When a fast-moving mountain river reaches a flat valley and slows down, what determines which sediment is deposited first?
AThe color of the sediment
BThe age of the sediment
CThe size and weight of the particles — the heaviest and largest are deposited first
DAll particles are deposited at the same time
When water slows down, it loses carrying power. The largest, heaviest particles (boulders, gravel) are dropped first because they require the most energy to transport. Smaller particles (sand) are carried farther before being deposited. The finest particles (silt and clay) travel the farthest and are the last to settle. This sorting by size is a fundamental feature of deposition.
Question 2 Short Answer
How does a river delta form?
Think about your answer, then reveal below.
Model answer: A delta forms where a river enters a standing body of water (ocean, lake, or sea) and slows down dramatically. The river loses its carrying power and deposits its sediment load. Over time, the accumulated sediment builds a fan-shaped or triangular deposit that extends into the water body. The Mississippi River delta is a classic example.
Deltas are named after the Greek letter delta (Δ) because early geographers noticed the triangular shape of the Nile River delta. Not all deltas are triangular — the Mississippi delta looks more like a bird's foot because its main channels extend far into the Gulf of Mexico.
Question 3 True / False
Beaches are permanent features that seldom change shape or size.
TTrue
FFalse
Answer: False
Beaches are some of the most dynamic landforms on Earth. They constantly change as waves, currents, and storms add and remove sand. Rivers supply new sand to coastlines, and longshore currents move it along the shore. A single strong storm can remove meters of beach in hours. Many beaches are slowly shrinking because dams trap river sediment before it can reach the coast.