I've seen a documentation on what would happen.
They say that shock waves would go all the way around the Earth, and then reflect back and cause a "mountain" to rise at some part of Earth due to the shock wave affecting the Earth's plates/crust.
The crater would be huge too, btw. It'd probably be the size of a city.
Also, the amount of dust that would fly out of the Earth and into the atmosphere would put Earth into a dark state. The plants would start to die out, and the only likely source of food would be fungus which would prosper. The people of Earth would have to rebuild society (Not repopulate...), and we'd have to make it with very little food/water.
In addition, because of collision with Earth, and the shifting of the plates and crust alteration and stuff, there would be more volcanic activity.
Now then, this is the ultimate doomsday!
*ahem*
Asteroid hits Earth!
Volcanic activity increase leads to Yellowstone's eruption!
The increase in ash in the air somehow causes global warming to speed up, and the "main event" of it to initiate. This would cause a "Day after Tomorrow" type of effect.
There would be no women within 100 miles!
Cheers,
-naota
