Rare metal found in samples at Serpent Mound

Scientists studying recent rock samples taken from beneath an ancient earthen mound are trying to determine what caused unusually high concentrations of a metal rarely seen anywhere but near Earths molten core or in asteroids and comets.
Serpent Mound, an earthen snake effigy believed to have been built from about 1000 B.C. to A.D. 200 is about 60 miles east of Cincinnati. Some believe the 1,348-foot-long mound had a religious function for its builders, although nobody knows for sure what philosophy and beliefs shaped its origin because the mound builders left no written records.
Geologists only recently discovered high concentrations of iridium 1,412 feet beneath the mound.
The levels of the silver-gray metal, occasionally brought up in lava from volcanoes, measured 10 times beyond what is usually present in the Earths crust.
Since there are no lava fields in Ohio, some geologists point to the iridium as evidence the mound sits upon a slightly oblong crater created when a massive extraterrestrial object slammed into Earth.
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