Tornado and Earthquake Safety program explains the preparation to take when a tornado occurs. An earthquake is sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity. A tornado is a dark funnel-shaped cloud made up of violently rotating winds that can reach speeds of up to 300 mph. Many people believe that earthquakes are more common in hot and dry weather. In fact, no correlation with weather has been found. Earthquakes begin many miles below the earth's surface and are not affected by surface weather, while a tornado begins in the atmosphere above the earth's surface.