This Earthquake Drowned the Pacific Northwest

[Music] meet pilio seismologist Bryant Atwater he and I are paddling up the go palace a coastal river that rises and falls with Pacific ocean tides we're here at low tide but at high tide the river can rise enough to overflow its banks letting the surrounding marshes with saltwater but it wasn't always that way once this was a lush coastal rainforest now all the remains are massive roots sticking out of the eroded riverbanks and the trunks of long dead leader trees a ghost forest Brian has brought me here to show me evidence of one of the worst earthquakes to hit North America since human beings arrived here slicing into the bank reveals three layers they tell a story of change over time the lowest once deported a healthy rainforest well this is almost like a garden soil right but it's got tree roots in it it's a forest floor soil just above it's a layer of thing entirely out of place it's sharp definition tilt out water that whatever put it here came fast and furious how do we do this combination how do we go from forest floor to some kind of muddy flat and have a sand layer brought in first the answer lies about 80 miles away at the bottom of the Pacific Ocean it's called the Cascadia subduction zone a 700 mile long crack in the crust of the planet it's where a Pacific Ocean plate is trying to slide under the North American plate but the plates were stuck they go closer and closer like that and the overriding plate gets short bulges up the old-growth forest that once stood around the copilot's river sat on that bulge but then the plates broke free along the fault causing a violent earthquake dropping 600 miles of coastline as much as five feet and into the tidal zone that same tectonic rupture also drove the edge of the continental plate upward and triggered a series of huge wave a tsunami what the forest theme is a rush of salt water and sand inundating the land the final blow from a massive fault rupture that turned an old-growth rainforest into this we now know that this cataclysmic one-two punch took place in the year 1700 today everyone wants to know will it happen again [Music] you

Channel: NOVA PBS Official

Views: 1,048,591

Keywords: science, pbs, nova, geology, seismology, kirk johnson, natural, history, river, pacific, northwest, fault, plate, tectonics, earthquake, tsunami, disaster, flood, nature, documentary

Id: K_sJ0QJ31fc

Length: 3min 7sec (187 seconds)

Published: Thu Jul 06 2017