38th parallel structures

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Structure Coordinates Hicks Dome 37.5° N 88.3° W Avon 37.8° N 90.2° W Crooked Creek 37.8° N 91.4° W Decaturville 37.9° N 92.7° W Hazelgreen 37.7° N 92.4° W Weaubleau-Osceola 38.0° N 93.6° W Rose Dome 37.7° N 95.7° W

The 38th parallel structures are a series of circular depressions or deformations stretching 700 km (435 mi) across southern Illinois and Missouri into eastern Kansas at a latitude of roughly 38 degrees north.

Rampino and Volk (1996) postulated that these structures could be the remains of a serial meteorite strike in the late Mississippian or early Pennsylvanian periods. 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. There is evidence that at least some of them, such as Hicks Dome, are volcanic in origin. (They are associated with faults and fractured rock, and are accompanied by igneous rocks and mineral deposits.)

Interest in the possibility of serial impacts on Earth was piqued by observations of comet Shoemaker-Levy 9 impacting on Jupiter in 1994. It is estimated, however, that the likelihood of such an event on Earth is vanishingly small because the Earth's weaker gravitational field is much less able than Jupiter's to pull a speeding object close enough to be torn apart by tidal forces. However, evidence of serial impacts on the Moon can be seen in several chains of craters.

[edit] See also

• Impact event
• Roche limit

[edit] References