Sediment facts for kids

Cobbles on a beach

River Rhône flowing into Lake Geneva. Brownish-grey water shows sediment from water runoff and erosion.

Sediment is tiny bits of material that settle at the bottom of a liquid. Think of it like dirt or sand that falls to the bottom of a glass of water. In nature, sediment is found in oceans, lakes, and rivers.

Over a very long time, these tiny pieces can get pressed together. They can even turn into sedimentary rocks. Sediment can also be carried by wind or water and dropped on land. This material might also become rock later on. The study of how these rocks form is called sedimentology.

What is Sediment?

Sediment is made of small pieces of natural stuff. It can be bits of rocks, minerals, or even parts of dead plants and animals. These pieces are moved around by wind, water, or ice. When the wind or water slows down, the sediment settles. This settling process is called deposition.

How Sediment Forms Rocks

When layers of sediment pile up, they get squeezed. The weight from the top layers presses down on the bottom ones. Over millions of years, this pressure and natural "glue" (minerals in the water) turn the loose sediment into solid rock. This is how many common rocks like sandstone and limestone are made.

Types of Sediment

Sediment in the Gulf of Mexico

Sediment off the Yucatán Peninsula

Scientists classify sediment in different ways. One way is by the size of its pieces. Another way is by what it's made of.

Sediment Size: From Clay to Boulders

Sediment pieces come in many sizes. They can be as tiny as dust or as big as a car! Scientists use a special scale to measure these sizes. It helps them understand how sediment moves and settles.

Here are some common sediment sizes:

You can see that clay is the smallest, and boulders are the biggest!

What Sediment is Made Of

Sediment can be made of different things. It depends on where it came from.

• Rock type: It can be tiny pieces of the original rock it broke off from.
• Minerals: It might be made of specific minerals, like quartz or feldspar.
• Chemicals: Sometimes, sediment forms when chemicals in water combine.

For example, clay can mean two things. It can be a very small size of sediment. But it can also mean sediment made of special clay minerals.

Images for kids

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  River discharging sediment into the ocean
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  Comparison chart for evaluating roundness of sediment grains

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  Sediment builds up on human-made breakwaters because they reduce the speed of water flow, so the stream cannot carry as much sediment load.

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  Glacial transport of boulders. These boulders will be deposited as the glacier retreats.

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  Hjulström curve: the speeds of currents needed to move or drop sediment
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  Modern asymmetric ripples developed in sand on the floor of the Hunter River, New South Wales, Australia. Flow direction is from right to left.

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  Sinuous-crested dunes exposed at low tide in the Cornwallis River near Wolfville, Nova Scotia

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  Ancient channel deposit in the Stellarton Formation (Pennsylvanian), Coalburn Pit, near Thorburn, Nova Scotia.

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  Glacial sediments from Montana

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  Holocene eolianite and a carbonate beach on Long Island, Bahamas

See also

In Spanish: Sedimento para niños