Glacial valleys, also known as ice valleys, are valleys carved by large-scale glaciers, leaving behind distinct glacial landforms. Glacial valleys are of great importance to the biodiversity of ecosystems and ecological balance.
Therefore, we are here to tell you everything you need to know about what a glacial valley is, its geomorphological characteristics and how they relate to glaciation.
What is a glacial valley
The glacial valleys, also commonly called glacial troughs, are those valleys in which we can find that they have left behind typical relief forms of glaciers.
In short, glacial valleys are like glaciers. Glacial valleys form when large amounts of ice accumulate in glacial cirques. The ice from the lower layers eventually moves to the valley floor, where it eventually becomes a lake.
One of the main characteristics of glacial valleys is that they have a trough-shaped cross section, which is why they are also called glacial troughs. This feature is the main feature that allows geologists to distinguish these types of valleys where large amounts of ice slide or ever slide. Other hallmarks of glacial valleys are their wear and over-excavation marks, caused by the friction of the ice and the dragging of material.
Ancient glaciers deposited material previously eroded by ice. This material is highly heterogeneous and generally forms different types of moraines, such as ground moraines, lateral moraines, and overturned moraines . Even more concerning, glacial lakes often form within these moraines. Examples of glacial lakes include those found along the margins of the European Alps (such as Como, Major, Garda, Geneva, Constanta, etc.) and in parts of central Sweden, among many other locations.
Dynamics of a glacial valley
In the mechanism of glacial erosion, it is important to note that glaciers are highly erosive and can act as conveyor belts for materials of all sizes brought up from the slopes, contributing to the formation of a glacial valley.
In addition, there is a considerable amount of meltwater in the glacier , which can circulate at high speed through tunnels inside the glacier, carrying material from the glacier's base. These subglacial currents are very effective. The material they transport creates abrasion, and the rocks within the glacier can be crushed and transformed into a fine mixture of silt and glacial clay flour.
Glaciers can function in three main ways: plucking, abrasion, and thrust. In block quarrying, the force of the ice flow can move and lift large chunks of broken bedrock. In fact, the longitudinal profile of the glacier bed is very irregular, with areas that widen and deepen into depressions called troughs or depressions, which are deepened by the over-excavation of less excavated, more resistant rock. The area then narrows and is called a lock or threshold.
In cross section, platforms are formed in stronger rocks that flatten out at a certain height, called shoulder pads. Abrasion includes the grinding, scraping, and grinding of bedrock by the rougher ice-borne rock fragments. This creates the scratches and grooves. In polishing, it is the finer elements, like sandpaper on stone.
At the same time, due to abrasion, the rocks are crushed, producing clay and silt, known as powder ice because of its fine grain size , which is contained in the meltwater and has the appearance of skim milk.
By thrust, the glacier transports and pushes towards itself the decomposing material that it crushes and transforms as described above.
forms of erosion
Among these features are cirques, tarns, ridges, horns, and cols . When shaping valleys, glacial glaciers tend to occupy pre-existing valleys, widening and deepening them in a U-shape. Glaciers corrected and simplified the curves of the original valleys and eroded rocky spurs, creating large triangular or truncated spurs.
In the typical longitudinal profile of a glacial valley, relatively flat basins and extensions follow one another, forming chains of lakes that receive the name of our parents when the basins fill with water.
For them, the Hanging Valley is an ancient tributary valley of a main glacier. They explain this by pointing out that glacial erosion depends on the thickness of the ice sheet, and glaciers can deepen their valleys but not their tributaries.
Fjords form when seawater intrudes into glacial valleys, such as those in Chile, Norway, Greenland, Labrador, and the southernmost fjords of Alaska. They are often associated with faults and geological differences. They reach great depths, such as the Messier Channel in Chile, which is 1228 meters deep. This can be explained by the excessive excavation of ice that erodes below sea level.
Glaciation can also mimic rocks that form sheep-like rocks, whose smooth, rounded surfaces resemble a flock of sheep viewed from a height. They range in size from one meter to tens of meters and are aligned along the direction of ice flow. The side of the ice fountain has a smooth profile due to the grinding effect, while the other side has angular and irregular profiles due to rock removal.
Forms of accumulation
The ice sheets have receded since the last ice age, about 18.000 years ago, showing an inherited relief along all the sections they occupied during the last ice age.
Glacial deposits are composed of material deposited directly by glaciers, lacking a stratified structure, and whose fragments exhibit striations. In terms of grain size, they are heterogeneous, ranging from glacial flour to unstable aggregates transported 500 km from their region of origin, such as those found in Central Park in New York; in Chile, in San Alfonso, and in the Maipo Canyon. When these deposits combine, they form tillites.
The term moraine is applied to several forms that consist mainly of mountains. There are several types of moraines and long hills called drumlins. The frontal moraine is the mound at the front of a glacier that builds up in an arc when the glacier remains stable in one position for years or decades. If flow on the glacier continues, sediment will continue to accumulate on this barrier. If the glaciers recede, a layer of gently undulating moraine, called basal moraine, is deposited, as in the wetlands of the Great Lakes region of the United States. On the other hand, if the glacier continues to retreat, its leading edge may stabilize again, forming a retreating moraine.
Lateral moraines are typical of valley glaciers and carry sediment along the valley edges, depositing long ridges. A central moraine forms where two lateral moraines meet, such as at the confluence of two valleys.
Drumlins are parallel, smooth, and slender hills composed of moraine deposits laid down by continental glaciers. They can reach up to 50 meters in height and one kilometer in length , but most are smaller. In Ontario, Canada, they are found in fields with hundreds of drumlins. Finally, landforms composed of stratified glacial fragments, such as kame, kame terraces, and eskers, are also identified.
I hope that with this information you can learn more about what a glacial valley is and its characteristics.
