Crack in the Ground

{{Short description|Volcanic fissure about 3.2 kilometers (2 miles) long}}

{{Use mdy dates|date=February 2025}}

Image:Crack in the Ground (9735636349).jpg

Crack in the Ground is a volcanic fissure about {{convert|2|mi}} long

{{cite web |title=Crack In The Ground |url=http://www.fortrockoregon.com/Crack.html |archive-url=https://web.archive.org/web/20160330064635/http://www.fortrockoregon.com/Crack.html |archive-date=2016-03-30 |accessdate=2007-10-16 |publisher=Fort Rock Museum}} with depths measuring nearly {{convert|30|ft|0}} below ground level in Central Oregon, United States. The formation of the fissure occurred approximately between 700,000 and 12,000 years ago.{{cite web

| url = https://www.researchgate.net/publication/258466304_Paleoseismology_of_Crack-in-the-Ground_Fault_Central_Oregon

| title = Paleoseismology of Crack-in-the-Ground Fault, Central Oregon

| publisher =

| date=December 2011

| access-date = 2019-08-15

}}

The eruptions from the Four Craters Lava Field were accompanied by a slight sinking of the older rock surface, forming a shallow, graben-like structure about {{convert|2|mi}} wide and extending to the south into an old lake basin. Crack in the Ground marks the western edge of this small, volcano-tectonic depression. The crack is the result of a tension fracture along a hingeline produced by the draping of Green Mountain lava flows over the edge of upthrown side of the concealed fault zone. The fissure is located at the southwest corner of Four Craters Lava Field.{{cite web

| url = http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/fourcraters.shtml

| archive-url = https://web.archive.org/web/20101109053810/http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/fourcraters.shtml

| title = Four Craters Field

| publisher = US Forest Service

| archive-date = 2010-11-09

| url-status = dead

| access-date = 2017-10-16

}} Hikers can walk the length of the main crack and explore its tributaries.