This hill was built by ants.  Grain by grain.  This sandcastle was built by kids.  One shovel of sand at a time.  This giant hill is . . .  just here.  This tree was struck by lightning.  This one was hit by a car.  But this one . . .  is just torn up.  What built this hill?  What tore up this tree?  Did you see anything?  It was not ants and it was not kids . . . One of the most powerful builders on the planet is something we cannot see.  Let's look at shapes made by the invisible hand of wind.

Wind gets its power from the sun.  The air moves up and down as the sun warms the Earth.  The sun heats the red rock of the desert and all the air moves up.  Then the air above it comes rushing down to fill the space, like a waterfall pouring down.  This is strong enough to carry things with it: leaves, umbrellas, sand. 

Have you ever wondered how builders make furniture so smooth?  They rub sandpaper against it.  Sandpaper is a piece of paper with sand and small rocks stuck to it that is used for smoothing things.  By breaking it down, they rub off the bumpy parts and make it smooth and nice.  Wind can do the same thing when it carries sand.  Like sandpaper, it can make things pretty or destroy them.

In the desert, you might feel a sting when the wind picks up.  It feels like something scratched you.  A claw you could not see.  This is the wind blowing a little bit of sand.  Sandstorms happen when the wind carries lots of sand into the air and whips it across the desert.  You do not want to get caught in a sandstorm.  They are like giant sand tornadoes, which means you want to stay away from these.  Stay out of the desert when there are strong winds.  When sandstorms happen where people live, they can be very dangerous.  We are not like lizards in the desert.  They have holes to crawl into.  We do not.

Where did everybody go? It's just a little sand.


Soil on farmland can become very dry when it's used over and over to grow food.  Farmers are constantly mixing up the soil to get to fresh soil that helps them grow their crops.  Food is good, but the dust this creates can be very bad.  Dust storms happen when the earth gets very dry and wind carries a lot of dust into the air.  The dirt can get in people's eyes and mouths, and it can kill crops.  If you ever see a sand or a dust storm coming, make sure to wear a hat, sunglasses, and a bandana around your nose and mouth so you don't breathe in dust.  Oh, and if you are going to drink a milkshake out there, better put a lid on it.  Nobody likes a gritty milkshake.

Do you know what time it is when you see this coming? Time to close your windows and doors.


Enough getting sand and dust in our eyes.  Let's look at some of the pretty things wind does.  If we go back into the desert, we can find a perfectly smooth rock that's soft to the touch and glows like water.  To polish something means to wear it down until it's smooth and shiny.  When wind whips dust and sand through the air, they act like sandpaper, making rocks smoother and smoother.  It would be smart for furniture builders to hire wind to polish their work.  As long as they do not mind waiting for years.  Wind comes and go as it pleases.

Wind may not be able to sand down stone or rock very fast and not into shapes that we could sit on, but it does make some very nice works of art.  Out in the desert, sand hills rise and fall like giant waves moving across the desert.  Dunes are hills of sand made by wind.  They all point in the same direction, where the wind likes to blow.  They can move up to 300 feet a year and be as tall as 900 feet!  Dunes are not just pretty.  They will protect some places from flooding by blocking waves of water that try to come in.  If you see danger coming, you could do a lot worse than hiding behind a dune.  Just do not forget the bandana.

Are you kidding me? Across the dunes? There must be an easier way!


Fun Fact!  If you filmed dunes and sped up the tape, the moving dunes would look like waves on the ocean.  This is why deserts are also called sand seas. 

The invisible hand of the world smooths the rocks and moves the dirt.  It can sting our skin with sand or choke our crops with dust.  Or it can build these things into beautiful hills that protect or inspire us.  You cannot see wind.  You can only see your hair whip across your eyes or what sails through the air on the ground below.

References:

Klein, Christopher. "Ten Things You May Not Know About the Dustbowl"  History, 2012.  <http://www.history.com/news/10-things-you-may-not-know-about-the-dust-bowl>

Layton, Julia.  "How Wind Power Works"  August 2006.  HowStuffWorks.com.  <http://science.howstuffworks.com/environmental/green-science/wind-power.htm>

Science News For Kids.  "The Wind in the Worlds"  Science News For Kids, 2007.  <http://www.sciencenewsforkids.org/2007/04/the-wind-in-the-worlds-3/>