Deck 1 - Tectonics distribution, plate boundaries and mechanisms of plate movement Flashcards
What are two categories of tectonic hazard?
1) Seismic
2) Volcanic
Where do the majority of earthquakes occur?
The majority of earthquakes are found along plate boundaries. About 70% of all earthquakes are found in the ‘Ring of Fire’ in the Pacific Ocean
What is a intra-plate earthquake?
Intra-plate earthquakes occur in the middle of a tectonic plate
What secondary hazards are associated with earthquakes?
Landslides, avalanches, tsunamis
Where are the majority of volcanoes found?
There are about 500 active volcanoes around the world with on average 50 erupting each year. The majority are found on plate boundaries with a large concentration around the Pacific Ocean (Ring of Fire
What is a hot spot volcano?
An intra-plate volcano that is located above a mantle plume
What is a constructive (divergent) plate margin?
A plate boundary where tectonic plates are moving away from each other allowing for magma to move to the surface to create new land
What is a destructive (convergent) plate margin?
A plate margin where tectonic plates are moving towards each other. Oceanic plate is denser than continental plate meaning it is subducted
What is a conservative plate margin?
A plate margin where tectonic plates move alongside each other. Plates are either moving in opposite direction or the same direction at different speeds
What is a collision boundary?
A destructive margin where both plates are of equal density meaning that neither plate subducts resulting in an upwards buckling creating fold mountains such as the Himalayas.
Which type of plate boundaries do you find earthquakes at?
All
Which type of plate boundary do you find volcanoes at?
Constructive and destructive
What are the two models for the internal structure of the Earth?
Physical properties and chemical composition
Where is the lithosphere found and what is it made of?
The lithosphere is the outermost layer of the Earth when viewed from the physical properties model. It is about 100km thick and is thicker beneath continents. Continental lithosphere is made of ‘granitic’ rocks whereas oceanic lithosphere is made of ‘basaltic’ rocks.
Where is the asthenosphere found and what is it made of?
The asthenosphere is 250km thick and is found to a depth of 350km. It is below the lithosphere and is made of solid rock that is ductile so flows easily.
How does the convection current model propose that tectonic plates move?
The core heats the base of the mantle. As heat rises it creates a current that moves upwards towards the crust. Once at the crust the current moves sideways (both ways) and drags the plate above with it. The current eventually cools and sinks back down to the base of the mantle. As it sinks it drags the overriding plate into the mantle. The current heats back up an a convection cell is created.
How does the slab pull/ridge push model propose that tectonic plates move?
This model suggests that the density of the tectonic plates is important. The denser oceanic crust subducts beneath the light continental plate which drags the remaining plate with it, creating its own momentum. At the other end of the plate magma is able to rise to the surface to fill the gap that has been created and pushes the tectonic plates away in either direction. This is ridge push.
What is paleomagnetism and what did it prove?
Paleomagnetism refers to the rock record of changes in the Earth’s magnetic field. As igneous rocks cool the minerals align themselves ‘north’. Through time magnetic north has not stayed stationary but has wandered. At mid ocean ridges scientists have mapped alternating strips of igneous rocks with minerals aligned north and south at eqi-distance from the volcanoes. They used this to prove sea flooring spreading as it proves that new land is created at the same speed either side of the volcanic ridge.
