Q: If the relief well set to be completed in August doesn't work, will the Deepwater Horizon eventually run dry?
A: It depends on what you mean by "eventually." Most parties agree that there is a large amount of oil at this site -- BP has been quoted as saying the amount is "huge." The underground formation that the rig was probing has been estimated to hold anywhere from 50 million to a billion barrels of oil that could be extracted economically. If 20,000 barrels a day is streaming from the well with nothing obstructing the flow, it could maintain that level for several years.
According to Ian MacDonald, an oceanographer at Florida State University, who has been studying the size of the spill, "not all the oil would flow out, due to what the oil field types would call 'natural bridging' of the well -- that means self-plugging. Nonetheless, there is no immediate prospect of 'running out' of oil and gas that can get out if they can't plug this damned thing."
Q: Why are the blobs washing up on the beach called tarballs? Isn't it a product of the spilled oil?
A: Yes, the little clumps called tarballs are, in fact, bits of oil. How do they transform from streams of viscous oil to hardened clumps of goo? Blame it on the weather.
According to the National Oceanic and Atmospheric Administration, when crude oil floats on the ocean surface, its physical characteristics change. During the first few hours of a spill, the oil spreads into a thin slick. The slick soon separates into smaller patches, courtesy of winds and waves. Then, NOAA says, various physical, chemical and biological processes change the appearance of the oil. These processes are generally called weathering.
As time goes on, some oil evaporates, according to NOAA, but some mixes with water to "form an emulsion that often looks like chocolate pudding." These chocolate-pudding-like oil patches continue to be pulled and torn by winds and waves until they end up as small balls of hardened oil washing ashore.
So, the short answer is that tarballs are small bits of weathered oil that take their name from their appearance, not their composition.
-- Sources: Minerals Management; ABC News; White House; NOAA