Photos Like a Truck on Ice
"We tried to use different kinds of loads to probe different properties of the lithosphere," Thatcher said. Mountains are one load that the crust responds to on the scale of tens of millions of years. Another load is glaciers, which grow and shrink on a mid-range timescale of hundreds to tens of thousands of years. Briefest of all loads are earthquakes, which trigger adjustments in the crust on the scale of just days, weeks and months. On the earthquake timescale, a patch of crust behaves rigidly, as does the mantle under it. Using the ice/truck analogy, the ice is thick and strong. At the glacial timescale, however, the mantle behaves more like jelly, effectively limiting the more rigid "ice" to just the crust. Finally, on the mountain-load timescales of millions of years, only the upper crust really behaves rigidly, making for the thinnest "ice," which bows the most under the weight of a truck. "It's a little different way of trying to put all of the pieces together than has been done before," Thatcher told Discovery News. "It turns out that what happens on the short term and what happens on the million-year timescale is different." Related Links: |
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