Crooked Creek
Key facts
- Country
- United States
- Diameter
- 7 km
- Age
- about 320 ± 80 million years
- Location
- 37.83° N, 91.38° W
A roughly circular area of hilly, wooded ground about 7 km across in Crawford County, Missouri, where rock layers are broken and tilted. Shatter cones occur in some outcrops.
Crooked Creek is an eroded impact structure about 7 km across in Crawford County, in the Ozark region of Missouri, in the United States. It is one of several round, disturbed structures in Missouri and neighbouring states that were once described as 'cryptovolcanic', a term for features thought to have been made by hidden volcanic explosions.
What it hit. The impactor struck a thick sequence of Cambrian and Ordovician sedimentary rocks, mainly dolomites and sandstones. The rebound of the crater floor lifted older layers in the centre, and the surrounding rocks were faulted and folded into a ring. Erosion has since removed the rim and upper part of the crater.
Proof of impact. Shatter cones, cone-shaped fractures produced only by the shock of an impact, have been found in the central part of the structure, together with breccia. These features show that an impact, not a volcanic explosion, was responsible.
Age. The age is poorly known. The youngest rocks affected and later deposits suggest an age somewhere around 320 million years, but with an uncertainty of up to about 80 million years either way.
Why it matters. Crooked Creek and its neighbour Decaturville helped change geologists' thinking about 'cryptovolcanic' structures in the American Midwest, most of which have now been shown to be impact structures. The impactor is unknown.
Visiting. The area is mostly private land. Ask permission before exploring outcrops.
Did you know?
Crooked Creek was once thought to be the result of a hidden volcanic explosion.
Shatter cones found in the centre proved it was an impact.
Its age is uncertain by tens of millions of years.