The Ames crater

Found in 1991, buried, and full of oil

The town of Ames in Major County, Oklahoma, southwest of Enid, sits near the middle of a meteorite crater that nobody knew was there until 1991. The astrobleme, a word that means star wound, is buried under about 9,000 feet of sediment and barely shows at the surface. Estimates of its width run from about eight to ten miles. Its age has shifted too: it was long put at around 470 million years, in the Ordovician, possibly one of several meteors of that time, but the American Oil & Gas Historical Society reports that researchers examining zircon crystals from inside the crater in 2026 dated the impact to around 370 million years ago.

When the meteor struck, this part of the Earth lay under a shallow sea. The impact punched a crater into the crust, and the pressure beneath made the floor rebound into a central uplift. The sea came back and laid down sediment over it for ages, later movements tilted the formation, and when the sea finally left, the crater lay hidden underground.

It was found on paper. In 1991 Rex Olson, an exploration manager for Continental Resources, was studying a map built from seismic data and saw a pattern like a hoof print, or a cow track in the mud. He showed it to the company's chief executive, Harold Hamm, and the two agreed it looked like an astrobleme. Many geologists then believed impact craters were unlikely places for oil, and although wells had been drilled near the site since the 1960s, none had gone into the crater. Continental drilled deep, to about 10,000 feet, and struck oil in the fractured Arbuckle Dolomite, with an initial flow of about 200 barrels a day. Rumours that the impact had made diamonds came to nothing.

At least 60 wells have been drilled in the crater since. By 2007 it had produced 17.4 million barrels of oil and 79.5 billion cubic feet of natural gas, the largest of six producing astroblemes in the United States, and its discovery led to the others. Ames, with about 190 people, claims the crater as its own. On 18 August 2007, during the annual Ames Day, the town opened the Ames Astrobleme Museum, an open A-frame with all-weather video panels that needs no staff and stays open 24 hours.