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Were You There?

What did North America look like 2 million years ago? Were there rivers and lakes? Were there mountains in the same places as modern day? Was North America in the same location as it is today?

To answer these questions, geologists construct maps of the lands and seas, as they existed in past ages. This process of reconstructing ancient geography is called paleogeography. Like a private detective, geologists analyze the clues they find preserved in the rocks. The types of fossils contained in the rocks are clues for the geologists. When interpreted, these clues not only give direct knowledge about the distribution of the lands and the seas, but also about the natural environment of the area. This helps the geologists to infer where the mountains and basins were located in the geologic past.

The distribution of fossils (skeletons, shells, leaf impressions, footprints, and dinosaur eggs) in rocks of a certain age tells something about the ancient distribution of lands and seas on the Earth's surface. The remains of coral found in land-locked Iowa indicate that this region was once covered by a coral reef. Clam shells found in old limestone of Pennsylvania and New York indicate a shallow sea once covered the area. The remains of ancestral horses and camels in rocks of South Dakota show that the area was then dry land or that land was nearby.

The distribution of the fossils will help to identify the ancient areas of land and sea and also the approximate shoreline. The distribution of living forms shows that thick-shelled fossil animals once lived in shallow water close to shore, while thin-shelled, delicate fossil animals probably lived in deeper, calmer water offshore.

Fossils can also be used to indicate the former temperature of water. In order to survive, certain types of present-day coral must live in warm and shallow tropical salt waters, such as in the seas around Florida and the Bahamas. When similar types of coral are found in the ancient limestone, they provide a good estimate of the marine environment that must have existed when they were alive.

All these factors -- depth, temperature and currents -- that are revealed by fossils are important to help clarify the picture of ancient geography.


Paleontology Activity

You are to be the paleontologist and use research to determine what fossil evidence you will see in your geologic column.

Combine with a couple of friends. Choose one of the areas listed below to study. For the area you have chosen to study, you are to learn about its geologic history. Imagine that you are a paleontologist and are trying to determine the evidence of change in your specific location. You might try to find pictures of the area as well as pictures of the fossil record found in that area. Present your fossil findings as a newspaper article announcing a continuous geologic column.

  1. Freshwater aquatic
  2. Marine aquatic
  3. Hot and dry desert
  4. Semi arid desert
  5. Coastal desert
  6. Cold desert
  7. Tropical forest
  8. Temperate forest
  9. Taiga (coniferous) forest
  10. Savanna
  11. Temperate
  12. Arctic tundra
  13. Alpine tundra

For information on ecosystems, you might look in a library or search on the Internet.

Your newspaper article should answer the following questions:

  1. How do your fossil findings indicate which ecosystem was once present?
  2. How will a change in ecosystems be evident in the fossil record?
  3. What specific fossils would you find in each layer of the geologic column?

Review Science safetey rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.

Updated October 24, 2008 by: Glen Westbroek

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