“Pitch lakes” represent surface deposits of oil bubbled up from subterranean reservoirs through faults or fissures, often formed when the layers of sedimentary rock that contain hydrocarbons are folded or squashed in tectonic upheaval. Evaporation removes the oil’s lighter elements to produce mucky ponds of asphalt, colloquially called pitch or tar, and technically referred to as bitumen.
Such seeps are widely scattered across the planet, both on land and in the oceans. One of the world’s biggest is Pitch Lake along Trinidad’s western coast, visited by Sir Walter Raleigh in 1595. A bizarre tract of semisolid asphalt strung with oily channels and pools, the lake — a popular tourist attraction — spans some 100 acres and plunges to 250 feet deep.
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