A common comment about southern Saskatchewan is that it is so flat you can see your dog run away for three days. Well this is far from true. Because of events before humans come to this part of the world, you will find that especially this area,the province is far from being flat.
Glaciers were the primary mechanism that formed the landscape of our province. The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glacial epochs, from 2.58 million years ago to the present. During the Late Pleistocene, the Laurentide ice sheet reached from the Rocky Mountains eastward through the Great Lakes, into New England, covering nearly all of Canada east of the Rocky Mountains. Three major ice centers formed in North America: the Labrador, Keewatin, and Cordilleran. The Cordilleran covered the region from the Pacific Ocean to the eastern front of the Rocky Mountains and the Labrador and Keewatin fields are referred to as the Laurentide Ice Sheet. Central North America has evidence of the numerous lobes and sublobes. The Keewatin covered the western interior plains of North America from the Mackenzie River to the Missouri River and the upper reaches of the Mississippi River. The Labrador covered spread over eastern Canada and the northeastern part of the United States abutting the Keewatin lobe in the western Great Lakes and Mississippi valley.
Glaciotectonic hills
The Dirt Hills represent the most defined and biggest Møns Klint glaciotectonic hills of the world. There are other similar hills created by ice action in southern Saskatchewan as well. Glaciotectonic hills or ice-shoved hills show thrusting, folds, ridges and push moraines.These hills consist of upper Cretaceous bedrock which rises to an elevation of 880 metres (2,890 ft) in the Dirt Hills. To the north is the Regina Lake Plain, which is 300 metres (980 ft) lower in elevation. The Missouri Coteau from whence the hills arise, is 120 metres (390 ft) lower than these hills. Between the Alberta and Saskatchewan Plains is the Missouri Coteau, dead ice moraine, a major escarpment, a long meandering ridge of hill country. The area is probably underlain with marine shale of the Bearpaw Formation. This area remained above the ice sheets, being pushed and folded by the glacier movement.
The Laurentide Ice Sheet was 3 kilometres (1.9 mi) thick, which advanced and receded several times across the prairies. There were multiple glaciations affecting the Saskatchewan area during the Pre-Illinoian, Illinoian, and Wisconsin stages of the last ice age. These glaciations occurred during the Quaternary period, which comprises the last two million years. Northern Saskatchewan and the shield area shows the effects of glacial erosion and scour; the Western Canada Sedimentary Basin is a location of glacial deposition and collection. In southern Saskatchewan there are late Pliocene, pre-Illinoian continental glaciation sand and gravel deposits left behind from water deposition (alluvial) and glacial edge deposits (colluvial). By the study of till, terrain, the limits of the Illinoian glaciation are evidenced around Willow Bunch Lake, Wood Mountain, Cypress Hills area
The melting glaciers left behind sand and, silt outwash plains. The Great Sand Hills of Saskatchewan are evidence of winds and sand storms which have accumulated the sands left behind. Retreating glaciers left meltwater, which pooled in lakes.
Glacial Lake Regina covered south-central area, and Glacial Lake Agassiz covered much of Saskatchewan and neighbouring regions of the US and Manitoba.The ice and water retreated, and the lake beds formed flat plains. The land exposed from under the ice sheets was rubble, and ridges of gravel. At least eight periods of glacial advance and retreat are recorded in Saskatchewan during the Middle to Late Pleistocene, affecting all but small areas of the CYPRESS HILLS and WOOD MOUNTAIN which stood above the ice sheets. Whereas the Shield is primarily a region of GLACIAL EROSION and scour, the Phanerozoic outcrop is largely a region of GLACIAL DEPOSITION, with till sequences as much as 100 m or more thick in many places. Strong movements of the ice sheets produced thrust-stacked sequences of the GLACIAL DEPOSITS and bedrock in some places.
As erosion takes place in one area, deposition may occur in another. Deposition is the process in which glaciers add sand, minerals and other materials to the bedrock underneath. Forms such as drumlins and certain kinds of ground moraines can form under moving ice. However, most glacier deposition takes place as the ice retreats.
Some examples of depositional features include: hummocky moraines (high-relief forms consisting of mounds, ridges and knobs, some of which are doughnut-shaped); cross-valley, ribbed, washboard, De Geer, push, ice-thrusted, and recessional moraines (bow-shaped ridges of varying heights and lengths); terminal moraines (single, prominent ridges marking the limit of a glacial advance); and ground moraines.
Most of these features contain a high percentage of glacial till, which is unstratified, unsorted material deposited directly from a glacier. It usually consists of a heterogeneous mixture of clay, silt, sand, pebbles, cobbles and boulders. The exact composition of till will generally reflect what’s in the local bedrock. Till can be divided into several types depending on the location of debris in the ice and how it was deposited.
To get a better idea of what moraines are, picture yourself with a toy bulldozer on a lawn that has a bunch of dry leaves all over it. When you run the bulldozer through the leaves, some of them get pushed aside, some of them get pushed forward, and some of them leave interesting patterns on the grass. Now think of these patterns and piles of pushed-away leaves—moraines—stretching for kilometers on the Earth.
Moraines only show up in places that have, or used to have, glaciers. Glaciers are extremely large, moving rivers of ice. Glaciers shape the landscape in a process called glaciation. Glaciation can affect the land, rocks, and water in an area for thousands of years. That is why moraines are often very old.
Moraines are divided into five main categories: lateral moraines, medial moraines, supraglacial moraines, ground moraines and terminal moraines.
Lateral Moraine
A lateral moraine forms along the sides of a glacier. As the glacier scrapes along, it tears off rock and soil from both sides of its path. This material is deposited as lateral moraine at the top of the glacier’s edges. Lateral moraines are usually found in matching ridges on either side of the glacier. The glacier pushes material up the sides of the valley at about the same time, so lateral moraines usually have similar heights.
If a glacier melts, the lateral moraine will often remain as the high rims of a valley.
Medial Moraine
A medial moraine is found on top of and inside an existing glacier. Medial moraines are formed when two glaciers meet. Two lateral moraines from the different glaciers are pushed together. This material forms one line of rocks and dirt in the middle of the new, bigger glacier.
If a glacier melts, the medial moraine it leaves behind will be a long ridge of earth in the middle of a valley.
Supraglacial Moraine
A supraglacial moraine is material on the surface of a glacier. Lateral and medial moraines can be supraglacial moraines. Supraglacial moraines are made up of rocks and earth that have fallen on the glacier from the surrounding landscape. Dust and dirt left by wind and rain become part of supraglacial moraines. Sometimes the supraglacial moraine is so heavy, it blocks the view of the ice river underneath.
If a glacier melts, supraglacial moraine is evenly distributed across a valley.
Ground Moraine
Ground moraines often show up as rolling, strangely shaped land covered in grass or other vegetation. They don’t have the sharp ridges of other moraines. A ground moraine is made of sediment that slowly builds up directly underneath a glacier by tiny streams, or as the result of a glacier meeting hills and valleys in the natural landscape. When a glacier melts, the ground moraine underneath is exposed.
Ground moraines are the most common type of moraine and can be found on every continent.
Terminal Moraine
A terminal moraine is also sometimes called an end moraine. It forms at the very end of a glacier, telling scientists today important information about the glacier and how it moved. At a terminal moraine, all the debris that was scooped up and pushed to the front of the glacier is deposited as a large clump of rocks, soil, and sediment.
Scientists study terminal moraines to see where the glacier flowed and how quickly it moved. Different rocks and minerals are located in specific places in the glacier’s path. If a mineral that is unique to one part of a landscape is present in a terminal moraine, geologists know the glacier must have flowed through that area.
Kettles
In situations where a glacier is receding, a block of ice might become separated from the main ice sheet and become buried in glaciofluvial sediments. When the ice block eventually melts, a depression forms, known as a kettle, and if this fills with water, it is known as a kettle lake. Kettle lakes are also known as pothole lakes or prairie potholes.
Drumlins
Drumlins are elongated, oval shaped ridges of englacial to subglacial sediments that form at the base of continental glaciers. They are often tens of metres high and hundreds of metres long, and often occur in clusters (“fields”) of tens to hundreds of drumlins . As the sediments are deposited, the glacier molds the drumlins’ shapes as the glacier moves over and around them. The long axis of a drumlin is aligned with the direction that the ice moved when the drumlin was deposited.
To Log this earthcache:
1. What type of moraines are in this area. What direction to you think the glacier was moving?
2. To the north west, what glacial formation do you see? What is the approxament width and length of the most westerly one.
3. Take an altimeter reading at posted as well as the two reference points.. Based on the description above, what area or formation does these measurements represent. (Glacial lake Regina lake bed, Missouri Couteau or the glaciotectonic hills). Please include your readings.
Please message me with your answers. Pictures of your visit is greatly appreciated.