This is a ghost forest near Seward, Alaska. It’s not the only one—ghost forests are found on coastlines up and down the Pacific Northwest. But how are they created?

Ghost forests are the long-preserved relic of terrifying events: the sudden subsidence of an entire coastline after a major earthquake rapidly submerging the forest. The saltwater incursion into the woods both kills the trees and helps preserve them, while the slow trapping of mud, muck, and saltwater-friendly plants slowly builds new land around the eerie forest that used to be.

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Destructive earthquakes come in two major varieties: those that move horizontally, like the transverse zone earthquakes in California, and those that move vertically, like the subduction zone megaquakes of the Pacific Northwest, Chile, Japan, and New Zealand. In subduction zones, two tectonic plates are slowly colliding together at about the same rate your fingernails grow, building stress. While the fault is locked in place, the stress builds by warping the upper plate, buckling it upwards. When the earthquake finally strikes, releasing the stress, the upper plate slams down and out, rapidly submerging the coast. Saltwater rushes into the subsided land, poisoning all the plants. Over time, the now-dead forest can trap sediments, helping create new land colonized by more salt-friendly marsh plants.

This particular ghost forest near Seward, Alaska was drowned during the magnitude 9.2 earthquake that hit Alaska in 1964. Other locations with well-preserved ghost forests include Copalis in Washington and Neskowin in Oregon. Similar ghost forests near Vancouver Island in British Columbia tend to still be drowned, found only through submarine surveys.

Top image: Ghost forest near Seward, Alaska submerged during subsidence from the 1964 Alaska earthquake. Credit: USGS


Contact the author at mika.mckinnon@io9.com or follow her at @MikaMcKinnon.

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