Cirques are formed when a glacier wears away a mountainside leaving a rounded hollow with steep, almost vertical, walls. Such basins are usually found at the top of a glacial valley. Arêtes are knife-edged ridges between cirques that are created when glacial erosion occurs on both sides of a mountain. Horns are peaks created when three or more cirques are formed back to back.

Cirque amphitheatre-shaped basin with precipitous walls, at the head of a glacial valley. It generally results from erosion beneath the bergschrund of a glacier. A bergschrund is a large crevasse that lies a short distance from the exposed rock walls and separates the stationary from the moving ice; in early summer it opens, exposing the rock at its base to diurnal changes of temperature. Frost action then causes rapid disintegration of lower rock, which causes the upper rock to avalanche and produce an almost vertical head wall. Resulting rock material is embedded in the glacier and scours a concave floor, which may contain a small lake (tarn) if the glacier disappears. Expansion of neighbouring cirques produces sharp arêtes, cols, and horns. Because glaciers must originate above the snowline, a survey of the elevations of ancient cirques provides information on climatic change and on the former position of the snow line.

Arête in geology, a sharp-crested serrate ridge separating the heads of opposing valleys (cirques) that formerly were occupied by Alpine glaciers. It has steep sides formed by the collapse of unsupported rock, undercut by continual freezing and thawing. Two opposing glaciers meeting at an arête will carve a low, smooth gap, or col. An arête may culminate in a high triangular peak or horn (such as the Matterhorn) formed by three or more glaciers eroding toward each other.

A glacial horn is a feature created by glaciers and what exactly this term means is intricately linked with how it formed. A horn is a peak that forms from three arêtes. It is also known as a pyramidal peak.

An arête is the edge that forms in the land from cirque erosion, or when two cirque glaciers form up against each other, creating that sharp edge. When more than two arêtes meet, this is a horn.

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How are mountains created?

Most of the world’s greatest mountain ranges the Himalayas, the Andes, the Rockies, the Caucasus and the Alps were created as Earth's tectonic plates collided. As the huge tectonic masses crashed into each other, they forced the layers of rock to fold. This is why these mountains form long, narrow ranges along the edges of continents. Mountains are also created as powerful earthquakes move Earth's crust and lift up huge blocks of rock. Volcanic eruptions can also create mountains.

Mountains are formed by movement within the Earth’s crust. The crust itself is made up of several large plates, called tectonic plates, which are free floating. These huge chunks of the Earth’s crust move within molten rock called magma, which allows them to shift and collide over time. Even though humans live on the crust, they do not often feel these movements as they are very slow, and the sheer size of each plate is so large. Nevertheless, these shifts still have great impacts on human life as the movement of plates is what creates changes in the geographical structure of the surface of the earth. In this way, mountains are created over time. When these plates collide, there is a great deal of mass and pressure which suddenly comes to a stop, and it is this movement that forces the Earth into buckles or protrusions which are known as mountains. Depending on how these plates move or collide, one of three types of mountains can be formed. The three types of mountains or mountain ranges are: volcanic, fold, and Block Mountains, each of which is formed in a different way.

Volcanic Mountains:

Volcanic mountains are formed when a tectonic plate is pushed beneath another (or above a mid-ocean ridge or hotspot) where magma is forced to the surface. When the magma reaches the surface, it often builds a volcanic mountain, such as s shield volcano or a strato-volcano.

Fold Mountains:

As the name suggests, Fold Mountains occur when two tectonic plates collide at a convergent plate boundary, causing the crust to over thicken. This process forces the less dense crust to float on top of the denser mantle rocks – with material being forced upwards to form hills, plateaus or mountains – while a greater volume of material is forced downward into the mantle.

Block Mountains:

Block Mountains are caused by faults in the crust, a seam where rocks can move past each other. Also known as rifting, this process occurs when rocks on one side of a fault rise relative to the other. The uplifted blocks become Block Mountains (also known as horsts) while the intervening dropped blocks are known as graben (i.e. depressed regions).

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Mont Blanc, Italian Monte Bianco, mountain massif and highest peak (15,771 feet [4,807 metres]) in Europe. Located in the Alps, the massif lies along the French-Italian border and reaches into Switzerland. It extends southwestward from Martigny, Switzerland, for about 25 miles (40 km) and has a maximum width of 10 miles (16 km). The summit is in French territory. Surrounding the massif are the Graian Alps (south), the Chamonix Valley and Savoy Alps (west), the Pennine Alps (northeast), and the Valley of Courmayeur (east). Other principal peaks within the massif include Mont Blanc du Tacul, Mont Maudit, Aiguille (“Peak”) du Géant, Les Grandes Jorasses, Mont Dolent, and Aiguille du Midi.

Glaciers cover approximately 40 square miles (100 square km) of Mont Blanc (whence its name, meaning “white mountain”). Ice streams stretch from the central ice dome down to below 4,900 feet (1,490 metres). The Mer de Glace, the second longest glacier in the Alps, reached the elevation of 4,100 feet (1,250 metres) in 1930. At the beginning of the 17th century, glaciers advanced to the bottom of the Chamonix Valley, destroying or burying cultivated land and dwellings. Since that time, the glaciers have periodically advanced and retreated.


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Japan's highest mountain, peaking at 3776 m, is Mount Fuji, an active volcano that sits on a triple junction of tectonic activity. Interestingly, it is made up of three different volcanoes. At the base is Komitake, in the middle, Kofuji, and at the top is Mount Fuji. The volcano last erupted in December, 1707.

Mount Fuji is a symbol of Japan. The mountain contributes to Japan's physical, cultural, and spiritual geography.

Mount Fuji is the tallest mountain in Japan, standing at 3,776 meters (12,380 feet). It is an active volcano, sitting on a "triple junction" of tectonic activity: the Amurian plate (associated with the Eurasian tectonic plate), the Okhotsk plate (associated with the North American plate) and the Filipino plate all converge in the region beneath Mount Fuji. It is only 100 kilometers (62 miles) from Tokyo, Japan's capital and largest city. In fact, the last time Mount Fuji erupted, in 1707, volcanic ash fell on Tokyo.

Mount Fuji is the single most popular tourist site in Japan, for both Japanese and foreign tourists. More than 200,000 people climb to the summit every year, mostly during the warmer summer months. "Huts" on the route up the mountains cater to climbers, providing refreshments, basic medical supplies, and room to rest. Many people start climbing Mount Fuji at night, as better to experience sunrise from the summit—Japan, after all, is nicknamed "the Land of the Rising Sun." The sunrise from Mount Fuji has a special name, Goraiko.

Mount Fuji has been a sacred site for practicers of Shinto since at least the 7th century. Shinto is the indigenous faith or spirituality of Japan, many Shinto shrines dot the base and ascent of Mount Fuji. Shinto shrines honor kami, the supernatural deities of the Shinto faith. The kami of Mount Fuji is Princess Konohanasakuya, whose symbol is the cherry blossom. Konohanasakuya has an entire series of shrines, called Segen shrines. The main Segen shrines are at the base and summit of Mount Fuji, but there are more than 1,000 across all of Japan.


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As altitude increases, the air gets colder. There comes a certain height, called the snow line, above which it is always too cold for the snow to melt, which is why some mountaintops are snow-capped all year round. The snowline is at 5000m in the tropics, 2700 m in the Alps and at sea level at the poles.

The top of the mountain is actually its coldest spot. As you climb a mountain to a higher altitude (height), the atmosphere gets thinner and thinner. This is because air pressure decreases with altitude.

Even though warm air rises, as it does so the rising air expands and cools. When it expands and cools, it can't absorb and retain heat the way it does at the bottom of the mountain.

Although mountaintops are closer to the Sun, they're also farther away from the thermal heat of the Earth's core that keeps the ground warm. So the top of the mountain can be much colder than the bottom.

In fact, the bottom of a mountain can be located in a tropical jungle while the top of the mountain has snow on it! That's why it's possible to have snow at the equator.

Cooler temperatures at the top of a mountain also mean that there's less evaporation taking place. This leads to greater amounts of moisture in the air. More moisture means more rain and, at the very top of a mountain, more snow.

Not all mountains have snowcaps, and not all mountains that get snow have snowcaps all year. A lot depends upon their location and how tall they are. Mountains lower in altitude are less likely to have snowcaps or to have them all year long.

Many mountains, though, have snowcaps year-round. Above a certain point — called the snow line — it stays cold enough that the snow never melts.

The height of the snow line varies around the globe. It depends upon both altitude (height of the mountain) and latitude (where the mountain is located). The snow line is much higher near the equator (about 15,000 feet), for example, than it is near the poles (sea level or 0 feet in altitude).

The snow line can be affected by other factors, too. For example, in the Andes Mountains of South America, it is so dry that the mountains rarely see snow, despite their height and distance from the equator. Monte Pissis in Argentina is the tallest mountain in the world without a permanent snowcap.

Mountains that are near coastlines may have a lower snow line than other areas with the same altitude and latitude. As you get closer to a coastline, the amount of moisture in the air tends to produce more snowfall at higher altitudes.

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