Glacial Geology at Buffalo River SP EarthCache

Welcome to Buffalo River State Park! This is a beautiful park in lovely Minnestoa with great prairies and intriguing woods. Today we will study some of the local glacial geology.

Glacial Geology and Lake Agassiz:

Agassiz is a well-known word in the Red River Valley. It refers to the massive Glacial Lake Agassiz which is thought to have covered the valley eight to ten thousand years ago. The rise and fall of this ancient lake formed the dominant landscape features within the park. This glacial lake was named after Louis Agassiz, a renowned geologist and first prominent advocate who stated that land ice, or glaciers, advanced and receded over the land. He is sometimes referred to as the “father of glacial geology.” As the last glaciers retreated north, meltwaters drained south until the receding ice reached the Red River Valley. Here, the slope of the land dictates drainage to the north. But retreating ice (in some places up to a half-mile thick) blocked the meltwaters from flowing north. The result was the enormous glacial lake. Slowly, the ice blockage melted and Lake Agassiz began draining. It left behind a fertile, level lake bottom landscape interrupted by prominent gravel ridges or beach lines. One of these ridges (Campbell Beach) can be observed in Buffalo River State Park. Look for the rise in elevation along the eastern edge of the park. This means that although Minnesota and the surrounding Red River Valley are thought of as extremely flat, there is some change in elevation. This was caused by the ancient Glacial Lake Agassiz.

Glacial Erratics:

Continental glaciations deeply scoured Canada's bedrock and later deposited the rock debris sometimes great distances from its source. This debris includes boulders like the ones found in the park. By examining the rock type of these boulders called erratics, geologists often can trace them back to their bedrock source to determine ice-flow directions.

On a side note:

Upon closer examination of the surface of these erratics, you can observe an alliance between kingdoms. The greenish, flake like organisms on the boulders are unusual creatures called Lichen. Lichen is not a single organism the way most other living things are, but rather it is a symbiotic combination of a fungus and in most cases, green algae. In some cases this relationship is crucial to the survival of each, meaning they have become dependent on each other for survival.

As you continue on the trails, look for boulders that are partially buried and consider the implication these erratics had on early settlement and agriculture.

Logging this EC:

Send an email note with the following:

1) name of this earthcache, and number of people in your group.

2) Mark the elevation here using your GPS. Go to the additional waypoint and mark the elevation there. Do the posted coordinates put you in the lake bed, or above the ancient lake (on shore)?

3) The additional waypoint; does it put you in the lake bottom, or above it?

Happy Caching!