What landforms form at each type of plate boundary?

Divergent boundaries (tension) form rift valleys and mid-ocean ridges, with normal faults and transform faults offsetting the ridge. Convergent boundaries (compression) form fold mountain ranges with reverse (thrust) faults and folds, plus deep ocean trenches at subduction zones. Transform boundaries (shear) form strike-slip faults that offset features sideways without building mountains or rifts.

What is the difference between a normal fault and a reverse fault?

A normal fault forms under tension: the hanging wall (the block above the tilted fault plane) drops down relative to the footwall, lengthening the crust — typical of divergent boundaries. A reverse fault forms under compression: the hanging wall is pushed up and over the footwall, shortening and thickening the crust — typical of convergent boundaries. A low-angle reverse fault is a thrust fault.

How does a rift valley form?

When the crust is stretched at a divergent boundary it breaks along normal faults. A central block then drops down between two roughly parallel normal faults, leaving raised shoulders on either side; the dropped block is the floor of the rift valley. The East African Rift is a continental example.

Why do fold mountains and ocean trenches form at convergent boundaries?

Compression at a convergent boundary buckles rock layers into folds (anticlines and synclines) and breaks them along reverse and thrust faults, thickening the crust into fold mountain ranges such as the Himalayas. Where a plate subducts, it bends sharply downward and drags the sea floor into a deep trench, so the highest and lowest land can form at the same boundary.

The landscapes plates build

A mountain range, a deep trench, a cliff-walled valley — none of it is random scenery. Each is the frozen record of one of three forces: pulling apart, pushing together, or grinding past. Learn how rock breaks and bends under each, and you can stand on a landform and name the plate boundary that made it.

stresses

fault types

short sections

The landscapes plates buildSection 1 of 5

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This book has 5 short sections. Read each one, answer the check, then use Next to move on — the bar above tracks how far you've come.

The landscape is a record of the forces

A mountain range, a deep ocean trench, a valley with cliffs on both sides — these are not random scenery. Each is a structure left behind by the forces of plate movement, frozen into the rock and the land. Learn to read them and you can stand on a landform far from any coastline and name the kind of plate boundary that built it.

The key is that each boundary type applies a particular kind of stress to the rock. Where plates pull apart, the crust is under tension. Where they push together, it is under compression. Where they grind past, it is under shear. Three forces — and rock responds to each in its own unmistakable way.

So the plan for this chapter is simple. First learn how rock breaks and bends under those three stresses (the faults and folds). Then tour the landscapes each boundary builds from them: the dropped valleys and ridges of pulling apart, the crumpled mountains and trenches of pushing together. By the end the land itself becomes readable.

New words

stress

Force acting on rock — tension (pulling apart), compression (pushing together) or shear (sliding past).

tectonic structure

A fault, fold, valley or range produced by plate movement — a record of the stress that made it.

🔒 Lock it in

Why can a geologist often identify the boundary type that shaped a region without watching the plates move?

Answer the check to continue

Quick reference & sources

The interactive book above is the lesson. What follows is a plain recap you can revise from, plus the sources and how this maps to the syllabus.

The three faults, by stress

Normal fault — tension; the hanging wall (block above the tilted fault plane) drops down; lengthens the crust; divergent boundaries. Reverse fault — compression; the hanging wall is pushed up over the footwall; shortens and thickens the crust; convergent boundaries (a low-angle reverse fault is a thrust fault). Strike-slip fault — shear; blocks slide horizontally past each other; transform boundaries.

Landforms by boundary type

Divergent (tension): rift valleys (a block dropped between normal faults, e.g. the East African Rift) and mid-ocean ridges, offset by transform faults. Convergent (compression): fold mountain ranges with anticlines, synclines and reverse/thrust faults (Himalayas, Andes), plus deep ocean trenches at subduction zones. Transform (shear): strike-slip faults that offset streams and ridges sideways, with little vertical relief.

Reading a boundary off the land

Match the structure to the stress and the stress to the boundary. Dropped valleys + ridges + normal faults → tension → divergent. Folds + reverse faults + mountains + trenches → compression → convergent. Sideways-offset features along a straight fault → shear → transform. This is the previous chapter (what happens to crust) read backwards from the evidence it leaves.

For HSC students

This powerbook covers the Plate Boundaries and Tectonic Structures thread of Module 2 (Plate Tectonics), framed by the inquiry question what geological and topographic features result from plate tectonics at each boundary type? Working through it, you should be able to:

model divergent boundaries and their features: rift valley, mid-ocean ridge, normal faults and transform faults;
model convergent boundaries and their features: mountain range, trench, reverse faults and folds;
distinguish normal, reverse and strike-slip faults by stress, motion, and hanging-wall behaviour;
relate each landform back to the tension, compression or shear that produced it.

The processes behind these features — what happens to crust at each boundary — are the previous chapter, what happens at plate boundaries. Explanations here are original and are a study aid, not a copy of the syllabus.

Sources

US Geological Survey, This Dynamic Earth — boundary types and their associated structures and landforms.
Geoscience Australia — faults, folds and the structural geology of plate boundaries.
Standard structural-geology references on fault classification (normal, reverse/thrust, strike-slip) and fold terminology (anticline, syncline).
NSW NESA Earth and Environmental Science Stage 6 Syllabus (2017) — used only to scope the Module 2 content; explanations above are original.

Keep going

Tension drops and stretches, compression lifts and crumples, shear slides aside — and every fault, fold, ridge, trench and range is just the land remembering which force passed through.