CompuServe Messages

Hi, Megan– "Plate tectonics" is the current theory that the Earth's crust is made of rigid plates of rock that "float" on the deeper rocks of the Earth (the mantle) which are under such pressure that they become able to flow almost like a liquid (though much more slowly, at speeds measured in inches per year). These crustal plates move, driven by currents in the mantle (again too slowly to know about without making very careful long term measurements), and the continents that sit on top of some of them are carried along by these movements. When two plates are pushed together, most often one pushes on top of and over the edge of the other, forcing the other to dive into the mantle; this creates the deep "trenches" under the ocean and volcanoes and earthquakes on the surface of the upper plate. The Pacific Ocean sea floor is a plate that is being forced under by the plate carrying Asia, thus Japan and other places near where the plates meet have many quakes and volcanoes, and trenches are found in the Pacific nearby. Where the plates are pulling apart, mantle rock is melted and wells up to fill in the gap, creating more crustal rock to make up for what is destroyed when plates collide. Is this the sort of thing you are looking for? Please feel free to ask any questions I have left you with. –Doug