IATCC - Mondeaux Flowage Tunnel Channel EarthCache

IATCC - Mondeaux Flowage Tunnel Channel

Parking location: N45 20.005 W090 27.120
EarthCache location: (approximately) N45 19.805 W90 27.005

Please note that this is an EarthCache and as such logging this cache requires special tasks be performed. Those tasks are detailed below. For this EarthCache you will need a GPS and a camera.

From the parking area, I would suggest taking a photo of the “Chequamegon National Forest Mondeaux Dam” sign to provide visual proof of your visit, then walk South along the Ice Age Trail along the west side of the flowage. Continue your walk towards Spearhead Point campground. You should expect to walk less than a half mile each way. The Coordinates for this feature are along the Ice Age Trail and are approximate (due to possible tree cover in the summer months) but try to answer the below tasks within about 100 feet of the published coordinates.

The Mondeaux Flowage is located on a seven-mile tunnel channel. What you today see as a channel was once covered by the Chippewa Lobe of a mighty Wisconsin glacier. As the glacier melted and retreated approximately 10,000 years ago, water under pressure flowed beneath the glacier forever changing the landscape. Today in the area you can see formally ice-walled lake plains, small kettle lakes and multiple eskers which form the “hogback” characteristic ridges throughout the flowage area.

Tunnel Channels

At one time much of Wisconsin was under as much as a mile of ice and snow. This thick blanket of snow and ice shaped our state in many ways one of which has been demonstrated in this area. After the most recent period of glaciation ended, the current shape of Wisconsin began to reveal itself.

This area has a series of lakes and ponds lying in a "tunnel channel" which is created when melt water under extreme pressure flows beneath the surface of a retreating glacier and blasts out a channel as the water moves toward the glacier’s margin. Eventually these tunnels refill with ice due to subsequent freezing or a tunnel collapse. When the glacier retreats these tunnels, which have a network of ice channels, are covered with sediment left by the glacier as it melts. The ice filled channels now covered with sediment (also known as outwash) eventually melt and create a valley which is often filled with water becoming a pond or lake. Tunnel channels are typically found to be between 16 and 98 feet in depth but have been found with depths as great as 164 feet.

In image A you can see a river in a channel beneath the glacier. In image B the glacier has retreated leaving a partially ice filled tunnel channel covered with sediment (outwash). In image C the ice which filled tunnel channel has melted dropping the level of sediment and leaving a depression in the ground. This depression often fills with water forming a pond or lake.