WTG - Ch 5. Earth in Motion

Question 1

Why are volcanoes so unstable?

Answer 1

A volcano is compressed of layers of solidified lava and pyroclastic debris. During and between eruption there is heat and there is gas. There is also liquid water. Therefore inside a volcano there are many different chemical reactions that will weather the volcano. This big pile of loose, weak rock is unstable volcanoes are prime to failure; they fall down, when water is added, pore water pressure increases and the contacts between rocks is lubricated thereby reducing friction, lastly weight is added to the structure. All these things will increase the possibility that rock will fall off the sides of the volcano. If more rock is removed then the likelihood of an eruption increases because there is less rock to contain the pressure.

Question 2

What is the link between volcanic eruptions and sea water temperature?

Answer 2

1. Volcanoes erupt when the rock surrounding the magma chamber cannot contain the pressure
2. The rock that makes up the volcano is weak and unstable
3. What makes this rock even more prone to failure is more water
4. extra water on a volcano comes from the atmosphere in the form of rain and snow
5. Most water that eventually falls as rain and snow come from evaporation of surface water in the oceans
6. warmer sea water increases the rate of evaporation which increases precipitation
   It appears then that warmer sea surface temperatures would coincide with more volcanic eruptions. However the link is not direct and the processes (ocean circulation and volcanic eruptions) are so complex and so different that any link is tenuous at best