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USGS Geology in the Parks

View of Earth, 650 million years ago Tmescale timebar 650 million years ago

650 million years ago

Late Proterozoic

What's going on here?

  • Many geology-buffs know about Pangaea; the supercontinent that formed at the end of the Paleozoic Era and broke-up during the Mesozoic Era. Few realize, however, that the continental land masses have probably collided to form supercontinents, then broken apart several times in the past!

    During the late Proterozoic Eon, about 1.1 billion years ago, the supercontinent Rodinia was assembled. There is not enough evidence preserved from that time to know exactly how big Rodinia was, but North America (find Laurentia on the image) probably formed its core.

    At that time, what is now the west coast of North America was attached to Australia and Antarctica! Notice the east coast of North America was sitting next to western South America.
  • Widespread glacial deposits laid down during the Late Proterozoic indicate that Earth was locked in a major Ice Age. This is no surprise, because the configuration of the continents has a strong effect on Earth's climate. During continental collision and supercontinent formation, especially when they pile up near one of the poles, the world enters a global Ice Age.

Reconstructing ancient Earth

These remarkable figures are produced by C.R. Scotese and the PALEOMAP project. Geologists call these illustrations paleogeographic reconstructions, because they illustrate the reconstructed geography of our Earth at some time in the past.

Making a paleogeographic reconstruction begins by examining several lines of evidence including: paleomagnetism, magnetic anomalies, paleobiogeography, paleoclimatology, and geologic history. By combining all available evidence, geologists are able to construct paleogeographic maps, such as these, that interpret how the geography might have appeared at a specific location and time in the past. Paleogeographic maps are continually being refined as more evidence is collected.

To find out more about how paleogeographic reconstructions are made visit the PALEOMAP project site.

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Scotese, C. R., 1997. Paleogeographic Atlas, PALEOMAP Progress Report 90-0497, Department of Geology, University of Texas at Arlington, Arlington, Texas, 37 pp.

| Into Earth | | Putting the pieces toge ther | | Action at the edges |
| National Parks by Tectonic Regions |
| Earth through time | | Detailed version: This Dynamic Earth |


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