![]() It could be a magnitude 9.0 "full rip" or a partial rupture (magnitude 8+). It could be tomorrow, or it could be many years from now. Evidence suggests it may not be too long before the next great earthquake shakes the region. In this time, stress has been building between the plates. It has been over 300 years since the 1700 event. Tsunami forecast model animation of the 1700 Cascadia tsunami Looking Ahead The southern section of the subduction zone south of Newport, Oregon, has historically been more active than the northern section. Like the 1700 event, at least 19 of these were around magnitude 9 and ruptured the entire length of the subduction zone. Sand layer from the 1700 Cascadia tsunami covering the remains of a Native American fishing camp exposed in a bank of Oregon's Salmon River. In fact, scientists have estimated that over the last 10,000 years, more than 40 earthquakes greater than magnitude 8 occurred somewhere along the Cascadia subduction zone. These scientific records tell the tales of other similar earthquakes and tsunamis. While the 1700 tsunami was the most recent great earthquake and tsunami event to strike the region, it was not the only one. The buried remains of tidal marshes provide more evidence of subsidence, and layers of sand in coastal marshes and lakes overlying more typical soils, like peat, confirm tsunami inundation.Įvidence of Other Great Earthquakes and Tsunamis.Rings of these trees tell the story of how and when they died. "Ghost forests" are found in tidal marshes and feature the remains of trees killed when the land subsided and saltwater rushed in.Submarine landslides (turbidity currents) are shaken loose by ground shaking, and their presence shows that great earthquakes have occurred in the region.To learn more about evidence for Cascadia's past earthquakes, watch this video about Ghost Forests of the Pacific NorthwestĮvidence is also found on shore in "ghost forests" and layers of sediment in coastal marshes and lakes that can only be explained by great earthquakes or their resulting tsunamis:
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