Our Changing Earth--Historical Satellite Imagery Lesson
Dr. Joseph J. Kerski
Geographer
Box 25046 - MS 507
Denver, CO 80225-0046 USA
Telephone 303 202-4315
Remote Sensing
Observing the earth from space using satellite images of the earth’s surface is important for understanding the planet. Since 1972, the USGS has operated the Landsat (“Land-satellite”) series of satellites to understand the earth in terms of global climate change, agriculture, forestry, geology, resource management, geography, mapping, water quality, and oceanography.
Landsat orbits at 705 kilometers and can visit the same area on the earth’s surface every 16 days. The Landsat images that you will be observing in this event illustrate some dramatic changes in the Earth over the past 20 years.
The Landsat images used in this Remote Sensing (or “From A Distance”) event are color composite images created by assigning colors to bands in the electromagnetic spectrum. Some of the bands are in the visible spectrum, while others are in the infrared part of the spectrum.
The band combination makes vegetation appear as shades of red. Brighter reds indicate more vigorously growing vegetation. Soils with no vegetation or sparse vegetation range from white, indicating sands, to greens or browns, depending on soil moisture and the content of organic matter.
Water bodies appear blue or black. Deep, clear water will be dark blue to black in color, while water that is shallow or laden with sediment will appear lighter in color. Urban areas appear blue-gray in color. Clouds and snow appear bright white. Clouds will have a puffy or popcorn shape with shadows often apparent.
1. Based on the what you learned above, do these images show the Earth’s surface in the same way as you’d see it if you were looking with the unaided eye from aboard the Landsat satellite? (1 point)
2. Why or why not? (2 points)
3. Based on what you learned above, are these Landsat images taken from higher or lower than aerial (airplane) photographs? Circle your answer. (1 point)
Higher Lower
4. Therefore, will each image cover more terrain or less terrain than aerial photographs do? (2 points)
5. Will each image include more detail or less detail than aerial photographs do? (1 point)
6. Will each image be a smaller map scale or larger map scale than aerial photographs? (2 points)
7. Based on the sentences above, what color would most of Colorado Springs or Fort Collins appear on a Landsat image? (1 point)
8. What color would most of the mountains west of Colorado Springs or Fort Collins appear on a Landsat image? (1 point)
9. What color would the arid Colorado Plateau appear near Cortez, Colorado, on a Landsat image? (1 point)
Examine the Denver From Space image from the Landsat satellite.
10. What are the darkest objects in the image? They are irregular in shape. (1 point)
11. Why do most of the dark objects that you identified above have one straight edge? (2 points)
12. What is the largest human-built feature on the image? It is in the northeast quadrant of the image. (1 point)
13. What are the long objects extending outward from this human-built feature? (1 point)
14. During what season of the year was this image taken? (1 point)
15. Examine the white irregularly-shaped objects that only exist near the eastern edge of the image. What are these? (2 points)
16. Based on the shadows that fall from the objects you identified in the previous question, during what time of day do you think the image was taken? Circle your answer. (3 points)
A Between Midnight and 6am
B Between 6am and Noon
C Between Noon and 6pm
D Between 6pm and Midnight
17. Explain why you answered the way you did to the question above. (3 points)
Turn now to your Historical Landsat Imagery book. Each image in your book for is oriented about 10 degrees east of north. Alternatively, you could use the USGS web page:
http://edcwww.cr.usgs.gov/earthshots/slow/tableofcontents
18. Therefore, true north on each image is (circle your answer) (2 points):
Slightly to the left Slightly to the right On the left side
of the top of each of the top of each of each image
image image
Turn to the first set of images in your book.
This set of Landsat images in northern Iran was taken in 1977 (left) and 1987 (right) and show the Elburz Mountains. These mountains act, as many mountains do, as a barrier to rain clouds.
19. Based on what you observe about the colors across each image, what side of the mountains receives the most rain? Circle your answer. (2 points)
North South East West
20. What is the reason you answered the way you did? (2 points)
21. Based on your answers above, what direction do the winds that carry rain clouds move? Fill in the blanks. (2 points)
from _______________________ to ____________________________
22. Observe the red areas in the valleys to the south of the mountains. What type of vegetation do you think exist in these areas? (circle your answer) (2 points)
Forest Cropland Wetlands
23. Did these vegetated areas in the valleys increase or decrease in extent from 1977 to 1987? (2 points)
24. Based on the above discussion, consider the following real phenomenon in North America. The Cascades are a long mountain range extending in a north-south direction from Washington to Oregon. Knowing that most rainfall blows in from west to east across the Cascade Mountains from the Pacific Ocean, where would you predict the most vegetation along the Cascades? Circle your answer. (2 points)
Along the West side Along the East side Along the North Side
25. What side of the Cascades would be reddest in a Landsat scene? Circle your answer. (2 points)
West East North
Turn to the next set of images in your book.
This set of images shows a portion of the state of Rondonia, Brazil, in a tropical rainforest environment. Approximately 30% of the world’s tropical forests are in Brazil. On the order of 98% of the world’s pharmaceuticals are developed from plants and animals in tropical rainforest environments.
26. What is happening to the amount of rainforest in this area, based on your observations of the images? (2 points)
Observe the main roads in the 1975 image.
27. Explain how the “fishbone” or “feather” pattern of fields that appear in the 1986 and 1992 images occurs. (3 points)
28. Based on the rate of change, when do you predict the area to be completely light blue? Circle your answer. (2 points)
2010 2020 2040 2060
Turn to the next set of images in your book.
These three images show the changes in the vicinity of the volcano Mount St Helens, Washington and Oregon, from 1973 to 1988.
29. Based on your observation of the images, when did the eruption of the volcano take place? Circle your answer. (1 point)
Before 1973 Between Between After 1988
1973 and 1983 and
1983 1988
30. Why did you answer the previous question as you did? (2 points)
31. What happened to the vegetation around the volcano after the eruption? (1 point)
32. How many square kilometers of vegetation was disrupted by the volcano? (3 points)
Turn to the next set of images in your book.
These images from July 1988 and October 1988 illustrate the huge forest fires that occurred in and adjacent to Yellowstone National Park during the summer and fall. These images were created in a different band combination (7, 4, and 3) to make burned areas easier to identify. Water bodies are dark blue, coniferous forest is in dark green, grassland is in light green, and burned vegetation is in shades of red and purple. Yellowstone Lake is visible as the largest lake in the east center of the image.
33. What direction does the river in the north central region of the image flow? Fill in the blanks. (1 point)
From ________________________ to __________________________
34. What direction do the rivers in the southwest region of the image flow? Fill in the blanks. (1 point)
From ________________________ to __________________________
35. In July, one large fire is visibly burning at the time of the image. What direction from Yellowstone Lake was this fire? (1 point)
36. What direction was the wind blowing during the time of the image? Fill in the blanks. (1 point)
From _______________________ to ________________________
37. Was this the only fire burning during July? (2 points)
38. What clue on the July image helped you answer the previous question? (2 points)
39. Approximately what percentage of the area in these images was burned according to your observations? (2 points)
Turn to the next set of images in your book.
This pair of images for Dallas-Fort Worth, Texas date from 1974 and 1989. In the 1974 image, the twin cities could each be identified. Dallas is on the east side, and Fort Worth is on the west side.
40. What color do the cities of Dallas and Fort Worth appear in the image? (1 point)
41. Based on your observations, which city is larger—Dallas or Forth Worth? (1 point)
42. Why is it more difficult to distinguish the two cities in 1989? (2 points)
Note the rectangular feature that appears white in the 1974 image at point “A”. This is Dallas-Fort Worth International Airport, recently completed when the 1974 image was taken.
43. What affect did the construction of the airport have on the amount of urban growth in the region by 1989? (2 points)
44. Why? Name 2 reasons. (2 points)
45. What affect did the construction of the airport have on the direction and pattern of urban growth in the region by 1989? (2 points)
46. Why? Name 2 reasons. (2 points)
47. Two new water bodies appear in the 1989 image. What direction are these from Dallas? Fill in the blanks. (2 points)
Water body #1 is _____________________ of Dallas.
Water body #2 is ______________________ of Dallas.
48. These water bodies are most certainly the following type (circle your answer): (1 points)
lakes reservoirs marshes
Turn to the next set of images in your book.
This pair of images from 1973 and 1987 shows the change in the Aral Sea, an inland sea in Kazakstan with no external drainage. The Amudar’ya and the SyrDar’ya Rivers flow into this sea. Over the past 30 years, water from these rivers has been diverted for another major use.
49. Describe how is the lake size and shape is changing. (2 points)
50.
Why is the lake size and shape changing? (2 points)
51. What is the most likely reason why the river was diverted? (2 points)
Turn to the next pair of images in your book.
This pair of images from summer 1985 and summer 1986 show Hubbard Glacier near Yakutat, Alaska. It also shows Russell Fjord, a saltwater arm of the Pacific Ocean that runs from the southeast part of the image, toward the glacier, turns the bend, and runs south-southwest toward the Pacific Ocean.
52. Did more snow and ice exist in the area in 1985 or 1986? Circle your answer. (2 points)
1985 1986
53. Which summer was warmer? (3 points)
54. Note what the “toe”, or end, of the glacier had done by 1986. Was the glacier advancing or retreating between 1985 and 1986? Circle your answer. (2 points)
Advancing Retreating
55. What would have happened to the salinity of the part of the Fjord to the southeast of the glacier while this was occurring? (2 points)
56. Name one consequence of this change on the aquatic wildlife in the fjord. (2 points)
57. Name one consequence of the glacier’s activity on the water level of the fjord. (2 points)