GEOL 104 Dinosaurs: A Natural History

Fall Semester 2006
Plate Tectonics and the Earth Engine

Great geological discovery of the 20th Century: Plate Tectonics

Some early indication that continents may have moved in past:

Alfred Wegener proposed model of continental drift (in 1915):

However, big flaws in continental drift:

Idea was considered unlikely by many geologists.

In 1940s through 1960s, new information. Fossil, radiometric, and magnetic dates showed that ocean basins were not ancient, but that they got younger closer to mid-ocean ridges, where new rock was forming: called "sea-floor spreading".

In 1960s, the models of continental drift and sea-floor spreading were combined to form plate tectonics.

Heat from Earth's core moves plates, forming mountain ranges at subduction and collision boundaries. Weather erodes uplifting mountains, wind and water and ice transports sediment to depositional environments. Over time, material becomes buried.

Plates wander over Earth's surface, so continents move from tropics to poles or back. Also, action of mid-ocean ridges causes sea levels to rise up (flooding continents) or lower (draining continents). (Current situation is very low sea level).

Big change from the 1960s-1970s model: now recognize there are LOTS of little plates (terranes) rather than just a few big plates.

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Last modified: 14 July 2006