What would happen if the moon got knocked closed to us?

Well in this book I'm reading called "Life as we knew it" (By Susan Pfeffer if you wanna check out out), the moon gets knocked closer to earth by a big asteroid. is this really possible? They also said that after that there were earthquakes, volcanoes erupted, which means that the sky turned gray from all the ash, tsunamis, etc etc? Would all this really happen?