What is a Hanging Valley?
A valley is usually an area which is found between hills and mountains. The low area lying between the two, therefore, can be termed as a valley. Valleys are discriminated on the basis of their shapes, which include U-shaped and V-shaped valleys. Most of the valleys either fall in one of the categories or are a mixture of both. There are different types and formations of valleys. One of them is the Hanging valley, which has a very interesting formation pattern and placement.
Hanging Valley is generally a geographical structure which is basically a shallow canyon formed over a large canyon. They can also be called as tributary valleys to larger valleys. These valleys are known as hanging valleys primarily because of their unique position. Besides, the valleys that are above the main valleys are always known as hanging valleys.
Hanging Valleys can always be spotted in the form of a U-shape. It is actually due to their peculiar positioning and structure above their main valleys. Apart from that, they also have a steep wall characteristic at the point where both the valleys meet. The valleys are not found in all the hilly regions but are formed only in regions with higher altitudes. It is the reason why mountainous regions which have high peaks, usually have hanging valleys.
The hanging valleys have ruptures and cracks which are formed naturally. It is seen that rivers usually flow through that path from the mountains. Also, where two cliffs meet, these rivers flow down dramatically in the form of waterfalls. Hanging valleys are smaller as compared to the main valley. However, in some cases, some exceptions occur naturally when the hanging valleys are found to be larger than the main valley, but this is a very rare phenomenon.
The most amazing part about hanging valleys is that they can be found underwater as well. They are normally found in fjord systems where the hanging fjords are shallower than the main fjords.
How is a Hanging Valley Formed?
Valleys usually are formed as a result of something that is caused naturally. Thus, hanging valleys are formed as a result of the erosion effects due to glaciation. Research says that the valleys are formed because of two different glaciers. These glaciers interact with each other and ultimately lead to the process of the formation of hanging valleys.
Interaction happens between a small and a large glacier. A glacier which is relatively smaller interacts and joins the larger glacier with glacial material. Thus, the main glacier which has large quantities of the glacial material usually erodes away as a result of different activities that include abrasion or plucking.
When the direction of the abrasion is vertical, extremely steep valleys are formed. They obviously contain vertical slopes. On the other hand, if lateral erosion has occurred, then they widen the distance between the walls of the valley continuously. This is the main reason why hanging valleys have a U-shape.
The rivers that flow through these valleys are normally formed because of the snow melting from the top of the mountain peaks. As the upper snow-clad slopes start melting, they turn into liquids which are then known as rivers. When they reach the mouth of the hanging valley which actually meets the steep walls of the main valley, it starts pouring down and is known as waterfall. This usually happens because of the steep wall and the gap between the two valleys.
The erosion that occurs on the slopes of the different mountains is not the same every time. It keeps on changing with every passing glacier and climatic conditions. Thus, the continuous variations in the rate of erosion also result in the formation of hanging valleys.
Apart from that, even the nature of the underlying rocks also plays a vital role in the formation of hanging valleys. The nature of some rocks can speed up the erosion rate of tributary valleys. Sometimes this erosion rate is higher on tributary valleys as compared to main valleys. It occurs in that fashion because the rocks in tributary valleys are more resistant to erosion as compared to the rocks in the main valleys.
Hence, with the passage of time, the difference in erosion rate also increases, thereby affecting the depths of the two valleys drastically. Both the valleys would have different depths, which make up the process of forming hanging valleys. In some cases, the main valley is much older as compared to the hanging valley and can come into existence through glacial erosion only, while the hanging one can be formed due to erosion by the river.
Examples of Hanging Valleys
Hanging Valleys found in Yosemite National Park, California, USA
Yosemite National Park of California is home to a lot of different types of hanging valleys. Most of them also have waterfalls which enter the main Yosemite Valley lying beneath. The different falls that can be viewed from these hanging valleys include Ribbon Fall, Yosemite Falls, Bridalveil Fall, and Illilouette Falls.
The Yosemite falls is the highest falls in California with a height of 2425 feet. It is a treat to watch this falls from the hanging valley. It also has the highest vertical drop in the whole of North America. The drop is at 1,430 feet. Even the Ribbon Fall has the highest uninterrupted drop at 1,612 feet. The falls make contact with the face of the cliff instead of taking the direct drop.
The Bridalveil Fall has a much lesser drop at 620 feet. It falls directly in the Yosemite Valley. However, it is the most impressive falls from the hanging valley. Many researchers debate on the fact that Yosemite Valley and hanging valleys were formed through glacial activity. However, it is believed that the flow of the Merced River is also responsible for the formation of these hanging valleys.
Bird Woman Falls, Glacier National Park, Montana, USA
Glacier National Park in Montana has a hanging valley. The hanging valley there actually feeds the Bird Woman Falls. This fall actually drops down in the Logan Creek which is situated in the main valley. Glaciers have cut and formed the hanging valleys and main valleys there.
The whole scenario at the Glacier National Park is that the smaller glacier is situated in the upper valley, which is feeding the larger glacier located in the below valley. Also, a glacier which is of a larger size and depth speeds the erosion and its process. It also cuts deep in the land which is responsible for the hanging valley and its formation with respect to the Bird Woman Falls.
A number of natural activities continue to happen in the mountainous regions and terrains. Erosion is a common activity there, and much of it occurs on the sides and bottoms of the valleys which actually guides the flow and pattern of the glaciers. The continuous flow usually widens and deepens the valley over a period of time.
This glacial erosion also hampers the cross-sectional shape of the valley and distorts it, which ultimately results in a U-shaped valley. In this process, the small adjoining valleys are also affected if they are entering the larger valleys. Some of their floors are usually elevated. This whole process gives rise to hanging valleys.