No. 11: Summer 1980
In 1978, J.M. Saul reported the discovery of hundreds of large terrestrial ring structures, many of them tens of kilometers in diameter. Around the rims were concentrated metal ores. Saul surmised that episodes of meteor bombardment about 4 billion years ago created these nearly perfect circles. Unfortunately for this theory, little of the earth's surface is 4 billion years old!
Now, a new population of circular structures 8-20 km across have been recognized in New Zealand, where the surface is dated at 100-320 million years. How could 4-billion-year-old meteor craters make themselves felt through all the layes of sediment? One possibility is that the rings are not meteoric but diapiric; that is, expressions of upwelling magma from inside the earth itself.
(Hawkes, Donald D.; "More Strange Circles on Earth," Open Earth, no. 7, p. 19, February 1980.)
Comment. The orphans in the preceding item may have been forced up from the interior, too. Could the lunar craters have originated in this fashion?
Reference. To read more about these huge "mineral" rings, consult Section ETC2 in our Catalog: Carolina Bays, Mima Mounds, which is described here.