Simplified drawing of ice lobes across Minnesota
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1-3 mm Rainy till sand grains
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A Munsel® color chart is the standard when describing till color.
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As early as 1.2 million years ago large “tongues” of ice covered Minnesota. Throughout the Ice Age, several different ice lobes advanced across the state.
The Quaternary Period began about 2 million years ago. It is divided into the Pleistocene Epoch (2 million to 10,000 years ago) and the Holocene Epoch (10,000 years ago to present).
The Pleistocene, also called the Ice Age, is the time when the Laurentide Ice Sheet covered much of northern North America. The bulk of glacial sediment (till) in Minnesota is attributed to one time interval within the Pleistocene, the Wisconsin Age, which began about 75,000 years ago.
Glacial sediments mask nearly all of Minnesota’s previous geologic history. These deposits are the “footprints” that allow geologist to retrace the history of glacier movement. Till of a particular color and containing distinct rock types may indicate the direction from which the glacier advanced. In Minnesota, where the glacial history is complex, it is important to be able of determine where and when a glacier originated.
The purpose of this collection is to supply samples of the “surface geology” or sediments (till) of the ice lobes that advanced across the state several different times from several different directions. There are eleven till samples in this collection. They represent the following ice lobes: Wadena, Rainy, Superior, Des Moines, Browerville, and the Anoka Sandplain. The first sample set (5 packets) illustrates the particular color and texture of the ice lobe till. The second sample set (6 packets) illustrates the distinct rock types (lithology) of the ice lobe till.
Education professionals, Home Schools, scout leaders, 4-H leaders, etc., are encouraged to see the Minnesota Sand Module. Aggregate, sand and till samples of the major glacial events are available either as 2x2 inch pouches,, or as 2x3 inch pouches. The former (2x2 pouches) have .5 oz of material; the latter (2x3 pouches) have 3 to 5 ozs. of material.
The collection and pouches are useful to non-professionals who simply wish to learn more about the geology of Minnesota. It is not intended to be a one-stop, comprehensive collection. It is useful to anyone with an interest in earth science or Minnesota.
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since March, 2006.