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National Park


cover of park brochure

park geology subheading
Scenic photo of Glacier views
Glacier National Park, Montana

Waterton-Glacier International Peace Park

The Lewis Overthrust of Waterton-Glacier International Peace Park provides scientists with dynamics of geologic processes that are going on today in other parts of the world, such as the Andes and the Himalaya Mountains. Because of the high degree of preservation of the original rock characteristics, the recent glacial sculpturing of the rocks, and the access by roads and trails, this major geologic structure in Waterton-Glacier is available for study by scientists from around the world.

The Lewis Overthrust began 170 million years ago, when a collision of the Earth’s crustal plates elevated numerous mountain chains and formed the ancestral Rocky Mountains. Ever-increasing stresses near the end of this great event shoved a huge rock wedge, several miles thick and several hundred miles wide, eastward more than 50 miles. Large masses of relatively stronger rocks were shoved over softer and more easily deformed rocks. Erosion stripped away the upper part of the original rock wedge and exposed the rocks and structures visible in the park today. Rarely have rocks of such ancient age been thrust over rocks that are so much younger. The overlying Precambrian (Proterozoic) rocks are over 1,400 million years older than the underlying Cretaceous age rocks. Thus, the Lewis Overthrust is significant as a structural feature, for the extent of lateral displacement (up to 80 kilometers), and because it has functioned to expose ancient sediments possessing an unparalleled degree of preservation.

Of particular scenic and geologic note is Chief Mountain, a spectacular monolith towering above the prairie along the eastern margin of Waterton-Glacier. Chief Mountain is an erosionally isolated remnant of the eastern edge of the upper plate of the Lewis Overthrust—a feature known as a klippa ranking with the Matterhorn as an example of this structural and erosional phenomenon.

Most of the rocks exposed in the park are sedimentary rocks of the Belt Series, of Mesoproterozoic age, which were deposited from around 1,600 to 800 million years ago. Rocks of that age in other parts of the world have been greatly altered by mountain building processes and no longer exhibit their original characteristics. These virtually unaltered Proterozoic rocks of Waterton-Glacier are unique in that they have preserved the subtle features of sedimentation such as milimetric lamination, ripple marks, mud cracks, salt-crystal casts, raindrop impressions, oolites, six species of fossil algae, mudchip breccias, and many other bedding characteristics.

photo of Ripple marks, Mount Shields Formation on Hucklebury Mountain Ripple marks, Mount Shields Formation on Hucklebury Mountain. Glacier National Park. photo of Cross-sectional exposure of mudcracks in the Snowslip Formation Cross-sectional exposure of mudcracks in the Snowslip Formation along Going-to-the-Sun Highway. Coin for scale. Glacier National Park.

photo of Mudchip breccia in Spokane Formation, along Going to the Sun Highway
Mudchip breccia in Spokane Formation, along Going to the Sun Highway. Glacier National Park.

These Proterozoic sedimentary rocks, while outcropping over an area extending from southern Montana to southern British Columbia, are most impressively exposed in Waterton-Glacier. Due to the extreme relief and unexcelled exposures, over 2,100 meters of stratigraphic thickness is exposed to scientific examination. These features plus their chemical characteristics make the Proterozoic sediments of Waterton-Glacier International Peace Park unique for studying the physical and chemical conditions that existed on the Earth over a billion years ago. Several of the sedimentary rock layers described above, contain fossils called stromatolites. They were colonial organisms of blue-green algae that lived in warm shallow seas marginal to ancient lands. Six species representing three genera of stromatolites are preserved in the ancient sediments of the park.

photo of PreCambrian stromatolites Close-up of PreCambrian stromatolites in Siyeh Formation, Going to the Sun Highway. Glacier National Park.

The Appekunny Formation contains bedding structures, which have being classified as the remains of the possibly oldest metazoan on Earth. Pushing the limits of the origin of the metazoans one billion years back.

The glaciers in Glacier National Park today are all geologically new having formed in the last few thousand years. Presently, all the glaciers in the park are shrinking. More snow melts each summer than accumulates each winter. As the climate changed over the last two million years, glaciers formed and melted away several times. During the Great Ice Age, or Pleistocene, the Park’s major valleys were filled with glacial ice over a mile in thickness, carving the outstanding glacial topography seen today. Textbook examples of glacially carved landforms are on display: the park is filled with horns, cirques, arêtes, hanging valleys, and moraines.

Aerial view of Kinnerly Peak a glacial horn
Aerial view of Kinnerly Peak a glacial horn. Glacier National Park. photo of U-shaped glacial trough of McDonald Valley, with snow-capped mountain

U-shaped glacial trough of McDonald Valley, with snow-capped mountain Glacier National Park.

A wide variety of landslide types exist in Waterton-Glacier, ranging from slow-moving slumps in glacial till to potentially catastrophic, high-speed sturzstroms (rock avalanches). Hazardous landslides in the parks include rockfalls, rockfall avalanches, debris flows, and snow avalanches. Several dozen historical incidents of rockfalls along Going-to-the-Sun Road, US Highway 2, and the Many Glacier Road have produced injuries and fatalities. Both Park visitors and employees have been injured by rockfalls. Rockfalls in the Park are triggered by freeze-thaw activity and precipitation.

photo of Blocky frost heaved boulders of Shepard FormationBlocky frost heaved boulders of Shepard Formation. Boulder Pass area. Glacier National Park.

Rockfall avalanches (sturzstrom) have occurred in several locations along the Lewis Overthrust Fault during the 20th Century; fortunately, no injuries have yet been recorded from these high-speed landslides, but their occurrence has caused temporary road and trail closures. Rockfall avalanches have also impounded two potentially hazardous landslide-dammed lakes (in 1910 and 1946) in the Otatso Creek drainage in the northeastern corner of the park. Debris flows in Glacier National Park are widespread, with literally thousands of debris flow deposits distributed throughout the park.

Photo of Disrupted ground, tilt trees and pressure ridge formed near the margins of the Kirkwood earthflow with a man for scale Disrupted ground, tilt trees and pressure ridge formed near the margins of the Kirkwood earthflow. Man for scale.

Debris flows produce frequent threats to visitors and Park employees along Going-to-the-Sun Road. During the evening of 28 July 1998, a strong frontal storm brought drenching rains to Waterton-Glacier, and numerous debris flows were triggered throughout the Park. Three flows crossed Sun Road, trapping cars between the flows and exposing their occupants to the possibility of further flows. National Park Service personnel quickly rescued the trapped vehicle occupants, but it took over 24 hours for the debris flow deposits (in excessive of 20-40 tons of sediment per deposit) to be cleared from the road, thus temporarily shutting down Going-to-the-Sun Road during the height of the tourist season.

David R. Butler, Ph.D.
Professor of Geography
Director, The James and Marilyn Lovell Center for Environmental Geography and Hazards Research



park maps subheading

The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

A photo album for this park can be found on the park's webpage.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

geologic research subheading

Information about the park's research program is available on the park's research webpage.

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/glac/index.cfm   I  Email: Webmaster
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