Workers construct a dam to keep oil from entering wetlands on Elmer's Island in Louisiana. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP

Oil leaks into the Gulf of Mexico from the end of the pipe that was supposed to pump oil from the sea floor before the Deepwater Horizon oil rig exploded and sunk last month. BP PLC/AP hide caption

itoggle caption BP PLC/AP

Researcher Sydney Levitus' work frequently transports him -- at least figuratively -- back to the helms of ships that plied the seas many decades ago. iStockphoto.com hide caption

itoggle caption iStockphoto.com

A boat with an oil boom tries to contain the spill, approximately seven miles from where the oil rig sunk last week. Gerald Herbert/AP hide caption

itoggle caption Gerald Herbert/AP

A satellite captured the erupting of the Okmok Caldera volcano on Umnak Island in Alaska in July 2008. The volcano spewed both steam and ash. NASA/AP hide caption

itoggle caption NASA/AP