Plate Boundaries

Earthquakes and volcanoes occur in regions where the edges of different plates are in contact
So, scientists have been able to identify tectonic plates by gathering and plotting data about:
- The epicentres of major earthquakes
- The sites of active volcanoes

earthquakes-and-volcanoes

The position of earthquakes and volcanoes provides evidence for tectonic plates

Volcanic eruptions and earthquakes most commonly occur at or near plate boundaries
There are main types of plate boundaries:
- Constructive
- Destructive
- Conservative

At a constructive boundary, tectonic plates are moving apart
- The Mid-Atlantic Ridge is an example of a constructive plate boundary
Both volcanic eruptions and earthquakes occur at this type of plate boundary
The volcanic activity produces new igneous rock

constructive-plate-boundary

At a constructive plate boundary, the tectonic plates move apart and lava erupts to form the new rock of the tectonic plates

At a destructive plate boundary, the plates are moving together
One tectonic plate is pushed down into the mantle where it melts to form magma
- The boundary between the Nazca plate and the South American plate is one example
Both volcanic eruptions and earthquakes occur at this type of plate boundary
Volcanoes at destructive plate boundaries are explosive

destructive-boundary-chemistry

At a destructive plate boundary, one tectonic plate is pushed under another and melts into the mantle

At a conservative boundary, the plates move past each other in opposite directions or the same direction at different speeds
- The San Andreas fault is an example of a conservative plate boundary
Powerful earthquakes are the only hazard at this type of boundary
There are no volcanoes because melting does not occur

conservative-plate-boundary

At a conservative plate boundary, tectonic plates slide past each other

You are not expected to recall the detailed structures of these boundary types

Plate Boundaries (WJEC GCSE Chemistry: Combined Science)