The Pitch Lake

Ten million tons of asphalt you can walk across

The Pitch Lake, in the village of La Brea in southwest Trinidad, is the largest natural deposit of bitumen in the world. It covers about 100 acres, is reported to be 250 feet deep in the centre, and holds an estimated ten million tons of pitch, in a hollow about 1,200 yards from the sea just south of a 140-foot hill. The asphalt is an emulsion of water, gas, bitumen and mineral matter, mostly fine silica sand with a little very fine clay. In places soft material wells up with a strong release of gas, mainly methane with carbon dioxide and hydrogen sulphide; it slowly hardens like the rest, and fresh material breaks out somewhere else.

The lake is thought to sit where two deep faults cross, linked to subduction under the Caribbean Plate, letting oil from a deep deposit be forced up. In the tropical heat the lighter parts evaporate and the heavy asphalt stays. It is alive, too. Researchers have found archaea and bacteria in it, with novel species, as well as fungi able to live on asphaltenes alone. At one time, as the Gulf of Paria broke in through the Bocas, waves reached a surface sheet of asphalt covering perhaps 3,000 acres, which flowed down the forming cliffs and protected them; large masses still lie in the sea off La Brea.

The Amerindians who told Walter Raleigh where the lake was had their own story of it. After a victory over a rival tribe, carried away in celebration, they cooked and ate the sacred hummingbirds believed to hold the souls of their ancestors, and their winged god opened the earth and conjured a lake of pitch to swallow the whole village. Amerindian pottery, a cranium and the remains of prehistoric animals have come out of the pitch. Raleigh used it to caulk his ship in 1595 and praised it as most excellent, since it did not melt in the sun like the pitch of Norway.

In the 1840s Abraham Gesner first obtained kerosene from a sample of its bitumen. In 1887 Amzi Barber, the Asphalt King, won a 42-year monopoly concession, and much of the first asphalt paving in New York City and Washington came from here. Lake Asphalt of Trinidad and Tobago, incorporated in 1978, still mines it, and about 20,000 visitors a year cross it with official guides from the small museum; people occasionally swim in its waters, which some call therapeutic for the sulphur.