When we talk about a glacial landscape, we analyze some of its components that help us understand its dynamics and evolution. As we know, glaciers Mountain glaciers generate terrains and geomorphologies that are quite interesting to discover. One of the elements that form near glaciers are the moraines. It is a mountain range of glacial material that is not stratified. Moraines are classified according to their relationship with the glacier.
In this article, we'll delve deeper into moraines: what types there are, how they form, and their importance to glaciers. If you'd like to learn more about some of their characteristics, you can consult the glacier formation in general.
What are moraines
The first thing we must be clear about is what a moraine is. It is a small mountain range that is formed with a material that we call till. This till is nothing more than material formed in glaciers and that is not stratified. The material has only been in this area for a short time and has not stratified under the weight of the snow and the passing of time. If we think about how a glacier's dynamics work, we see that snow accumulates every year after the winter season. After the snowfall, it accumulates due to the effect of gravity and stratifies with the layers of snow that fell and haven't melted from previous years. For a deeper understanding of how a glacier forms, we recommend reading about .
This is how a snowfall profile is established. The deeper we go, the more years back we will be investigating. The set of snow layers is called stratifications. Well, when the rest of the materials are piled up (so to speak) but without being stratified, it is called till.
There are different types of moraines depending on the relationship it has with the existing glacier. We are going to analyze the different types of moraines:
- Background moraine. It is the type of moraine that forms under the ice of the glacier. This pile of till will be on the bed and will be affected by the melting of the ice and the meltwater flow.
- Lateral moraine. It is the one where the materials are found on the edges of the glacier bed. On the sides of the ice sheets you can see all the materials that make up this moraine.
- Central moraine. When the lateral moraines reach great amplitude, it may happen that they join each other in the center of a valley where two glaciers converge. This union is called the central moraine.
- Terminal moraine. They are made up of glacier debris deposits. They are usually located at the end of the glacier and it is the result of the transport of these materials and the effect of gravity.
- Ablation moraine. They are those that have been deposited on the bed of a glacier.
Key features
The characteristics of moraines are summarized in the content of erratic blocks of ice and materials such as stone fragments that are arranged along the entire length of the glacier. The ice drags the soil materials due to its weight and its continuous annual freezing and thawing. Therefore, the relief transforms over the years until the moraines are formed. glacial valleys and other formations. If you'd like to learn more about these valleys, I invite you to check out .
The stones of the ablation moraines also present several different types of materials to be found in the glacier bed. Another element that is also called moraine is the sediment that is settled by a glacier. This is because, after all the journey that it has taken from considerable heights, the glacier is dragging all the materials that have been found along the way.
Till dynamics
What we call as till are the accumulations of sediments that are originated by the glacier and its dynamics. They can also be called drift or glacier drag when completely heterogeneous groups are formed that are generated in the glacier. The till is the fragment of the glacial drift that has been deposited along the way.
These characteristics mean that the composition of till is not always the same. We can find mixtures of clay, boulders, gravel, and sand. The clay in till takes on a spherical shape after movement and subsequent accumulation. They are called till balls. These balls roll down the bed of a stream and can add rocks to its composition. This ends up covering the entire path with rocks. To learn more about phenomena like this, you can consult the article on glaciation.
These till balls are often called armored till balls because they have more rocks. All this material called till is deposited at the end of the moraine, on the sides, in the middle and at the base. As the time of thaw arrives and the glacier begins to melt, the masses of till are dragging and depositing in sandurs of the rivers that come from the glacier. This is more pronounced if it is a continental glacier that begins to melt. Tills can also carry certain alluvial deposits made up of minerals or precious stones. These materials are collected throughout the entire journey of the glacier and acquire great economic value for being something unique. For example, it occurs with diamonds in Wisconsin, Indiana and Canada.
Experts searching for these minerals focus on following the traces left by the tills and use them as clues to determine the direction the glacier took during its descent down the mountain. Among the most sought-after deposits are kimberlite deposits, where you can find abundant diamonds or different types of minerals. More information on this topic can be found in the article on the glaciers of the Himalayas.
There are several cases in which you can find solidified or lithified till. This happens because they have been buried and, with the action of the pressure of the upper layers it has become rock. This type of rock is known as tillite and it is a type of sedimentary rock.
I hope that with this information you can learn more about moraines and tills.
