Explore Geology
geology fieldnotes title

Apostle Islands

National Lakeshore


cover of park brochure

park geology subheading
Photo of coastline at Apostle Islands
Apostle Islands National Lakeshore, Wisconsin

The designated lakeshores in the national park system have shorelines and are, therefore, considered coastal and are managed accordingly. Nevertheless, because even the largest lakes are very small compared to oceans, some distinct differences exist, geomorphically speaking. Many lakeshores have much smaller waves and currents. Furthermore, lakes are naturally short-lived: they tend to fill with sediments and to be emptied by streams downcutting their edges. Thus, some lake waves and currents have insufficient time for creating large landforms. Also, lake tides, where they do exist, are generally too slight to provide waves and currents with a wide vertical range to work in (Wyckoff 1999).

Although astronomical lake tides (those caused by Moon–Sun gravitational attraction) are relatively insignificant, other movements of lake water can be substantial. In the event known as a seiche, wind pushes water up against one shore and the water then flows back to the opposite shore, like water in a washtub being rocked. Seiches can be important in the transportation of sediments. Investigators have measured seiches in Lake Erie up to 8 feet (2.4 m) in height. Seiches also can be produced by earthquakes, sudden changes in atmospheric pressure, heavy rains, surges in glacial meltwater from nearby mountains, and variations in water density (Wyckoff 1999).

Waves on large bodies of water such as the Great Lakes shape shores of loose material, building sand barriers (including spits), as well as beaches with scarps, berms, and beach ridges. Storm waves can attack weak bedrock that fringes lakeshores, undercutting them and creating cliffs. In cold regions in winter, expanding lake ice pushes sand and rock fragments up the beach, creating ridges. Waves on the largest lakes, such as Lake Bonneville during the pluvial period, have cut terraces on adjacent highland slopes (Wyckoff 1999). Lakeshores also exhibit rill marks, swash marks, and ripple marks.

The Rock
During the million-year "Ice Age", huge glaciers intermittently advanced and retreated through the region, scouring the sandstone bedrock and enlarging channels between what would become the Apostle Islands. During glacial retreat, Glacial Lake Duluth formed. Sand beaches formed and cliffs were exposed as it receded. These beaches rest 500 feet above today's shoreline.

Shoreline sandstone supplied top grade brownstone for urban Midwest buildings for about 30 years beginning in 1869. Quarry pits remain on Stockton, Hermit, and Basswood Islands. Easy access to boat transport made quarrying economical until extraction costs increased and architectural styles changed. The Old Bayfield County Courthouse, built of brownstone in 1883, houses the Apostle Islands National Lakeshore Visitor Center.

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.

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A geology photo album for this park can be found here.

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 needs 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.

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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

A school visit to a national park can be more than just a field trip; for teachers and students alike it can be an exciting extension of their classrooms. Service-learning (student volunteer work within an academic framework) brings the real world into the classroom. Any successful service-learning demands careful planning, but there are specific things to include when working with a national park.

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/apis/index.cfm   I  Email: Webmaster
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