Crack in the Ground, Fissure vent near Christmas Valley, Oregon, United States.

Crack in the Ground is a volcanic fissure about 2 miles (3.2 km) long in the Four Craters Lava Field of Lake County, central Oregon, reaching nearly 30 feet (9 m) below ground level. It marks the western edge of a shallow graben-like depression formed when Four Craters eruptions sank the older rock surface. Hikers can walk the length of the main crack and explore its tributaries.

Crack in the Ground formed between roughly 700,000 and 12,000 years ago as a tension fracture along a hingeline, where Green Mountain lava flows draped over the upthrown side of a concealed fault zone. Eruptions from the Four Craters Lava Field also caused the older rock surface to sink slightly, creating a shallow graben-like depression about 2 miles wide. The fissure marks the western edge of that depression, at the southwest corner of the lava field.

Crack in the Ground marks the western edge of a shallow, graben-like depression about 2 miles wide that extends south into an old lake basin, formed when eruptions from the Four Craters Lava Field caused the older rock surface to sink slightly. Hikers can walk the length of the main crack and explore its tributaries.

Bring sturdy shoes and a flashlight, as the path descends into the narrow fissure with uneven ground and limited daylight below. Most visitors need about an hour to walk through the entire crack, making it a short to moderate outing depending on your pace.

The fissure marks the western edge of a shallow, graben-like depression about 2 miles wide that extends south into an old lake basin, formed as Four Craters Lava Field eruptions caused the older rock surface to sink slightly.