Hole-in-the-Ground is a large maar (volcanic explosion crater) in the Fort Rock–Christmas Lake Valley basin of Lake County, central

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

, northeast of

Crater Lake Crater Lake ( Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fill ...

, near Oregon Route 31. It is about across, a little longer N-S than E-W. Its floor is about below the surrounding ground level and has a rim that rises above, the highest point on the east side. The crater formed during the late

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

, between 13,500 and 18,000 years ago, at which time the Fort Rock basin was a lake and the location was near the shore. Basaltic

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

intruding near the surface flashed ground water to steam, which blew out overlying rock and soil, along with some juvenile material. As material slid into the hole formed, it closed the vent and the process repeated, eventually forming the huge hole. Blocks as large as in size were flung as far as from the crater. To the west of Hole-in-the-Ground is an even bigger maar, , but older and more eroded, called

Big Hole The Kimberley Mine or Tim Kuilmine ( af, Groot Gat) is an open-pit and underground mine in Kimberley, South Africa, and claimed to be the deepest hole excavated by hand, although this claim is disputed. History and size The first diamonds he ...

References

Maars of Oregon Landforms of Lake County, Oregon Volcanoes of Oregon {{US-geology-stub

See also

References