The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on an occasional schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Thursday, January 16, 2014

January 12. Cratons of North America


By Richard I. Gibson


Continental crust contains most of the lighter elements in the solid earth, things like aluminum, silicon, and carbon. Continental crust is less dense than the basaltic oceanic crust, an a lot less dense than the mantle.

The continents are kind of like light blobs that forms on top of the iron and other dense stuff that mostly sank deeper into the earth. The separation of light and dense crust happened pretty early in the earth’s formation. We talked about that on January 2. And the blobs have been drifting around the surface ever since.

Map from U.S. Geological Survey.

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