Crack in the Ground is a volcanic fissure over two miles (3 km) long and up to 70 feet (21 m) deep in central Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

, US.
The eruptions from the Four Craters Lava Field were accompanied by a slight sinking of the older rock surface, forming a shallow, graben

Graben

In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....

-like structure about 3 kilometers 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.
It is located in the southwest corner of Four Craters Lava Field

Four Craters Lava Field

Portions of this article include public domain text from the USFS .Four Craters Lava Field is a basaltic volcanic field located south east of Newberry Caldera in the U.S. state of Oregon. The volcanic field covers about 30 square kilometers. Four Pleistocene cinder cones are the source of the flows...

 in the Deschutes National Forest

Deschutes National Forest

The Deschutes National Forest is a United States National Forest located in parts of Deschutes, Klamath, Lake, and Jefferson counties in central Oregon. It comprises 1.8 million acres along the east side of the Cascade mountains. In 1908, the Deschutes National Forest was established from parts...

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