Earthquakes 1 Flashcards
What is an Earthquake?
Ground shaking, caused by seismic waves moving through the earth
- many sources but we only worry about the big ones
- scale can go negative
___ are responsible for most EQs we care about
Earth’s layers
Name the three components of the Earth
- Crust
- Mantle
- Core
What is the crust
top part
cold
up to 100km thick
What is the mantle
middle part
warmer
- narrow range in compositio
- includes the asthenosphere and parts of lithosphere
What is the core
centre part
hot
- metallic iron/nickel
- outer core is liquid
- inner core is solid
Tectonic plates are made of
solid crust and upper part of mantle
Where are tectonic plates and what do they consist of?
in the lithosphere
- solid crust and upper part of mantle
The lithosphere is the
solid crust and upper part of mantle
Alfred Lothar Wegner came up with
the Theory of continental drift
- continents were once together and drifted through the oceans
True or False: each tectonic plate movement depends on that of others
False
plates move independently of the others
- they move relative to each other
The speed of plate tectonics
slow, about as fast as a fingernail grows
(units are in mm/year)
- significant motion take a long time
Unifying theory of earth dynamics
Plate Tectonics
- controls how our planet functions
- direct cause of earthquakes, volcanoes, tsunamis, landslides
- responsible for continents, mountain belts, ocean basins, islands
- etc!
Continental positions influence
- winds and currents, climate
- evolution!
almost all earthquakes occur ___
near plate boundaries
Plate tectonics are controlled by
Physical properties
- composition, density, temp
Energy
- gravity, heat
Plate tectonics does not work unless
the earth is layered
Stratification or layering is caused by
differences in density
The crust ___ on the mantle
FLOATS
density increases with ___
depth
Phase changes are controlled by?
temperature AND pressure
Rheology
how a material deforms
How does a solid material respond when put under stress?
by deforming (undergoing strain)
What are the types of deformation
Elastic
- springs back and reversible
Ductile
- plastic flow
- permanent
Brittle
- breaks
- permanent
Rheology is controlled by
- temperature
- speed of deformation
- duration of deformation
T or F: solid material can be all three types of deformation
T
The mantle is mostly what phase?
solid
- rock that flows cuz high temp
- ductile deformation, not melting
i.e. viscous flow of a solid
Describe the Lithosphere
- consist of crust and uppermost mantle
- cool, solid, exterior shell
- brittle (sometimes ductile)
Describe the Asthenosphere
- the mantle
- hotter
- SOLID but almost melting
- super ductile (geological time)
Describe the mesosphere
- lower mantle
- even hotter but very high pressure
- SOLID and stiff
- ductile (geological time)
Describe the outer core
- metallic
- super hot liquid
- extremely high pressure
Describe the inner core
- metallic
- hotter and higher pressure!!
- solid
The plates are the ___ (sphere)
lithosphere
-> it’s broken into plates that move around on top of asthenosphere
-> strong, cool, brittle, fractured shell
___ plates are thinner and more dense than ____ plates
Oceanic // continental
Describe convection cycle of the mantle
«_space;refer to slides»_space;
- lithosphere forms from hot rising magma
- cools as it spreads, then sinks
- gravity also pulls cool, dense plate down
In earth’s convection cycle, what gets recycled?
oceanic lithosphere
Why do continents “float”?
- plate tectonics is top of huge ductile convection cycle
- mantle & oceanic crust convecting
- low density continental crust floats
