The Pitch Lake is the largest natural deposit of asphalt in the world, estimated to contain 10 million tons. It is located in La Brea in southwest Trinidad, within the Siparia Regional Corporation. The lake covers about 100 acres and is reported to be 250 feet deep.
Pitch Lake is a popular tourist attraction, that includes a small museum, from where official tour guides can escort people across the lake.
The lake is mined for asphalt by Lake Asphalt of Trinidad and Tobago. The origin of The Pitch Lake is related to deep faults in connection with subduction under the Caribbean Plate related to Barbados Arc.
The lake has not been studied extensively, but it is believed that the lake is at the intersection of two faults, which allows oil from a deep deposit to be forced up. The lighter elements in the oil evaporate under the hot tropical sun, leaving behind the heavier asphalt.
According to en.wikipedia