Volume: how much oil was this?
The area affected by the spill measures only one dimension of how much oil entered the Gulf — the size of the sheen that could be seen on the top of the water. The other dimension is how deep that oil is below the surface. Oil only 1 micron (µm) thick (that’s 0.000001 meters — less than 1/3,000th the thickness of a human hair) can leave a surface sheen that is visible by satellites. In many cases, the oil is much thicker than that, but scientists don’t know just how thick.
To estimate the minimum amount of oil entering the Gulf, SkyTruth used the thinnest amount of oil it would take to change the surface characteristics of the water and be detected by satellite images, or 1 µm. It then multiplied that amount by the area of the spill to calculate the volume.
Exercise: use the calculations worksheet to calculate the volume of oil in the oil spill for each date using the formulas provided.
To calculate its minimum estimate, SkyTruth assumed the oil was the thinnest possible and still be detected by satellite images. But on April 27, one week after the spill, a BP executive stated that 3% of the spill area was actually 100 µm thick. If 3% of the spill area on April 27 was 100 µm thick and 97% was at least 1 µm thick, how much oil had spilled into the Gulf of Mexico in the first week?