Marseilles moraine facts for kids
The Marseilles moraine is a long, low ridge of hills that circles the southern part of Lake Michigan in North America. It starts near Elgin, Illinois, and stretches southwest of Chicago metropolitan area. Then, it turns east, about 30 to 40 miles (48 to 64 km) south of the lake, going through Kankakee and Iroquois counties before entering Indiana.
This moraine formed during the Wisconsin glaciation, which was a very cold period when large ice sheets covered much of North America. The glacier had been melting and moving back (retreating). But then, it stopped in one place for a long time. As the glacier melted, it left behind a lot of rock, sand, and clay, which piled up to create the hills we now call the Marseilles moraine.
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Where is the Marseilles Moraine Located?
The Marseilles moraine is named after the village of Marseilles, Illinois. This is where the Illinois River cuts right through the moraine. You can easily see this moraine as far north as South Elgin, about 4 miles (6.4 km) south of Elgin, Illinois. Further north, it blends in with other landforms.
For about 25 miles (40 km) south, the Marseilles moraine joins up with another ridge called the Minooka Ridge. This combined ridge follows the east side of the Fox River. It passes through cities like St. Charles, Geneva, Batavia, and Aurora. The outer edge of the moraine runs along the east side of these cities. The moraine belt here is usually 2 or 3 miles (3.2 or 4.8 km) wide.
The moraine continues south along the border of Will and Kendall counties. It stays about 2 or 3 miles (3.2 or 4.8 km) away from the Fox River. Near Oswego and Yorkville, the Marseilles moraine turns west. The Minooka Ridge keeps going south towards the Illinois River.
In Kendall County, the moraine is only 2 or 3 miles (3.2 or 4.8 km) wide. But it gets wider in northeastern LaSalle County, reaching 5 or 6 miles (8.0 or 9.7 km) wide near the Illinois River.
How Does the Moraine Continue East?
When the moraine reaches the Illinois Valley, it changes direction. It goes from a south-southwest path to a south-southeast path. It stays about 3 to 5 miles (4.8 to 8.0 km) wide through southeastern LaSalle and northern Livingston counties.
Near Odell, the moraine turns east. Then, near the border of Livingston and Ford counties, it curves northeast. This curve is quite wide, about 8 or 10 miles (13 or 16 km) across. It then reaches the area of Ste. Anne, where it turns southeast again.
The Iroquois Moraine: A Continuation
From Ste. Anne, the moraine continues southeast and crosses into Indiana. Here, its name changes to the Iroquois moraine. It goes through Newton and Jasper counties in Indiana. The Iroquois moraine spreads out, covering an area 3 to 6 miles (4.8 to 9.7 km) wide, all the way to Medaryville in Pulaski County, Indiana.
To the east of Medaryville, the moraine seems to disappear. It might end there, or its remaining parts could be hidden under the sand ridges of Lake Kankakee.
The Iroquois moraine is generally 2 to 4 miles (3.2 to 6.4 km) wide. Its southern edge is about 1 to 4 miles (1.6 to 6.4 km) north of the Iroquois River in Newton and Jasper counties. In eastern Jasper County, it turns north. It stops being a clear ridge about 4 or 5 miles (6.4 or 8.0 km) south of the Kankakee River.
What is the Height and Shape of the Moraine?
The highest part, or crest, of the Marseilles moraine is usually around 750 feet (229 m) above sea level. Its height doesn't change much, only about 25 feet (7.6 m) up or down. The outer edge of the moraine generally follows the 650-foot (198 m) elevation line. The inner edge is closer to the 700-foot (213 m) line.
The Marseilles moraine has a clear crest that acts like a natural dividing line for water. North of the Illinois River, it separates the waters flowing into the Fox River from those flowing into the Dupage River, Au Sable Creek, and Nettle Creek. South of the Illinois River, it divides the tributaries of the Vermilion River from the Kankakee River.
The steepest parts of the moraine are in Kendall County, Illinois. Here, a ridge stands 30 to 40 feet (9.1 to 12.2 m) higher than the land next to it. This is a bit unusual. Most of the crest is a wide, wavy ridge, about 1 to 2 miles (1.6 to 3.2 km) wide. It has low spots that can fill with water during certain seasons. Most of the crest has gentle slopes and small rises, usually less than 20 feet (6.1 m) high.
In Livingston County, some of these rises reach 50 feet (15 m) above the surrounding wet areas called sloughs. There are also noticeable hills along the border of Kankakee and Iroquois counties. Here, these hills can be 75 feet (23 m) or more above the rest of the moraine.
The highest points on the Marseilles system north of the Iroquois River are north of Rensselaer, Indiana. They reach altitudes of 755 to 760 feet (230 to 232 m) above sea level. Much of the moraine is between 700 and 725 feet (213 and 221 m) high.
What is Outwash?
Along the Fox River in Kane and Kendall counties, there's a wide area of coarse gravel. This gravel was left behind by the melting glacier and is called "outwash." It lies mostly on the opposite side of the river from the Marseilles moraine. For example, at Batavia, the gravel is mainly on the west side. At Aurora, it's on the east side. And at Yorkville, it's on the west side. This large amount of gravel in Kane and Kendall counties suggests that it formed a type of delta, where the glacier's meltwater flowed out.
Near the Illinois River, there are signs that the meltwater spread out like a lake. This means the Illinois Valley might have been blocked between the Marseilles moraine and an older moraine called the Bloomington series.
The area now drained by the Iroquois River into the Kankakee was once blocked by ice. The water would have flowed west across the edge of the basin in northern Ford County into the east fork of the Vermilion River. Evidence of fine sand and silt covering the flat land shows that a lake, called Lake Watseka, once filled this part of the Iroquois valley.
