Depression in Australia

Most meteors are small, pea-size to walnut-size things that get their brilliance from their enormous speed. Only a few are big enough to reach the earth's surface before they evaporate. Once in a great while, a really big meteor smacks the earth with a vast concussion, digging an "explosion crater" like the one near Canyon Diablo, Ariz. Such craters are rare. Unless the meteor hits in an arid region, its dent is smoothed down quickly (in terms of geological time) by erosion and other natural forces.

The latest Sky and Telescope magazine described a great meteor crater recently identified at Wolf Creek in the dry wilderness 400 miles inland from Broome, Western Australia. From ground level the crater is not impressive. Its rim looks like a low, rocky ridge above a featureless plain. Apparently the few who have passed near it hardly ever gave it a second glance.

In 1947, two geologists, Dr. Frank Reeves and N. B. Sauve of the Vacuum Oil Co., spotted the crater from an airplane. What they saw was a circular depression more than half a mile across and 100 ft. deep, with a splashed-out looking rim. In general appearance it looked much like Arizona's meteor crater (570 ft. deep, four-fifths of a mile in diameter).

Months later Dr. Reeves went back and examined his discovery. He did not find any chunks of meteorite, nor could he prove conclusively that the hole was made by a meteor. But all signs indicated that it was. There were no volcanic materials in the vicinity, and the strata around the rim seemed to be tilted upward as if from an underground explosion.

Geologists from Australia's Bureau of Mineral Resources have studied the crater and found some proof that it was made by a large mass of meteoric material that plunged into the earth at enormous speed and exploded like a bomb. The piles of rock in the rim are fractured as if they were blown out of the depression. The undisturbed rock layers of the region are horizontal, or nearly so, while the strata near the crater dip downward from the rim. The geologists found no meteoric iron, but they did find chunks of peculiar rock containing 3% of nickel that may have been part of a "stony" meteor.

Dr. H. G. Raggatt, the bureau's chief, thinks the meteor must have struck thousands of years ago, before the black aborigines settled in Australia. Otherwise, he says, "there must have been such a hell of a bang that it would have been recorded in native legend."

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