How often do oil spills occur daily?

Do crude oil spills occur naturally? If so, where, why, and how often?

• (such as petroleum leaking into the ocean in tectonic fault zones or something of the like)

• Answer:

  Natural petroleum seeps are not uncommon and are found in most of the major petroleum producing regions of the world, both underwater and on land. The La Brea tar pits in Los Angeles are one famous example, and others can be found in the Santa Barbara Basin of California, the Gulf Coast of the southern US, the Persian Gulf, Venezuela, Nigeria, the Persian Gulf and the Caspian Sea region (to name a few). Because of its low density relative to rock (and water), oil has a natural tendency to "float" upward, either through natural porosity in the rock or along faults or fractures. Once in the water, oil can wash ashore through the action of wind or waves. The total volume of oil leaked naturally is high globally, but because it tends to be widely distributed in space and at a relatively slow rate such seeps do not generally have the negative consequences on wildlife that manmade spills do. In fact some bacteria are actually adapted to feed on the hydrocarbons and other organisms feed on these bacteria leading to the development of "seep communities" around offshore oil seeps with a characteristic fauna similar in some ways to the vent faunas found at mid-ocean spreading ridges. Natural petroleum seeps can trap animals and kill them, however, sometimes leading to sites of spectacular fossil preservation (e.g. the La Brea tar pits). An excellent, more detailed summary can be found here: http://www.theoildrum.com/node/6552