Hole-in-the-Ground

Hole- in-the- Ground, panoramic view

Hole- in-the- Ground ( " hole in the ground " ) is a large maar crater in the Fort Rock Basin, Lake County, Oregon near the Oregon Route 31, northeast of Crater Lake. It has a slightly oval diameter of 1,600 m, the long axis lies in a north-south direction. Its soil is 150 m deeper than the surrounding landscape and 185 m lower than its edge, whose highest point is located on the east side. Hole-in- the-ground lies to the west and near the larger, but not so well preserved Maarkraters Big Hole.

Formation

The crater was formed during the late Pleistocene 13500-18000 years ago. At that time, Fort Rock Basin a lake, and the maar lay near its shore. Basaltic magma intruded along tectonic faults in the rock near the surface and came in about 300 to 500 m depth in contact with groundwater. The following phreatomagmatic explosion blew the overlying rock and soil from above along with some volcanic material. The process was repeated at least four times, so that eventually the large hole was formed. The explosions produced immensely high pressures and hurling boulders of up to 8 m in diameter up to a distance of 3.7 km from the crater. Similar processes have also led to the emergence of large Eifelmaare, such as in the case of sea fields Maar or Dreiser Weiher.

Surroundings

Hole- in-the- Ground is part of the volcanic Cascade Range ( Cascade Range), which extends from northern California to southern British Columbia. The base of the Cascade Range consists of fragments of the Earth's crust that have been added since the Paleogene by the subduction of the Juan de Fuca plate to the west coast of North America ( accretion ). Since about five million years ago volcanic activity caused by the melting of the subducted crust is particularly active. Due to the influenced by crustal material composition of the ascending magma ( andesite and dacite ) volcanic activity is often explosive.