Turnagain Heights Slide

Turnagain Heights Slide. . , You are standing on the edge of the Turnagain Heights Slide, 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 which slid toward Cook Inlet. With a savage and grinding roll, the slide transported some homes 500 feet seaward, and broke apart or crushed other homes. Residents rushed outside their homes only to be thrown to the ground as the blocks pulled apart and heaved around them. Others were trapped in their homes. The slide movement continued for 90 seconds after the earthquake stopped shaking Anchorage. Over 12 million cubic yards of sand, clay and gravel slid off toward the inlet, 75 homes were destroyed, and four people perished., Bootlegger Cove Clay , Underneath most coastal Anchorage is a deep layer of gray- blue material called Bootlegger Cove Clay. This silty plastic clay is composed of estuary-miarine sediment, and was deposited 15,000 to 30,000 years ago by massive glaciers that covered most of south-central Alaska. Unfortunately, it can be extremely soft and unstable. During an earthquake Bootlegger Cove Clay tends to liquefy and lose strength and where the upper clay layers contain loose sand layers, it can dramatically fail.