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Glacial Relicts
Kettle Lakes and Small Glacial Wetlands


James Whittington
Emporia State University
Quaternary Geology

November 2006


Table of Contents

1. Introduction 2. Origins of Kettle Lakes and Glacial Wetlands 3. Kettle Lake and Glacial Wetland Ecology 4. Summary 5. References






Introduction

At the end of the Pleistocene Ice Age, as the last ice sheets retreated back into the Arctic, glaciers left behind many relicts. In addition to the many glacial landforms and sediments seen on a large scale through out North America, they also left behind small pockets of wetlands and lakes that continue to provide biodiversity across the upper Midwestern United States.

These small wetland environments provide habitat for a variety of species of plants and animals, which are often unique in their region. In some instances, these isolated communities form subspecies, which may be unique to a few acres. In other instances these wetlands provide sanctuaries for local animals in times of draught or during migrations.

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Origins of glacial wetlands

There are a variety of different manners in which retreating glaciers formed these small wetlands. Kettle lakes are formed when a large detached fragment of ice becomes buried in glacial sediments. As the glacier retreats the black melts and leaves a depression in the sediments. These buried ice blocks can be thousands of feet across and take thousands of years to melt and form a lake.

Walden Pond, made famous by the writer Henry David Thoreau, is a 61-acre kettle lake located in upstate New York. Kettle lakes can be found dotting the landscape from the upper reaches of New England to the Western High Plains of Montana.

Kettle Lakes (or Kettle Holes as they are often known) frequently occur in groups in formerly glaciated regions. The terrain, known as kame and kettle topography, is typically chaotic and is normally not associated with flowing water, though it often forms on abandoned glacial drainages. These lakes can range in size from a few feet across up to several thousand acres. Many are hundreds of feet deep.

The shallower lakes, especially in poorly drained low-lying areas, are often the origin of small peat bogs. Over time, the bogs will eventually clog with vegetation and sediment and form glades.

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Kettle Lake and Glacial Wetland Ecology

There are numerous examples of modern wetlands that owe their origin to glacial activities. Portage Lake and the Burton Wetlands in north central Ohio are examples of the many kettle lake complexes found throughout Ohio. Many of the Ohio kettle lakes have developed into mature sphagnum bogs. These bogs are typified by cold, low pH waters that are inhospitable to plant and animal life found in adjacent upland areas. Instead, these bogs support Tamarack and Yew trees hundreds of miles south of their native habitat of Canada. The thick moss and peat insulates the kettle lakes and keeps the water temperatures low. Carnivorous pitcher plants also thrive in the nutrient deficient bog.

Many of the species that reside in these wetlands are what are called glacial relicts. These are species that are holdovers from a time when glaciers still covered much of North America. The cyclical advance and retreat of ice sheets isolated different populations. Over time the ice retreated for good and these isolated populations of plants and animals exist in these small ecosystems.

The kettle lakes and peat bogs provide a cool sheltered environment that mimics the alpine meadows and prairie wetlands where these populations originated. These environments are now home to rare snails, salamanders, frogs and fish. In addition a great number of plants, lichens, mosses, and fungi also make their homes in these remnant ice age outposts.





The Burton Wetlands near Cleveland Ohio, a small complex of kettle lakes and peat bogs. Image from Ohio Department of Natural Resources.


The Four Toed Salamander, a frequent inhabitant of relict glacial wetlands. Image from Missouri Department of Natural Resources

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Summary

Relict glacial wetlands are found scattered across the northern United States. Many of these wetlands consist of small lakes and peat bogs created by retreating glaciers known as kettle lakes. These wetlands provide habitat to a variety of plants and animals that are survivors of the ice age, as well as a refuge for regional wildlife and migratory birds. In addition to providing habitat, these wetlands help to conserve water resources and provide a buffer for larger watersheds. New species continue to be discovered and the vital role of these wetlands explored.

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References

Where Water and Land Embrace, Ohio Department of Natural Resources URL:
http://www.ohiodnr.com/parks/explore/magazine/sprsum97/wetland.htm.

Kettle Ecosystems URL:
http://www.kenaiwetlands.net/EcosystemDescriptions/Kettle.htm.

Northeast Ohio Glacial Wetlands, The Nature Conservancy URL:
http://www.nature.org/wherewework/northamerica/states/ohio/preserves/art16210.html.

Ritter, Dale F., 1978; Process Geomorphology, William C. Brown Company

Hambrey, Michael. and Alean, Jurg., 2004; Glaciers, Cambridge Press

Aber, J.S. 2006. Earth Science 767 Quaternary Geology, Course Handouts; Emporia State University

Aber, J.S. 2005. Earth Science 767 Wetlands, Course Handouts; Emporia State University


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This web presentation prepared for
Earth Science 767 ES 767 : Quaternary Geology
by James Whittington (November 2006)