Ice and its meltwater are the most important deposition agent for soil parent material in Canada. The last ice age occurred during the Pleistocene epoch, starting about 2 million years ago and ending about 10,000 years ago. During the ice age, there was a series of glacial advances and retreats. The last glacial advance peaked about 25,000 years ago, and during that time ice covered most of Canada and extended south well into the US.
Glaciers are powerful transportation agents that can move earth material ranging in size from clays to boulders. They act as bulldozers, scraping material underneath them, and conveyor belts, moving material that falls on them. These actions create glacial till type of parent material.
Very often, water re-works the material deposited by glacier. When meltwater streams are involved, the resulting parent material is called glacio-fluvial, while when glacial lakes are involved, the parent material is called glacio-lacustrine. In the case of the interaction between ice and the ocean (or sea), the parent material is called glacio-marine.
Quaternary Glaciation
Glacial Geomorphology
Morainal (Till)
Morainal sediments are deposited directly by glacial ice and their structure varies from relatively loose near the surface, to very compact at depth. This is related to the origin of the till: the more compact and fine matrix till was deposited as basal (or lodgement) till under the glacier, whereas the less compact and coarser ablation till was deposited by melting of ice. The finer particles of the upper till are commonly washed away by meltwater from the glacier and deposited in lacustrine and marine environments.
Basal Till
Erratics
Kettle Holes Morainal (Till)
Processes at the Toe of the Glacier
Ablation Till
Glacio-fluvial
Glacial-fluvial sediments are deposited by glacial meltwater in a floodplain environment. These deposits consist of coarse to medium grained sand and gravel, poorly to well sorted and bedded, with numerous cobbles, boulders, and lenses of till. They were deposited in ice contact or near-ice positions by glacial meltwater during the last phase of glaciation, when glaciers were stagnant or retreating.
Ice Cave
Moulin, Kame, and Esker Formation
Outwash Landforms
An Esker Today
Glacio-Lacustrine
Glacio-lacustrine sediments are deposited by glacial meltwater in lakes. These lakes include ice margin lakes or other types formed from glacial erosion or deposition. Sediments in the bedload and suspended load of meltwater streams are carried into lakes and deposited.
The bedload of a stream (mostly sands and gravels) is deposited at the lake margin (e.g., deltas), while the suspended load is deposited all over the lake. Sediments that are carried in the suspended load of a stream (commonly silts and clays) are transported into the lake in suspension or by currents along the lake floor.
Particles in the suspended load tend to be larger in summer, when glacier melt results in high amounts of turbid meltwater entering the lake. These larger particles settle quickly over the lake bottom. During the winter, freezing temperature reduces discharge of inbound streams and may result in a frozen lake surface. The lake water is very calm and this is when the finer particles settle. This annual cycle of deposition produces layered sediments known as rhythmites. Each annual layer of sediment is called a varve.
Glacio-lacustrine Parent Material
Formation of Glacio-lacustrine Deposits
Icebergs and Rafting
Glacio-Marine
Glacio-marine sediments are deposited by glacial metlwater in an ocean environment. Glacial seas were not in the same place as the seas of today. In fact, during glaciation the weight of the ice cap was sufficient to depress the surface of the continent to a level below that of the ocean. As the ice cap disappeared, the ocean invaded the lower parts of the continent, creating seas. Once the continent was relieved of the weight of the ice, it gradually rebounded and the ocean waters withdrew to form the shoreline we are familiar with today. As a result of this rebound effect, which is still happening today, glacio-marine deposits are now exposed in places which may be far from the nearest modern-day oceans.
Glacio-marine Parent Material
Retreating Glaciers?
Glacial retreat has been occurring since 1850 around the world, affecting the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants. These all depend on glacier-melt, and in the long term so does the level of the oceans.
The retreat of glaciers has a number of different impacts. In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished. Many species of freshwater and saltwater plants and animals are dependent on glacier-fed waters to ensure the cold water habitat to which they have adapted. Some species of freshwater fish (salmon and cutthroat trout) need cold water to survive and to reproduce and reduced glacial runoff can lead to insufficient stream flow to allow these species to thrive.
Some of this retreat has resulted in efforts to slow down the loss of glaciers. To retard melting of the glaciers in Alps used by certain Austrian and Swiss ski resorts, portions of glaciers were partially covered with plastic. While covering glaciers with plastic sheeting may prove advantageous to ski resorts on a small scale, this practice is not expected to be economically practical on a much larger scale.