Sediment — Science definition

Small, loose pieces of rock, mineral, or organic material produced by weathering.

Where it is taught

In use

Once rock has been broken into loose sediment, erosion is the step that picks it up and carries it somewhere new.

Weathering, Erosion & Deposition

Questions using sediment

Problem 1

A stream slows on entering a lake and deposits gravel near its mouth and finer sediment farther out. Explain. Explain the reasoning in your own words.
Answer and explanation

Deposition and sorting occur as the stream loses energy; size, density and shape influence settling.

Reduced flow speed lowers transport capacity.

Larger grains commonly settle earlier under these conditions.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 2

Why might sediment settle when a river enters a lake?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Flow speed often falls, reducing transport capacity; particle size and density affect settling.

Problem 3

Trial A produces 12 g of sediment in 120 mL runoff; trial B 9 g in 60 mL. Compare total sediment export and concentration, then name two conditions to control when testing a surface cover.
Answer and explanation

B exports less mass (9 vs 12 g) but greater concentration (0.15 vs 0.10 g/mL). Control rain input, slope, material and collection interval, except for the planned cover change.

Calculate A: 12/120 = 0.10 g/mL.

Calculate B: 9/60 = 0.15 g/mL.

Distinguish total export from concentration and match test conditions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 4

Independent chapter check: Trial A produces 12 g of sediment in 120 mL runoff; trial B 9 g in 60 mL. Compare total sediment export and concentration, then name two conditions to control when testing a surface cover.
Answer and explanation

B exports less mass (9 vs 12 g) but greater concentration (0.15 vs 0.10 g/mL). Control rain input, slope, material and collection interval, except for the planned cover change.

Calculate A: 12/120 = 0.10 g/mL.

Calculate B: 9/60 = 0.15 g/mL.

Distinguish total export from concentration and match test conditions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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