Diamicton , glacial , glaciolacustrine , and lacustrine origin deposits exist in many areas of the Copper River Basin . All major rivers present today occupy narrow valleys that have cut up to into the bottom of the basin . Lacustrine sediments of the lake are visible in many river bluffs throughout the basin . Several extant lakes in the basin are remnants of the lake , including Tazlina Lake , Klutina Lake , and Tonsina Lake . Much of the unconsolidated fill of the basin is in permafrost , down to a maximum depth of in the central basin area . The postulated Matanuska Valley flood produced by Lake Atna 17,000 years ago may have been responsible for the deposition of a thin stratum of clay and silt grains in the Anchorage area . The collapse of this stratum caused catastrophic landslides in the Anchorage area during the 1964 Alaska earthquake contributing to the collapse of structures built above it
1964 Alaska earthquake
1964 Alaska earthquake
Lake Atna