Alaskan Geology History and Timeline

History of geological investigations

The first geologists in Alaska were Russians performing mineral exploration during Russian ownership of the territory. Minor geological work was carried out from 1741 to 1867. Gold and coal mining operations were active during this time. In 1867, Alaska was sold to the United States. Americans explored for metals and fossil fuels from 1867-1906. Significant reconnaissance mapping began in 1907, and the search for metal and fuel resources intensified. Systematic reconnaissance mapping began in 1940, but due to difficulty of travel and access and to the huge size of the state, progress was slow. Alaska became a U.S. state in 1959. Detailed and reconnaissance geologic mapping has continued since 1960.

Mapping in Alaska was always difficult. Field seasons are short, especially in the Brooks Range. Snow can fall any day of the year. Until the 1940's and the introduction of the short wave radio, mapping parties had no contact with the outside world during the field season. Until the 1920's the only way to reach remote areas of Alaska was by foot or horseback. The common use of fixed-wing aircraft began in the 1920's and allowed ferrying of supplies and personnel all over Alaska. Until this time, topographic surveys were conducted concurrent with geological mapping since topographic base maps of the areas did not exist. Fixed wing aircraft made aerial photography possible, and from this time on most geological mapping was done on such photos and the topographic maps prepared from them. Aircraft were also used for reconnaissance, allowing much more efficient use of the short field seasons.

The 1950's saw the introduction of the helicopter, another breakthrough for geologists in Alaska. Access was easier than ever, although still dangerous and expensive. Helicopters caused a revolution in mapping around the world. Geologists could now choose an area of interest by referring to aerial photographs, and then be dropped off by helicopter to complete their fieldwork.

Photograph by Steve Beukema


1741 First geological observations in Alaska: Georg Wilhelm Steller

1848-1850 first recorded gold mining (Kenai peninsula)

1854 Coal mining (Kenai peninsula)

1867 Alaska purchased from Russia by the U.S.

1877 First lode-gold mine; gold major contributor to AK economy ever since

1896 Bonanza gold discovery on upper Yukon River (starts the Gold Rush)

1898 USGS and US Army efforts at Alaskan resource evaluations, geo mapping begins in earnest

1900 Kennicott copper deposits discovered

1906 First summary of AK geology published by AH Brooks, less than 25% of AK had been visited by geologists

1906-1914 Privately funded mapping in Brooks Range by E. deK. Leffingwell

1909-1910 Nat Geo Soc funds glaciological studies

1911-1938 major production from Kennicott mines

1912 Alaska becomes territory

1916-1970 significant coal mining in Matanuska Valley

1920ís and 30ís unsuccessful oil wells drilled along Gulf of AK and on AK peninsula

1939 Second summary of AK geology published by PS Smith. Less than half of AK geology surveyed at recon standards (Smith, 1939)

1940ís USGS explores AK to locate strategic mineral reserves and petroleum

1944 USGS searches for radioactive minerals for atomic weapons development, one uranium mine eventually developed

1944-1953 US Navy conducts oil exploration in Northern AK using tracked vehicles

1957-1963 First economic oil discoveries found in Southern AK, USGS focus changes to basin geology

1959 Recon geology in about 80% of the territory

1960 AK becomes a state

1964 Largest EQ ever recorded in North America (M=9.2) in southern AK

1968 "Supergiant" Prudhoe Bay field discovered on the North Slope

1968-1971 Trans-Alaska pipeline constructed

1977 Production begins from Prudhoe Bay field (13 bill recoverable barrels, 30 trill cu ft gas), geological investigations of the north slope and offshore areas intensifies

1977 Recon gravity mapping of most of AK completed

1991 Red Dog Zinc-lead-silver-barite deposit mining begins, located in Brooks Range



Tectonic Evolution



Arc Rocks