1. Activity at plate boundaries - volcanoes
Chapter 3
Activity at plate boundaries - volcanoes

2. Volcanic activity
Most volcanic activity takes place along the margins or boundaries of plates.
Volcanic activity can result in:
mid-ocean ridges and islands
volcanic cones.
Eruption in Iceland
Eruption in Hawaii

3. Mid-ocean ridge and islands
They form when two plates separate beneath the ocean floor.
The Mid-Atlantic Ridge formed when the American and European plates separated.

4. Volcanic fissure
When two plates separate, magma comes to the surface through a long crack called a fissure.

5. Volcanic fissure
The Giants Causeway in Northern Ireland formed when magma poured up through a fissure and cooled into hexagonal (six-sided) shapes.

6. The Mid-Atlantic Ridge and Iceland
The Mid-Atlantic Ridge (E) was formed when the American plate (C) pulled away from the Eurasian (A) and African (B) plates.
The ridge breaks the surface of the ocean to form Iceland (D).

7. Iceland: a volcanic island
Iceland was formed when the North American plate pulled away from the Eurasian and African plates.
At 20 million years old, it is the youngest country in Europe

8. Volcanic plume (Iceland)
Some volcanic eruptions in Iceland send large plumes of smoke and ash into the atmosphere.
Some of these have interfered with air traffic over Europe.

9. Iceland: a volcanic island
A large fissure (crack) runs through Iceland where the American plate (left) and Eurasian plate (right) pulled apart.
Today, it is used as a tourist trail.

10. The Blue Lagoon, Iceland
Iceland uses geothermal energy to generate electricity and heating
The Blue Lagoon is one source of geothermal energy.
Its hot springs are also a major tourism attraction.

11. Volcanic cones
Volcanic cones are formed when magma finds its way to the surface through a hole called a vent (1).
Layers of lava and ash build up as the cone grows.
The opening at the top of the pipe (2) is called a crater (3).

12. Active volcano during an eruption.
Volcanic cones
Active volcano during an eruption.

13. The Ring of Fire
The Pacific Ring of Fire is the most active volcanic zone in the world.
It encircles the Pacific Ocean where most of the Earth’s plates are in collision.

14. Mount St. Helen’s volcano
Mount St Helens is a volcano in the Rocky Mountains.
Photograph show the cone and its surrounding area before the eruption.
Note the bulges to the front of the mountain

15. Mount St. Helen’s volcano
Photograph shows the cone and its surrounding area after the eruption.
Note the absence of forest and the scars left by the mudflows.

16. Mount St. Helen’s volcano
Image showing the destruction caused to the
forests that surrounded Mt. St. Helens.

17. Mount St. Helen’s now
The volcano is still active – but not violently so. Note the new cone building up in the large crater.
Vegetation has returned to some of the area.

18. NASA satellite image of a volcano on Mars
And, away from Earth …!
NASA satellite image of a volcano on Mars

19. NASA
USGS
Shutterstock
Compuscript
Illustration credits