Bang!  A wrecking ball swings down, breaking apart an old building to make room for a new one.  It's too hard to move the building in one piece.   Instead, workers break it down into smaller bits and use trucks to move pieces off the site.  Rocks are moved in the same way.  Weathering breaks them down into smaller rocks.  Then they can be easily moved to new places by wind and water.  In the future, those pieces can be used to make something new.
Picture yourself trying to move a whole building in one piece.  It would be much too heavy and awkward.  It's a lot easier to take the building apart and move smaller bits of concrete, metal and other building parts.  In the same way, rocks break down into smaller rocks, which turn into sand, dirt and clay.  These smaller pieces are much easier to move around.  Sediment is the name for tiny pieces of rocks, dirt, sand, and leftovers of living things.  Sediment can gather on land, or be pushed down rivers to the ocean floor. 

The Mississippi River bank; one of the most famous sources of sediment in America.

At the construction site, big dump trucks carry the broken down building bits to the recycling center.  With rocks, they will become small enough for wind, water and even ice to move them from place to place.  The distance they move depends on the speed of the wind and water and the size of the rocks.  After heavy storms, fast-moving waters can carry sand and even larger rocks a long way.  Strong winds like tornadoes can move soil as well as cars and furniture.  We can use the word transport when something is moved from one place to another.  Sediment can be transported by wind, water, ice or gravity, like landslides.

Heavy rains often transport very large amounts of sediment down rivers.

When the dump truck reaches the recycling center, it dumps its load.  Then the waste is sorted.  Wood goes into one pile, stone in another, metal in yet another.  The movement of rocks and sand works in the same way.  If the flow of a river slows down, small rocks may gather on the bottom.  The mud keeps moving, but if the river slows down even more, the mud may also drop to the bottom.  A deposit is when parts of broken down rock, dirt, sand or living things are set down in one place by things like wind and water.  The sediment is sorted by size, with big, heavy rocks being laid down on the bottom and smaller, lighter parts on the top.

A deposit like this can really change how a river will be used.

When a dump truck sets down what it is carrying, the different kinds of building materials are sorted out.  Each pile has pieces of a different size.  Big parts go with other big parts and small things like sand go with more sand.  This is not how broken down rock is sorted out.  In cold places, huge pieces of ice called glaciers move rocks down mountains.  Snow and ice build up and push down on rocks below them, moving them down the hill.  When the ice sheets melt, the rock is dumped all at once.  It is not sorted.  Scree is a mix of loose stones and big rocks that have piled up.  You can also see this when rocks fall off a cliff over and over again and make a pile at the bottom of the cliff.

As mountains break down, scree builds up.

Moving smaller pieces from place to place is easier than moving a large building or boulder.  As rocks are broken down and moved, these pieces are sorted by size and laid down.  When huge glaciers melt, they will also dump the rocks they were carrying, but they are not very neat about it.  All this sediment gets moved around the Earth over and over again.  It forms new beaches and new rocks before being broken down again, moved around and built up into something else.  In the same way, the wood, stone and metal from the buildings you see around you will be recycled and used again too.


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