tectonics eq1 (1) Flashcards
convergent/destructive plate boundary
plates involves- continental and oceanic
direction of movement- move towards each other
landforms created- volcanoes, earthquakes (subduction)
Divergent/ constructive
plates involved- two oceanic plates
direction of movement- plates move apart
landforms created- volcano, earthquake
conservative/ transform
plates involved- continental with continental or continental with oceanic
direction of movement- same direction with lots of friction
landforms created- earthquakes only
collision zones
plates involved- continental with continental
direction of movement- towards each other
landforms created- earthquake, fold mountains
slab pull
pull of gravity on a plate thats been subducted
intra-plate
hazard (ie volcano) taking place within a single tectonic plate
why does subduction happen?
continental plate has a lower density to the oceanic plate and gravity pulls the oceanic plate beneath the continental plate
The wadati-benioff zone
area in which there is a concentration of earthquake hypocenters - shows evidence towards plate tectonics
focus/hypocenter
the location in the earth where the earthquake starts
seismic waves
vibrations caused by movement within the tectonic plates
Name physical processes that cause hazards
- history and evidence of plate tectonic theory
- sea floor spreading, paleomagnetism
- subduction processes
- anatomy of an earthquake
- seismic waves
Timeline of plate theory
What did Wegner propose in 1912?
Wegner proposed the theory of continental drift and in 1967 his theory was accepted.
Timeline of plate theory
What did Holmes suggest in 1930?
Holmes suggests that convection currents fueled by radioactive decay in the earth’s core play a role in continental drift and driving the earth’s plates
Where do aftershocks occur?
near the fault zone of the main earthquake
What are aftershocks the result of?
the readjustment process which is when the plates settle back into their natural position after the initial earthquake
Primary impacts
earthquakes
the direct impacts of the natural hazard, so they are caused by the earth shaking
examples
What do primary impacts include?
earthquakes
death, injuries, buildings being destroyed
What do secondary impacts include?
earthquakes
landslides, fires, tsunamis, habitat and historical buildings loss, people suffering from illness from diseased water, people become unemployed
Where does sea floor spreading happen?
divergent plate boundaries
paleomagnetism
is where lines of different type of rock, which are facing different poles, pull away from each other at divergent boundaries
hot spots
A hot spot is an area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the rocky crust and widespread volcanic activity.
How is a chain of intra-plate volcanoes created?
Because the mantle plumes that cause them don’t move when the tectonic plates do
Primary impacts of a volcano
- release of tephra
- release of volcanic gas into the atmosphere
-pyroclastic flow
-lava flow
tephra
solid material that can range in size which are ejected into the atmosphere eg ash
secondary impacts of a volcano
- lahars
- Jökulhlaups
pyroclastic flow
Very large, dense clouds of hot ash and gas at temperatures of up to 600’C. They can flow down the flanks of volcanoes and devastate large areas.
lahars
Volcanic mudflows, which occur when rainfall mobilises volcanic ash. They travel at high speed down river systems and cause major destruction.
Occurs at:
Subduction zone volcanoes (composite)
Jökulhlaups
Devastating floods caused when volcanoes erupt beneath glaciers and ice caps, creating huge volumes of meltwater. They are common in Iceland.
Occurs at:
Constructive plate margin volcanoes (cinder cone, fissure eruption)
