GCSE · Geography · AQA · Spec 8035

Interlocking spurs

A river racing down a steep hillside must be strong enough to cut through anything. Right? So why does it bend round ridges of land instead?

Interlocking spurs

An upper-course valley, seen from above

View: 1 · The ridges. Showing 2 layers: Valley floor, Ridges of land

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Ridges of high land stick out into the valley, one from this side, the next from that side, slotting together like the fingers of two hands. So where can a river go?

Interlocking spurs are a landform of river erosion in the upper course, part of the same family as V-shaped valleys, waterfalls and gorges.

Slice across the valley

Why the valley is a narrow V

Imagine cutting straight across the valley and looking at the cut end. Step across it zone by zone.

Zone 1 of 5

Valley side

Start high on one side. The ground is steep, and two things are responsible: weathering and erosion. Both work on these slopes.

Weathering
Erosion

Steep side, narrow shallow channel, steep side: a V. Vertical erosion deepens it from below, and the sides are steep because of weathering and erosion.

What do you really think?

Why doesn't the river just go straight?

You're standing by a river high in the hills. The valley is steep, and the river bends left, right, left around ridges of land.

Which idea is closest to what you think right now?

It's steep up here, so the river must be fast and powerful. Something other than its strength must be making it bend.The river is eating sideways into the valley sides, carving out those bends as it goes.The ridges are piles of rock that the river dropped in its own way.The river doesn't have enough power to erode the ridges, so it has to wind its way between them.

How sure are you?

I'm sureI think soI'm guessing

It's steep up here, so the river must be fast and powerful. Something other than its strength must be making it bend.

This is a common misconception

That's the trap. Think back to the channel you just crossed: shallow, narrow and full of boulders, with friction slowing the water. And strength is exactly what this river lacks. It doesn't have the power to erode the spurs, so it winds round them.

The river is eating sideways into the valley sides, carving out those bends as it goes.

This is a common misconception

Not up here. In the upper course the main process is vertical erosion: the river cuts downwards, deepening the valley. The valley it's deepening is narrow and V-shaped, not wide. The bends come from the river going round the spurs, which it can't erode.

The ridges are piles of rock that the river dropped in its own way.

This is a common misconception

The spurs aren't something the river has built. They're ridges of the land itself, sticking out into the river's course. Interlocking spurs are a landform of river erosion, like V-shaped valleys, waterfalls and gorges.

The river doesn't have enough power to erode the ridges, so it has to wind its way between them.

This matches the evidence

Exactly right. The spurs stick out into its course, the river hasn't the power to erode them, so it goes round. Meanwhile its erosion is mainly vertical, deepening the V-shaped valley beneath it.

Round the spurs, not through them. A steep upper-course river is slowed by friction and too weak to erode them.

Your turn to explain

Put it in your own words

Describe interlocking spurs and explain why a river in its upper course winds between them. [4 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Spurs are ridges of land that stick out (extend) into the river's course. (1 mark)
They come from alternate sides of the valley, so they interlock and the river winds between them. (1 mark)
The river winds around the spurs because it does not have the power to erode them. (1 mark)
In the upper course, vertical erosion is the main process, deepening the valley. (1 mark)
The valley is narrow and steep-sided, with a V-shaped cross-section. (1 mark)

Model answer

Interlocking spurs are ridges of land that stick out into a river's course from alternate sides of the valley, so they lock together like fingers and the river winds between them. The river winds around them because it does not have the power to erode them. They are found in the upper course, where vertical erosion is the main process, deepening a narrow, steep-sided, V-shaped valley.

Describe what you would see, give the reason (no power to erode the spurs), then set it in its valley.

Exam line: A strong answer describes the spurs, then gives the reason the river winds, then places it in a narrow, V-shaped upper-course valley.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

High in the hills, a river zigzags round ridges of land instead of cutting straight through them. Here's why.

What you need to know

What interlocking spurs are, and what they look like from above
Why the river winds between the spurs instead of going through them
Why the upper-course valley is a narrow, steep-sided V
Why a river on a steep gradient can still be slow and weak

The big picture

Interlocking spurs are ridges of land that stick out into a river's course in its upper course, and the river winds between them because it doesn't have the power to erode them. The valley they sit in is narrow and steep-sided, a V shape, deepened mainly by vertical erosion. They are one of the river's upper-course erosion landforms, alongside V-shaped valleys, waterfalls and gorges.

Key points

1Interlocking spurs are ridges of land that extend into the river's course; the river winds between them.

2The river winds around the spurs because it does not have the power to erode them.

3They are a landform of river erosion in the upper course, like V-shaped valleys, waterfalls and gorges.

4In the upper course vertical erosion is the main process, deepening the valley into a narrow, steep-sided V.

5The valley sides are steep because of both weathering and erosion.

6The channel is shallow and narrow; despite the steep gradient, friction with rocks and boulders the river can't move slows its flow.

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Worked example

Problem

The gradient in a river's upper course is steep. Explain why the river's flow there is still slowed.

⚠ Watch out

Assuming a steep upper-course river must be fast and powerful. In fact the channel is shallow and narrow, friction with rocks and boulders slows the flow, and the river doesn't have the power to erode the spurs, which is why it winds round them.

🧠

Memory hook

Round, not through; down, not out. The river goes round the spurs because it can't erode them, and its main erosion is down into its bed, deepening a narrow, steep-sided V.

✓

Check yourself

Without looking back: say what a spur is, explain why the river winds between spurs instead of cutting through them, and name the main process deepening the valley.

Flashcards

(8)

What are interlocking spurs?

Ridges of land that extend into a river's course, which the river winds between.

Why are the spurs called 'interlocking'?

They stick out from alternate sides of the valley, so they slot together like fingers.

In which part of a river's course are interlocking spurs found?

The upper course.

Interlocking spurs are made by river erosion. Name three other upper-course erosion landforms.

V-shaped valleys, waterfalls and gorges.

Why does the river wind around the spurs?

It does not have the power to erode them.

What is the main erosion process in the upper course?

Vertical erosion, which deepens the valley.

What shape is the valley in cross-section in the upper course?

A V: narrow and steep-sided.

What makes the upper-course valley sides steep?

Both weathering and erosion.

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Why the valley is a narrow V

Why doesn't the river just go straight?

Put it in your own words

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