QUITO, Ecuador (AP) -- A volcano has begun to erupt on one of the Galapagos Islands known for its diverse flora and fauna, including the archipelago's famed giant tortoises, park officials said Sunday.The 1,500-meter (4,920-feet) Sierra Negra volcano, located on seahorse-shaped Isabela, the largest of the Galapagos Islands, began erupting late Saturday afternoon, producing three lava flows, officials from the Galapagos National Park told The Associated Press in a statement.It has not yet been determined whether the island's plant and animal life have been affected.Many Galapagos tortoises, some of which have a lifespan of more than 150 years, live near volcano craters.Puerto Villamil on Isabela's southern coast is home to 2,000 people, but the eruption posed "no risk to the population," the statement said. Tourist centers near Sierra Negra were closed as a precaution.The Galapagos Islands, located 1,000 kilometers (625 miles) off Ecuador's Pacific coast, were declared a UNESCO World Heritage Site in 1979 for their exotic wildlife such as marine iguanas and blue-footed boobies.The islands' rich biodiversity inspired Charles Darwin's theory of evolution.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.