Lake Atna Research Project

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Lake Atna MapLake Atna Stage 1

Proposed timeline 2006 - 2008

Lake Atna Background: Lake Atna was one of the most recent in a series of late ice age lakes filling portions of the Copper River Basin and upper Susitna Valley. Prior to 9,000 to 14,000 years ago, Lake Atna was a vast water body extending from the Chugach Mountains north to the Alphabet Hills, and west from the Wrangell Mountains to the Lake Louise Plateau. During the height of the last ice age, surrounding glaciers in the Chugach, Wrangell, and Talkeetna Mountains as well as in the Alaska Range flowed into the Copper River Basin. These glacial tongues covered large areas of the basin in great ice sheets. As the climate warmed these glaciers retreated to the basin’s margins and beyond, leaving behind dams of glacial ice in the lower Copper River’s cut through the Chugach Mountains. Glacial dams held back the waters of Lake Atna for thousands of years as willows, alders and spruce reclaimed the slopes around the lake. Shortly afterward caribou from the Tanana Valley claimed new territory in the northern part of the Copper River Basin. It still isn’t known when Lake Atna itself finally drained.


Lake Atna Pollen

BLM is working with the University of Alaska, Fairbanks to determine the age of Lake Atna and what its surrounding ecology was like. The goal is to determine if Lake Atna’s shorelines were inhabited by plants and animals that were attractive to human hunters in Alaska over 10,000 years ago.


Lake Ahtna volunteersStage II Lake Atna Archaeological Modeling Research

Proposed timeline 2008-2009

The BLM is using Geographic Information Systems (GIS) to combine information from a large number of geology reports in the Copper River Basin with new information from our partnership with the University of Alaska, Fairbanks. This newly combined information will then be used to model and locate areas that would have been used by human hunters in the past. This stage is largely based on topographic features that have held previously located archaeological sites throughout the state of Alaska. The GIS model’s resulting study areas are often referred to as “high probability locations” because of their greater likelihood than other nearby areas to have archaeological sites.


Glennallen Field Office Archeology student.Stage III Lake Atna Archaeological Surveys

Proposed timeline 2009 - 2011

Using a combination of volunteers and professionals, the BLM will examine GIS predicted high probability locations that it manages, such as various old river or shoreline features within the Gulkana Wild and Scenic River corridor or along the Tonsina River drainage. Initial surveys of the Gulkana River, using preliminary mapping information, began in 2002 and continues as funding is available through 2006. These preliminary surveys have located a variety of archaeological sites, most of which are no older than a few hundred years. However, a few sites are potentially as old as 5000 years.

Archaeological surveys systematically locate archaeological and historical sites using airborne spotting and ground surveys. Archaeologists search areas in a grid pattern looking for any sign of past human use. Future surveys will also use soil augers and deep test pits to reach some of the oldest sites that may lay under several feet of wind blown sand and silt uncovered from the bottom of Lake Atna when it drained several thousand years ago.

They then record information about any newly discovered sites using several techniques. Extremely accurate GPS (Global Positioning Systems) and aerial photographs are used to precisely map sites for future reference. Information about the nature of the site and its artifacts is then documented on several forms allowing us to document observations about the use and age of the site. Most of this information is then shared with the State of Alaska’s Office of History and Archaeology, which maintains a database of sites called the Alaska Heritage Resource Survey.


Tangle Lakes Archeological DigStage IV Lake Atna Archaeological Surveys

Proposed timeline 2011+

Scientific excavation of an archaeological site is the best way to gather the most detailed view of past human lives. It is also the most destructive since once a site has been dug up, there is no way to reconstruct it other than by mentally picturing it using the archaeologist’s notes and the uncovered artifacts. It is like reading a book that has its pages burned one by one as you read it, leaving you with only a few charred scraps of paper, your notes and your memory. For that reason BLM works with and grants excavation permits to professional public and private researchers who carefully document and analyze their work. Any future excavations of archaeological sites related to Lake Atna will require the expertise that professional archaeologist’s inside and outside of the BLM can provide.