How Dangerous Are Tsunamis? Activity Source: Adapted with permission by Geological Society of America. Imagine playing beside the ocean, when suddenly, the water drops. Where the water used to be, there are wriggling fish and ribbons of seaweed. What do you do? You could be seeing the first sign of a tsunami ─ a long wave formed in the ocean when the sea floor moves suddenly. Most tsunamis happen because of large earthquakes on the ocean floor. [Read More]

ShakeAlert Earthquake Early Warning Activity Source: U.S. Geological Survey, Adapted with permission. Have you ever felt an earthquake? What was it like? Where were you? What did you do? More than 143 million people are exposed to potentially damaging shaking in the United States. When an earthquake happens, seismic waves travel outward in all directions. Primary (P) waves travel faster than secondary (S) waves, which do most damage. But electronic information can be sent faster than P and S waves. [Read More]