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USGS Geology in the Parks

View of Earth, 425 million years ago Tmescale timebar 425 million years ago

425 million years ago


What's going on here?

  • Find Baltica (northern Europe) again. By 425 million years ago, Baltica collided with North America's core, building a huge Himalaya-like mountain range. Notice that Baltica is close to the Equator. It shouldn't be any surprise that there are 425 million year old tropical fossils found in Scandinavia!
  • But that's not all! Avalonia (England and USA's New England) has moved northward and is just beginning to collide with Laurentia along a southern subduction zone. As you can see, much of the northern Appalachian region of North America owes its origins to Early Paleozoic plate collisions.
  • Now find Florida. That's it, far to the south and part of Africa! You'll have to wait for a few million years before the basement rocks of Florida start heading north.

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.

Move forward or back in time.
| Today | 0.018 | 14 | 50 | 69 | 94 | 152 | 195 | 237 | 255 | 306 | 356 | 390 | 425 | 458 | 514 | 650 |
Time in millions of years. Jump back to visit any time!

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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