5.2 My Sediments Exactly
Properties of Sediments
Sediment, also called clasts, that has been weathered away is sometimes transported away from the parent rock. Depending on the characteristics of the sediment you might find on a river bed, a steep slope, or just down the road, you can determine the distance, energy, and identity of the likely transportation source. Here are some identifying characteristics:
Sediment Sorting
Well-sorted sediment: All the clasts have a similar size and shape. This usually indicates that the clasts have traveled a long distance from the parent rock.
Poorly-sorted sediment: There is a mixture of clasts of different sizes present. This indicates that the clasts have traveled only a short distance from the parent rock.
Sediment Shape
Rounded Clasts: The clasts present are round in shape. This indicates that the clasts have traveled a far distance from the parent rock to undergo repeated physical shaping by the transport source. Rivers or streams are typically the transport source for this type of clast.
Angular Clasts: The clasts present have angular or jagged edges. This can indicate that the clasts have traveled a short distance or down a steep slope from the parent rock. This usually indicates a gravity flow such as a landslide or debris flow as the transport source.
Sediment Size
Boulder: Greater than 25 cm in length.
Cobble: Between 25 cm and 6 cm in length.
Pebble: Between 2 mm and 6 cm.
Sand: Between 0.06 mm and 2 mm.
Silt: Between 0.004 mm and 0.06 mm
Mud or Clay: Less than 0.004 mm.
Let’s Review!
Use these definitions to aid you in describing the sediment types in the videos below.
