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REGION IV: West Central Minnesota (Home!!)
GEOLOGIC OVERVIEW
West Central Minnesota is a land of glacial features. Look all around the
Faribault and Brainerd Lakes Regions and you can find evidence of glaciers
easily.
Four major glacier ice advances have occurred in the last 40,000 years. All of
Minnesota was covered by ice three times but southeastern Minnesota was not
covered during the last ice age – the Wisconsin- 10,000 years ago.
Each time glaciers moved south, they pushed sediment like a snowplow
pushes snow. When the glaciers stopped moving forward all of the dirt, rocks
and other materials were left there. The ice and hills left behind by glaciers
shaped West Central Minnesota’s landscape.
ROCKS
The rocks found in this region were mostly brought by glaciers and were
formed somewhere else. Many are very large showing how much power the
glaciers had. Most rocks are rounded caused by the dragging and friction of
the glaciers. You can see large erratic boulders that formed in Canada or the
North Shore region that were carried here by the ice. The processes from the
rock cycle in the past were weathering and erosion from the glaciers advancing
and retreating. Rock cycle processes today include weathering and erosion
from water movement and precipitation.
MAJOR FEATURES
LAKES: Lakes formed two ways in Minnesota. End moraine lakes and the
more common ice-block lakes are found all over West Central Minnesota.
Ice-block lakes make up 80 – 85 % of all Minnesota lakes. When the
glaciers started melting, some large (huge) chunks of ice were left behind. The
ice chunks sunk into the ground and were buried. They later melted and
formed lakes. Most of these lakes are sitting on top of clay soils. Clay holds
water like a bowl and does not let much water soak into the ground.
End moraine lakes can be the most famous. Lake Mille Lacs and Lake
Minnetonka are end moraine lakes. When the glaciers started to melt, they
dumped huge rows of sediment called end moraine. This end moraine
formed hills around low areas. The low area filled in with glacial melt water.
Most of these lakes are also on top of clay sediment and water does not soak
into the ground well.
GLACIAL FEATURES: Glaciers formed all prominent geologic features in
this region. Notable features caused by glaciers are: end moraines, ground
moraines, outwash plains, lakes, eskers, drumlins, kettles, erratics, and thick
till.
FOSSILS: Any of the fossils in this region were moved or crushed by the
glaciers as they repeatedly moved south as they advanced and then back north
as they retreated.