GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 1
Introduction to the Earth
GEOSCI/ENVIRON 118 Laboratory
Name:________________________________
Section:________
This first laboratory is based on a program called ArcView. ArcView is a fairly
common program, one that you might run into time and time again if you take more
science credits. This lab is designed to help you learn a bit about the Earth in a way that
is NOT difficult, especially if you follow the directions and do much of the lab in order. If
you have any questions, though, make sure you ask your GSI right away.
1. Lets Get Started.
1.1.- Login to your Kerberos account.
To begin, you need to map drive to server: Right click on My Computer icon (will say
<username> or <Computer name> or <user ID on computer name>). Select Map
Network Drive. Folder is \\lsa\dfs\labs\geo\gs118. Click Finish.
Go to the Start button, hit Programs > ESRI > ArcView > ArcView GIS 3.3.
Once you find the ArcView GIS 3.3 shortcut, click on it to open the program.
Select Open An Existing Project from the Welcome to ArcView GIS window, and then
click OK. Go to Drives (option in lower right) and select drive Z.
On the right-side window, select Z: \dynamic_earth.
On the left-side window select the file dynamic.apr, and click OK.
Answer Yes to the pop-up question about adding tools to the project, if you get it.
On the opened window, select clues from the menu shown, and double click or open.
You now should have opened a map of the earth. If you do not have a map, ask your GSI
for help. You can adjust the size of the windows by clicking the appropriate
maximizing button in the upper right corners, or by dragging the lower right corner to an
ideal size, just as you would with any other window.
QUESTION: Take a look at the map in front of you. The small colored bar scale below
the map shows elevation. Answer the following questions:
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 2
1.1.1.- What color is the highest elevation? The lowest?
1.1.2.- What color are most of the continents? Does this indicate „high‟ or „low‟
elevation?
1.1.3.- Find 3 places where the elevation is above 3 km. List their locations
below. Where do places of high elevation occur on continents? Where do places
of extreme depth occur in the oceans?
1.2 Getting to Know Latitude and Longitude
OK, wait a minute! You‟ve found 3 places (or maybe more) where the elevation is at
least 3 km. But how can you describe where these places are? It would be nice to be
able to describe WHERE the highest, the lowest, etc. elevations are on the earth, with a
UNIFORM reference, or starting point, so that everyone could find the exact same spot.
It would be much easier using some sort of mathematical grid system, rather than trying
to find “that island right next to that peninsula that Disney World‟s on…” There are
several grid or reference systems we can use – we‟ll learn about one of them in this lab,
called latitude and longitude.
On the map, click on the small box next to “latitude and longitude.” By clicking this
box, you‟ve turned this function “on.” (Clicking the words “latitude and longitude” will
only activate this function, and does not actually turn it on.) This places a grid over the
map. These are lines of latitude and longitude.
The Earth is segmented by previous-determined lines, called Latitude and Longitude.
Lines of Latitude (also called “parallels”) run east-west, and are numbered from zero to
90 . The 0 latitude line is the equator, halfway between the north and south poles.
90 can be either the North or South Pole. Therefore, one must always distinguish
between lines of latitude north or south of the equator. By convention, this is done by
adding an “N” or “S” to your latitude (or by using + and -). For example, Ann Arbor,
Michigan, is located at a latitude of approximately 42 North, or 42 N, or +42 . Buenos
Aires, Argentina is located at approximately 36 South, or 36 S, or -36 .
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 3
One can make different projections of the world map: examples discussed here are
orthographic and geographic (cylindrical). You can switch between these in your
computer map using a button with an open circle on the top toolbar (about in the middle).
Try it.
Each line of latitude is equally spaced. Furthermore, each degree can be further separated
into smaller sections; in this case, One Degree = 60 minutes. Each minute = 60 seconds.
These subdivisions are useful to those who frequently must navigate on large bodies of
water. The term KNOT (as in “aye aye, Captain, we‟re making good time towards
Gloucester at 12 knots!”) comes from the term nautical mile. Each nautical mile is
equal to one minute of latitude.
Lines of longitude run north-south. On a large scale, one can use lines of longitude to
divide the earth into two 180-degree halves, referred to as the East and West
hemispheres.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 4
The East and West Hemispheres
Lines of longitude originate at the Prime Meridian (0˚ longitude) and meet at the
International Date Line (180˚ East and West longitude). The Prime Meridian runs
through Greenwich, England (Greenwich is quite close to London). A line connecting
the North Pole, Greenwich, and the South Pole describes a line of longitude. All lines of
longitude converge at the poles, and are farthest apart at the equator. Longitude values
can run from zero to 180 east or west. As with latitude, it is important to distinguish
whether you are east or west of the Prime Meridian, so make sure you include „East‟ or
„West‟ signifiers with your longitude value. Now, to completely describe a location, we
can use both latitude and longitude.
EXAMPLE: Using latitude and longitude, describe the location of Ann Arbor Michigan.
Answer: Ann Arbor is located at 42.25 N, 83.7 W. (Hint: Remember the zoom tool on
the toolbar that allows you to take a closer look at the world map).
Latitude, by convention, is given before longitude.
Latitude and longitude are given in the upper right corner of the clues map. As you move
your cursor over the world map, notice that the values change, just as they do in Google
Earth.
QUESTIONS:
1.2.1.- What is the top number telling you? The bottom?
1.2.2.- Notice that the numbers are sometimes negative. When are latitude
values given as „negative?‟ When are longitude lines „negative?‟ Why might
this be so?
1.2.3.- What continents does the equator (0 degrees latitude) pass through?
Name 1 country on each continent the equator passes through. (To help, click on
the “circle-i” button in the upper left corner – this is the „identify‟ button. When
activated, you can click on any country to obtain its population, name, location, and
surface area. Also, make sure that the ‘countries’ and ‘latitude and longitude’
buttons are activated, in addition to having a checkmark next to it. When activated,
the word will have a box around it. Simply clicking on the word will not activate this
feature.)
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 5
CONTINENTS
COUNTRY
1.2.4.- Name 3 countries the Prime Meridian passes through.
There are several lines of latitude that are important for climatology and geography.
These are:
Tropic of Cancer (23 N)
Tropic of Capricorn (23 S)
Arctic Circle (66 N)
Antarctic Circle (66 S)
The tropics are important, season-wise, in that the sun‟s direct rays are aimed at the
Tropic of Capricorn or Tropic of Cancer during the summer or winter solstice,
respectively. Remember, the earth orbits around the sun. Furthermore, the earth is
somewhat tilted on it‟s axis; this is the reason that the sun‟s direct rays change position
throughout the year. The Arctic and Antarctic circles define lines above or below which,
during their hemisphere‟s respective winters, no sunlight shines. During the peak of their
respective summers, however, there is constant sunlight in these regions.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 6
QUESTIONS:
1.2.5.- Name 3 countries the Arctic Circle passes through. Are there any states
in the United States that wholly or partially lie above the Arctic Circle? If so,
name them.
1.2.6.- Name 3 Continents the Tropic of Capricorn passes through. Are there
any large geographical features located on or near this tropic (i.e. deserts, rain
forests, mountain ranges, etc)?
1.2.7.- What is the only continent the Antarctic Circle passes through?
Turn on and activate the „Block Diagrams‟ theme. Hit the „hot-links‟ button (It
looks like a lightning bolt) located on the top toolbar. Your mouse icon should
now look like a lightning bolt. Click on the pink line that cuts across Antarctica.
You now should see a block diagram of Antarctica. What substance covers most
of the continent? Does the presence of this substance have anything to do with
Antarctica‟s location below the Antarctic Circle? If so, what is the connection?
Close the block diagram, click on the arrow in the toolbar.
1.2.8.- Why is the nautical mile equivalent to a minute of latitude, rather than
a minute of longitude? (hint: think about how and where lines of longitude
converge. Does a line of latitude ever touch another line of latitude?) To help
see this, click on the hollow-circle button on the top toolbar. This changes the
map from a geographic view to an orthographic projection. What do lines of
longitude do as they get closer to the poles?
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1.3 Measuring Michigan In Hot Dogs…The Importance of Scale
One important map feature we have to learn about is SCALE. Scale tells you how much
area you‟re looking at when examining a map. There are 2 basic ways of showing scale.
The one most people are familiar with is that of a bar scale. A bar scale gives a
graphical representation of how much „ground‟ distance is covered by a smaller unit on a
map.
This is a simple example of a bar scale.
A more useful method is that of a ratio scale. A ratio scale gives a dimensionless
representation of „how many on a map are found on the ground.‟ For example, look at
the geographical map in ArcView. Scale is given, as a ratio, in the upper right on the
map. The ratio is approximately 1: 198,000,000. This means that every ONE unit on the
map corresponds to 198,000,000 of the same units “in real life.” The nice thing about a
ratio scale is that it does NOT matter what kind of unit you use: the ratio is always the
same. So, every inch is equivalent to 198,000,000 inches. Every one meter on the map is
equivalent to 198,000,000 meters on the ground, every one hot dog on the map is
equivalent to 198,000,000 hot dogs. It doesn‟t matter what item or unit you use to
measure the map with, it‟s always equivalent to 198,000,000 of them in the field.
Ratio scales can change, depending on how „zoomed in‟ you are for any particular map.
Below are several problems in which you must convert/determine true units from a ratio
scale. You might need to remember a few conversion factors to do this part.
(remember, 12 inches = 1 foot, 2.54 cm = 1 inch, 5280 feet = 1 mile, and 1.6 km = 1
mile).
RATIO SCALE
1: 24,000
VERBAL SCALE
1 inch = ____________________ inches
1 inch = ____________________ feet
1 inch = ____________________ miles
1 cm = ____________________ meters
1 cm = ____________________ kilometers
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 8
1: 62,500
1 inch = ____________________ feet
1 inch = ____________________ miles
1 cm = ____________________ meters
1 cm = _____________________ kilometers
1:250,000
1 inch = ____________________ feet
1 inch = ____________________ miles
1 cm = _____________________ meters
1 cm = _____________________ kilometers
Let‟s try it as a word problem…
QUESTIONS:
1.3.1.- The distance between two airports is 3 inches on a map, and 12 miles
on the ground. Calculate the ratio scale for this map.
Ratio scale = (distance on map) / (distance on ground)
= 3 inches on map / 12 miles on ground
convert to common units…
= 3 inches on map/ (_________________) inches on the ground
= 1: (__________________) in a ratio scale.
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1.3.2.- On a map with a ratio scale of 1:250,000, two points are separated by
3.7 inches. What is the distance in miles and kilometers between these points
on the ground?
1.3.3.- You have 2 maps in front of you, one with a scale of 1:62,500 and
another with a scale of 1:24,000. Which will show more area? If you‟re
hiking in the area, and you want a map with greater detail to allow you to
better identify surface features, which map should you buy?
1.3.4.- Click on the magnifying glass with the „+‟ – this is your zoom tool.
Zoom in on the state of Michigan until your scale is approximately 1:3,000,000.
Turn on and activate the „Cities‟ function. Click the „circle-i‟ button from the
toolbar.
Find, and click, on Ann Arbor, Michigan. What is the latitude and
longitude?
What is the biggest city in the state of MI? Give the latitude and longitude.
What is the biggest city in the United States? Give the latitude and longitude.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 10
1.4 Highs, lows, the distribution of elevation…
Turn on and Activate the „Topographic Profiles‟ theme. To see whether Topogr.
Profiles is activated, check whether it looks “elevated” or in “relief” in addition to having
a check mark next to it (if it is not activated, the following won‟t work for you!). The
colored lines in this theme mark the locations of topographic profiles, or cross-sectional
views of the land surface. Imagine slicing through the Earth, pulling the halves apart, and
viewing one half from the side. The result is a topographic profile (that is, it shows an
outline, or profile, of the topography).
EXAMPLE: Click on the „hot-link‟ button (the lightning bolt) in the toolbar. Using
the lightning bolt, click on the green line that crosses the Yucatan Peninsula (in
Mexico). To make land features easier to see, topographic profiles are usually stretched
vertically, a process called vertical exaggeration. On this profile, one can see the highest
point (the Sierra Madre del Sur, at about 3.5 km), the lowest point (in the ocean, in the
Middle America Trench at about 6 km deep), and a broad, flat area marking most of the
Yucatan Peninsula at an elevation of less than 1 km. Notice that the deepest areas in the
oceans are often found in deep linear features called “Trenches” while the highest
elevations on land are, generally, in mountain ranges. We‟ll come back to trenches and
mountains later on…
In the boxes below, sketch several of the profiles, and answer the following questions
about them.
Using the “Hot Links” tool, click on the topographic profile on the Western coast of
South America. Sketch the profile in the box below—be sure to include labels and
units in your sketch.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 11
QUESTIONS:
1.4.1.- What is the highest elevation in your profile of the Andes Mountains?
Name three countries covered by the Andes. (You are free to zoom in and out,
as well as to use the „circle-i' button to find these three countries).
As you can see from the full map view, the Andes Mountain range is one of the highest in
the world. To discover some of the lowest places in the world, we will now explore a
region that is amongst the least explored areas on Earth: the oceans.
Make sure that your „Topographic Profiles‟ theme is still turned on and activated.
Using the Hot Links tool, look at several block diagrams of the Earth‟s coasts and
oceans.
1.4.2.- Where are ocean trenches located with respect to coasts? Are they in
the middle of the oceans, or closer to shore? Is this surprising? If so,
speculate as to why this might be.
Locate the Mariana Trench (Hint: this trench lies north of Indonesia and Papua
New Guinea in the Pacific Ocean). The Mariana Trench is known to be the Earth‟s
deepest. Using the Hot Links tool to view a block diagram, sketch the diagram in
the box below, remembering to include labels and units.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 12
1.4.3.- What is the elevation at the deepest part of the Mariana Trench?
Most of us are familiar with the general topography of land surfaces. We know that some
areas are mountainous, while other areas (like Michigan) are quite flat. Since the ocean
floor is covered by water, we rarely think about topography of the ocean floor. For
centuries, the oceans were thought to be flat, abyssal plains with little or no change in
elevation. It came as a great surprise, then, to discover the largest mountain chain on
earth located on the ocean floor! To view a profile of this mountain range, we must go to
the floor of the Atlantic Ocean. Use your Hot Links tool to click on the profile that
extends from the Eastern edge of Florida to the Northwestern edge of Africa.
Sketch the profile of the ocean floor in the box below. Remember, include labels
and units.
The mountain range in the middle of your profile is called the Mid-Atlantic ridge. In
general, these oceanic mountain ranges are referred to as Mid Ocean Ridges (MOR).
What is the elevation of the Mid-Atlantic Ridge, compared to the North American
Basin and the Canary Basin?
1.5 The Hypsometric Curve
We have now examined the topography of mountain ranges, ocean trenches, and ocean
basins. Now, turn off the „Topographic Profiles‟ theme, as well as the
„Latitude/Longitude‟ theme. Although it is important to observe the Earth‟s “highest
highs” and “lowest lows,” it is also important to observe that the vast majority of Earth‟s
land surfaces lie in a small range of elevation. Most of the ocean floor, also, lies at a
relatively uniform elevation.
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 13
Looking at the world map in front of you, observe the elevation bar scale at the
bottom.
QUESTIONS:
1.5.1.- Using this scale, approximate the average elevation of the land surface
in North America. What is the average elevation in China? Estimate the
average elevation of the entire land surface of the Earth.
1.5.2.- Now, use the same method to approximate the average elevation of the
Earth‟s oceans.
Although the color scheme in this map is helpful, it probably hard to make a good
estimate based on the scale here. To better demonstrate average topography, geologists
employ a chart called the hypsometric curve. The next few questions will ask you to
interpret this graph:
GEOSCI/ENVIRON 118 – Laboratory 1 “Meet the Earth”, page 14
QUESTIONS:
1.5.3.- What does the hypsometric curve tell you about average elevation on
land? In the oceans? How do these averages compare to the approximations
you formed above?
1.5.4.- You know that the vast majority of earth‟s surface falls in the more
level parts of the hypsometric curve. From the topographic profiles you‟ve
sketched and seen today, what would you say accounts for the steep parts of
the curve, at the highest and lowest elevations?