How are fold mountains formed?

Two plates push towards each other with the rock between them, and the rock has nowhere to go, so it buckles upwards in folds. The Himalayas and the Alps are that, and it is still happening: the Himalayas grow by about a centimetre a year.

What is a block mountain?

Where the crust is pulled apart it breaks along faults, and a piece between two of them can end up standing higher than the ground either side. It is flat on top because it has not been bent, only lifted.

What about volcanic mountains?

They are the third kind and they are built up rather than pushed up: every eruption leaves ash and lava on the outside, so the mountain is made of what came out of it. The volcano tool is that, in cross-section.

Is the picture to scale?

No, and it says so here rather than pretending. The crust in these boards is a few hundred units deep so the layers can be seen at all; in reality it is tens of kilometres thick under a mountain range and the folds are far gentler than these.

Mountains

Geography · Year 3–Year 6

Two ways the ground makes a mountain: squeezed, or broken.

About the mountains

Two boards for the two ways the ground itself makes a mountain. On the fold board two plates squeeze the rock until it buckles up into a range; on the block board the crust is pulled apart and one piece stands higher than the rest between two faults. Tap a part to name it: peak, slope, valley, folds, faults and the block.

The two boards are the same plates doing opposite things, which is why they are worth putting side by side: the arrows point IN on one and OUT on the other. Squeezed or stretched is the whole difference, and it is drawn rather than written.

The fold is one curve. Every band of rock under the surface is that curve moved down, so the layers bend together, and the two peaks, the valley between them and the slope are all measured off the same line. It is why the rock reads as bent rather than broken.

A block mountain is flat on top, because it has not been bent: it has been broken either side and pushed up as one piece, so its layers are still level and they line up with the layers outside the faults, one step down.

The third kind is a volcano, built up out of what came out of it, and that has a tool of its own with the plumbing inside it. Drawing it again here would be two pictures of one thing.

How to use it on your whiteboard

1Tap a part to name it and see what it is.
2Tap Fold or Block to change the kind of mountain.
3Tap Next to work round the board in order.
4Tap Show all to put every label up at once, and Hide to ask the class again.

Questions

How are fold mountains formed?: Two plates push towards each other with the rock between them, and the rock has nowhere to go, so it buckles upwards in folds. The Himalayas and the Alps are that, and it is still happening: the Himalayas grow by about a centimetre a year.
What is a block mountain?: Where the crust is pulled apart it breaks along faults, and a piece between two of them can end up standing higher than the ground either side. It is flat on top because it has not been bent, only lifted.
What about volcanic mountains?: They are the third kind and they are built up rather than pushed up: every eruption leaves ash and lava on the outside, so the mountain is made of what came out of it. The volcano tool is that, in cross-section.
Is the picture to scale?: No, and it says so here rather than pretending. The crust in these boards is a few hundred units deep so the layers can be seen at all; in reality it is tens of kilometres thick under a mountain range and the folds are far gentler than these.