Hole-in-the-Ground

Infobox Mountain
Name = Hole-in-the-Groundcite web | title=Deschutes & Ochoco National Forests - Hole-in-the-Ground Volcano | publisher=USDA Forest Service | date=2003-12-24 | url=http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/holeground.shtml | accessdate = 2007-05-22 ]
Photo = Holeintheground.jpg
Caption = Hole-in-the-Ground
Elevation = convert|4650|ft|m|lk=on
Location = Lake County, Oregon, USA
Range = Cascades
Prominence =
Coordinates = coord|43.4029089|-121.1983457|format=dms|region:US_type:mountain [GNIS|1143660]
Topographic

Type = maar
Volcanic_Arc/Belt =
Age =
Last eruption = about 50,000 to 100,000 years ago
First ascent =
Easiest route =

Hole-in-the-Ground is a large maar (explosion crater) in the Fort Rock Basin of Lake County, central Oregon, northeast of Crater Lake, near Oregon Route 31.

It is about convert|1600|m|mi|1|sp=us across, a little longer N-S than E-W. Its floor is about convert|150|m|ft|sigfig=2|sp=us below the surrounding ground level and has a rim that rises convert|35|to|65|m|ft|sigfig=2|sp=us above, the highest point on the east side. The crater formed during the late Pleistocene, 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 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.cite web | last=Heiken | first=G. H. | coauthors=R. V. Fisher and N. V. Peterson | title=A Field Trip to the Maar Volcanoes of the Fort Rock - Christmas Lake Valley Basin, Oregon | work=Geological Survey Circular 838: Guides to Some Volcanic Terrances in Washington, Idaho, Oregon, and Northern California | publisher=United States Geological Survey | date=2006-03-28 | url=http://www.cr.nps.gov/history/online_books/geology/publications/circ/838/roadlog6.htm | accessdate = 2007-05-22 ] Blocks as large as convert|8|m|ft|0|sp=us in size were flung as far as convert|3.7|km|mi|1|sp=us from the crater.cite book | last=Wood | first=Charles A. | coauthors = Jurgen Kienle | title=Volcanoes of North America | publisher=Cambridge University Press | date=1993 | pages=p. 205 |isbn = 0-512-43811-X ]

To the west of Hole-in-the-Ground is an even bigger maar, convert|1820|m|mi|1|sp=us, but older and more eroded, called Big Hole.

References


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