---
title: "Hanging Valley | Intro to Geology"
description: "Hanging Valley in Intro to Geology is a tributary valley left perched above a glacial trough, often ending in a waterfall after uneven glacier erosion."
canonical: "https://fiveable.me/introduction-geology/key-terms/hanging-valley"
type: "key-term"
subject: "Intro to Geology"
unit: "Unit 12"
---

# Hanging Valley | Intro to Geology

## Definition

A hanging valley is a smaller valley that sits above the floor of a larger glacial valley. In Intro to Geology, it is a classic landform made by unequal glacial erosion.

## What It Is

A hanging valley in Intro to Geology is a tributary valley that ends higher than the main valley floor, usually because a smaller glacier did not carve as deeply as the larger glacier it joined. After the ice melts, the tributary valley is left “hanging” above the main U-shaped valley.

The shape makes a lot more sense when you picture two glaciers meeting. The main glacier in the larger valley is thicker, faster, and has more erosive power. It can scour bedrock deeply, widen the valley, and lower the floor a great deal. The tributary glacier feeding into it is usually smaller, so it erodes less and leaves its valley floor stranded at a higher elevation.

That difference in erosion is the main idea behind the landform. It is not that the tributary valley was built up somehow. Instead, the main valley was carved down farther, which creates a noticeable step between the side valley and the main trough. The result is often a steep drop, cliff, or waterfall where the tributary stream meets the main valley.

You usually see hanging valleys in landscapes that were once heavily glaciated, especially mountain regions. They are one of the easiest clues that a valley system was shaped by ice rather than just by river erosion. A normal river junction usually does not leave one stream perched high above another like this.

In a lab or field ID setting, you would connect a hanging valley with other glacial landforms such as a U-shaped valley, cirques, and signs of glacial erosion. It is a landform that shows how glaciers do not all erode equally, and how the landscape records that imbalance long after the ice is gone.

## Why It Matters

Hanging valleys matter because they show one of the clearest ways glaciers reshape topography through differential erosion. In Intro to Geology, they are a good clue that a landscape has a glacial past, even if the ice itself is long gone.

They also connect several big course ideas at once: erosion, transportation, valley shape, and landscape evolution. If you can explain why a hanging valley sits above the main trough, you are already using the logic of glacial mechanics instead of just memorizing a landform name.

This term also helps you read landforms in photos and maps. A waterfall dropping from a side valley into a broad main valley is a strong visual cue that the area was shaped by glaciers, not just running water. That kind of visual identification shows up a lot in labs, image questions, and field-sketch activities.

Hanging valleys are also useful because they help separate glacial erosion from fluvial erosion. Rivers tend to connect tributaries more smoothly, while glaciers can leave abrupt height differences between valleys. That contrast is one of the easiest ways to spot the difference between a river-cut landscape and an ice-cut one.

## Connections

### [U-shaped Valley](/introduction-geology/key-terms/u-shaped-valley)

A hanging valley usually sits along the wall of a U-shaped valley, which is the larger trough carved by the main glacier. The U-shaped valley shows the broad erosion of ice across a whole valley floor, while the hanging valley marks a smaller tributary that was not eroded as deeply. Together, they are a strong glacial pair.

### [Glacial Erosion](/introduction-geology/key-terms/glacial-erosion)

Hanging valleys are a direct result of glacial erosion, especially when two glaciers of different sizes erode the landscape unevenly. The main glacier cuts deeper and wider, while the tributary glacier leaves a shallower valley behind. If you understand how glacial erosion works, the height difference makes sense fast.

### Cirque

A cirque is another landform made by glacier erosion, but it forms at the head of a glacier instead of where tributaries meet. Both cirques and hanging valleys are clues to past ice, yet they show different parts of the glacier's work. Cirques mark where ice begins, while hanging valleys show how tributary valleys were left stranded.

### [Glacial Retreat](/introduction-geology/key-terms/glacial-retreat)

Hanging valleys become visible after glacial retreat removes the ice that once filled the main and tributary valleys. Once the glacier melts back, the shape of the carved landscape is exposed. That is why hanging valleys are often studied as evidence of former ice cover rather than active glacier movement.

## On the AP Exam

A photo ID question may show a steep side valley entering a broader trough and ask you to name the landform. The move is to spot the height difference, connect it to unequal glacial erosion, and explain why a waterfall often forms at the junction. In a short-answer or lab response, you might compare the hanging valley to the main U-shaped valley and say which glacier did more cutting. If you get a landscape map or outcrop sketch, look for the tributary valley ending above the floor of the main valley, not joining it smoothly like a river system would.

## Hanging Valley vs U-shaped Valley

A U-shaped valley is the broad main glacial trough, while a hanging valley is a smaller tributary valley left perched above it. They are related, but they are not the same landform. If the question shows the whole glacial valley, think U-shape. If it shows the side valley dropping into the main valley with a waterfall, think hanging valley.

## Key Takeaways

- A hanging valley is a tributary valley that ends above the floor of a larger glacial valley.
- It forms because the main glacier erodes more deeply than the smaller tributary glacier.
- Waterfalls often appear where the hanging valley meets the main valley floor.
- The landform is a strong clue that the area was shaped by past glaciation.
- In geology class, you use it to identify glacial landscapes and explain differential erosion.

## FAQs

### What is a Hanging Valley in Intro to Geology?

It is a smaller valley left elevated above the floor of a larger glacial valley. The main glacier carved down more deeply than the tributary glacier, so the side valley is left “hanging” after the ice retreats.

### Why do hanging valleys often have waterfalls?

The tributary stream drops from a higher valley floor into the deeper main valley below. That sudden elevation change creates a steep drop, so waterfalls are common at the junction.

### How is a hanging valley different from a U-shaped valley?

A U-shaped valley is the broad trough carved by the main glacier. A hanging valley is the smaller side valley that joins it from above. They are both glacial landforms, but they describe different parts of the same landscape.

### How do you identify a hanging valley in a lab photo?

Look for a side valley that enters a larger valley high above the bottom, often with a waterfall or cliff at the meeting point. The key clue is the mismatch in elevation between the tributary valley and the main glacial trough.

## Related Study Guides

- [12.2 Glacial and periglacial processes and landforms](/introduction-geology/unit-12/glacial-periglacial-processes-landforms/study-guide/WV84heotSclvaDZW)

## About This Document

Canonical Fiveable pages are available as Markdown at the same path plus `.md`.

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- [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing
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