What are Alpine Glaciers and How Do They Shape the Landscape?
Glaciers are large masses of ice that move slowly over the land, eroding and depositing rocks and sediments along the way. Glaciers can be classified into two main types: alpine glaciers and continental glaciers. In this article, we will focus on alpine glaciers, which are also known as mountain glaciers. We will explore how they form, where they are found, what types of features they create, and why they are important for the environment and human society.
How do Alpine Glaciers Form?
Alpine glaciers form in high mountain regions, where snow accumulates year after year and turns into ice over time. The process of snow turning into ice can take more than a hundred years, depending on the temperature and pressure conditions. The ice becomes thicker and heavier, and starts to flow downhill under the influence of gravity. The flow of ice is also affected by the shape and slope of the valley, as well as by the friction and resistance of the underlying rock.
As alpine glaciers move, they erode the surface of the land by scraping, plucking, grinding, and polishing the bedrock. They also transport rocks and sediments of various sizes, from fine dust to huge boulders. These materials are either embedded in the ice, carried on top of it, or pushed along by it. When alpine glaciers melt or retreat, they leave behind these materials in different forms and patterns.
Where are Alpine Glaciers Found?
Alpine glaciers are found in many mountain ranges around the world, such as the Alps, the Rockies, the Andes, the Himalayas, and the Alaska Range. They are more common at higher latitudes (closer to either the north or south pole), where the climate is colder and snowfall is more abundant. However, they can also exist at lower latitudes (closer to the equator), if the elevation is high enough to maintain low temperatures.
Alpine glaciers vary in size and shape, depending on the local topography and climate. Some alpine glaciers are small and confined to a single cirque or bowl-shaped depression on a mountain slope. Others are long and narrow, filling up an entire valley between steep walls. Some alpine glaciers reach the sea level and calve off icebergs into the ocean. These are called tidewater glaciers. Some alpine glaciers merge with other glaciers to form larger ice masses or ice fields.
What Types of Features do Alpine Glaciers Create?
Alpine glaciers create distinctive features that reflect their erosional and depositional processes. Some of these features include:
- Cirques: These are bowl-shaped depressions on a mountain slope that mark the origin of an alpine glacier. They are formed by the accumulation and compaction of snow into ice, which then erodes the surrounding rock by plucking and abrasion. Cirques often have steep walls and a flat floor. If a cirque fills up with water from melted ice or precipitation, it forms a small lake called a tarn.
- Horns: These are pyramid-like peaks that result from the erosion of three or more cirques around a mountain summit. Horns have sharp edges and steep slopes that make them difficult to climb. A famous example of a horn is the Matterhorn in the Swiss Alps.
- Aretes: These are narrow ridges that separate two adjacent cirques or valleys carved by alpine glaciers. Aretes have jagged edges and serrated profiles that resemble a saw blade. They are formed by the mutual erosion of two opposing glaciers that meet along a crest. An example of an arete is the Garden Wall in Glacier National Park, Montana.
- U-shaped valleys: These are valleys that have been widened and deepened by alpine glaciers that flow through them. U-shaped valleys have a flat bottom and steep sides that curve inward at the base. They contrast with V-shaped valleys that are formed by rivers that cut through rock by abrasion. U-shaped valleys often have tributary valleys that hang above them at different heights. These are called hanging valleys.