Cirque

A cirque is a large bowl in a mountain.

It has steep walls on three sides. The fourth side is a low lip.

Ice helps make this shape. Snow piles up in the mountain. The snow turns into thick ice. This ice scrapes the rock. It acts like sandpaper.

As the ice moves, the bowl gets deeper. This makes the bowl much larger. The ice can even flow out. It can form a long glacier.

Sometimes the ice melts away. A small lake may stay in the bowl.

This lake is called a tarn. It sits behind a wall of rock.

These bowls are found all over the world. They tell us about the past. They show us how the Earth changes.

A cirque is a large, bowl-shaped valley. It looks like a giant theater built into a mountain.

Most cirques are made by glaciers. These are huge sheets of moving ice.

Glaciers form when snow piles up high. The snow turns into thick ice. In some places, the ice scrapes the rock. This is called abrasion. It works like sandpaper.

Other parts of the rock break apart. This happens when water freezes in cracks. This is called frost shattering. The ice also pulls rocks away. This is called plucking.

As the ice moves, the bowl gets deeper. The highest wall is called a headwall. The low side is called a lip.

When the ice melts, a lake may stay behind. This small lake is called a tarn. The lake sits behind a dam of rock or debris.

If two cirques grow toward each other, they make a sharp ridge. This ridge is called an arête. If three cirques meet, they make a pointy peak.

These shapes tell us how the climate has changed.

A cirque is a special kind of valley that looks like a giant theater.

It is shaped like a large bowl or an amphitheatre. Most cirques are made by glaciers, which are huge sheets of moving ice. These ice shapes are often called corries or cwm. A glacial cirque is open on the downhill side. The inside part is very steep. The floor of the bowl is often deeper than the area where the ice flows out. This happens because many ice flows meet in the center. This meeting creates strong forces that scrape the ground deep.

Glaciers create these bowls through a few different steps. First, snow piles up in a sheltered spot on a mountain. In the Northern Hemisphere, this often happens on north-east slopes. These spots are protected from the sun and wind. As the snow grows, it turns into thick glacial ice. The ice starts to move and scrape the bedrock. This scraping is called abrasion, and it works like sandpaper.

The ice also pulls rocks away from the mountain. This is called plucking. At the same time, water can freeze in cracks in the rock. This process is called frost shattering or ice segregation. It helps break the steep headwall, which is the highest cliff side.

Scientists have studied these shapes for a long time. By looking at where cirques are today, they learn about the past. Cirques only form above the snowline. Because of this, they tell us about old climate patterns. They show us where glaciers used to be much larger. Studying these landforms helps us understand how our planet's climate changes over time.

There are many interesting facts about these mountain shapes. A classic cirque is often about one kilometer long and one kilometer wide.

The fourth side of the bowl is called a lip or a sill. If the ice melts, a small lake called a tarn may form. This lake sits behind a dam made of rock or debris. Sometimes, two cirques erode toward each other to make a sharp ridge called an arête. If three or more cirques meet, they create a pointy pyramidal peak. The Matterhorn in the European Alps is a famous example of this.

Not all cirques are made by ice. Some are made by water, which is called fluvial erosion. These are often found in landscapes made of limestone or chalk.

In these places, rivers cut through the rock to make steep walls. One example is the Cirque du Bout du Monde in France. You can also find cirques in places like the Negev desert in Israel. These water-made shapes still look like the giant bowls made by ice. Both types show how nature can carve amazing shapes into the Earth.

A cirque is a mountain landform shaped like a large, open-ended amphitheatre.

This bowl-shaped valley is created through intense erosion. In many regions, people use different names for this feature. It may be called a corrie or a cwm. While most cirques are formed by glaciers, some are created by rivers. These river-carved versions are known as fluvial cirques. Understanding these shapes helps scientists study how landscapes change over time.

Glacial cirques form through a specific sequence of physical processes. It begins when snow accumulates in a sheltered mountain hollow. In the Northern Hemisphere, this often occurs on north-east slopes. These slopes are protected from prevailing winds and the sun's energy. As snow piles up, it eventually turns into thick glacial ice. This process leads to nivation, where a hollow is enlarged by ice segregation weathering. This weathering helps break down the rock face to grow the glacier.

Once the ice is established, several types of erosion work together. One process is called abrasion, where debris in the ice scrapes the bedrock like sandpaper. Another process is plucking, where the glacier pulls rocks away from the mountain. The steep back wall of the cirque is called a headwall. This headwall is often weathered by ice segregation, also known as frost shattering. Water flows into cracks and freezes, causing the rock to disintegrate. This can cause avalanches that add more snow and rock to the glacier.

A unique feature called a bergschrund may also form. This is a large crevasse that appears when moving ice separates from stationary ice. The temperature inside a bergschrund stays relatively steady. However, water flowing into this gap can freeze due to the surrounding ice. This helps the freeze-thaw mechanism continue to erode the mountain. As these processes continue, the basin becomes deeper and wider. The floor of the cirque is often overdeepened because multiple ice flows converge there.

Glacial cirques have distinct parts and measurements. A classic cirque is typically about one kilometer long and one kilometer wide. The steep sides are formed by converging ice and rock debris. The fourth side, where the glacier flows away, is called the lip, threshold, or sill. If the ice melts, a small lake called a tarn often forms on the floor. This tarn is held in place by a natural dam. This dam might be made of bedrock or glacial till, which is rock debris.

When multiple cirques interact, they create dramatic mountain shapes. If two adjacent cirques erode toward one another, they form a sharp ridge called an arête. If three or more cirques erode toward each other, they create a pyramidal peak. The Matterhorn in the European Alps is a famous example of such a peak.

In other cases, cirques forming one after another create a feature called a cirque stairway. These landforms provide vital clues about the Earth's history. Because glaciers only form above the snowline, they reveal past climate patterns.

Not all cirques are made by ice; some result from fluvial erosion. These fluvial cirques are often found in karst landscapes made of limestone or chalk. They are formed by intermittent river flow cutting through rock layers. This process leaves behind very steep, sheer cliffs. One example is the Cirque du Bout du Monde in France. Another example is found in the Negev highlands of Israel. These water-carved shapes still maintain the characteristic amphitheatre appearance of glacial cirques.