re: Looks like the Norway 'meteorite hit' was exaggerated.
Hiroshima bomb magnitude explosion are fairly common from small impactors. Where the explosion occurs is important in terms causing damage on the ground. One wouldn't expect a crater from small impactors- when they explode in high atmosphere one can get fragments landing on the ground at a relatively slow speed and perhaps creating very small craters. A 1000' crater would a quite rare event in regards to any impactor- a small solid iron asteriod could do this and it would about 100' in diameter and be about 100 times power of Hiroshima bomb.