Danke Professor Agassiz EarthCache
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This EarthCache is located in Hawley's Riverbend Park, on the south
side of Highway 10. Coordinates are given for the parking area and
for the EarthCache. The EarthCache is a short walk over level grass
most of the year and snow in winter. The EarthCache does not have a
sidewalk or path leading to it and snow is not removed from the
park.
To claim a Find for this EarthCache e-mail me the answers to the
following questions.
1) About 10,000 years ago the most recent stage of glaciations in
the area was ending. What is that stage called?
2) According to the Geological Society of Minnesota plaque, what
was the greatest depth of Lake Agassiz?
3) What event allowed the impounded water to flow north to Hudson
Bay?
4) While standing at the geological marker look to the north. The
three tallest structures in town can be seen from here. To the
northwest you can see the city water tower. To the east of the
water tower are the other two tallest structures, both of which tie
in with the last line of information on the plaque. What do these
structures have to do with Lake Agassiz?
Approximately 10,000 years ago the most recent stage of glaciations
was ending in what would become Minnesota. As the glacier melted
the resulting water drained into the Minnesota River Valley, later
into Lake Superior and finally into Hudson Bay. Whether you accept
D.B. Lawrence’s estimation that the lake lasted for 3,000
years or Thomas Waters’ 5,000 years, Lake Agassiz was a major
physical feature of the North American landscape.
The great glacial lake is named for Swiss scientist Jean Louis
Rodolphe Agassiz (1807-1873). Louis Agassiz was an early believer
of the idea of a large glacial lake. Lake Agassiz was the largest
body of fresh water to have existed in North America. At its
largest Lake Agassiz covered about 80,000 square miles (207,200
square km), 17,000 sq. miles (44,030 sq. km) in Minnesota.
As Lake Agassiz receded it left behind sand dunes and deltas, as
well as beaches and an expansive level lake bed. The lake bed has
been used in many ways. It was the surface over which pioneers
created the Pembina Wagon Road, it was cut into blocks for sod
houses and pioneers tilled the lake bed to raise crops. From small
family farms to the large Bonanza Farms, the rich soil, created by
thousands of years of lake sediments, helped run the economy of the
mid to late 1800s. Even today Lake Agassiz and the changes it made
to the landscape are driving parts of the economy, in ways both
large and small.
Here are two examples; a mile east of this EarthCache is a sand and
gravel pit. A company is in business mining part of Lake Agassiz's
lake bed. A half mile east of the sand opperation is a ridge that
is one of Lake Agassiz's old shorelines, Herman Beach. A
communications tower was built on the ridge, taking advantage of
the extra height of Lake Agassiz's old shoreline.
Photos are appreciated, but please don't post images of the marker
or the tall structures. Thanks.
References
Waters, Thomas F. (1973). The Streams and Rivers of Minnesota.
Minneapolis, MN: University of Minnesota Press.
Lawrence, D. B. (1969). Agassiz Dunes Natural Area. Fertile, MN:
The Nature Conservancy – Minnesota Chapter.
Roadside Signage, placed by Geological Society of Minnesota.
Thank you to the City of Hawley and Lisa Jatvig for granting
permission for this EarthCache. City Hall can be contacted at
info@hawley.govoffice.com
Congratulation to Former Hawkeye for scoring the First To Find.
Additional Hints
(No hints available.)