High school physics question: What is amount of energy released in joules by an impact from a iron sphere 30 meters in diameter (density of iron = 7870 kg/m^2) hitting the earth at a speed of 15 km/s?
Bonus: Convert your answer to megatons.
So you’re thinking more like a couple thousand square miles vaporized.
OTOH, six-inchers have crashed through roof without too much damage.