Sediment on the Move: Rivers, Coasts and Where It Settles · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Following a grain to the sea

Science · Earth's Systems · ages 15-16
Name ______________________   Date ____________

  1. How does a riverbed change on the way to the sea?

    • Mud to sand to gravel
    • Gravel to sand to mud
    • It stays one grade throughout

  2. A current slows down. Which grains drop out first?

    • The finest mud
    • The coarsest gravel
    • All grains together

  3. Where does a delta grow, and why?

    • At the source, where water is fastest
    • Where the river meets the sea and slows
    • Underground, where caves widen

  4. A dam traps gravel upstream. What happens downstream?

    • Deltas grow faster than ever
    • The river erodes and beaches shrink
    • Nothing changes at all

  5. Why do dunes march downwind?

    • Wind drops sand where it slows, gust by gust
    • Sand melts and refreezes daily
    • Dunes are pushed by rivers

  6. Cutting a delta's sediment supply makes the delta grow faster.

    Circle one:   True   False

  7. After a storm a slope shows gravel high up and mud far below. What does that tell you?

    • Water slowed along the way, dropping heavy grains first
    • Wind carried the gravel uphill
    • Mud is heavier than gravel

  8. A sea wall saves one beach, but the next beach along shrinks. Why?

    • The wall eats sand directly
    • Swimmers moved to the other beach
    • The wall starves its neighbour of drifting sand
LightMySky · lightmysky.comW1-mt_d1vVJBG6K7-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Following a grain to the sea W1-mt_d1vVJBG6K7-s1

  1. Gravel to sand to mud · Slowing water sorts the load from heavy to fine.
  2. The coarsest gravel · Heavy grains fall out as soon as the grip weakens.
  3. Where the river meets the sea and slows · Sudden slowing dumps the carried load grain by grain.
  4. The river erodes and beaches shrink · Starved of supply, erosion wins over building.
  5. Wind drops sand where it slows, gust by gust · Wind is a river of air with the same drop rule.
  6. False · Less supply means washing away beats building up.
  7. Water slowed along the way, dropping heavy grains first · The grades map the slowing current downhill.
  8. The wall starves its neighbour of drifting sand · One system shares the sediment, so blocking it shifts erosion along.
Worksheet · LightMySky