Turnagain Heights Slide

The Turnagain Heights Slide was the largest and most destructive landslide in Anchorage. Ninety seconds into the Good Friday Earthquake, an 8,000-foot strip of bluff 1,200 feet wide began cracking apart into larger blocks that slid toward Cook Inlet. The slide carried some homes 500 feet seaward and broke apart or crushed others, while residents who rushed outside were thrown to the ground as the blocks pulled apart and heaved around them, and others were trapped in their homes. Movement continued for 90 seconds after the earthquake stopped shaking Anchorage. More than 12 million cubic yards of sand, clay, and gravel slid toward the inlet, 75 homes were destroyed, and four people died. Beneath most coastal Anchorage lies Bootlegger Cove Clay, a deep gray-blue layer of silty plastic clay made of estuary-marine sediment deposited 15,000 to 30,000 years ago by massive glaciers that covered most of south-central Alaska; during earthquakes it can liquefy, lose strength, and fail dramatically where upper clay layers contain loose sand.

Anchorage, Alaska · United States