The last ice age, known as the Wisconsin Glaciation, occurred 75,000 to 10,000 years ago. The massive Laurentide Ice Sheet covered much of what is now Minnesota.
As the glaciers moved south, they ground down terrain features. The glaciers accumulated and transported rocks, sand and gravel.
Image source: Dyke and Prest, 1986
12,000 to 14,000 years ago the climate began to warm and the glaciers began to melt and retreat north. The melting and retreating ice deposited its load of debris, forming moraines – piles or layers of rock, sand and gravel.
As the ice receded to the north, the glacial meltwater formed huge lakes, such as Lakes Agassiz (Ag-a-see) and Koochiching (Koo-chee-ching). The map shows the total extent of Lake Agassiz over time. At no time did the lake flood the entire area shown. At its largest, the lake was larger than any lake that exists today.
The southern area of the lake, in today’s Minnesota and North Dakota, would have been flooded about 11,700 years ago at a time when the northern areas would have still been covered with ice. By the time the northern areas (Manitoba) were flooded much of the southern area of the lake would have already drained. The lake left behind a small amount of sediment in the form of clay layers in the Red River Basin.
Source: University of Manitoba Libraries Map Collection
The Leaf Hills Moraine was located between Lake Koochiching and Lake Agassiz. Water drained from Lake Koochiching, eroding the Leaf Hills Moraine, and flowing into Lake Agassiz. The fast-moving water transported sand from the moraine. Upon entering Lake Agassiz, the water slowed and deposited the sand into a delta where we are now standing.
As Lake Agassiz grew, the glaciers to the north prevented drainage in that direction. The water flowed from the lake to the south, forming a huge river along the approximate course of today’s Minnesota River. As the size and shape of Lake Agassiz changed over time, various beach ridges were left behind. You can observe these ridges as you drive east from the Red River.
The glaciers continued to recede north exposing the sand delta. For the next 5,000 years (9,000 to 4,000 years ago) the climate becomes drier and warmer. Winds arrange the sands into dunes.
Barcan dunes formed when there was little vegetation. These dunes tend to be moved forward by the force of the wind.
As the climate became wetter, vegetation became established. This vegetation anchored the tails of the dunes, preventing them from moving. These dunes are called parabolic dunes.
Vegetation now covers much of the Fertile Sand Hills, but you can see examples of the exposed dunes in both Death Valley 1 and Death Valley 2. A short hike from the nature center and you can immerse yourself in ancient geological history!
The Sand Hill River and its valley have produced a rich lowland forest community. Wildflowers, ferns, shrubs and trees greet visitors. Expect to meet a variety of songbirds, waterfowl, and birds of prey.
The north facing bluffs harbor an unusual community of intermixed birch and boreal forest species. Steep bluffs and deep valleys were carved by the Sand Hill River over thousands of years.
A rare experience awaiting visitors is a hike through the oak savanna. This prairie landscape has gnarled bur oaks scattered throughout, and was once maintained by naturally occurring fire and bison.
Wide-open expanses of shifting sand dunes were once the predominant feature of the Fertile Sand Hills. Vegetation has stabilized the dunes. Remnant patches offer a window into geological history and host some of the site's rarest species.
Visitors are treated to beautiful panoramas and rolling hills covered by grasses and wildflowers. An amazing variety of plants and insects are found on these dry sand prairies.
Follow the winding course of the Sand Hill River as these dancing waters flow over Glacial Lake Agassiz beach ridges on their way west to the Red River, and ultimately northward into Hudson Bay.
The Ojibway named it "ga-papiqwutawangawi zibi", or "the river of the sand hills, scattered here and there in places." In 1800, Alexander Henry, a fur trader, passed the mouth of the river which he called the Riviere aux Buttes de Sable. This French phrase translates into English as river with hills of sand.
In 1806-07, William Henry had an outpost on the Sand Hill River. During the trading season he collected 500 beaver, 41 black bear, 1 grizzly bear (the last reported in Minnesota), 15 martens, 33 mink, 22 muskrats, 24 otters, 91 fishers, 250 wolves, 43 deer skins, 43 red fox, and 3 wolverines. He also reported an overwhelming abundance of bison, elk and waterfowl.
From 1820-1870, the Woods Trail (a major route on the Red River Oxcart Trails from Winnipeg to St. Paul) passed through this area in the general vicinity of Fertile. This route was taken to escape the Beltrami Marsh and dunes to the west, and the marshes and lakes east of Fertile. For some distance the trail followed one of the old dry beach ridges of Glacial Lake Agassiz.
In March of 2009 the Sand Hill River reached record high levels, eventually flooding up to the threshold of the building. Flooding is a natural process of the Sand Hill River. In 2009 snow melt resulted in the exceptional amount of flooding. Click on the link below to watch a short clip of the flood.
In 1976, the City of Fertile purchased 640 acres of the Sand Hills to be used as a wilderness sanctuary and recreation area. A grant in 1985 allowed the nature center building and trail system to be created. The Agassiz Environmental Learning Center (AELC) was established as a private non-profit corporation in 1991.