Lesson 6 - Hazard Distribution: Volcanoes Flashcards
How many active volcanoes are there currently + how many erupt per year?
Roughly 500
Roughly 50 per year
Where are volcanoes most regularly found?
Destructive boundaries
Divergent boundaries
Above hotspots
What occurs at a destructive boundary?
2 plates move towards each other
Form either subduction zone or continental collision
Describe the formation of a subduction zone and the volcano that is created as a result
Oceanic - Continental convergence
Oceanic plate subducted
Magma form in subduction zone
Surface volcanism appears above the magma
Describe a continental collision and the volcano that is created as a result
2 continental plates collide
Large mountain ranges formed
Ranges consist of volcanoes
What are the eruptions which take place at destructive boundaries characterised by?
Infrequent
Explosive
Highly destructive
What takes place at a divergent boundary?
2 plates diverge at the site of a thermally buoyant mid-ocean ridge
Describe the volcanoes which form at divergent boundaries
Rift volcanoes
Less explosive
More effusive (Especially with greater depth underwater)
Produce basaltic lava
Where are hotspot volcanoes found?
The middle of plates
What are hotspot volcanoes fed by?
Mantle plumes which are hotter than their surroundings
What is a volcanic hotspot?
Area within the mantle
Heat rises as hot thermal plume from deep in the Earth
How does this lead to the formation of a volcano?
High heat + lower pressure at base of lithosphere enables melting of rock
Molten material rises through fissures
Erupts to form active volcanoes on the surface
What happens as the plate moves over the hotspot?
Volcanoes are rafted away
New ones form in their place
