What would happen if the moon were to disappear?

it's the moons orbit that keeps it away from the earth, if it stopped moving it would be pulled in by earth's gravity and crash.

it wouldn't be immediate but it would take a reletively short time to come down, we would also lose Tides and other things that are linked into the moons cycle, but the effect of that much rock hitting the planet would mean that there is unlikely to be any life left to notice a lack of tides.