Medial moraines
Introduction
A medial moraine is a type of moraine that forms when two glaciers meet and the debris on the edges of the adjacent valley sides join and are carried on top of the enlarged glacier. As the glacier melts or retreats, the debris is deposited and a ridge down the middle of the valley floor is created. The ridge is often clearly visible when the glacier has receded.
Formation
The formation of a medial moraine begins with two adjacent glaciers flowing down a mountain. Each glacier has a lateral moraine at its edges, which is a collection of rock debris that has fallen onto the glacier from the valley walls due to erosion. When the two glaciers meet, the two inner lateral moraines merge. This merged debris is then carried on top of the glacier, forming a line of debris down the center of the glacier. This line of debris is the medial moraine.
Characteristics
Medial moraines are characterized by their location in the center of a glacier and by their composition of rock debris. The size and shape of a medial moraine can vary greatly depending on the size of the glacier and the amount of debris. Some medial moraines are only a few meters wide, while others can be several kilometers wide. The height of a medial moraine can also vary, with some reaching several meters high. The debris in a medial moraine is often angular and poorly sorted, reflecting its origin from the valley walls.
Examples
There are many examples of medial moraines around the world. One notable example is the medial moraine on the Aletsch Glacier in Switzerland, which is one of the largest in the Alps. Another example is the medial moraine on the Ruth Glacier in Alaska, which is one of the most visually striking due to its large size and prominent location.
Importance
Medial moraines are important indicators of glacier dynamics and past glacial activity. They can provide valuable information about the direction and rate of glacier movement, as well as the amount of erosion that has occurred in the valley. In addition, medial moraines can serve as a source of sediment for downstream environments, influencing the geomorphology and ecology of these areas.