Deposition

Figure 3.11: Where streams enter bodies of standing water, deltas are formed. Here is an example of a forming delta in the Berkeley Pit in Butte. Click on the image to open a larger version in a new window.

Figure 3.11: Where streams enter bodies of standing water, deltas are formed. Here is an example of a forming delta in the Berkeley Pit in Butte. Click on the image to open a larger version in a new window.

Landforms are also created where eroded materials come to rest, or are deposited through a process called deposition. A classic example of this in Montana is alluvial fans that form where fast-running mountain streams enter valleys and slow down, and the sediments they carry fall out of suspension. Take a look at The Perfect Alluvial Fan for an example from the Madison Valley.

Doable Demo: Pour a layer of sand in a flat-bottomed plastic storage box. Pour water over it and create streams, valleys and deltas. Try using different kinds of dirt and soils and see what happens. What do you notice about how different grain sizes are distributed by running water?

Try filling a series of storage boxes with different kinds of soils and sediments and with sod. Drill some drain holes and pour water from a watering can over all of them. What do you notice about the valleys and deltas formed in the different boxes? What do you notice about the water that flows out of the drain holes of the different boxes?

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The MSP project is funded by an ESEA, Title II Part B Mathematics and Science Partnership Grant through the Montana Office of Public Instruction. MSP was developed by the Clark Fork Watershed Education Program and faculty from Montana Tech of The University of Montana and Montana State University, with support from other Montana University System Faculty.