Where this was said
What Is a Megathrust Earthquake?
At 4:50 · chapter starts 4:00
This chapter digs into the geology that makes the 1964 earthquake so scientifically significant. Chuck explains that megathrust earthquakes — all 10 of the 10 biggest ever recorded — occur when two tectonic plates collide, with the heavier plate diving beneath the lighter one in a process called subduction [1] — Chuck "All 10 of the 10 largest earthquakes ever recorded are megathrust earthquakes — and now we know why. Two tectonic plates collide, lock toge…" 03:55 . The trouble comes when the plates lock rather than slide smoothly past each other. Under enormous pressure, the locked zone builds stress over decades or centuries until it catastrophically releases, lurching an entire region of the Earth's surface forward by dozens of feet in seconds. Josh uses a game-of-chicken analogy that lands perfectly. The 1964 quake happened along the Alaska-Aleutian subduction zone, where North American plates slide over Pacific plates — a boundary running from the Gulf of Alaska all the way to Russia's Kamchatka Peninsula. Critically, this boundary is offshore and invisible from the surface, meaning the towns that would suffer most — Anchorage, Valdez, Seward — had no idea they were sitting atop one of the most dangerous seismic zones on Earth.
