Tectonic Hazards EQ1 - Locations at risk from tectonic hazards Flashcards
What is a natural hazard?
A naturally occurring process or event that has the potential to affect people
What is the global distribution of earthquakes?
The main earthquake zones are often found in clusters along plate boundaries - 90% of earthquakes are found at plate boundaries
What is the global distribution of volcanoes?
Commonly found at the regions where plate margins occur, for example around the Pacific Ring of Fire. However they can occur away from plate boundaries, at ‘hotspot’ regions
What is the global distribution of tsunamis?
Most tsunamis are generated along subduction zones, and 90% occur around the Pacific Basin
What happens at divergent plate boundaries?
Two plates are moving away from each other (can be continental or oceanic), leading to new crust being created by magma being pushed up from the mantle
What happens at convergent plate boundaries? (oceanic-continental)
Where two plates meet, the denser oceanic lithosphere is forced down and under the more buoyant continental lithosphere in the process of subduction. The friction between the plates prevents the subducting oceanic plate from sliding smoothly, so it drags over the overlying plate causing both to fracture and deform.
What happens at transform plate boundaries?
Two plates are sliding past each other, often at different speeds. This causes a build up of friction as they drag against each other.
What is a volcanic hotspot, and how do volcanoes form here?
A volcanic hotspot is an area in the mantle from which heat rises as a hot thermal plume from deep in the Earth. This is able to melt through the lithosphere, rising through the cracks to form active volcanoes on the Earth’s surface. As the tectonic plate moves over the hotspot like a conveyer belt, a series chain of volcanoes forms (e.g. Hawaii)
What are the properties of the two different types of crust?
Oceanic crust - thin, composed primarily of basalt but denser
Continental crust - thicker, composed primarily of granite and less dense
How do convection currents drive plate movement?
Heat derived from the Earth’s core rises within the mantle to drive rocks upwards. Near the crust, these rocks drag along the tectonic plates, slowly moving them before sinking as they lose heat from the Earth’s core. This creates a convection current cell, heat constantly rising and falling to power plate movement
How does slab pull drive plate movement?
The force of a cold, dense oceanic plate plunging into the mantle due to it’s own weight drives the movement of the plate
How does ridge push drive plate movement?
Rigid lithosphere slides down the hot, raised asthenosphere below mid ocean ridges, pushing plates away from each other
What is sea floor spreading?
The continuous input of magma forming a mid ocean ridge, for example the Mid-Atlantic Ridge
What is paleomagnetism?
Paleomagnetism is the record of the Earth’s magnetic field in rocks, sediment and archaeological materials
How does paleomagnetism provide evidence for sea floor spreading?
Zones of magma ‘lock in’ the Earth’s magnetic polarity, when it changes every million or so years, so scientists can use this to create a ‘geo-timeline’
