Asphalt Lakes And The Secrets in Their Depths

Some of the world’s strangest lakes are filled not with water but with asphalt, also known bitumen, the same material that roads are paved with.

The great majority of asphalt that is used today is derived from petroleum, but asphalt is also found in concentrated form in nature. Sometimes they seep from the ground and create large puddles known as tar pits or asphalt lakes. At other times, they are found soaked in sands, as in Athabasca oil sands in northeastern Alberta, Canada, which is the world’s largest deposit of natural bitumen. Asphalt is also known to erupt in underwater volcanoes, but these are relatively rare and were discovered only in 2003.

There are only a few known large asphalt lakes around the world. The largest of these is located in the village of La Brea in southwest Trinidad, and is called the Pitch Lake. The lake covers about 40 hectares and is reported to be 75 meters deep. The liquid asphalt is so thick and viscous, that the surface can be walked upon. But if you stand on the surface for too long, you will slowly sink into it. Although the lake appears quiescent the asphalt is slowly moving and you can see flow lines on the surface. As the tar moves, sometimes prehistoric trees and other objects that had fallen into the lake appears, then disappears and then reappears again.

The lake was created thousands of years ago by the process of subduction when the Caribbean continental plate was forced under another plate. This opened fault lines that allowed crude oil from deep underground deposits to rise to the surface, where it collected in a volcanic crater. The air caused lighter elements of the oil to evaporate, leaving behind the heavy asphalt, a mix of oil, clay and water.

The lake was discovered in 1595, and has been commercially mined since 1867. An estimated 10 million tons of asphalt has been extracted from the Pitch Lake so far. About 6 million tons of asphalt is still left.

The La Brea Pitch Lake is also a tourist attraction and brings about 20,000 visitors annually. Sometimes people swim in the waters of the pitch lake because they believe it has therapeutic properties.