ground, air, and sea navigation. It is used to produce highly accurate maps and record land deformation caused by earthquakes and volcanic eruptions. GPS is showing up in a number of commercial products available to the public from standalone units to automobiles, cell phones, and digital cameras interfaces. A popular use of gps units is geocaching, a high-tech "treasure" hunting game.
Assess your basic understanding of the preceding material by "Looking Back: Tools of the Geographer" or continue reading.
Locational Systems
The fundamental work of a geographer begins by describing location. Locational reference systems have been created to accurately identify the location of earth phenomena.
Latitude and Longitude
Figure 1.31 The Geographic Grid: Latitude and Longitude (Courtesy The National Atlas)
Latitude and longitude comprises a grid system of lines encircling the globe and is used to determine the locations of points on the earth. Lines of latitude, also called parallels, run east - west. Latitude lines always run parallel to each other, and hence, they are always an equal distance apart. Latitude lines never converge or cross.
Figure 1.32 The Equator (Courtesy The National Atlas)
Lines of latitude measure distance north or south of the equator. The latitude of a particular location is the distance, measured in degrees, between that place and the equator along a meridian, or line of longitude. The equator is 0o latitude, and the North and South Poles are located at 90o north and 90o south latitude respectively. In other words, values for latitude range from a minimum of 0o to a maximum of 90o.
Figure 1.33 Measuring Latitude. (Courtesy The National Atlas)
If the earth were a perfect sphere (which it isn't), the distance, or the length, of 1o of latitude would be constant everywhere. In reality, the earth is slightly flattened at the poles, so the length of 1o of latitude at the poles is slightly more than at the equator. At the equator, the length of 1o of latitude is equal to 110.6 km (68.7 mi.) and at the poles, the length of 1o of latitude is equal to 111.7 km (69.4 mi.). For our purposes, we will assume the length of one degree of latitude is 111 km.
Figure 1.34 Longitude (Courtesy The National Atlas)
Lines of longitude, also called meridians, run north - south. Meridians are farthest apart at the equator, and converge at the North and South Poles. Lines of longitude measure distance east or west of the prime meridian. The longitude of a particular location is the distance along a parallel, measured in degrees, between that place and the prime meridian. The prime meridian passes through the old Royal Observatory at Greenwich, England, and is sometimes referred to as the Greenwich meridian. Since meridians are farthest apart at the equator and converge at the poles, the distance in kilometers (or miles) of 1o of longitude varies from a maximum at the equator, to a minimum at the poles. At the equator the approximate length of 1o is approximately 111 km (69 mi.). At 60o north and south latitudes, the length of 1o of longitude is approximately 55.5 km (34.5 mi.), or half what it is at the equator.
Figure 1.35 The prime meridian (Courtesy The National Atlas)
The prime meridian, which runs through Greenwich, England, is referred to as 0o longitude. Points are measured east or west of the prime meridian until one reaches the opposite side of the prime meridian, which is referred to as the International Date Line. This is considered 180o longitude, and is the highest value which longitude can take. In other words, values for longitude range from a minimum of 0o to a maximum of 180o.
An infinite number of parallels or meridians can be drawn on a globe. Thus, parallels and meridians exist for any point on the earth. Generally, only selected parallels and meridians are marked on maps and globes, and these are usually spaced equal distances apart. Parallels and meridians always intersect each other at right angles. In order to locate a particular point on the earth, a latitude and a longitude measurement is necessary. As stated above, these measurements are in degrees, but sometimes measurements smaller than degrees are necessary. In this case, minutes and seconds are used.
When we travel, we usually like to take the shortest route between two locations. If you pass a plane through the center of a sphere, the intersection of the plane and the surface of the sphere creates a great circle. Planes passing through any other part of a sphere without going through the center create small circles. An arc of a great circle is the shortest distance between two points on a sphere and therefore is the preferred route for planes traveling great distances, like crossing an ocean. The concept of great and small circles relates to meridians (longitude) and parallels (latitude). Meridians are half of a great circle (180o) whose ends are at the North and South poles. Parallels of latitude are small circles, except for the equator which is a great circle. Figure 1.36 Great Circle
Source: Wikipedia |
Figure 1.37 Small Circle
Source: Wikipedia |
Geographical Zones
Natural systems of climate, vegetation, and soil change substantially as one travels from the equator to the pole due largely to the latitudinal variation in energy input to the earth system. The early Greek scholar Aristotle was the first to divide the Earth into zones based on climate. His "torrid zone", thought to be too hot for human habitation, lay between 23.5o N and 23.5o S. Aristotle thought that the "temperate zones" between 23.5o N - 66.5o N and 23.5o S - 66.5o S were the only livable zones. From the arctic (66.5 N) and and antarctic circles (66.5 S) to the the poles (90 N and S) were the uninhabitable "frigid zones". Figure 1.38a Torrid ZoneImage Source: WikiMedia | Figure 1.38b Temperate ZonesImage Source: WikiMedia |

Figure 1.38c Frigid ZonesImage Source: WikiMedia |
Geographers continue to use latitudinal variation of climate characteristics as a way of dividing the Earth into fairly homogeneous geographical zones. These zones are:

Equatorial: 10o N - 10o S

Tropical: 10oN - 25oN and 10oS - 25oS

Subtropical: 25oN - 35oN and 25oS - 35oS Midlatitude: 35oN - 55oN and 35oS - 55oS

Subarctic: 55oN - 60oN

Subantarctic: 55oS - 60oS

Arctic: 60oN - 75No

Antarctic: 60oS - 75oS

North Polar: 75oN - 90oN

South Polar: 75oS - 90oS
[Figure 1.39 Geographical Zones Not Available Yet]
The equatorial zone is characterized by warm temperatures and nearly uniform day length throughout the year. The boundary of the tropical zone lies close to the Tropic of Cancer (23.5oN) and Capricorn (23.5oS), the latitudinal limit where the Sun is directly over head at noon at different times of the year. The subtropical zone includes Aristotle's home of Greece, and seasonal changes in temperature become more pronounced. The temperate midlatitude zone is noted for is variable weather conditions. Large annual swings in temperature are characteristic of the subarctic and subantarctic zone where extensive areas of cold air form during winter and milder conditions prevail during summer. The coldest zones are the Arctic and Antarctic, where the Sun never rises above the horizon for several months at a time. Much of the light that does reach the surface is reflected off the light colored surfaces of the North (sea ice) and South (mostly glacial ice) poles. The coldest zones are the North and South Polar. Like the Arctic and Antarctic Zones, the Sun never rises above the horizon for many months of the year. The coldest temperatures are near the South Pole, far from any moderating influence of an ocean and the little light that does make it to the surface is reflected from glacier ice. Time
Early agricultural societies found that local noon could be determined by observing the changing length of the shadow cast by a stick placed placed perpendicular to the ground. Local noon is the time at which the shadow is the shortest length cast. Romans used this principle to design their sundials and called their noon position of the Sun the "meridian" (meridiem - the Sun's highest point of the day). It was difficult to compare time as one traveled to different localities as each city adjusted its clocks to their own local noon. Because the Earth rotates toward the east, towns to the east experienced solar noon earlier while those to the west later.
Standard time
As cross-country travel and communication became faster and more efficient, a standardized system of global time was required. Given the Earth rotates once throughout a 24 hour period, 24 standard times zones were agreed upon at the 1884 International Prime Meridian Conference. The local solar time at Greenwich, England was designated the prime meridian. Each time zone extends 7.5o on either side of a central meridian. For years the global standard for reporting time was Greenwich mean time (GMT). GMT is now referred to as Universal Time Coordinated (UTC) or Coordinated Universal Time but the prime meridian is still the reference for standard time. It uses the 24-hour time (military) notation based on the local standard time at the prime meridian of 0o longitude. Midnight corresponds to 00:00 UTC and noon to 12:00 UTC. (For more conversions, see Table 1.3 UTC Conversion Table)

Figure 1.40 UTC zones
(Image Courtesy NASA MSFC)
International Date Line
Ferdinand Magellan and crew in 1519 set out on their westward journey from Spain to circumnavigate the Earth. Upon their return three years later, they discovered that their meticulously kept logs were off by one day. This was one of the first recorded experience with changing global time. This earlier experience would ultimately lead to the establishment of the international date line. The International Date Line is an imaginary line the separates one day from another. It roughly follows the 180osup> meridian form the North Pole to the South Pole through the Pacific ocean, deviating around some territories. Crossing the line when traveling east one turns their calendar back a full day. Traveling west one moves their calendar forward one day. The Prime Meridian lies opposite of the International Date Line.
Daylight Saving Time
Many countries observe daylight saving time - the practice of setting clocks forward one hour in the spring and back one hour in the fall. First proposed by Benjamin Franklin, the notion of extending daylight one hour into the evening didn't catch hold until World War One as a means of energy savings. Some countries,territories, and states in the U.S. do not observe daylight saving time.
Future Geographies: The Geographer's Role in Understanding Environmental Change
During the summer of 2005, the United States was pounded by a record number of hurricanes, some the most intense to ever strike the mainland. The southwest desert of the United States continues in the grip of one of the longest periods of drought. For the first time in centuries, the fabled arctic northern route is open between North America and Asia. Are these events caused by climate change due to global warming? If so, the future physical geography of planet Earth may be drastically and irreversibly changed if current global warming predictions are realized. Figure 1.41 Major Components needed to understand the climate systems and climate change. (Source: US Climate Change Science Program).
Environmental change caused by global warming involves a complex set of interactions between the subsystems of the earth system and human activities. These interactions vary across geographic scales. The timing and impact of future warming will not be the same for all regions of the Earth. Research methodologies that consider place and scale are therefore essential in understanding future environmental changes.

Figure 1.42 Schematic Framework of anthropogenic climate change drivers, impacts, and responses. Courtesy IPCC
The continuum of geography permits a holistic view of earth systems analysis. Geographers are therefore perfectly positioned to answer questions concerning global warming and environmental change. Geographers are engaged in all aspects of environmental change research, from field monitoring glacier movements to computer modeling of future climates. Straddling both social and physical sciences, geographers play an important role in unwinding the social and economic drivers behind climate change.

Observing environmental change
Geographers bring their unique talents to recording changes in earth systems. Geographical positioning systems (GPS) provide precise measurements of environmental change. For example, isostatic rebound of the earth's surface after the last ice age complicates measurements of melt from the expansive ice sheets that cover present-day Greenland and Antarctica. Recently, several GPS stations were deployed around the Greenland ice sheet to measure minute changes in earth surface elevation as a result of rebound. This data is being combined with that from sensors measuring elevation changes, glacial outflow rates and the mass balance to provide a more complete assessment of the sheets' melting.
Figure 1.43 A one-meter tall station (above) was installed last Thursday near Ilulissat to measure how much the earth’s crust rebounds as the ice sheet melts. Courtesy Thomas Nylen (UNAVCO) Source
Databases for analyzing the effects of climate change are large and complex. As databases documenting environmental changes across the earth are developed, geographers will provide the tools for teasing out spatial and temporal signals in the observations. Geographic Information Systems are well-suited for handling complex databases to map the potential spread of diseases, ecosystem changes, and sea-level rise as a result of global warming.
Analyzing environmental change
Geographer's have a number of tools and skills to analyze impact of environmental change on earth systems. Geographers are actively engaged in projects to identify and understand patterns of deforestation and habitat fragmentation. Geographer Eric Larsen has studied the decline of aspen trees in Yellowstone for several years. Though climate change was first suspected, he and ecologist William Ripple, realized that aspens outside the park flourished. If climate change was responsible, trees inside and outside the park would have suffered a decline. Analyzing cores from trees within the park, they found that most were 70 years old, aspens had apparently stopped regenerating around the 1930s
Figure 1.44 Reintroduced wolf in Yellowstone Park. Courtesy NPS.
Between the late 1880s until the mid-1900s, more than bounty hunters killed 100,000 wolves in wyoming and Montana. By the 1970s, the wolf was classified as an endangered species. A controversial reintroduction program brought 31 gray wolves back to the Yellowstone ecosystem. It appears that the removal of a top predator, allowed browsing elk populations to flourish and devastate young aspens. With the reintroduction, diversity and stability of the ecosystem appears to be on the rise.
Explaining environmental change
Geographers can play a significant role in hypothesis and theory development. Geographers are particularly suited for building numerical models of the complex coupling between the earth's surface and atmosphere above. Their strong field orientation and integrated methods will help hone the parameterization of climate models.

Figure 1.45 Comparison between modeled and observed temperature rise without human factors, with human factors and both. Courtesy IPCC
Geography's human-environment tradition provides a foundation for answering some of the most vexing issues of the global warming. The crux of the global warming issue is identifying the "fingerprint" of human activities in creating the enhanced greenhouse effect. For example, models that attempt to explain the warming experienced over the last several decades using only natural factors fail to adequately explain the actual pattern temperature. When human factors that influence warming are added, a much better correspondence with reality is uncovered.
Because geography uniquely straddles both physical and social sciences, geographers play an important role will play a role in future policy formulation and decision making. Geographers are well-suited for evaluating the costs and benefits of various global warming mitigation strategies.
Predicting environmental change
Climate models have demonstrated that the impact of global warming will vary across the earth. Geographers have been at the forefront of predicting the potential changes that our environment will undergo. Based on recent analyses, Geographer Jack Williams found that, we're headed for major change -- fast. He suggests areas that currently have a tropical climate will become warmer, pushing vegetation and animal life northward. Williams believes these changes will lead to the spread of insect-borne diseases like Malaria, increased catastrophic natural disasters and greater risks to human well-being. Temperatures rising just a few degrees will affect where particular plant and animal species will thrive. The question is if they will be able to migrate or adapt to a rapidly changing climate. If not, some face extinction.
Williams work predicts that many current climates may entirely vanish by the year 2100. He foresees "no-analog" communities of plants and animals arising from "novel" climates. No-analog communities consist of species that exist today but in differ net combinations from those presently inhabiting the earth. The species exist today, they have just been "reshuffled" into new combinations not found at the present. Such no-analog combinations have been found recorded in fossil pollen assemblages extracted from lake sediments dating from the late-glacial periods in North America. These seemingly odd past combinations of species are thought to be a product of of "novel" or no-analog climates, characterized by higher-than-present temperature seasonality. Professor Williams recognizes that with current trends in global warming, such new communities of species may be in our future. His climate models project the disappearance of many existing climates in tropical highlands and near the poles. Large swaths of the tropics and subtropics may develop new climates unlike anything seen today.
In coming chapters we'll examine the future geography of earth as predicted by geoscientists of all kinds and particularly physical geographers. You'll explore how earth's gaseous composition is predicted to change, how and where temperature changes occur, the impact of rising oceans, and the displacement of ecosystems. Though dire conditions are predicted, the challenges posed can be addressed ... and geographers will be at the forefront.