Have you ever been to a beach? Or have you seen a beach in a movie or read about one in a book? Imagine what the soft sand feels like beneath your toes. No wonder beaches are so popular for vacations.
Did you ever stop to think how beaches were made, though? They certainly were not there when the world was made more than four billion years ago. At that time, we think the world was very hot and covered in lava. It had no oceans, no trees, and no land. Today things are much cooler. Earth is now covered with land that we can walk on, oceans we can swim in, and fresh air we can breathe. In fact, all of these things helped make beaches, caves and other interesting landforms.
Just another day at the beach.
Sometimes wind, water and ice cause bits of the Earth's land to wear down. This is called erosion. If you were to pick up a rock and throw it away from where you found it, pieces might break off. If you were to do this enough times, you would be left with smaller and smaller pieces that are now in different places from where they started. This is similar to how erosion works. The force of wind against a rock causes small pieces of rock to break off. Over many, many years, that rock is going to look very different. Where do the bits and pieces from the rock go? All the sand on a beach was once a part of big rocks.
Wind and water are two things that wear away rocks. When they break down and destroy mountains, hills, and other things, it is called deconstruction
. I am sure you have seen pictures of a volcano that looks like a whole mountain. Think of when it erupts. During that time, it spits out a lot of rock, gas and ash into the air. When it's done, most of the mountain may be gone. This is one way of breaking parts of the land up.
Does anyone else smell smoke?
There are also things that help build mountains and hills. Remember how an erupting volcano blows most of its top? Well, where does all that stuff go? It is blown into the air and it lands on all the things around it. Lava might cover some of the land. When it dries up, it's hard rock. After enough time, the rock builds and builds and creates new land on top of the old land. When things are built up from smaller parts, it's called construction
Lava, it's what makes an island grow.
All this talk of volcanoes might make you want to think about the beach again. There are a lot of beaches in the world. Did you know that there are places covered in only sand with no water in sight? These are called deserts. Instead of mountains built of big, hard rocks, desert mountains are made up of sand. Some of them are places where an ocean used to be a very, very long time ago, and others are just a place where the sand from broken down rocks got stuck. How weird is it for a place to be covered in all sand and not even have any water around? That does not sound like a very fun beach.
As all the rocks in the world around us are broken down into little pieces, a lot of them end up following the water to the beach. Deposition
is when wind or water start to drop a lot of small pieces of rock into one place. This builds up really big sand dunes. Wind picks up tiny bits of rock and dirt and drops it into the same place. After a really long time, the place is covered in sand. The sand builds up and pretty soon you have hills made up of only sand.
However, this does not just happen with sand. The water in a river picks up sediment and drops it farther down the river. Over time, the river picks more and more stuff up and drops more and more of it on top of each other. Someday, the river might dry up and then something else happens. Given enough time and enough rocks on top of each other, all that stuff starts to squeeze together. All that rock and dirt is heavy! Think of putting a peanut butter and jelly sandwich in your backpack. The sandwich might end up crushed by your books, but you can still see the different layers. Sedimentary rock
is a kind of rock that is made from many different layers being squeezed together. It's easy to tell if a rock is sedimentary. You will be able to see the different colored layers.
Sandstone, the layered look.
Even though erosion breaks things down, it is not all bad. In fact, without it there would not be any beaches or caves. If there were no caves, where would all the bats live? In a way, it helps break down things so other things can form. It's been a part of Earth for a very long time. If we did not have erosion, where would you go on vacation?References:
CoolGeography. "Erosion Landforms"
Geographic Education. "Erosion" National Geographic
Geography4Kids. "Break It Down" Geography4Kids.com, 2012.