The Only Thing Constant Is Change

Students will learn about changes that occur over time in given areas. They will learn that human actions and natural disasters such as earthquakes, volcanoes, or floods, as well as a combination of them, are responsible for these changes. By looking at maps, black and white and color photos and other remote sensing images, the students will be able to locate and discuss these changes.

Time Duration: one 50-minute class period

Grade Level: 4-5

Concepts Explored:
scale, change, observation, analysis


Black and white and color photos of images of an area are useful for showing changes in an area over time. Other remote sensing images using thermal infrared, digital scanning or false-color are even more useful because they can penetrate cloud, dust, ash and smoke cover.

Divide the students into four groups and assign for study one of the four given areas above to each group. Find the location of each area on a national map. The students in each group should analyze the photos and other images available for the assigned area and prepare to discuss the following and other possible questions pertaining to the area.

  1. Mt. St. Helens Eruption of 1980
    (The following scenes and many more maybe found on the US Geological Survey home page devoted to the Mt. St. Helens eruption.)
    • Before the Eruption
      Read the information about the pictures of Mt. St. Helens before the eruption. And view the pictures. Picture 1 caption. View Picture 1. Picture 2 caption. View Picture 2. Can you find distinctive features at high and low altitudes? Do you see a lake? What shape is Mt. St. Helens? Is it symmetrical? How do you know that it is a volcano? What covers the upper slopes of the mountain? The lower slopes? Do you see evidence of running water such as a stream or river?

    • During the eruption
      Read the information about the picture of Mt. St. Helens during the eruption. And view the pictures. Picture 3 caption. View Picture 3. What is very obvious in the photo of the erupting mountain?
    • After the Eruption
      Read the information about the pictures of Mt. St. Helens after the eruption. And view the pictures. Picture 4 caption. View Picture 4. Picture 5 caption. View Picture 5. A map of the extent of the damage done by the Mt. St. Helens eruption of May 18, 1980 is available. View the Damage Map. North is to the top.

      In the photos taken immediately after and a few days following the main eruption, what changes do you see? What is the shape of Mt. St. Helens? In which compass direction is the sector facing with the blown out the slope? How did the upper slopes change? The lower slopes? What has happened to the surrounding vegetation? Can you find running water or a lake? From the images obtained a year or so after the eruption, can you tell what has happened to the vegetation? To the still or running water? Can you see a new feature inside the crater? Will the contour map for this area have to be re-drawn?

  2. Oakland Hills Fire of 1991
    • Before the Fire
      By looking at contour and physical relief maps and other images of the area, what can you tell about the topography of the Oakland Hills? Do you see evidence of vegetation? Of human effect?

    • During the Fire of 1991
      Can you see any evidence of contours in the thermal infrared image obtained during the fire? How can you tell? Can you tell where the ridges are? The valleys?

    • After the Fire
      From any available photos or other images after the fire, can you tell what has happened to the vegetation? To homes? If heavy rains fell following the fire and before vegetation could hold the soil on the hillsides, do you think such rain might affect the contours? How? Can you think of a some terms that might describe the effects of such downpours?

  3. The Mississippi River Flood of 1993

  4. OTTER Project
    From the available maps, photos and other images for OTTER, as well as any that might be available before clear-cutting started, what are some of the significant features of the area? Look at images from different altitudes and read the documentation about the instruments used to produce the images. An image from 450 miles above (an AVHRR image). An image from 65,000 feet above (a Daedalus TMS image). An image from 12,000 feet above (a TIMS image). An image from 5,000 feet above (a CASI image). An image from 1500 feet above (a digital video image).

    Can you find evidence of humans and their effects? Can you see different kinds of vegetation? Do you see streams or rivers? At which altitude do some of the these features become evident? Do the various images obtained at different altitudes and with different instruments give you different information? Are they all useful, do some seem more useful than others, or does their value depend on their use?

Additional thoughts and Ideas
The questions as presented above certainly are not the only ones that could be asked. Other questions could also be asked, some of which might be generated during class discussion.

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