Researchers from Northwestern University and the University of New Mexico report evidence for potentially oceans worth of water deep beneath the United States. Though not in the familiar liquid form -- the ingredients for water are bound up in rock deep in the Earths mantle1 -- the discovery may represent the planets largest water reservoir. The presence of liquid water on the surface is what makes our blue planet habitable, and scientists have long been trying to figure out just how much water may be cycling between Earths surface and interior reservoirs through plate tectonics（板块架构论）.Northwestern geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma located about 400 miles beneath North America, a likely signature of the presence of water at these depths. The discovery suggests water from the Earths surface can be driven to such great depths by plate tectonics, eventually causing partial melting of the rocks found deep in the mantle.The findings, to be published June 13 in the journal Science, will aid scientists in understanding how the Earth formed, what its current composition and inner workings are and how much water is trapped in mantle rock.Geological processes on the Earths surface, such as earthquakes or erupting volcanoes, are an expression of what is going on inside the Earth, out of our sight, said Jacobsen, a co-author of the paper. I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades.Scientists have long speculated that water is trapped in a rocky layer of the Earths mantle located between the lower mantle and upper mantle, at depths between 250 miles and 410 miles. Jacobsen and Schmandt are the first to provide direct evidence that there may be water in this area of the mantle, known as the transition zone, on a regional scale. The region extends across most of the interior of the United States.Schmandt, an assistant professor of geophysics at the University of New Mexico, uses seismic2 waves from earthquakes to investigate the structure of the deep crust and mantle. Jacobsen, an associate professor of Earth and planetary sciences at Northwesterns Weinberg College of Arts and Sciences, uses observations in the laboratory to make predictions about geophysical processes occurring far beyond our direct observation.The study combined Jacobsens lab experiments in which he studies mantle rock under the simulated high pressures of 400 miles below the Earths surface with Schmandts observations using vast amounts of seismic data from the USArray, a dense3 network of more than 2,000 seismometers（地震仪） across the United States.Jacobsens and Schmandts findings converged4 to produce evidence that melting may occur about 400 miles deep in the Earth. H2O stored in mantle rocks, such as those containing the mineral ringwoodite（尖晶橄榄石）, likely is the key to the process, the researchers said.
点击收听单词发音
1 mantle n.斗篷，覆罩之物，罩子；v.罩住，覆盖，脸红 参考例句： The earth had donned her mantle of brightest green.大地披上了苍翠欲滴的绿色斗篷。 The mountain was covered with a mantle of snow.山上覆盖着一层雪。
相关文章推荐
