Earth has a long list of hits—and not of the musical variety, but of the rocky, celestial sort. In fact, asteroids have slammed into our planet and caused cataclysmic damage many times in its violent past. On less dramatic occassions, Earth is frequently hit with small asteroids that enter and disintegrate in its atmosphere. According to NASA’s Jet Propulsion Laboratory, Earth was hit by 556 small asteroids between 1994 and 2013. Most don’t make it through the atmosphere, but some—like the Chelyabinsk meteorite—crash-land with considerable force.
What would happen if a larger asteroid collided with Earth? A simulation by the Discovery Channel has provided a visual scenario to take us through it. According to the video's description box, these are the details: "An asteroid with a diameter of 500 km. Destination: The Pacific Ocean. The impact peels the 10 km crust off the surface. The shockwave travels at hypersonic speeds. Debris is blasted across into low Earth orbit, and returns to destroy the surface of the Earth. The firestorm encircles the Earth, vaporizing all life in its way.”
If you want to test out your own apocalyptic scenario, there is an online site by Purdue University called Impact Earth that allows users to input their own parameters. Test it out here.