U-shaped valleys , also called trough valleys or glacial troughs , are formed by the process of glaciation . They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight sides and a flat or rounded bottom (by contrast, valleys carved by rivers tend to be V-shaped in cross-section). Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice, called glacial till or glacial erratic .
23-617: The Rob Roy Glacier is a small hanging glacier in the Southern Alps of New Zealand's South Island . It is located within the Mount Aspiring National Park , 9 kilometres (6 mi) south of Mount Aspiring / Tititea . The glacier covers the steep slopes of the mountains surrounding the head of the Rob Roy Valley. The most prominent part of the glacier is on the northwestern side of the valley on
46-594: A glacial valley and descends only part of the way to the surface of the main glacier and abruptly stops, typically at a cliff. Avalanching and icefalls are the mechanisms for ice and snow transfer to the valley floor below. Hanging glaciers are inherently unstable, and may produce catastrophic break-off events. These glaciers are often partially frozen to their bedrock, allowing them to locate on steep slopes. Break-off events leading to substantial ice avalanches pose severe hazards to humans, settlements, and infrastructure in alpine terrain worldwide. Rock and icefall from
69-407: A U-shaped, glaciated valley is often stepwise where flat basins are interrupted by thresholds. Rivers often dig a V-shaped valley or gorge through the threshold. Surrounding smaller tributary valleys will often join the main valleys during glaciation periods, leaving behind features known as hanging valleys high in the trough walls after the ice melts. After deglaciation, snow and ice melt from
92-714: A classic U-shaped valley that is also a fjord is the Western Brook Pond Fjord in Gros Morne National Park in Newfoundland , Canada. Formation of a U-shaped valley happens over geologic time , meaning not during a human's lifespan. It can take anywhere between 10,000 and 100,000 years for a V-shaped valley to be carved into a U-shaped valley. These valleys can be several thousand feet deep and tens of miles long. Glaciers will spread out evenly in open areas, but tend to carve deep into
115-542: A continuous river of ice all the way down the Clutha Valley to close to where Cromwell is now. Now all that remains of Rob Roy Glacier is a hanging glacier at the valley head . The Rob Roy Valley leading out into the Matukituki Valley is now covered with lush beech forest and an open understory of ferns and mosses. The forest supports small birds such as fantail , tomtit and rifleman , while above
138-494: A hanging glacier was responsible for triggering the Kolka-Karmadon rock ice slide in 2002, which killed 125 people. Hanging glaciers occur when a major valley glacier system retreats and thins, leaving the tributary glaciers in smaller valleys high above the shrunken central glacier surface. If the entire system has melted and disappeared, the empty high valleys are called hanging valleys. This glaciology article
161-438: A sheer cliff face south of Rob Roy Glacier. On cold sunny days, the meltwater from the glacier and snow on the sunlit slopes above can re-freeze as it falls through the cold air in the shade of the cliff, depositing again as ice and snow at the base of the waterfall. The walking track is publicly accessible for independent walking, but can also be done as part of a guided tour from Wānaka . A regular shuttle service for trampers
184-653: Is a stub . You can help Misplaced Pages by expanding it . Glacial valley Examples of U-shaped valleys are found in mountainous regions throughout the world including the Andes , Alps , Caucasus Mountains , Himalaya , Rocky Mountains , New Zealand and the Scandinavian Mountains . They are found also in other major European mountains including the Carpathian Mountains , the Pyrenees ,
207-405: Is also available, as Raspberry Creek shelter is also the start of longer hiking trails into Mount Aspiring National Park. In 2015, wingsuit flier David Walden leapt from a cliff at the top of Rob Roy Low Peak (2560 m) and was the first person to fly over Rob Roy Glacier and into the valley below via BASE jumping . Hanging glacier A hanging glacier originates high on the wall of
230-456: Is quite soft and it was unbelievable to many that it could be responsible for the severe carving of bedrock characteristic of glacial erosion. German geologist Penck and American geologist Davis were vocal supporters of this unprecedented glacial erosion. Progress was made in the 1970s and 1980s on the possible mechanisms of glacial erosion and U-shaped valleys via models proposed by various scientists. Numerical models have been created to explain
253-749: The Lake District , Yosemite Valley , and the Rottal and Engstlige [ de ] valleys in Switzerland . Glacial troughs also exist as submarine valleys on continental shelves, such as the Laurentian Channel . These geomorphic features significantly influence sediment distribution and biological communities through their modification of current patterns. Geologists did not always believe that glaciers were responsible for U-shaped valleys and other glacial erosional features. Ice
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#1732793081895276-568: The Principal Cordillera of the Andes, glacial valley floors may be covered by thick lava flows . A glacial trough or glaciated mountain valley often ends in an abrupt head known as the 'trough end' or 'trough head'. This may have almost sheer rock walls and spectacular waterfalls . They are believed to have been formed where a number of small glaciers merge to produce a much larger glacier. Examples include: Warnscale Bottom in
299-1043: The Rila and Pirin mountains in Bulgaria , and the Scottish Highlands . A classic glacial trough is in Glacier National Park in Montana , USA in which the St. Mary River runs. Another well-known U-shaped valley is the Nant Ffrancon valley in Snowdonia , Wales . When a U-shaped valley extends into saltwater, becoming an inlet of the sea, it is called a fjord , from the Norwegian word for these features that are common in Norway. Outside of Norway,
322-526: The Aspinall family. The Rob Roy Valley Track is a popular walk of 3–4 hours return and leads to a sub-alpine basin at the valley head and a lookout across the valley to Rob Roy Glacier. Apart from the drive to get there, it is the most easily accessible glacier in the region. About 20,000 people visit Rob Roy Glacier per year. The walking track starts at the Raspberry Creek car park and shelter at
345-650: The contact surfaces with greatest resistance to flow, and the resulting section minimises friction. There are two main variations of this U-shape. The first is called the Rocky Mountain model and it is attributed to alpine glacial valleys, showing an overall deepening effect on the valley. The second variation is referred to as the Patagonia-Antarctica model, attributed to continental ice sheets and displaying an overall widening effect on its surroundings. The floors of these glacial valleys are where
368-563: The end of the Wanaka Mount Aspiring Road, which is unsealed for the last 30 kilometres (19 mi) and a "fine weather only" road for the very last 10 kilometres, crossing seven fords. The track starts off on farmland and then crosses the Matukituki River via a swing bridge before following Rob Roy Stream to climb 330 metres (1,080 ft) up into the Rob Roy Valley. The end point is a lookout just above
391-493: The glacier's terminal face on the northwestern side of the valley. Bigger blocks of ice can tumble and crash all the way to the valley floor. In the distant past, Rob Roy Glacier extended not only to fill all of the Rob Roy Valley, but flowed into the large Matukituki Glacier at the peak of the last ice age around 20,000 years ago. The Matukituki Glacier later combined with the Wānaka Glacier, also non-existent anymore, to form
414-403: The ground when confined to a valley. Ice thickness is a major contributing factor to valley depth and carving rates. As a glacier moves downhill through a valley, usually with a stream running through it, the shape of the valley is transformed. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. This parabolic shape is caused by glacial erosion removing
437-799: The most evidence can be found regarding glaciation cycles. For the most part, the valley floor is wide and flat, but there are various glacial features that signify periods of ice transgression and regression. The valley can have various steps, known as valley steps , and over-deepenings anywhere from ten to hundreds of meters deep. These then fill in with sediments to create plains or water to create lakes, sometimes referred to as "string-of-pearl" or ribbon lakes. Such water filled U-valley basins are also known as "fjord-lakes" or "valley-lakes" (Norwegian: fjordsjø or dalsjø ). Gjende and Bandak lakes in Norway are examples of fjord -lakes. Some of these fjord-lakes are very deep for instance Mjøsa (453 meters) and Hornindalsvatnet (514 m). The longitudinal profile of
460-493: The mountain tops can create streams and rivers in U-shaped valleys. These are referred to as misfit streams. The streams that form in hanging valleys create waterfalls that flow into the main valley branch. Glacial valleys may also have natural, often dam-like, structures within them, called moraines . They are created due to excess sediment and glacial till moved and deposited by the glacier. In volcanic mountain ranges, such as
483-501: The slopes below the 2,644 metres (8,675 ft) tall Rob Roy Peak. This part of the glacier extends from just below Rob Roy Peak down to a bench high on the valley's side where it abruptly breaks over the cliff's edge at around 1,500 metres (4,900 ft). The glacier covers most of the headwalls encircling the valley, except the eastern side where the bordering peaks are all just below 2,000 metres (6,600 ft). The spring melt causes frequent small avalanches, and seracs breaking off
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#1732793081895506-442: The tree line kea can be heard and seen regularly. Rob Roy Peak was named after Scottish hero Rob Roy MacGregor when the first Europeans began exploring this area and began farming in the Matukituki Valley in the 1870s. Rob Roy Glacier has a history of attracting expeditions and tourists for over 100 years. Since the 1920s, access across Mt Aspiring Station into Mount Aspiring National Park has been allowed by four generations of
529-419: The tree line overlooking the valley head and across the valley to Rob Roy Glacier dramatically breaking over the rock ledge towering high above on the other side of the valley. Avalanches and ice blocks breaking off the glacier's terminal face are a regular sight in spring, and kea can often be heard and seen flying above. Also clearly visible are the 261 metres (856 ft) tall Rob Roy Falls, free-falling down
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