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

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