What was lake agassiz

Enter your suggested edit s to this article in the form field below. Accessed 12 November In The Canadian Encyclopedia. Historica Canada. Article published February 06, ; Last Edited January 23, The Canadian Encyclopedia , s. Thank you for your submission Our team will be reviewing your submission and get back to you with any further questions. Thanks for contributing to The Canadian Encyclopedia. Article by N. Lake Agassiz was the largest glacial lake in North America. So the newer beaches sport Manitoba names.

However, Niverville is suspected of being a ridge created by the keels of icebergs floating in Lake Agassiz, rather than an actual beach. These beaches were all created more than 4, years after the Herman. The oldest of the Manitoba beaches, the Gladstone, runs just east of the Town of Gladstone. Just below the Gladstone Beach is the Burnside Beach, named for a village that once existed near the junction of the Trans-Canada Highway and Highway 16, and marking the place where Lake Agassiz's western shore lay.

Farther east, the Burnside Beach once wrapped around Birds Hill, during a period when Birds Hill was an island see page It is the highest of the four beaches that ring Birds Hill. Several beach ridges run parallel to the eastern boundary of Riding Mountain National Park.

The park has a hiking trail, called Beach Ridges Trail, on its northeast corner. The beaches have been eroded and covered with vegetation, however, making them difficult to detect. The way to find them is by their trees. The dry, sandy, better-drained soils of the former beaches are preferred by stands of bur oak, and there are swathes of oaks on Riding Mountain's eastern slope. Once the forest along the trail changes to poplar, you know you're off the beach. The last two beaches before it drained into Hudson Bay are the Kinojevis Beach—Kinojevis being a river in eastern Quebec—and the Fidler Beach, named for fur trader and surveyor Peter Fidler.

The Kinojevis Beach was formed when glacial lakes Agassiz and Ojibway combined, while Fidler was the final beach before the waters flowed into Hudson Bay, or its larger ancestor, the Tyrrell Sea. Matile and I drove southeast of Steinbach on Highway Just before you get to the junction of highways and , there is a small, unimpressive beach ridge. It can't be more than 30 metres long, and perhaps two metres high.

Highway runs through it. It has its own marker, the twin road signs for Highways and fastened to a post. It just takes a couple of minutes to walk its width and feel connected with Manitoba's ancient history.

If you look across the road from the Ukrainian Orthodox cemetery, you see falling-down fence posts following a small arc in the landscape. That's the continuation of an Agassiz beach. Matile pointed out similar small beaches ridges along Highway The directions in Chapter 14 are for much more prominent beaches than these, with a definite wow factor.

In fact, one of the best locations to see Lake Agassiz beaches is right around Steinbach. The reason for this is Steinbach is at the edge of Lake Agassiz's clay plain, where the land starts rising to the east into the Canadian Shield. The rise means the lake beaches are clustered together. The Sandilands were submerged during Lake Agassiz's deepest stages but later became a prominent island. So the Sandilands isn't so much a beach ridge as the edge of an island that the Campbell Beach wrapped around.

Standing on a sand cliff in the Sandilands facing west, Matile said we were looking across more than kilometres of Lake Agassiz. The shore across to the west would have reached to Brandon. That was quite a lake. Sandilands Provincial Forest is part of an extraordinary land formation that we don't fully appreciate except where it turns into Grand Beach, one of the world's best beaches.

We can thank our glacial past for that. Sandilands has been thought of by some as an end moraine—a place where the ice sheet stalled. That means the glacier was melting and refreezing in lock step, allowing debris to drop off its leading edge for perhaps hundreds of years and forming a ridge. Today, however, this land formation is believed to have been created by what's called outwash, and that's Matile's interpretation, too.

Outwash is runoff from glaciers. This particular outwash formation was at the juncture of two enormous glaciers: the Labradoran glacier with its dome east of Hudson Bay, in northern Quebec; and the Keewatin glacier, with its ice dome west of Hudson Bay, in Nunavut.

The Keewatin glacier was ploughing south, and the Labradoran glacier was ploughing southwest, and eventually they ran into each other, or at least side-swiped one another, to form one giant ice mass we know as the Laurentide Ice Sheet.

But when they started to melt, or become "unzippered", as Matile put it, the sand that had accumulated inside the glaciers was washed by meltwater into the giant trough opening between them. This raised mass of sand is kilometres long, and it's often mistaken for a moraine. But moraines are made of till—the geological name for a mix of sand, gravel, silt and clay. This extensive ridge is too sandy to be a moraine, Matile maintains, and the sand is 30 metres deep.

It had to have been formed by outwash. The Sandilands are the highest point in southeastern Manitoba, reaching an elevation of metres above sea level. The Campbell Beach surrounded them but near the bottom.

While Campbell Beach was at the foot of the Sandilands, one of the older beaches, the Norcross Beach, crossed higher up on the Sandilands. Adding to the complexity of studying the Sandilands is that the prevailing winds were northwesterly, or nor'westers. These sent giant waves crashing into the Sandilands, eroding sand on points that were sticking out into Lake Agassiz. The waves carried the sand along the shoreline to the south, forming spits, not unlike sandy ocean spits. Elaborate beaches were developed this way; they are now covered with trees and other vegetation.

Other complexities in these ancient beaches are that some are wave-cut scarps, where wave action has eaten into small shoreline cliffs. The lake also formed offshore sand bars leading up to a beach, and experts often can't tell the difference between beaches and sand bars. It might even have acted as a barricade that contained the water and helped to create Whitemouth Lake. If you're wondering why there are no beach ridges in the Canadian Shield, it's because the Shield was an archipelago of islands in Lake Agassiz.

The rock ridges poking out of the water muted the power of Lake Agassiz's wave action and prevented the development of good beaches inside the Canadian Shield.

So, who cares? What difference does it make that Manitoba has ridges of sand and gravel running all over the province? The reality is that we all cared. The early Indigenous people, the settlers, the first highway and railroad builders, and the grave diggers, all cared. Even animals cared, and often followed beach ridges when they migrated or moved from one area to another. Lake Agassiz's beach ridges made awesome trails for Indigenous people beginning with the lake's earliest paleoshorelines.

Much later, they did the same for fur traders, and European settlers with their ox carts and horse-drawn wagons, particularly when the travel was north and south.

The beaches hindered east-west travel somewhat because their north-south configurations trapped water behind them, creating lagoons and sloughs. In the spring, when the grasslands and woodlands were wet, people could travel and hunt on the beach ridges. Because of their sandy soil and elevation above their surroundings, they were the first to dry.

Also, forests were unable to thrive as they could elsewhere. Only bur oaks could stand the sand and swift drainage. As Joseph Tyrrell wrote in the 19th century, "They often form beautiful dry roads through the country that would otherwise be an impenetrable forest.

They made good camp sites because they were high and well-drained, especially where streams cut through a beach ridge and provided water. Over time, however, plant cover developed and various forms of marine life which had survived glaciation managed to invade the lake by the various inlets and outlets which connected it with other water systems to the south and east.

A few species of small molluscs and the bony plate of a sturgeon have been found in the beach deposits of Lake Agassiz. The former are of significance as they require fish as hosts during part of their period of growth. It is improbable, however, that either of these would have been attractive resources for big game hunting plains nomads. Muskox remains have been recovered from beach deposits in southwestern Manitoba. The presence of this tundra-adapted animal serves as some indication of the nature of the environment to the south of the glacier.

Bison were present in south-western Manitoba at least 10, years ago and were being hunted in southeastern Manitoba more than 8, years ago. By the time these early cultures had run their course, the lake too had vanished. As these raised ridges hindered the drainage of water to the lakes in the east, extensive bogs and sloughs formed behind them, thus making east-west travel difficult.

At the same time, these well-drained beaches served as natural north-south migration corridors. Having good drainage and being elevated above the surrounding terrain, the beaches served as lookout stations for Native hunters from which they might spot approaching game. As many of the ridges traverse rich ecological zones abundant in the resources of both the grasslands to the west and the lakes, streams and forests to the east, they provided strategic locations for the establishment of more permanent encampments as well as transient hunting camps.

Complementing their intermediate location relative to major ecological zones was the local environmental diversity that the beaches offered. Surveys have shown that portions of beaches which are cut by rivers were exceptionally favoured locations for prehistoric campsites. These afforded a ready supply of clean water as well as an east-west riverine transportation route. Two types of stone, quartz and Swan River Chert, occur in these beach deposits, and these were popular materials for the manufacture of stone tools throughout prehistory.

Nodules of these are particularly easy to find on the banks of rivers which transect such deposits. In addition to their contribution to the day-to-day life of prehistoric Manitobans, the beaches witnessed religious or ceremonial activities as well. The relative ease with which they may be excavated and their prominence on the landscape rendered the ridges suitable places for the burial of the dead and the construction of burial mounds.

These circular, often spoked arrangements of stones served different functions for various groups of people, but are frequently associated with such ceremonial themes as spiritual cleansing or renewal, revitalization of the earth and its resources, and appeasement of supernatural forces and beings.

Coincidentally, the beaches continue to have significance to transportation and habitation, providing as they do an almost inexhaustible supply of sands and gravels for the construction of buildings and highways within our province.