The Earth's plates in motion
| The applications to the theory of Plate Tectonics can help scientists understand not only the present state of the Earth's crust, but past and future conditions as well. Through geologic time, the arrangement of the continents and land masses upon the face of the planet (along with other orbital and axial geometries of Earth) could have had profound impacts on climate, and hence affected plant and animal life. Data collected by geophysicists suggests that the continents have been in motion for millions of years. The sections of the Earth's crust have been colliding, separating, folding, rising, falling and recycling over time. Based on rock types and ages, as well as fossil information, scientists can deduce where a continent or island may have been in the past (in relation to the Earth's equator), and with careful measurement detect the speed and direction of the continents today. From there, computer models can even predict where these continents may be arranged in the future! The animation shown here is a model which hypothesizes the appearance of the world from 740 million years ago, up to the present day. The equator runs left to right through the middle of the map, with the poles at the top and bottom (land masses near the edges of the map appear to move faster because of the nature of this particular projection). Notice how the majority of the land surface was joined together around 230 million years ago. This supercontinent is commonly referred to as Pangaea (meaning "all-Earth"), originally proposed by meteorologist Alfred Wegener in 1915. To support his idea of the moving land masses (which he called "continental drift"), he demonstrated the similarity in geometry of the coastlines of eastern South America and western Africa, which looked like they could fit together like jigsaw puzzle pieces. It seemed logical to him that the two continents were once joined, and then drifted apart. He was also able to illustrate striking similarities between both coastlines of rock types, climatic histories, and fossil records. |
Credit: Dr. Chris Scotese, University of Texas
For more info: http://www.geog.ucsb.edu/~dylan/mtpe/geosphere/topics/pt/plate_tectonics.html