tectonics Flashcards
convection currents
heat from earths core will heat up the mental causing it to be less dense and rises.
the mental will then spread beneath the plates, dragging them apart, contributing to divergent plate movement.
the mental will then loss heat and sinks towards the core.
convergent plate movement occurs where the convection current collide.
the mental will get heats up again and the cycle repeats.
slab pull
as two plates converge, the denser plate will be pulled down be gravity as it subduct beneath the less dense plate.
the denser plate will continue to sink down by its own weight, pulling the rest of the plate with it, contributing to further convergence.
earthquake
rocks on either side of the fault are pushed by tectonic force.
friction causes them to get locked, and stress builds up.
when stress exceeds the strength of the fault, the rocks snap.
this sudden movement causes seismic wave to be released, causing ground shaking.
stratovlcanoes
high viscosity lava rises through weak areas of the crust explosively as ash, lava and rocks.
the ash, lava and rocks then settle at the sides of the volcanoes which is then later covered by lava.
over excessive explosion, a tall volcanoes consisting of alternating layers of ash and lava develops. as the highly viscous lava travels a short distance before cooling and solidifying , the volcanoes have steep sides and narrow summit
shield volcanoes
low viscosity lava rises through weak areas of the crust effusively over successive eruptions. a volcanoes consisting of multiple layers of lava develops.
as less viscous lava travels a longer distance before cooling and solidifying, the volcano has a gentler sloping sides and broad summit
Seafloor spreading
It is where two plates move away from each other at divergent plate boundaries
Magma from deep within the earth rises from the mid-oceanic ridge
New oceanic crust is formed
Evidence of seafloor spreading (3)
- rocks nearer to the centre of the mid- oceanic ridge are the youngest
- little sentiments are found at the oceanic trenches as older oceanic crust is being destroyed at the oceanic trenches
- oceanic crust are usually younger than continental crust
Magnetic stripping ( zebra- like pattern)
Oceanic plates move away
Iron rich lava erupt from centre of ridge
Cools and solids to form new oceanic crust
Crust is push in both direction away from the ridge when new lava erupts and solidify as plates move apart
When earth’s polarity reverses, the rocks record down the reversals
Overtime, zebra- like pattern forms
Volcanoes caused by divergent plate movements
- plates move apart, fractures formed
- increase in overlying pressure causes parts of underlying mental to melt, forming magma
- magma contains dissolved gas which is less dense than the surrounding materials
- magma rises through weak areas of the crust as lava
- cools and solidify and accumulates to form volcanoes
Volcanoes caused by convergent plate movements
- when two plates move towards each other, the denser plate with subduction beneath the less dense plate
- as mental sinks down, water is forced out of its oceanic crust, lowering the melting point of mental
- mental melt to form magma
- there are gas dissolved in the magma, which is less dense than the surrounding materials
- magma rises through weak areas of the crust as lava
- lava cools and solidify and accumulates to form volcanoes
Tephra
- ash can suffocate and kill animals
- respiratory illness and eye irritation
- ash can accumulate on roofs of buildings
Volcanic gas
- sulfur dioxide causes acid rain—> destroy building
- damage vegetation’s and kill animals
- irritation to eye nose and throat
Benefits of volcanic eruptions
- fertile soil—> produce higher crop yield
- precious minerals and fossil fuels may be produced—> increase employment/ job to mine those minerals. —> generate revenue
- tourists—> job opportunity
—> boost local economic development
Environmental disaster risks
- land slides will destroy forests and ecosystem
- water pollution caused by debris
Social disaster risks
- losing loved ones
- trauma
- people will be homeless
