First Ever Digital Geologic Map of Alaska Published

A new digital geologic map of Alaska is being released today providing land users, managers and scientists geologic information for the evaluation of land use in relation to resource extraction, conservation, natural hazards and recreation.

The map gives visual context to the abundant mineral and energy resources found throughout the state in a beautifully detailed and accessible format.

“I am pleased that Alaska now has a state-wide digital map detailing surface geologic features of this vast region of the United States that is difficult to access,” said Suzette Kimball, USGS newly-confirmed director. “This geologic map provides important information for the mineral and energy industries for exploration and remediation strategies. It will enable resource managers and land management agencies to evaluate resources and land use, and to prepare for natural hazards, such as earthquakes.”

“The data contained in this digital map will be invaluable,” said National Park Service Director Jonathan B. Jarvis. “It is a great resource and especially enhances the capacity for science-informed decision making for natural and cultural resources, interpretive programs, and visitor safety.”
“A better understanding of Alaska’s geology is vital to our state’s future. This new map makes a real contribution to our state, from the scientific work it embodies to the responsible resource production it may facilitate. Projects like this one underscore the important mission of the U.S. Geological Survey, and I’m thankful to them for completing it,” said Sen. Lisa Murkowski, R-Alaska.

This map is a completely new compilation, carrying the distinction of being the first 100 percent digital statewide geologic map of Alaska. It reflects the changes in our modern understanding of geology as it builds on the past. More than 750 references were used in creating the map, some as old as 1908 and others as new as 2015. As a digital map, it has multiple associated databases that allow creation of a variety of derivative maps and other products.

“This work is an important synthesis that will both increase public access to critical information and enhance the fundamental understanding of Alaska's history, natural resources and environment,” said Mark Myers, Commissioner of Alaska’s Department of Natural Resources. “I applaud the collaborative nature of this effort, including the input provided by the Alaska Division of Geological and Geophysical Surveys, which will be useful for natural disaster preparation, resource development, land use planning and management, infrastructure and urban planning and management, education, and scientific research.”


Geologists and resource managers alike can utilize this latest geologic map of Alaska, and a lay person can enjoy the colorful patterns on the map showing the state’s geologic past and present.

More than other areas of the United States, Alaska reflects a wide range of past and current geologic environments and processes. The map sheds light on the geologic past and present. Today, geologic processes are still very important in Alaska with many active volcanoes, frequent earthquakes, receding and advancing glaciers and visible climate impacts.

“This map is the continuation of a long line of USGS maps of Alaska, reflecting ever increasing knowledge of the geology of the state,” said Frederic Wilson, USGS research geologist and lead author of the new map. “In the past, starting in 1904, geologic maps of Alaska were revised once a generation; this latest edition reflects major new mapping efforts in Alaska by the USGS and the Alaska state survey, as well as a revolution in the science of geology through the paradigm shift to plate tectonics, and the development of digital methods. Completion of this map celebrates the 200th anniversary of world's first geologic map by William Smith of England in 1815.” 

The Alaska Geologic Map shows the generalized geology of the state, each color representing a different type or age of rock. This map detail, of the Anchorage area, shows the city spread out on a plain of loose glacial deposits shown in yellow, and the bedrock making up the hillsides of Anchorage shown in green and brown. The rocks shown in green, called the Valdez Group, are sedimentary rocks formed in a trench 65 to 75 million years ago from thousands of undersea debris flows similar to the modern Aleutian trench where oceanic crust dives under continental crust (a subduction zone). The rocks shown in brown on the map are a chaotic mix of rock types called the McHugh Complex that were also formed about the same time, adjacent to this ancient subduction zone. Some time after deposition of the Valdez Group, hot fluids formed gold-bearing quartz veins; the veins were mined starting in the 1890's. The rocks were pushed up, and attached (accreted) to North America through plate tectonic forces in the past 65 million years. The dotted line passing through the east side of Anchorage is the approximate trace of the Border Ranges Fault system, the boundary between the accreted rocks and the rest of the continent.



Contact Information:
Email Contact
Phone: 907-786-7448

Email Contact
Phone: 650-329-4046

Source

USGS Projects Large Loss of Alaska Permafrost by 2100

Using statistically modeled maps drawn from satellite data and other sources, U.S. Geological Survey scientists have projected that the near-surface permafrost that presently underlies 38 percent of boreal and arctic Alaska would be reduced by 16 to 24 percent by the end of the 21st century under widely accepted climate scenarios. Permafrost declines are more likely in central Alaska than northern Alaska.

Northern latitude tundra and boreal forests are experiencing an accelerated warming trend that is greater than in other parts of the world. This warming trend degrades permafrost, defined as ground that stays below freezing for at least two consecutive years. Some of the adverse impacts of melting permafrost are changing pathways of ground and surface water, interruptions of regional transportation, and the release to the atmosphere of previously stored carbon.

“A warming climate is affecting the Arctic in the most complex ways,” said Virginia Burkett, USGS Associate Director for Climate and Land Use Change. “Understanding the current distribution of permafrost and estimating where it is likely to disappear are key factors in predicting the future responses of northern ecosystems to climate change.”

In addition to developing maps of near-surface permafrost distributions, the researchers developed maps of maximum thaw depth, or active-layer depth, and provided uncertainty estimates. Future permafrost distribution probabilities, based on future climate scenarios produced by the Intergovernmental Panel on Climate Change (IPCC), were also estimated by the USGS scientists. Widely used IPCC climate scenarios anticipate varied levels of climate mitigation action by the global community.

These future projections of permafrost distribution, however, did not include other possible future disturbances in the future, such as wildland fires. In general, the results support concerns about permafrost carbon becoming available to decomposition and greenhouse gas emission.

The research has been published in Remote Sensing of Environment. The current near-surface permafrost map is available via ScienceBase.

Current probability of near-surface permafrost in Alaska. Future scenarios. ( High resolution image)


Contacts:
Email Contact
Phone: 703-648-4180

Email Contact
Phone: 605-594-6078

Source

Geologic Map of Baranof Island, Southeastern Alaska Now Online

In the 20th century, Baranof Island in Southeastern Alaska has drawn attention for its gold, chrome and nickel deposits, timber industry, potential activity of the dormant Mount Edgecumbe volcano, and for numerous commercially developed hot springs. In addition, Baranof Island is known for its outstanding scenic fjords, pristine rainforests, and prolific fishing grounds.

A new map from the U.S. Geological Survey updates the geology of Baranof Island based on field studies, petrographic analyses of minerals, fossil ages, and isotopic ages for igneous, metamorphic, and sedimentary rocks. These new data provide constraints on ages of rock units and the structures that separate them, as well as insights on the regional tectonic processes that affected the rocks on Baranof Island. This work provides stratigraphic, geochemical, and structural evidence that ties Baranof Island geologically to Vancouver Island and Haida Gwaii rather than other islands in southeast Alaska.

" This report is a modern synthesis of new work and many years of topical investigations," said USGS geologist Susan Karl. "Pulling together all of this information in one product is a benefit to scientists working on similar or related studies, and is of interest to the general public for explanations of local geologic features such as the Mount Edgecumbe volcano, the Fairweather, Chatham Strait, and Peril Strait Faults, gold deposits, and hot springs."

A pamphlet complements the map and includes a geologic overview of the results of USGS studies and detailed rock unit descriptions. The map is available at the USGS Alaska Science Center website.


Contact Information:
Susan Karl
Email Contact
( Phone: 907-786-7428 );

Paul Laustsen
Email Contact
( Phone: 650-329-4046 );

Source