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An avalanche is a big pile of snow, dirt, and other objects, that come crashing down a mountainside. When there is an avalanche it is usually a sliding avalanche. A sliding avalanche is when the snow piles up and weighs too much to stay on top of the slope and slides down the mountain.
Here is a picture of an avalanche. You can see the dirt and rocks that came down the mountain with the snow.
There are two other types of avalanches also. They are called wind avalanches, and summer avalanches. A wind avalanche happens when a strong wind blows dry snow down the side of the mountain. A summer avalanche happens in the summer when a glacier starts to melt. A big piece of ice is hanging off the glacier attached by a small piece of ice. When the small piece melts, the large piece rolls down the mountain.
Avalanches are most likely to happen when loose layers of snow fall on top of ice. A slide can easily start, crashing down and burying everything in its path. The breeze of air in front of the avalanche is usually very strong, strong enough to wipe out tall buildings and break glass.
Ice caves are made by meltwater on the inside of a glacier. A hole that is formed gets so big that it becomes a cave. In ice caves the ice is so compacted that it looks blue. Ice caves are dangerous. When the glacier is melting the sides of the cave can get thin and fall in, burying everything. The other danger is that there can be flash floods in the ice cave. If you are too far inside you might not be able to get out fast enough.
The lynx, hare, ptarmigan, snowy owl, and grouse get an extra layer of fur or feathers on their paws and feet during the winter. That helps even out the animal's weight so they will stay on top of the snow.
To reach branches for it to eat in the winter, the snowshoe hare stands on its hind legs! When the snow is so deep that the snowshoe hare has trouble getting around, it will make paths through the snow by hopping in the same spots a lot.
The ptarmigan & grouse make a home that looks like a den in the snow called a kieppe. It protects them from snow storms, wind, and other bad weather that winter brings.
Mice, voles, moles, and other rodents make burrows under the ground to get away from the cold. Red squirrels usually stay on top of the snow, but when the temperatures change to -22 F they make a burrow too, and live with their cousins under the snow.
To keep warm some birds puff up their feathers and snuggle up together on the branches of trees.
Chioneuphores are animals like moose, elk, fox, and wolves that survive in snow by changing the way they live. They walk on packed down paths and eat the food on the side of the paths, unless they have to catch their own food.
Some animals turn a different color in the winter than in the summer. They turn white in the winter and brown in the summer to help keep them safe from their predators, and it also helps them creep up and pounce on their prey.
Some animals hibernate. That means that they eat tons of food during the summer and sleep all winter in a den that they find or make.
Other animals migrate. They go to a cooler place in the summer and to a warmer place in the winter.
How A Glacier Is Formed: In some places it is cold all year long. On the tops of mountains it can snow any time of the year. When the first snow falls there is a lot of air space between the flakes. As more and more snow falls, the snow begins to pack together and get much heavier. The heavy snow compacts and presses down on the ground. Then when other snowstorms come the snow packs down even more, and the flakes start to lose their shape. Then the air gets sucked out of the flakes and most of the flakes turn into ice. The snowflakes get rounder as they absorb water in between the left over air spaces. As the years go by the the ice fields grow deeper and stronger until they form a glacier.
How Glaciers Move: Glaciers move in two ways. The first way is through the pull of gravity and meltwater. Gravity pulls the heavy weight of the glacier down a hill very slowly. If you were watching one, you probably wouldn't see it moving. Under the glacier, as it slowly moves, the rocks it is dragging underneath cause the ice to melt. The water under the glacier is called melt water. The meltwater makes it slippery and helps the glacier to move down hills.
There is also meltwater on top of the glaciers that gets into cracks. When it refreezes the ice cracks and moves, kind of like the way an ice cube might crack and melt in a glass of soda. The amount of melt water in the glacier depends on the weather. Different parts of the glacier move at different speeds.
Glacier Life: Do you ever wonder if anything lives on or in a glacier? The top of a glacier is only rocks, ice, dirt, and snow, so who or what would want to live there? Well actually, there is life on a glacier. The reason why is because of the wind. When the wind blows over the ground it collects dust and other things like insects, pollen, minerals, and bacteria that are in the air. Then when the wind blows over the glacier it drops everything on it.
Snow fleas and ice worms live on a glacier. The wind brings them their food. Ice worms are related to the earth worm, but much smaller. They are at less than an inch long!! They move around by squeezing in between the ice crystals at the top of the glacier. They can go as deep as six feet. Ice worms lay their eggs and hatch in the ice. Sometimes you can find over 100 ice worms in one area while another area won't have any.
Not many people get lucky enough to see ice worms and some people think they don't exist. Ice worms only live if the temperature is below 40 degrees Fahrenheit. If the ice gets below 22 degrees Fahrenheit, the ice worms will freeze. Ice worms only live in a glacier if it is beside the ocean or has a lot of meltwater. Ice worms eat algae, that is near the top of the glacier. Snow algae is red instead of green like most algae.
Along with the ice worm, some land insects like spiders and flies might live on a glacier. They usually get eaten by animals that are bigger, like the birds. Animals other the than ice worm also use glaciers. Tidewater glaciers give a home or resting place to large animals. Seals climb up onto the icebergs to have their babies. The new born babies, or pups, and their mothers can rest on the icebergs safe from their predators. Eagles like to stand on icebergs to look for food.
The Size of a Glacier:
Some glaciers can be very small, maybe a few hundred square feet. Glaciers can be very thick. A glacier could get as big as 60 school buses on top of each other. The edges of a glacier are thinner than the center.
Glaciers in Alaska:
Did you know that no one has ever counted all of the glaciers in Alaska? There are nearly 100,000 of them, but most of them don't have names. Most of the glaciers are in the southern part of Alaska. About anywhere in Alaska where you drive or go boating, you can see the remains of the ice age and movement of glaciers.
A crevasse is an open break or cut in the surface of the glacier. They are dangerous because you can't always see them. It looks like part of the surface, but it really is a deep hole. Snow bridges form on top of crevasses.
Glaciers form valleys that are rounder and smoother than those that are formed by rivers. You can see the difference in these pictures.
When the glacier slides into the water it becomes an iceberg. Only the tip of an iceberg (about 10%) can be seen above the water. Wind and the water currents can move icebergs. Icebergs can weigh as much as several tons. Since most of the iceberg is under water it can easily sink and hurt ships and boats that don't see them. For example, the reason the Titanic sank is because it hit an iceberg.
The shape of the iceberg is always changing. In the distance and mist icebergs can have weird shapes that can look like anything from a dog to a knight. When exposed to the sun and water, icebergs melt very fast. In Alaska icebergs live about 2 months. When an iceberg melts, it can become unbalanced and flip over unsuspectingly, making a huge splash and shock waves.
You might wonder, how old is the ice that calves off the glacier? Well it depends on how fast the glacier is moving and how far it travels. Lots of people think that the ice in Portage Lake (in Alaska) is over a thousand years old, but it is only about 50-100 years old. Portage Glacier is six miles long. The ice there moves about 400 ft. every year. It takes about 80 years for the glacier to reach the lake. Even though Portage Glacier has been resting in Portage Valley for over a thousand years, the ice on the outside is only about 100 or so years old. People tend to think that glacial ice is colder than ice in your freezer, but it's not.
Here is a picture of the water cycle. The water cycle is the process of how water goes from one state of matter to another.
Have you ever heard that no two snowflakes have the same shape? If you have, have you ever wondered how that can be with the billions of snowflakes that fall each year? Well, there have been 2 snowflakes found that were identical. If someone says that phrase again, you can tell them the truth!
Snowflakes start as ice crystals that are the size of a speck of dust. When the crystals fall they join up with other crystals to form a snowflake. The size of the snowflake depends on how many crystals hook together. Snowflakes usually have six sides. Here are the different kinds of snowflake shapes.
Interesting Snow Facts
Guess what, it can get cold enough that it doesn't snow! Because snow is frozen water, if there are not enough water droplets in the air it can't snow.
You probably know that it snows when water is lifted into the sky from rivers, lakes, and oceans as water vapor. You can not see water vapor but it is there. There is enough in the air to cover the earth with 3 feet of water. The warmer the air the more water vapor there is.
You can make your own cloud by breathing in cold weather. Or, try breathing on a mirror; there will be a clear gray cloud on it!
For it to snow the tops of the clouds must be below 0 degrees Celsius, or 32 degrees Fahrenheit.
Snow can come from any cloud that is layered.
Sometimes the snow can be feet deep in one place while it is bare in another because the wind has blown all the snow off that spot.
As snow falls snowflakes connect to make bigger snowflakes.
Snow at the North and South Pole reflect heat into space!! That happens because the ice acts like a mirror with the heat of the sun, and the heat bounces off the ice and into space.