---
title: "What the Ice Left Behind"
description: "Glaciers flow slowly and erode rock beneath and beside them. They can widen valleys into U-shaped troughs and leave sediment, transported boulders and hollows that later hold lakes. Many landscapes in"
canonical: https://lightmysky.com/learn/geography/what-the-ice-left-behind-mt_D-aB1k0K73
source: https://lightmysky.com/learn/geography/what-the-ice-left-behind-mt_D-aB1k0K73.md
retrieved: 2026-11-12
---

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# What the Ice Left Behind

Glaciers flow slowly and erode rock beneath and beside them. They can widen valleys into U-shaped troughs and leave sediment, transported boulders and hollows that later hold lakes. Many landscapes in northern Europe and North America retain traces of past ice.

Subject: Geography · Area: Physical Geography · Ages 12 to 13
Page: https://lightmysky.com/learn/geography/what-the-ice-left-behind-mt_D-aB1k0K73

## Ready when they can

- Say how a glacial valley differs in cross-section from a river valley, and why
- Name two things a glacier leaves behind when it melts
- Explain why lakes are common in landscapes that were once under ice

## Lesson: Valleys carved by ancient ice

A glacier flows slowly as its ice deforms. Some glaciers also slide over their beds. Rock fragments carried at the base scrape the valley floor and sides. Ice can also pull away blocks. These processes can widen and deepen a valley into a broad U-shaped trough.

**Example.** A river cutting down into upland ground often forms a V-shaped valley as the sides also wear back. A glacier may widen it into a U shape with steep sides and a broad floor. These are clues, not rules for every valley. A river can later occupy a valley shaped by ice.

Glaciers carry mixed rock fragments. Material left directly by ice is often unsorted, with different sizes together. An accumulation of glacial debris is called a moraine. Some moraines form ridges beside or beyond the ice. Moving fragments can scratch bedrock. Ice can also carry boulders far from their source rock.

*(drawing: This shows how debris can be left behind, not a valley cross-section.)*

Glacial erosion can leave hollows that collect rain, meltwater or stream water. Moraines can also block drainage and form lakes. A lake alone does not prove that ice shaped the land. Compare several clues: a U-shaped cross-section, scratched bedrock, moraines and transported boulders. Together they can support a glacial explanation.

**Recap.** Moving ice can widen valleys, scratch rock and leave sediment. Use several clues together to investigate a glacial landscape.

*Lesson, question and flashcard revisions written for this dataset.*

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Erosion and weathering](https://lightmysky.com/learn/science/erosion-and-weathering-mt_vAP_A986IQ)

## Optional connections

- [Coasts on the Move](https://lightmysky.com/learn/geography/coasts-on-the-move-mt_IVnXDRpfqE)
- [How a River Shapes Its Valley](https://lightmysky.com/learn/geography/how-a-river-shapes-its-valley-mt_v6D9mgcf0P)

## Opens up

- [Reading a Landscape Off a Map](https://lightmysky.com/learn/geography/reading-a-landscape-off-a-map-mt_MWlY_e59Rg)