If a small black hole (say about .1 mm radius or 1% of Earth's mass) came flying along at the speed of a comet or higher and impacted the earth, what would happen? Would it pass through the earth (and atmosphere) with minimal damage? Would it leave a crater (entry or exit?) Would it create a big enough shock wave to significantly damage the earth? Would it be captured and wander around inside the earth?
I read a book a few years ago with this as the primary part of the plot, and I have wondered about the physics ever since.