You can respond to earthquakes, volcanic eruptions, hurricanes or tornadoes, but you could never stop them from happening. But if you found an asteroid on a track to hit the earth several years in the future—at least in principle—you could use technology to change its orbit and have no bad effects whatever.
David Morrison is credited as the founder of the multi-disciplinary field of astrobiology, and is best known for his work in risk assessment of asteroids and comets. He wrote the "Ask an Astrobiologist" series on NASA's website, and has written more than 150 papers primarily on planetary science, astrobiology, and near Earth objects. Asteroid 2410 Morrison was named in his honor.