This EarthCache was developed with permission of the Leelanau
Conservancy in the Lighthouse West Natural Area. The Lighthouse
West Natural Area contains 42 acres in the northern part of
Leelanau County. There are about two miles of natural surfaced
trails for hiking, walking, skiing, and bird watching. For more
information about the Lighthouse West Natural Area and the Leelanau
Conservancy, please follow this link: Leelanau Conservancy.
Parking is available just off Cathead Bay Road at N 45 12.320 W
85 32.828. From there follow the trail to the west toward the
posted coordinates. As you walk the trail, keep in mind that this
area was covered by a glacier over a mile thick until just 11,000
years ago.
Around that time, the Wisconsin Glacier that once covered
Michigan was retreating. A glacier is said to be retreating if it
is melting faster than it is advancing. As it melted, whatever
clay, dirt, gravel, and boulders it was carrying was deposited on
the land. The accumulation of this debris makes up the moraine.
As the glacier retreated, several glacial lakes were formed. As
the glacier continued to retreat, some lakes would merge with
others, creating larger lakes. Other times, a new outlet would be
uncovered that would drain the lakes, sometimes completely. Lake
Algonquin was one of the largest glacial lakes covering more area
than the modern Lake Michigan, Lake Huron, and parts of Lake
Superior. It existed from just over 11,000 years ago up until about
7,000 years ago.
Near N 45 12.340 W 85 33.208 you will find a series of steps.
This is the ancient shoreline of Lake Algonquin. Using your GPSr,
determine the elevation at the top of the steps. This elevation
will represent the elevation of the Lake Algonquin shoreline. As
you walk down the steps and continue along the trail take note of
the slope, soil and any rocks or boulders that you may see along
the way.
The weight of the glacier over the previous millions of years
had compacted the Earth’s crust. Now that the glacier had
retreated, the Earth’s crust began to rebound by about 1 ft
per century. This process is called isostatic rebound. As the crust
rose, several of the outlets draining the lakes became blocked.
This caused the lakes to fill back up with water. About 5500 years
ago, with these outlets blocked and the water levels rising, Lake
Nipissing was formed. Lake Nipissing, much like Lake Algonquin,
filled up the Michigan, Huron, and Superior basins. Lake Nipissing
existed from about 5500 years ago to about 4000 years ago.
Along the trail near the posted coordinates, you will find
another set of steps and a walkway. This is the ancient shoreline
of Lake Nipissing. Using your GPSr, determine the elevation at the
top of the steps. This elevation will represent the elevation of
the Lake Nipissing shoreline. As you walk down the steps, take note
of the slope, soil and any rocks or boulders that you may see along
the way.
Just beyond these steps is modern day Lake Michigan. Using your
GPSr, determine the elevation at the shoreline. Take note of the
slope, soil and any rocks or boulders that you may see in the
area.
To log this EarthCache, you must compare the three
shorelines.
1) What is the difference in elevation between the three
shorelines?
2) How is the slope of the three shorelines similar or
different?
3) Describe the ground makeup of each shoreline, soil,
rocks,etc.
Email me your answers to #1-3 through my profile.
4) Near the base of the steps at the Lake Algonquin shoreline,
there is a very large example of what the glacier left behind and
what the lake rolled around. Post a picture of this and estimate
it's weight in your online log. Faces aren't required in the
picture, but they are appreciated.
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