Scientists Study Puget Sound Tsunami Risk by Digging into the Past

Washington's tsunami threat comes from several sources, but the main one is known as the Cascadia Subduction Zone.

It's a 700-mile long fault running off the Northwest coast where the North American continent is locked into a series of small tectonic plates forming to the ocean floor. The ocean floor moves slowly and creates pressure against the continent causing the Washington coast to move to the northwest and be lifted up.

It's expected to be devastating when the earthquake that drives it strikes again...

Bre MacInnes, an associate professor of geological sciences at Central Washington University, along with graduate student David Bruce, are studying the Seattle Fault.

The pair drilled holes and took core samples of mud from a marsh near Deer Lagoon at the southern end of the island. Some of those samples show light gray layers of sand in between layers of mud. It is an indicator a powerful wave or that waves drove sand from elsewhere into the back reaches of the marsh.

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