There are three main types of volcanoes that form from different geological processes: 1) Hotspot volcanoes like those in Hawaii form when magma rises from a hotspot in the mantle as a tectonic plate moves over it. Eruptions are less explosive due to fluid magma. 2) Shield volcanoes form at divergent plate boundaries and from hotspots, with low, wide shapes from fluid basaltic magma. 3) Composite volcanoes form at convergent plate boundaries, where one plate subducts under another. They have steep sides due to more viscous magma and explosive eruptions, producing hazards like pyroclastic flows and lahars.

1. Learning Goals:
Be able to identify different types of volcanoes.
Understand and explain how different types of
volcanoes form, and the hazards linked with them.
Consider why people might live near volcanoes

2. Why are some volcanoes more
violent than others?
There are different types of volcanoes that form as a
result of different processes…

4. Hotspot
Volcano
Some volcanoes do not cluster at plate boundaries...
Why?
•When a tectonic plate moves over a very
hot part of the mantle, a plume of magma
rises. This is known as a HOT SPOT.
•Hot spots are responsible for the chain of
islands we know as Hawaii.

5. Eruptions are not usually explosive because the magma tends to
be more fluid, so less pressure builds up.
Lava is the main hazard linked to hotspot
The shape of the volcano is usually low and wide and is called a
SHIELD VOLCANO

6. Hawaii
E.g. Kilauea in Hawaii
This is the most active volcano
in the world.

7. Shield volcanoes also form at divergent plate
boundaries:
When the plates move away from each other,
molten magma rises up from deep inside the
mantle, and melts the upper mantle.

8. Like hotspot volcanoes, the magma rising up from the
mantle is very hot, and therefore very fluid.
Main hazards linked with volcanoes at divergent
boundaries are:
Lava
Ash
The magma runs down the sides of the volcano
creating a low, wide shape
Shield Volcano

9. An example of a volcano at a
divergent plate boundary is:
Grimsvötn, Iceland

10. Oceanic crust and continental crust are forced
together
Oceanic crust is dense and heavy, and is forced
underneath the continental crust
This is known as SUBDUCTION

11. As the oceanic crust is subducted, it heats up
making a very VISCOUS or very sticky magma
Volcanoes become steep sided and eruptions are
very explosive

12. Explosive eruptions result in rocks, lava
and ash exploding from the volcano.
This mixes with gas and steam and
causes PYROCLASTIC FLOWS.
Lahars are also common.
A lahar is a type of mudflow or debris
flow composed of
a slurry of pyroclastic material, rocky
debris, and water.

13. Layers of lava and ash gather around the vent
and this creates a COMPOSITE VOLCANO
White Island
– New
Zealand
(north of the
North Island)

15. An example of a
composite volcano at
a convergent plate
boundary is:
Mount St
Helens, Washington,
USA