And, since they were created underground and not from flowing surface water, not all these passageways have an opening to the outside world.

并且，由于它们是在地下形成的，而不是由地表水流形成，所以并不是所有的通道都有通向外部世界的开口。

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The latter two sources are limited to those few areas where surface water seeps down through underground faults or fractures to reach deep rocks heated by the recent activity of molten rock material.

后两种来源局限于少数区域，在这些区域，地表水通过地下断层或断裂往下渗透，从而接触到被近期的熔岩活动加热的深层岩石。

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In 1972 UNICEF initiates a project to install tube Wells that pull pure underground water to the surface.

1972年联合国儿童基金会启动一个项目旨在打口深井并将纯净的地下水引到地表。

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But, like Larderello, today's geothermal electricity comes from unique geologies, where hot rocks and underground water sit together, close to the surface of the earth.

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That seemed to support the notion that underground liquid water may reside close enough to the surface in some places that it can seep out periodically.

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Detailed studies of the surface indicate that these were formed by a lake caused by the flow of underground water that periodically made its way to the bottom of the crater.

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