Hole-in-the-Ground

Hole-in-the-Ground
	Hole-in-the-Ground, panoramic view
height	1420 m
location	United States ( Lake County , Oregon )
Mountains	Cascade Range (Cascade Range)
Coordinates	43 ° 24 '40 " N , 121 ° 11' 52" W Coordinates: 43 ° 24 '40 " N , 121 ° 11' 52" W
Type	Maar
Last eruption	about 50,000 to 100,000 years ago

Hole-in-the-Ground is a large maar crater in the Fort Rock Basin , Lake County , Oregon near 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 bottom is 150 m lower than the surrounding landscape and 185 m lower than its edge, the highest point of which is on the east side. Hole-in-the-Ground is to the west and near the larger but not so well preserved maar crater Big Hole .

Emergence

The crater was formed during the late Pleistocene 13,500 to 18,000 years ago. At that time, Fort Rock Basin was a lake and the maar was near its shore. Basaltic magma intruded into the rock near the surface along tectonic faults and came into contact with the groundwater at a depth of approximately 300 to 500 m. The subsequent phreatomagmatic explosion blew out the overlying rock and soil above along with some volcanic material. The process was repeated at least four times, so that eventually the large hole was formed. The explosions generated immensely high pressures and hurled boulders up to 8 m in diameter up to a distance of 3.7 km from the crater. Similar processes have also led to the formation of the large Eifel maars, for example in the case of the Meerfelder Maar or the Dreiser Weiher .

environment

Aerial view of the crater

Hole-in-the-ground part is the volcanic Cascade Range (Cascade Range), which extends from northern California to southern British Columbia extends. The subsurface of the cascade chain consists of fragments of the earth's crust that have been added to the west coast of North America ( accretion ) by the subduction of the Juan de Fuca plate since the Paleogene . For about five million years, the volcanic activity caused by the melting of the subducted earth's crust has been particularly brisk. Due to the composition of the rising magma ( andesite and dacite ), which is influenced by the crust material, volcanism is often explosive.

Individual evidence

^ Deschutes & Ochoco National Forests - Hole-in-the-Ground Volcano . USDA Forest Service . December 24, 2003. Retrieved September 19, 2008.
^ ^A ^b G. H. Heiken, RV Fisher and NV Peterson: A Field Trip to the Maar Volcanoes of the Fort Rock - Christmas Lake Valley Basin, Oregon . In: Geological Survey Circular 838: Guides to Some Volcanic Terrances in Washington, Idaho, Oregon, and Northern California . United States Geological Survey . March 28, 2006. Retrieved May 22, 2007.
^ Gerhard H. Eisbacher: North America . In: Geology of the Earth . 1st edition. tape 2 . Ferdinand Enke Verlag, Stuttgart 1986, ISBN 3-432-96901-5 .

[USDA-1] Deschutes & Ochoco National Forests - Hole-in-the-Ground Volcano . USDA Forest Service . December 24, 2003. Retrieved September 19, 2008.

[USGS838-2] A ^b G. H. Heiken, RV Fisher and NV Peterson: A Field Trip to the Maar Volcanoes of the Fort Rock - Christmas Lake Valley Basin, Oregon . In: Geological Survey Circular 838: Guides to Some Volcanic Terrances in Washington, Idaho, Oregon, and Northern California . United States Geological Survey . March 28, 2006. Retrieved May 22, 2007.

[3] Gerhard H. Eisbacher: North America . In: Geology of the Earth . 1st edition. tape 2 . Ferdinand Enke Verlag, Stuttgart 1986, ISBN 3-432-96901-5 .