If it is wild to your own heart. Protect it. Preserve it. Love it. And fight for it. Rick Bass
By: calpoppy , 8:05 PM GMT on October 02, 2012
Glaciers have been described as great rivers of ice, they have sculpted valleys and mountains. If you have ever seen them from the air you will have realized their amazing size! And how graceful they look from above.
What is a glacier?
Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses. Glaciers form when snow remains in one location long enough to transform into ice. What makes glaciers unique is their ability to move. Due to sheer mass, glaciers flow like very slow rivers. Some glaciers are as small as football fields, while others grow to be over a hundred kilometers long.
Here is the Exit glacier just outside of Seward. Not very pretty is it.
How to glaciers form?
Glaciers begin to form when snow remains in the same area year-round, where enough snow accumulates to transform into ice. Each year, new layers of snow bury and compress the previous layers. This compression forces the snow to re-crystallize, forming grains similar in size and shape to grains of sugar. Gradually the grains grow larger and the air pockets between the grains get smaller, causing the snow to slowly compact and increase in density. After about two winters, the snow turns into firn—an intermediate state between snow and glacier ice. At this point, it is about half as dense as water. Over time, larger ice crystals become so compressed that any air pockets between them are very tiny. In very old glacier ice, crystals can reach several inches in length. For most glaciers, this process takes over a hundred years.
How do glaciers move?
The sheer weight of a thick layer of ice and the fact that it deforms as a "plastic" material, combined with gravity's influence, causes glaciers to flow very slowly. Ice may flow down mountain valleys, fan across plains, or in some locations, spread out to the sea. Movement along the underside of a glacier is slower than movement at the top due to the friction created as it slides along the ground's surface.
You can see from my photo how the glacier was impacting the mountain.
What are the components of a glacier?
Several visible features are common to most glaciers. At locations where a glacier flows rapidly, giant cracks called crevasses are created, which may make travel across a glacier treacherous. Underneath the glacier, where glacier ice meets the ground, large amounts of rock and soil are ground up by the tremendous weight of the glacier.
Other common glacial features are moraines, created when the glacier pushes or carries along rocky debris as it moves. These long, dark bands of debris are visible on top and along the edges of glaciers. Medial moraines run down the middle of a glacier, lateral moraines along the sides, and terminal moraines are found at the terminus, or snout, of a glacier.
How do glaciers effect the land?
Common all over the world, glaciated valleys are probably the most readily visible glacial landform. Similar to fjords, they are trough-shaped, often with steep vertical cliffs where entire mountainsides were removed by glacial action. One of the most striking examples of glaciated valleys can be seen in Yosemite National Park, where glaciers literally sheared away mountainsides, creating deep valleys with vertical walls.
Glaciated rock from the Exit glacier
Material a glacier picks up or pushes as it moves forms moraines along the surface and sides of the glacier. As a glacier retreats, the ice literally melts away from underneath the moraines, so they leave long, narrow ridges that show where the glacier used to be. Glaciers don't always leave moraines behind, because sometimes the glacier's own meltwater carries the material away.
Streams flowing from glaciers often carry some of the rock and soil debris out with them. These streams deposit the debris as they flow. Consequently, after many years, small steep-sided mounds of soil and gravel begin to form adjacent to the glacier, called kames.
Here is the outflow from the Exit glacier. The road to the glacier was impacted as well with the glacier melt flooding it. Notice the moraines on the sides. The water is grey and not pretty like it is later when you see the glacier water that goes into Kenai Lake.
How does a glacier effect people?
In certain cities including Anchorage Alaska they get their drinking water and hydroelectric power from a glacier. The Eklutna glacier provides all of this to the city.
In the Mat-Su valley outside of Anchorage, glaciers formed a valley and created many lakes. This is the agricultural area of Alaska. Alaskans wonder if the Russians had found the Mat-Su valley would they have sold Alaska to the US at all.
They are beautiful to see on a cloudy day as the light reflects on the ice differently as you can see from my pictures of the Portage glaciers.
Here is a picture of Portage Lake.
More pictures of the Portage glaciers, notice the waterfall coming off the side of the mountain on the left.
The shear size of some of these glaciers are just awe inspiring. There are so many of them in Alaska and only a few are really accessible
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