Introduction:
Moving rivers of frozen ice, also called glaciers can be often found in colder areas. Those giant movers are getting less and less which each day. When they will finally disappear, we will forget what a huge impact they have had on earth. When glaciers form on a mountain they move down because of gravity, changing the land with them through erosion. On their way down, they create beautiful and stunning pieces of land. An example of this would be Yosemite National Park. Today there are just few glaciers left including Lyell and Maclure. At the Yosemite Nation Park many glaciers have evolved and disappeared through time. Those glaciers played a major role when they were sculpting and forming the land of Yosemite.

General Information:
Glaciers are slow moving masses of ice which mainly occur in the high mountain valleys and colder Polar Regions. Those masses cover 10 percent of land area on Earth and that’s about 15 million square kilometers. (“Facts about glaciers”) To be called a glacier, ice must be at least 1560 square kilometers in size and more than 50 meters thick. They develop in regions where a lot of snow falls during winter than it melts in summer. That’s why most of the glaciers are found in the Antarctic, just like the biggest of them which is called Lambert glacier. Other examples of glaciers include: The Novaya Zemlya Glacier which is located in the Arctic Ocean in northern Russia. It is about 418 km in length. The Arctic Institute Glacier which is located in the Antarctica and measures about 362 kilometers in length and the Nimrod-Lennox-King Glacier which is located in the Antarctica. It measures about 290 kilometers in length. Those ice giants develop in areas where it is cold, and they have to have a total length and thickness to be a glacier. (“What is a glacier?”)

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Overview of the formation and movement of a glacier:
The formation of the glaciers need many years and there are two ways of moving. Retreating or advancing. It’s important that it starts on a mountain or generally a cold place with a high elevation. When a substantial amount of snow remains in the same area but doesn’t melt, the process begins. Each year, new layers of snow bury and compress the previous layers. After about two winters firn develops, it’s a state between ice and snow. The still existing pressure forces the firn to melt which recrystallize to glacial ice. Roughly said is a glacier a system. There is a zone of accumulation where snow is added. This is normally at the start of a glacier. Ice moves downhill due to the force of gravity. At the end, or snout, of the glacier ice melts. This is the zone is more likely to occur in warm summer months. (“How do glaciers form?”; “How are glaciers formed?”; “What is a Glacier?”)

Case study:
When glaciers move they sculpt land. They erode rock and sediment, carry it from one place to another and leave it somewhere else. Glaciers cause both erosional and depositional landforms. An example of glacial erosion is the Matterhorn in Switzerland. It’s a mountain which was sculpted through glaciers. On the other hand, there is glacial deposition. A landscape formed by this process is Long Island in New York. The process starts when a glacier begins to move. Through their journey to the bottom of the mountain they pick up materials. When the glacier passes over land it scrapes up soil and rock. Different glaciers have different causes. The glacier then would erode the underlying surface with plucking and abrasion, which would leave large holes behind. Other objects in the ice could polish the area. This is known as abrasion. Glacial deposition is when the ice displaces the carried rocks, leaving the rock behind when moving on. (“Glacial Erosion”; “Landforms of Glacial Deposition”; “How do glaciers affect land?”; Didier Jean-Michel)

Forming of the landscape
The Glaciers in Yosemite played an important role when creating the landscape of the park.
They created hanging valleys waterfalls, moraines, lakes, U-shaped canyons, rounded domes and jagged peaks, mainly through glacial erosion. Examples of those shapes include: Yosemite Valley, Hetch Hetchy, Yosemite Falls, Vernal and Nevada Falls, Bridalveil Fall, Half Dome, the Clark Range, and the Cathedral Range. Glacially-polished granites can be found throughout Yosemite indicating glaciation. The sculpting began about 2 or 3 million years ago when the Sierra Nevada had risen high enough for glaciers to develop. Those glaciers went down the mountain. On their way down, glacial ice transported vast volumes of rubble and used it to help modify the landscape. During the time of maximum glacial advance, a large trunk glacier filled Yosemite Valley. Smaller secondary glaciers flowed down next to the valleys and merged into the trunk. When the glaciers retreated, the trunk glacier had made a much deeper valley than the secondary glaciers, forming hanging valleys where the secondary glaciers joined the trunk. Today waterfalls such as Yosemite Falls and Bridalveil Fall mark these hanging valleys. The glacial retreat also left deposited materials that created a dam across Yosemite Valley. Behind it lake Yosemite formed. Meltwater washed millions of tons of rock, sand and mud into the lake, filling it in some places with over 1000 feet of glacial sediment. Today those sediments lie under the flat floor of Yosemite Valley. (Hobart M. King; STAFF, 2013; “Geology”, 2016)

Human Impact:
The Glaciers of Yosemite have been melting mostly because of the climate change but also the as the result of natural melting. Both Lyell and Maclure glaciers have been shrinking in size and experts claim that the glaciers will completely disappear within a few decades.
In 1883s the total volume of glacier Lyell was measured at 1.2 million square meters. In 2015 the total volume was 270,426 square meters. In 132 years it loses 90 percent of its volume and 80 percent of surface area. The side confec.com claims that Maclure glacier reduced approximate 60% in glacier surface area and thinned about 30 m. Glaciers are sensitive indicators of climatic changes because their health depends on winter precipitation and summer temperatures. Both the Lyell and Maclure glaciers have been retreating since they were first found in 1883, but the melting has become faster in the past decade, especially during the drought that began in 2012. Scientists agree that the melting is primarily due to warmer temperatures caused by human activities. Real solutions to this problem doesn’t exists when excluding that people should be more environmentally friendly to reduce the climate change in general. Other small solutions to slow down the melting is raising awareness. This is what Caroline Gleich and Meg Haywood Sullivan did. They went on a backpacking/peak-bagging adventure to bring awareness to climate change for the glaciers in Sierra. (STAFF, 2013; Caroline Gleich, 2016)

Significance:
Glaciers have many useful functions. Those moving rivers of ice provide drinking water. They store about 75 percent of the world’s fresh water. This can be important to the whole world. Other functions include irrigating easier the crops and generating hydroelectric power.
These ice bodies are important to the local ecosystems because they provide a
supply of cold water to the Lyell Fork of the Tuolumne River. Another disadvantage of the melting of both glaciers is that very few visitors come to Lyell and Maclure because long strenuous hikes are required to reach their high elevations, which affects the parks income. (“Do glaciers affect people?”; “Glaciers”, National Park Service)

Conclusion:
It begins with the accumulation of snow on an area with high elevation. Over time the snow forms to ice. The ice block then slides down, because of gravity. During its ride to the ground erosion, abrasion and deposition form the land. It can create many landforms including valleys waterfalls, moraines and lakes. But in the future glacier won’t be able any more to do that since they’re melting away.