GEOHERITAGE IN ALASKA – SENSE OF PLACE IN ANCHORAGE, ALASKA (Invited Presentation)

There are many sites of geologic interest and importance in Alaska. The geology of most of the National Parks and Monuments in Alaska was a critical feature in defining the parks. In several of the parks, the geologic features present have had significant human impact. For example, the 1912 eruption of Novarupta in Katmai National Park, deposited as much as 30 cm of ash in Kodiak, Alaska 150 km away. Residents of the nearby Katmai village ultimately relocated some 320 km southwest to a new village named Perryville. Much earlier, the eruption 3,700 years ago at Aniakchak Caldera southwest of Katmai likely had significant impact on Indigenous communities in nearby areas. Archeologic evidence suggests that Indigenous communities were present along the Alaska Peninsula but any evidence of pre-existing inhabitation in the Aniakchak region is likely buried, and region was not re-inhabited until about 2,000 years ago.

The subduction related 1964 Great Alaska earthquake (magnitude 9.2) had massive impact in southern Alaska and beyond. Massive rotational block landslides devastated a significant portion of downtown Anchorage and some residential areas, particularly Turnagain Heights subdivision west of downtown. There sandy and clay-rich deposits of the underlying Bootlegger Cove Formation liquefied during the quake and formed the surface upon which overlying deposits (and about 75 homes) slid towards Knik Arm and the “open” face of the inlet. In the Turnagain Heights subdivision, a section of the bluff 2.5 km long and as much as 360 meters wide slid toward the inlet. Earthquake Park in Anchorage preserves some of the rotational block slides, provides an easily accessible view of earthquake effects, and is an educational tool to explain the nature and impact of the earthquake. The park, situated along the Coastal Trail, is visited by hundreds of people annually. This park is a reminder of the dynamic environment in Anchorage and helps to provide an aspect of sense of place to visitors and members of the community. Much information about earthquakes and risky areas for building is available, yet risks are still being taken. Post-earthquake construction over earthquake debris east of the park indicates despite all that was learned geologically following the earthquake, homes have been rebuilt in the same area.