Appropriate Point of Reference

http://bigthink.com/blogs/strange-maps

          The above picture depicts BP's “Deep Horizon Rig”, which spilled about 50 million gallons of oil into the Gulf of Mexico. This geographic catastrophe began on April 20th and continued for 86 days. The above map to the right shows how much area was affected by the spill (10, 000 square miles). When looking at the map depicting the spill over the ocean it doesn’t seem quite as ominous as when it is superimposed over a land map close to home.

This site http://www.ifitweremyhome.com/disasters/bp can move the oil blob around for you and explains a little about Mercator projection as well.