Assignment 1: Introduction to Earth and Maps
Graticule
To know specifically where something is located on Earth's surface, a coordinated grid system (that is agreed to internationally) is needed. The terms latitude and longitude were in use on maps as early as the first century A.D., with the concepts themselves dating back to Eratosthenes and others.
Adapting from the Babylonians, Ptolemy divided the circle into 360 degrees (360°), with each degree subdivided into 60 minutes (60'), and each minute further subdivided into 60 seconds (60"). This method of dividing degrees into minutes and seconds is often referred to as DMS coordinates. Note that GIS, GPS, and other computer-based systems often use decimal degrees or DD coordinates. In this method, each degree is divided into a more familiar base ten system.
Figure 1 Latitude and parallels
1. What is the highest latitude?
2. What is the highest longitude?
Figure 2 Longitude and meridians
3. List 3 countries that the Prime Meridian passes through.
4. When you look at the Prime Meridian on the globe, which hemisphere is located to the left of the Prime Meridian?
5. Now locate the International Date Line on the globe. Which hemisphere is located to the left of the IDL?
6. Using a globe, find 30°S, 60°W. What country is located at these coordinates?
7. Starting from the same coordinates (30°S, 60°W), move your finger 20 degrees toward the north. List the country closest to this location along with the latitude and longitude.
Figure 3 Measuring longitudes on Earth
8. Figure 3 is a view of the Earth from directly above the North Pole; the equator is the full circumference around the edge. A line has been drawn from the North Pole to the equator and labeled 0°, representing the Prime Meridian. Earth's Prime Meridian through Greenwich, England, was not generally agreed to by most nations until 1884.
a. Label the Eastern Hemisphere on the above diagram.
b. Label the Western Hemisphere on the diagram.
9. On the diagram above, draw another line from the North Pole to the other side of Earth, opposite the Prime Meridian, and label it 180°.
a. What is the name of this line (180°)?
b. Use a protractor to measure, draw, and label the meridians that are 100° east and 60°west of the Greenwich meridian on the above diagram.
10. Why do you think the International Date Line (on the globe) is not straight, but zigs and zags?
Time Zones
11. Write the longitude for each location and indicate if it is in the Eastern or Western Hemisphere. Then use the time zone map (projected in the classroom, or on page 25 of your textbook to determine: If it is noon at the following locations, what time is it in our time zone?
Location
Longitude (E/W)
Time in VA
Kiev, Ukraine
London, England
Los Angeles, CA
Lagos, Nigeria
Tokyo, Japan
Map Scale
Map scale is the relationship of the distances separating two points on a map to the distance separating the same two points on the surface of the Earth, measured in the same units. Both the numerator and the denominator must be in the same units. Scale may be expressed as a fractional scale (ratio or representative fraction), verbally, or graphically.
The denominator of a fractional scale can be difficult to visualize. A verbal scale can concert these to more understandable units. For example, the denominator of the fractional scale 1:24,000 can be converted by dividing by 12 to get to inches, and by 63,360 to get to miles. So 24,000 inches equals 2,000 feet or .378 of a mile.
We can also set up an equation based on the equivalency statement, and then cross-multiply. For example:
1 foot = 12 inches (start with the equivalency statement)
X 24,000 inches (fill in the other values, keeping the same units on the same side of the equation)
12X = 24,000 (cross-multiply)
X = 2,000 feet (divide by 12 to isolate X)
12. Convert the fractional scales to verbal scales using the following conversion factors: 1 foot = 12 inches
1 mile = 5,280 feet = 63,360 inches
Representative fraction: 1:10,000
Verbal scale: One inch on the map represents 10,000 inches or feet, or miles on the ground.
Representative fraction: 1:24,000
Verbal scale: One inch on the map represents 24,000 inches or feet, or miles on the ground.
Representative fraction: 1:3,168,000
Verbal scale: One inch on the map represents 3,168,000 inches or feet, or miles on the ground.
13. Compare the fractional scale 1:10,000 to 1:3,168,000. Which would show MORE AREA?
14. Compare the fractional scale 1:10,000 to 1:3,168,000. Which would show MORE DETAIL?
Map Projections
Cartography, or mapmaking, is the study and practice of making representations of the Earth on a flat surface. Cartographers design maps based on the properties they want to preserve and the information they want to portray.
A map projection is a systematic means to portray shape, area, distance, and direction of the Earth on a two- dimensional surface. Map projections are created by projecting landmasses and the graticule onto a flat surface. All map projections contain distortions since no one projection preserves all four properties simultaneously. A globe is the only accurate representation of shape, area, distance, and direction of the Earth's surface.
There are three main properties of projections. Equal area projections maintain equal area relationships; conformal projections maintain angular relationships in order to preserve shape; and equidistant projections maintain distances between points.
The class of a map projection can be conic, cylindrical, or planar. Conic-class maps result from wrapping a flat surface of a cone around a reference globe and are often used to project the midlatitudes. Wrapping a cylindrical surface (a rectangle) around a globe creates a cylindrical-class map. Cylindrical-class maps are usually centered on the equator. A planar-class map results from placing a flat surface next to the surface of a globe, so that the two only touch at a single point, and is most often used to project the poles.
In order to reduce some of the distortion created by projecting a map, cartographers center their maps on a standard line or point. The points where the developable surface (flat piece of paper with no tears) touches the globe creates the standard line or point where distortion is minimal. Distortion increases as you move away from the standard line or point. Generally, cylindrical projections employ the equator as the standard line and thus are greatly distorted in the higher latitudes. Conical projections typically have a standard line somewhere in the midlatitudes, so this type of projection is often used for the United States. Planar projections typically have a single standard point because the developable surface of the plane contacts the globe in only one place.
15. List two advantages that a globe has compared to a map.
16. List two advantages that a map has compared to a globe.
Figure 6 Mercator, Peters, and Goode's projections
17. The Mercator projection (conformal cylindrical equatorial) maintains the correct shape of landmasses, but not their sizes. As a result, Greenland (0.8 million square miles) appears larger than the entire continent of Africa (11.6 million square miles). The Peters projection (equal area cylindrical equatorial) maintains the correct size of countries, but not their shapes. Goode's projection maintains the size and shape of landmasses, but interrupts the oceans. Are you more accustomed to viewing one of these in particular? How do these maps influence your perception of the world?
18. Take a look through pages 12-13 in Goode's World Atlas (if you have the 23rd edition, pages xvi and xvii). These pages describe and show examples of the main map projections used in the atlas. List one benefit and one drawback specific to Goode's Interrupted Homolosine Equal Area Projection (also shown above in Figure 6).
19. What is a map projection?
Types of Maps
Look over the thematic map types on pages 14-15 (or xviii-xix in newer edition) and types of map projections on pages 12-13 (xvi and xvii) in Goode's World Atlas to answer the following:
20. What type of thematic map are the temperature maps on pages 32-33 (or in 23rd edition, pages 22-23)? Select one of the following:
a. Choropleth map
b. Isoline map
c. Area class map
21. On page 39 (or page 30 in 23rd edition), examine the map of carbon dioxide emissions.
a. What type of thematic map is this?
b. What does the size of the circle represent?
c. What does the color of the circle represent?
22. On the Rock Type map pp. 96-97 (or in 23rd edition, the Geology map on pages 42-43), would the Colorado Plateau appear larger or smaller at a scale of 1:1,000,000?
23. Looking at the Rock Type of the US map on pages 96-97 (42-43 in newer edition), can you discern which rock type is more common at the surface (igneous, metamorphic, or sedimentary)?
Isoline and Topographic Maps
A topographic map displays the relative positions and elevations of physical features on the Earth's surface. The United States Geological Survey (USGS) publishes topographic maps for the United States in a variety of sizes and scales (ranging from 1:24,000 to 1:1,000,000). The most commonly used scale of a topographic map is 1:24,000, which covers an area measuring 7.5 minutes latitude by 7.5 minutes longitude and is referred to as a 7.5-minute quadrangle.
An isoline is a line that connects points of equal value, and contour lines are a specific type of isoline that connect points of equal elevation. Contours are usually printed in brown on topographic maps, and index contours are heavier brown lines usually marked with the elevation. The contour interval is the change in elevation between contours, and varies from map to map.
Figure 5 Contour lines and a corresponding landscape.
Contour Line Characteristics:
• A contour line represents only one elevation.
• Contour lines do not divide or split.
• Contour lines do not end. They may run off maps that represent only a small portion of the landscape.
• Contours are closer together on steep slopes and farther apart on gentler slopes. On vertical slopes, contour lines will overlap, but they never cross each other.
• Contour lines bend upstream into an inverted "V" when crossing streams, and bend downslope when
crossing ridges.
• Hatchured contours indicate a depression. The hatchured lines have small tick marks on the downhill side.
Examine the map of Lake Contouria with elevational points. The 170 foot contour has already been drawn. Draw the remaining contour lines at intervals of 10 feet. Be sure that all points with a lower elevation than the contour line you are drawing are on the downhill side of the line. Use a pencil and draw lightly until you are sure the contour positions are correct, then darken the lines. The inverted "V"s should coincide with the stream channels.
Assignment 2: Plate Tectonics
The model of plate tectonics is the starting point for understanding the distribution and formation of many collections of landforms around the world. The lithospheric plates are 65 to 100 kilometers (40 to 60 miles) thick and consist of the crust and upper mantle. The plates move over the layer of the mantle known as the asthenosphere at speeds averaging from 2.4 to 10 centimeters (1 to 4 inches) per year.
Major Lithospheric Plates.
The three different kinds of plate boundaries are associated with different kinds of topographic features and tectonic activity.
Divergent Boundaries: At divergent boundaries (also called "spreading centers") plates are moving apart. The most common kind of spreading center is the midocean ridge where new basaltic ocean floor is created. Spreading may also take place within a continent. In this case, blocks of crust may drop down as the land is pulled apart, producing a continental rift valley (such as the Great East African Rift Valley).
Convergent Boundaries: At convergent boundaries, where plates collide, three circumstances are possible:
1. If the edge of an oceanic plate collides with the edge of a continental plate a subduction zone is formed. The denser oceanic plate is subducted below the continent, producing an oceanic trench. As the oceanic lithosphere descends, water and other volatile materials are driven out of the ocean rocks, leading to a partial melting of the mantle. The magma that is generated rises, producing intrusions of plutonic rock such as granite and a chain of andesitic volcanoes, such as the Andes in South America or the Cascades in North America.
2. If the edge of an oceanic plate collides with the edge of another oceanic plate, subduction also takes place. An oceanic trench forms, along with a chain of andesitic volcanic islands known as an island arc, such as the Aleutian Islands in Alaska and the Mariana Islands of the western Pacific Ocean.
3. If the edge of a continent collides with the edge of another continent, the relatively buoyant continental material is not subducted. Instead, a mountain range is uplifted. The Himalayas are a dramatic example of this kind of plate boundary interaction.
Transform Boundaries: Plates slide past each other at transform boundaries, such as along the San Andreas fault system in California.
Evidence supporting the theory of plate tectonics comes from global patterns of landforms and tectonic activity. In addition to the matching shape of the continental margins on both sides of the Atlantic Ocean (which spread apart from the Mid-Atlantic Ridge), the age of the ocean floor provides evidence of movement. The ocean floors are youngest at midocean ridges, where new lithosphere is being formed, and become progressively older away from a ridge in both directions. This was verified through ocean core samples, as well as paleomagnetic evidence (changes in Earth's magnetic field that have been recorded in the volcanic rocks of the ocean floor).
Plate boundaries are often the sites of significant volcanic activity. At spreading centers, magma is moving up to the surface, creating new lithosphere as the plates spread apart. Magma generated in subduction zones can produce a chain of continental volcanoes or a volcanic island arc.
The distribution of earthquakes also provides clues to plate activity. Most earthquakes around the world occur in association with plate boundaries. Shallow-focus earthquakes, within about 70 kilometers (45 miles) of the surface, occur at all plate boundaries. However, in subduction zones, bands of progressively deeper earthquakes are observed, produced when an oceanic plate is thrust deep down into the asthenosphere.
Hot Spots
One of the important modifications of basic plate tectonic theory is the concept of the hot spot. These are locations where a fairly narrow plume of magma is rising from the asthenosphere to the surface, producing volcanoes. Many hot spots apparently develop from mantle plumes that originate deep within the mantle.
Hot spots may occur well away from plate boundaries, often in the middle of a plate. It is not yet completely understood why these hot spots occur where they do, but the existence of hot spots has been helpful in verifying plate motion.
Evidently, hot spots can remain active in the same location for millions of years. While the hot spot remains in the same place, the plate above continues to move above it. Currently active volcanoes are found directly over the hot spot, while the moving plate carries older volcanoes off the plume, at which time they become inactive. Ongoing plate motion carries these old volcanoes farther and farther away from the hot spot, resulting in a chain of extinct volcanoes.
The Hawaiian Islands are the best-known example of an island chain produced by a hot spot. The only currently active volcanoes are found on the island of Hawaii in the southeast part of the island chain. It is believed that this island is currently over the hot spot.
The map below shows the ages of volcanic rocks in the Hawaiian chain. Notice that the ages (in millions of years) of the volcanic rocks becomes progressively older as we follow the islands to the northwest. The pattern of islands in the Hawaiian chain shows the general direction of movement of the Pacific Plate, and from the ages of the rocks, we can infer the rate of plate movement.
Island Ages of the Hawaiian Archipelago.
Activity
Study the tectonic map of a hypothetical ocean basin (page 6 of this packet). The map shows the location of volcanoes, earthquakes, and the age of ocean floor rocks. From this map, you will determine the probable location of the plate boundaries and the locations of major topographic features in the region.
The edges of two continents are shown (in the upper right corner and lower left corner). Six islands are also shown. The symbols used on the tectonic map are described below.
Earthquake Epicenter Location and Depth:
The locations of earthquake epicenters are shown with letters. The depth of the earthquake (the distance of the earthquake hypocenter or "focus" below the surface) is indicated with an "S" (shallow focus), "I" (intermediate focus), or "D" (deep focus):
S = Shallow Earthquakes 0-70 kilometers (0-45 miles) deep
I = Intermediate Earthquakes 70-200 kilometers (45-125 miles) deep
D = Deep Earthquakes 200-500 kilometers (125-310 miles) deep
Active Volcano:
Continent or Island:
Activity Procedure:
The first step of the activity is to draw in the approximate plate boundaries as indicated by the tectonic activity on the map.
Clues include:
a) The pattern of earthquakes. For example, subduction produces a pattern of deeper and deeper earthquakes as one plate plunges below the other.
b) The age pattern of volcanic ocean floor rocks suggests the location where new ocean floor is being created at a midocean ridge.
c) Volcanic activity may be associated with subduction, spreading centers, or hot spots.
Use the following symbols to indicate the extent of all plate boundaries. Both the map symbols, and a side view of the circumstance they represent, are shown below. Arrows indicate direction of plate movement.
Convergent Boundary (Subduction) Divergent Boundary
Map symbol to be used: Map symbol to be used:
Side view: Side view:
Note: No transform boundaries are found on the map. Assume that only one of the volcanoes on the map is associated with a hot spot.
Draw the plate boundaries using the appropriate symbols on the tectonic map, and then answer the questions on the following page. When asked to cite evidence to support your answers, only cite evidence that you can see on this map.
1. How many different plates (not boundaries) are clearly shown on the map?
2. Indicate on the map the most likely location of a midocean ridge (such as the Mid-Atlantic Ridge). Write the label "Midocean Ridge" on the map.
a. What type of plate boundary is this?
b. What evidence shown on the map indicates that this type of boundary is present?
3. Indicate the most likely location on the map of a major volcanic mountain range similar to the Andes in South America with the label "Volcanic Mountain Range".
a. What type of plate boundary is this?
b. What evidence shown on the map indicates that this type of boundary is present?
4. Label all plate boundaries where oceanic trenches should be found with the label "Trench".
5. Assume only one of the volcanoes on the map is a hot spot. Label this volcano "Hot Spot".
a. Draw an arrow extending from this volcano, indicating the direction of plate movement (and the direction in which you would expect to find progressively older, extinct volcanoes).
6. In the space below, draw an approximate continuous cross section ("side view") of the ocean basin from Point A to Point B (from lower left to upper right). Use the "side view" drawings for reference, and use arrows to indicate the relative direction of plate motion. If subduction is taking place, clearly show which plate is subducting beneath the other.
Use pages 22-23 (or pages 6-7 in the 23rd edition) in Goode's World Atlasto answer the following questions.
7. The Sumatra-Andaman earthquake on 12/26/2004 was centered near 3° N latitude, 96° E longitude.
a. What type of plate boundary is present (for example, is this a convergent or a divergent boundary)?
b. Name the plates involved Check the Atlas or the figure "Major Lithospheric Plates" on the first page of this packet to find the plate names (for example, the North American plate and the Juan de Fuca plate).
c. Since this earthquake occurred under water, what additional natural disaster accompanied this earthquake?
8. Locate Tonga near 21° S latitude, 175° W longitude.
a. The Tonga islands are located along the Tonga Trench. What type of plate boundary is present?
b. Would you expect to find volcanoes in Tonga? Why or why not?
9. The Cascadia earthquake of 1700 occurred at 47° N latitude, 122° W longitude, and generated a tsunami that traveled to Japan.
a. What type of plate boundary produced the Cascadia earthquake?
b. When oceanic crust meets continental crust, which type of crust is subducted? Explain your answer.
c. Name two active volcanic mountains located in this area.
10. Locate the East African Rift Valley and the Red Sea. Name the plates involved and describe the tectonic activity (which is happening here: subduction or rifting?).
11. For each of the following locations, identify the plate that is being subducted.
a. Santiago, Chile
b. Attu Island, Alaska
c. Taipei, Taiwan
For the remaining questions, use the maps and Index in Goode's World Atlas to identify the features, and draw them on your copy of the blank world map (last page of this packet). Be precise in your drawings.
12. Locate and draw the boundary between the Nazca and South American plates.
a. What type of boundary is this (convergent or divergent)? What tectonic activity occurs here (subduction or rifting or sea-floor spreading)?
b. List two tectonic landforms that occur here.
13. Locate and draw the boundary that runs south from Iceland to near Antarctica.
a. What type of boundary is this? What tectonic activity occurs here?
14. Locate and draw the boundary between the Philippine and Pacific Plates.
a. What type of boundary is this? What tectonic activity occurs here?
b. List two tectonic landforms that occur here.
15. Locate the Hawaiian islands on the map.
a. Draw an arrow that shows the direction of movement of the Pacific Plate. The arrow should point in the same direction as the oldest islands.
b. What is the term that describes the volcanic activity that occurs far away from a plate boundary?
Format your assignment according to the following formatting requirements:
1. The answer should be typed, double spaced, using Times New Roman font (size 12), with one-inch margins on all sides.
2. The response also include a cover page containing the title of the assignment, the student's name, the course title, and the date. The cover page is not included in the required page length.
3. Also Include a reference page. The Citations and references should follow APA format. The reference page is not included in the required page length.
Attachment:- ICA-Plate-Tectonics.rar