Step 3: Deposition (Sediments Settling Down!)

These pebbles were deposited in a stream that once flowed over this area in Indiana, USA thousands of years ago. Now they are part of a clastic sedimentary rock called conglomerate. Click on image for full size (59K JPG) Courtesy of Bruce Molnia, Terra Photographics

When water or wind loses energy and slows down, sediment can no longer be carried in it. The particles of sediment fall through the water or air and form a blanket of sediment on the bottom of a river, a lake, ocean, or on the surface of the land. This process is called deposition.

Settling out of the wind or water depends on the size of the clast. Larger clasts with high mass will settle more quickly than smaller clasts with less mass. Conversely, it takes more energy to move larger clasts through the water or air (a process called entrainment).

How does deposition happen?
Try this and find out!

1. Add a handful or two of sediment to a jar that includes particles of different sizes such as pebbles, sand and mud.
2. Fill the jar with water and seal the lid on top.
3. Shake the jar and watch the pebbles and dirt become entrained in the water.
4. Let the jar sit still for a few minutes. What has been deposited on the bottom of the jar? Are any of the small particles still in the water? (The heaviest items fall out of the water more quickly than the small ones once you stop shaking the jar.)
   
   

These pebbles were deposited in a stream that once flowed over this area in Indiana, USA thousands of years ago. Click on image for full size (59K JPG) Courtesy of Bruce Molnia, Terra Photographics

When water or wind loses energy and slows down, sediment can no longer be carried in it. The particles fall through the water or air and form a blanket of sediment on the bottom of a river, a lake, ocean, or on the surface of the land.

Settling out of the wind or water depends on the size of the sediment. Larger pieces will settle more quickly than smaller ones. The opposite is true as well, so it takes more energy to move larger sediment through the water or air than small sediment.

The process of settling down is called deposition. How does deposition happen?
Try this experiment and find out!

1. Add a handful or two of sediment to a jar that includes particles of different sizes such as pebbles, sand and mud.
2. Fill the jar with water and seal the lid on top.
3. Shake the jar and watch the pebbles and dirt fill the water.
4. Let the jar sit still for a few minutes. What has been deposited on the bottom of the jar? Are any of the small particles still in the water? (The heaviest items fall out of the water more quickly than the small ones once you stop shaking the jar.)

These pebbles settled out of the water in a stream that once flowed over this area thousands of years ago. Click on image for full size (59K JPG) Courtesy of Bruce Molnia, Terra Photographics

When water or wind slows down, sediment can no longer be carried in it. The particles of sediment fall through the water or air and form a blanket of sediment on the bottom of a river, a lake, ocean, or on the surface of the land.

Settling down depends on the size of the sediment. Larger pieces will settle more quickly than smaller ones. How does this happen? Try this experiment to see for yourself!

1. Add a handful or two of sediment to a jar that includes particles of different sizes such as pebbles, sand and mud.
2. Fill the jar with water and seal the lid on top.
3. Shake the jar and watch the pebbles and dirt fill the water.
4. Let the jar sit still for a few minutes. What settles on the bottom of the jar? Are any of the small particles still in the water? (The heaviest ones will fall out of the water faster than the small ones once you stop shaking the jar.)