In what ways does volcanic activity vary in relation to the type of plate margin on which it occurs (10)

Volcanic eruptions can occur along both destructive and constructive plate boundaries; however the eruptions are different at the two different plate boundaries. Generally the eruptions are considered to be more violent at constructive plate boundaries compared to eruptions at destructive plate boundaries.

At constructive plate margins the lava has a low viscosity meaning it is very runny lava and more of a liquid than it is a solid which has high, comparatively the lava at destructive plate boundaries is typically described as ‘blocky’ lava due to the fact that it has a higher viscosity (high in silica- acidic). The fact that it has a higher viscosity can actually make the lava more dangerous because it typically has a higher density and is more explosive. This is because gas bubbles cannot escape from within the magma and so they expand from the heat and build up pressure before they are released. At constructive plate boundaries however, gas can easily escape and so pressure is constantly released, leading to less violent eruptions.

Linked with this is the frequency of the eruptions. As pressure is being constantly released at constructive plate boundaries, there are regular eruptions. This is much unlike what occurs on destructive plate boundaries as here, the pressure builds up over time and the volcano can remain dormant for hundreds, potentially thousands millions of years until one violent eruption releases the pressure in one go. Another key difference between the two different types of plate boundary is the shape of the volcano. At constructive plate boundaries, the volcanoes are typically shield volcanoes, which many are found in Iceland. At destructive plate boundaries, the volcanoes are typically dome or composite ones so they have sides