Our primary topic this week is the Theory of Plate Tectonics, with an emphasis on how the dynamic Earth has affected the evolution of life. We can start with this beautiful world map, showing continents, mountains, ridges, transform faults and trenches in the Pacific and Atlantic Oceans. An excellent, world-class site for ancient maps of the evolving Earth is the Paleomap Project. The US Geological Survey has a thorough site called This Dynamic Earth which covers the basics of plate tectonic theory. The University of Texas hosts The Plates Project which concentrates on producing accurate plate reconstructions of the past. Of course, plate tectonics is an ideal subject for web animations. PBS reviews plate tectonic theory with a simple and clear set of images and animations. Here is a global history of continental movement in the last 750 million years from UC Berkeley. This YouTube video on plate tectonics is narrated with a cool Irish accent.
Here, by the way, is a description of the Ordovician fossiliferous marine limestone at the top of Mount Everest. That fact alone shows the incredible dynamic nature of the Earth’s crust.
As for the primary effect of plate tectonics on us, visit the real-time global earthquake website maintained by the U.S. Geological Survey. You will see how very common earthquakes are around the world, and where you do not want to buy a house. PBS has a nice set of animations of earthquakes from a global perspective, along with volcanoes and the geological phenomenon we now know all too well, tsunamis. Here are summary pages on the devastating 2004 tsunami in the Indian Ocean, the January 2010 Haiti Earthquake and the 2011 earthquake and tsunami in Japan. The new page on last month’s terrible tsunami in Indonesia is now available as well. Note that geologists are still debating the origins of the tsunami.
Geology in the News –
Here’s a nice summary of the latest ideas on the evolution of modern birds. It appears that the Cretaceous extinctions may have sped up their evolution, primarily by selecting for small body sizes which have higher rates of evolution.
Speaking of bird evolution, here’s that story of the “messy new species” of dinosaur-bird found in China. (This was on the back of your Quiz #5.) “The 127-million-year-old species, which they have named Jinguofortis perplexus, retains other features of its dinosaur ancestors, such as claws on the fingers of its wings, a jaw with tiny teeth rather than a beak, and a fused shoulder girdle. That last trait is seemingly poorly adapted to flight, hence the name perplexus.”
Here’s a strange new dinosaur from the Jurassic of South Africa: Ledumahadi mafube. It “crouched like a cat” and had strangely flexible forelimbs for a 12-ton animal. We are in a golden age of dinosaur paleontology. There are new discoveries every week.