How oil spills lay low.
Some of the oil from the 2010 Deepwater Horizon disaster is missing in action. Scientists may now know where it went, as Beth Mole explained in "Oil from BP spill sits on seafloor" (SN: 11/29/14, p. 16). Oil is less dense than water, so the idea of it settling near the bottom of the ocean confused some readers. "Shouldn't it float?" asked Gary Baker.
Two major factors kept some of the Deepwater Horizon oil from surfacing, says lead author David Valentine of the University of California, Santa Barbara. First, oil shot out of the well with such force that some of it fragmented into tiny droplets. They were too small to push through the cohesive forces that hold water molecules together and were trapped below the surface. Second, some components of the oil are water-soluble and simply dissolved in the surrounding ocean.