What the Ice Left Behind · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Valleys carved by ancient ice

Geography · Physical Geography · ages 12-13
Name ______________________   Date ____________

  1. Which cross-section commonly forms where a river cuts down into upland ground?

    • A broad U-shaped trough
    • A narrow V-shaped valley
    • A level plain without sides

  2. Which cross-section is commonly associated with a valley widened by glacial erosion?

    • A narrow V-shaped valley
    • A broad U-shaped trough
    • A level plain without sides

  3. What is a moraine?

    • An accumulation of debris left by a glacier
    • A channel of water cut through solid rock
    • A hollow enlarged by waves along a coastline

  4. A glacier eroded bedrock hollows. After it disappears, why can lakes remain in those hollows?

    • The hollows collect rain, meltwater or stream water
    • All lake water comes from ice still buried beneath the bedrock
    • Rain dissolves the bedrock to create the original hollows

  5. Why can a glacier widen a river's V-shaped valley into a U-shaped trough?

    • Ice freezes the rock and stops erosion of the valley
    • Ice and carried rocks erode the floor and sides
    • Ice leaves the sides untouched and cuts one channel

  6. Scratched bedrock and transported boulders can be evidence that a glacier once moved across an area.

    Circle one:   True   False

  7. A boulder in glacial deposits matches bedrock far up the former ice-flow route, but not local bedrock. Which explanation fits?

    • The boulder formed from local bedrock despite its different rock type
    • The different rock type shows that the boulder could not have moved
    • The glacier carried the boulder from another place

  8. A river occupies a broad U-shaped valley with scratched bedrock and moraines. A friend says the present river alone made every feature. What challenges that claim?

    • Any river in a valley rules out a glacier's past work
    • Several observed features support past glacial erosion
    • The present river proves the ridges are all river deposits
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Answer key

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

Valleys carved by ancient ice W1-mt_D-aB1k0K73-s1

  1. A narrow V-shaped valley · River downcutting and the wearing back of valley sides often produce a V-shaped upland valley.
  2. A broad U-shaped trough · Glacial erosion can widen the floor and sides into a broad U-shaped trough.
  3. An accumulation of debris left by a glacier · Moraines are accumulations of glacial debris; some form ridges.
  4. The hollows collect rain, meltwater or stream water · The glacier made the hollows. Water from rain, melting ice or streams can collect where drainage allows.
  5. Ice and carried rocks erode the floor and sides · Glacial erosion can act across the floor and against the sides, widening the trough.
  6. True · Rock carried by ice can scratch the bed and be left far from its source.
  7. The glacier carried the boulder from another place · A glacier can transport rock from its source and leave it on different bedrock.
  8. Several observed features support past glacial erosion · The combined clues support earlier glacial activity, even though a river flows there now.
Worksheet · LightMySky