What is Arete?
Arete Definition Geography
A narrow ridge of rock that separates two valleys is known as an arête. It is typically formed when two parallel U-shaped valleys are eroded by glaciers. A horn is formed when glaciers erode three or more aretes, resulting in a sharp-edged peak.
Aretes can also form when two glacial cirques erode headward towards each other, though this usually results in a saddle-shaped pass known as a col. The edge is then sharpened by freeze-thaw weathering, and the slope on either side of the arête is steepened by mass wasting and erosion of exposed, unstable rock.
Hence, we can say that the Arete glacier consists of horns and serrated ridges which are formed by glacial erosions.
The term 'arete' actually refers to a ridge or edge in French; similar features in the Alps are often described with the German equivalent term Grat.
A pyramidal peak is formed when three or more cirques intersect.
Arete Glacier Type: Cleaver
A cleaver is a type of arete that divides a unified flow of glacial ice from its uphill side into two glaciers flanking the ridge and flowing parallel to it. The name Cleaver comes from the way it resembles a meat cleaver slicing meat into two pieces. A cleaver can be compared to an island in a river.
A common scenario involves two flanking glaciers melting to their respective ends before their courses can reconnect them; an extremely rare analogy involves two branches of a river drying up before the downstream tip of the island due to evaporation or absorption into the ground.
The location of a cleaver is frequently a deciding factor in the choice of glacier flow routes. For example, following a cleaver up or down a mountain will help you avoid travelling on or through an unstable glacial, snow, or rock field.
This is typically the case on summer routes to Mount Rainier's summit that traverse the 'flats' of Ingraham Glacier, but ascend Disappointment Cleaver and follow its ridgeline rather than ascending the headwalls of either that glacier or Emmons Glacier (on the other side of the cleaver).
FAQs on Arete
1. What is an arête in geography?
In geography, an arête is a thin, sharp, knife-like ridge of rock which is typically formed when two glaciers erode parallel U-shaped valleys or two glacial cirques erode headwards towards each other. The ridge is the remnant of the rock that separated the two valleys.
2. How is an arête formed by glacial action?
An arête is a classic erosional landform created by glaciers. The process involves two main stages:
- First, two glaciers in adjacent valleys or cirques pluck and abrade the rock, deepening and widening their respective troughs.
- As the glaciers continue to erode the valley walls, the ridge of land separating them becomes progressively narrower, steeper, and more jagged, resulting in the characteristic sharp crest known as an arête.
3. What is the difference between an arête and a horn in glacial topography?
While both are features of glacial erosion, their formation and shape differ. An arête is a linear, sharp-crested ridge formed between two adjacent glacial valleys. A horn, on the other hand, is a sharp-pointed, pyramidal peak that is formed when three or more cirques erode back-to-back around a single mountain. The Matterhorn in the Alps is a world-famous example of a horn.
4. Can you provide some real-world examples of arêtes?
Yes, many prominent mountain ranges feature arêtes. Some well-known examples include:
- Crib Goch on Mount Snowdon in Wales.
- Striding Edge on Helvellyn in the English Lake District.
- The Carn Mor Dearg Arête on the way to Ben Nevis in Scotland.
- Numerous ridges found throughout the Himalayas, the Alps, and the Rocky Mountains.
5. Why are arêtes considered a key indicator of past glaciation?
Arêtes are considered a key indicator because their unique, sharp-edged shape can only be formed by the powerful and specific erosional processes of valley glaciers. The presence of an arête in a landscape provides geographers with definitive evidence that the area was once home to large glaciers that carved out the surrounding valleys. They help in reconstructing the extent and impact of past ice ages.
6. Where on a mountain does an arête typically form?
An arête typically forms high up on a mountain, serving as a steep dividing wall between two glacial cirques (armchair-shaped hollows at the head of glacial valleys). As these cirques on opposite sides of a divide are enlarged by glacial erosion, the intervening ridge is sharpened into an arête.
