Gerald Herbert, File, Associated Press
In this April 21, 2010 file aerial photo taken in the Gulf of Mexico more than 50 miles southeast of Venice on Louisiana's tip, the Deepwater Horizon oil rig is seen burning. New research shows that the BP oil spill left an oily “bathub ring” on the seafloor that’s about the size of Rhode Island.

WASHINGTON — New research shows that the BP oil spill left an oily "bathub ring" on the sea floor that's about the size of Rhode Island.

The study by David Valentine, the chief scientist on the federal damage assessment research ships, estimates that about 10 million gallons of oil coagulated on the floor of the Gulf of Mexico around the damaged Deepwater Horizons oil rig. Valentine said the spill left other splotches containing even more oil.

The rig blew on April 20, 2010 and spewed 172 million gallons of oil into the Gulf through the summer. Scientists are still trying to figure where all the oil went and what effects it had.

This study is in Monday's Proceedings of the National Academy of Sciences.