WalesGeographySyllabus dot point

How do plate tectonics create earthquakes and volcanoes, and what landforms and hazards result?

Key Idea 3.1 (Theme 3): tectonic processes and landforms, the structure of the Earth and plate tectonics, the three main plate boundaries (constructive, destructive and conservative) and the landforms and hazards (earthquakes and volcanoes) associated with each.

A focused answer on Key Idea 3.1 for WJEC GCSE Geography Unit 1 (Theme 3): the structure of the Earth and plate tectonics, constructive, destructive and conservative plate boundaries, and the landforms and hazards (earthquakes and volcanoes) at each.

Generated by Claude Opus 4.814 min answerUpdated 2026-06-15

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Quick answer

The Earth has a layered structure: a thin solid crust, a thick semi-molten mantle, and a core. The crust is broken into tectonic plates that float on the mantle and are moved slowly by convection currents (and slab pull) in the mantle. There are two kinds of crust: thin, dense oceanic crust and thick, less dense continental crust. Plates meet at boundaries, and there are three main types. At a constructive (divergent) boundary plates move apart; magma rises into the gap to form new crust, creating mid-ocean ridges and gentle shield volcanoes, with mostly mild earthquakes (for example the Mid-Atlantic Ridge). At a destructive (convergent) boundary plates move together; the denser oceanic plate is subducted beneath the lighter continental plate, melts, and rises as explosive volcanoes, while friction triggers powerful earthquakes and forms ocean trenches and fold mountains (for example the Andes). At a conservative (transform) boundary plates slide past each other; no crust is made or destroyed, but friction causes powerful earthquakes and no volcanoes (for example the San Andreas Fault). Earthquakes happen when locked plates suddenly slip and release stored energy as seismic waves; the focus is underground and the epicentre is above it on the surface.

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What this dot point is asking
The structure of the Earth and plate tectonics
The three plate boundaries
How earthquakes happen
Volcanoes and their landforms
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What this dot point is asking

This dot point covers Key Idea 3.1 of WJEC Unit 1 Theme 3 (a Section B option): tectonic processes and landforms. You need the structure of the Earth and plate tectonics, the three main plate boundaries (constructive, destructive, conservative), and the landforms and hazards (earthquakes and volcanoes) at each.

The structure of the Earth and plate tectonics

The three plate boundaries

How earthquakes happen

Volcanoes and their landforms

Model answer: "Explain the formation of volcanoes at a destructive plate boundary"

A worked structure for a 6-mark explain question.

step Set out the boundary

Explain that at a destructive boundary an oceanic plate and a continental plate move towards each other.

step Describe subduction

Show that the denser oceanic plate is forced down (subducted) beneath the lighter continental plate into the hot mantle, where it melts.

step Form the magma and volcano

Explain that the melted plate forms magma, which is less dense and gas-rich, so it rises through cracks in the crust and erupts. Because it is sticky and explosive, it builds a steep composite volcano.

step Link to the landscape

Conclude that this is why explosive volcanoes, such as those of the Andes, are found along destructive boundaries, alongside ocean trenches and fold mountains.

Try this

Q1. Name the three main types of plate boundary. [Knowledge recall]

Cue. Constructive (divergent, plates move apart), destructive (convergent, plates move together with subduction) and conservative (transform, plates slide past each other).

Q2. Explain why earthquakes occur at a conservative plate boundary. [Short explanation]

Cue. The two plates try to slide past each other but lock together because of friction, so pressure builds up; when the rocks suddenly slip, the stored energy is released as seismic waves, causing a powerful earthquake.

Exam-style practice questions

Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

WJEC Unit 1 (Theme 3)4 marksDescribe what happens at a destructive plate boundary.

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A short data-response describe question, often with a diagram. Reward described processes, ideally using the resource.

The movement. Two plates move towards each other; the denser oceanic plate is forced down (subducted) beneath the less dense continental plate.

The result. The subducting plate melts in the mantle, forming magma that can rise to make explosive volcanoes, and the friction and pressure trigger powerful earthquakes; a deep ocean trench and fold mountains can form.

Top marks. Subduction of the denser plate, plus volcanoes and earthquakes, with a trench or mountains.

WJEC Unit 1 (Theme 3)6 marksExplain why earthquakes occur at plate boundaries.

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A short explain question (levels marking). Reward a developed mechanism linked to plate movement.

The build-up. At plate boundaries, plates try to move past or against each other but lock together because of friction, so pressure (stress) builds up in the rocks.

The release. When the pressure becomes too great, the rocks suddenly slip and the stored energy is released as seismic waves. This is the earthquake. The point underground is the focus; the point above on the surface is the epicentre.

Top band. Link the build-up of pressure and sudden release to the boundary type (for example friction at a conservative or destructive boundary).

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Sources & how we know this

WJEC GCSE Geography (Wales) specification (3110) — WJEC (2019)