Kankakee Outwash Plain

On the south side of the moraine, where the elevation drops, the meltwaters eroded away valleys, carrying sand and mud with them.

As the muddy meltwater reached the valley where the slope lessened, the water slowed, depositing the sand on the outwash plain.

Beginning 14,000 years ago, the head of the glacier stood along a line across the middle of Lake, Porter, and LaPorte counties.

Today, the bedrock is hidden deep beneath the sediments left by the glaciers, but it still played a role in developing the lay of the land.

Here, all the water flowing off the front of the glacier had to pass westward, for south of glacial Lake Kankakee, the Iroquois Moraine blocked all drainage.

Runoff from the Valparaiso Moraine built[2]: 52  outwash ridges of sand leading into the lake.

As the volume of water decreased from the glacier melting northward, the lake slowly drained and filled.

Not being able to cut a channel through the limestone ridge in Momence, the Kankakee Lake became 500,000 acres (200,000 ha) of marshland.

It stretches south from Valparaiso to below the Kankakee River, nearly 15 miles (24 km) wide.

Along the Michigan and Indiana border, the outwash plain forms a 10-to-15-mile-wide (16 to 24 km) band along the St. Joseph River.