December 11, 2012 - International Mountain Day

What have mountains done for you lately?

Aside from the obvious—being places of beauty and wildlife and winter play in the snow—mountains often cause rain to fall, hold much of the world's fresh water supply, and help to create beaches.

Mountains Cause Rain?

When breezes carry moist air from the oceans inland, that moisture often remains invisible, as water vapor. But if the air begins to cool as it blows against mountains and is forced upward, the water vapor forms drops, and now we can see it: it forms a cloud. If the air is moist enough, and if it gets cool enough, the drops forming the cloud become so large and heavy that they fall to the ground as rain, sleet, hail, or snow (depending on conditions).

You can see how often mountains cause rain by studying yearly precipitation totals. The areas on the seaward side of mountain ranges often enjoy much more rainfall per year than the otherwise similar areas on the other side of those mountains. The moisture has been forced out of the air on the seaward side of the mountains; by the time it has reached the other side of the mountains, and begins to sink and warm, there is often no more moisture for rainfall. These dry areas are considered to be in the mountains' rain shadow.

Mountains Hold Fresh Water?

Mountains collect and hold much of the year's precipitation as snow and ice and then release it during warmer—and usually drier—times of the year.

Also, because mountains cause a lot of rainfall as well as snowfall, they are often dotted with freshwater lakes. This water tends to move downhill in creeks and then gather into rivers.

In semi-arid and arid regions, 70 to 90 percent of river flows come from the mountains, and even in moister areas, 30 to 60 percent of freshwater comes from mountains. All the major rivers in the world have their headwaters in mountains. Half of all the people in the world depend on mountain water for drinking, as a source of energy or income, or for growing food. (I found all these incredible statistics here.) 

Mountains help create beaches?

Sand grains are incredibly varied
and surprisingly beautiful.
As the creeks and rivers flow downhill from mountains, they erode rocks and carry particles of rock to the oceans. Whenever the rushing rivers are forced to slow down, they dump a lot of the rock particles they are carrying. This creates fertile, mineral-rich soil for farming as well as beautiful sandy beaches.

Actually, we humans get a lot of important ores and minerals from mining in mountainous areas, and fossil hunters often benefit from erosion in uplifted areas, too.

Celebrate mountains!

You can either head for the hills, drink a toast of tap water (which probably originated in mountains somewhere), or browse through some mountain loveliness here or here or here

Also on this date:

Physicist Max Born's birthday 

Anniversary of the first recorded sighting of the Aurora Borealis in America 

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