Download coordinates as: The 38th parallel structures, also known as the 38th parallel lineament,[1] are a series of seven circular depressions or deformations stretching 700 kilometres (430 mi) across southern Illinois and Missouri and into eastern Kansas, in the United States, at a latitude of roughly 38 degrees north.

Estimated at 300 million years old, three are believed to be impact events from meteorites, but other structures are possibly remnants of volcanos.

Rampino and Volk (1996) postulated that these structures could be the remains of a serial meteorite strike during the late Mississippian or early Pennsylvanian periods (320 ± 10 Ma).

[2] Difficulty in determining the age of many of the structures and doubts about the exogenic origins of several of them leave some geologists skeptical of this hypothesis.

However, evidence of serial impacts on the Moon, whose gravitational field is even weaker, can be seen in several chains of craters on the lunar surface.