DEFINITION: "A tsunami occurs when there is a sudden, large-scale movement of the sea floor that displaces the water above it. While earthquakes are the most common cause, volcanoes and landslides can also trigger tsunamis. Tsunamis move the entire column of water, from surface, to sea floor-- Unlike storm waves, in which wind only moves the water's surface. Multiple waves or surges then ripple out in all directions, moving at speeds of 500 miles per hour or more in deep water. As the tsunami approaches the coast, it slows down significantly to about 25 to 30 miles per hour, causing the water behind it to build up and the tsunami to grow higher." (California State University) 

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Tsunamis are typically classified as local or distant, depending on the location of their source in comparison to where waves occur. A distant tsunami may take many hours to arrive on the Del Norte coast, whereas a tsunami triggered by local earth movement can arrive in mere minutes. 

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Remember, if you feel an earthquake:

DROP, COVER, and HOLD ON.

If the shaking is long and strong and you are in the inundation zone (areas in yellow on the map):

Exit your location on foot, being mindful of hazards, and walk to a safe area (areas in green on the map)

The first tsunami wave is often not the largest, and waves can continue for many hours. Stay put in your safe location until officials say it is safe to return.