[Travis McGee]

It's Meteor Crater, about 20 some miles east of Flagstaff AZ. It's about a mile across. Very impressive tours can be had, with a great meteor museum full of artifacts, dioramas and so on.

Someone told me it would take about a hundred megatons to get that effect, but I have no idea if that's correct.

[Tijeras_Slim]

Someone told me it would take about a hundred megatons to get that effect, but I have no idea if that's correct.

The Sedan test (plowshare) was a 104KT device at a depth of 632 feet, which just happened to scale identically to a 1MT surface burst. It left a crater ~400 feet deep and 1200 feet across. It's at the north end of Yucca Flats, and pretty impressive.

[Poohbah]

Someone told me it would take about a hundred megatons to get that effect, but I have no idea if that's correct.

If it's a surface burst (as a meteor impact effectively is).

It would take somewhat less for a subsurface burst.