Hundreds of thousands of years ago, undersea geysers spewed more than 10 cubic kilometers of sand across the floor of the North Sea. Researchers discovered the resulting blob of material—by far the largest single volume of sand ever extruded from an underground reservoir , they claim—by studying seismic data and samples drilled from the ocean bottom during oil and gas exploration off the southwestern coast of Norway. The fine- to medium-grained sand in the layer (depicted above in various shades of red, green, and blue; samples drilled from sites marked with red dots) covers an area of at least 260 square kilometers and is 125 meters thick in some spots, the researchers report online today in Geology. Large volumes of sandy water spewed from beneath a thick, impermeable layer of clay and onto the ocean floor during a lengthy period, possibly on and off for many decades, sometime between 400,000 and 2.6 million years ago, the researchers say. The volume of sand in the layer, which has been long smothered by seafloor sediments that have accumulated since its eruption, is enough to bury all of Manhattan to a depth of 160 meters.
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