Tectonics 3.1.1 Flashcards
name the layers of the earth and their thickness and state
Inner core 5000km, solid
outer core 3000km, liquid
mantle thickest, involves the asthenosphere
crust 0-11km
two types of crust and their characteristics
Oceanic crust
new
created and destroyed
5-8km
dense basalt rock
deep beneath ocean
continental crust
old
not created nor destroyed
30-70 km
less dense
beneath land masses and shallow seas
characteristics of the asthenosphere
80-200 km thick
very viscous
below the lithosphere where the plates float and move
name the three plate boundaries and which plate mechanism occurs at which
Divergent - convection currents AND Ridge push
convergent - Slab pull
conservative - Earthquakes
How do you explain convection currents
Magma rises and moves either left or right, which causes friction with the plate above this magma, leading to divergent boundaries because the plates are being separated
How do you explain Ridge Push
Ridge push is when hot magma rises up and pushes the ocean floor upwards forming a topographic high. Due to the earth’s gravitational pull downwards, the ridge gets pulled back down, separating the plates.
How do you explain Slab Pull
Slab pull is when the oceanic crust is denser, so subducts under the continental crust going down into the magma, which pulls the slab more downward
What is the process of hotspots
Hotspots are formed due to the presence of a mantle plume, that cause an upwelling of magma.
The magma bursts through from the mantle, to the lithosphere. Overtime, the magma breaks through and causes an explosion in the ocean.
Islands are created when the continuous eruptions appear above the ocean surface.
Overtime, the plates above this plume are constantly moving, so when the next eruption occurs it forms another island next the the previous one which is now extinct because there is not a hotspot underneath it anymore.
This is known as anomalous volcanism, due to the trail/chain of islands created over time.
Divergent plate boundary’s
what is it
name the two types
D PB is when the plates diverge from each other, where magma chamber in asthenosphere erupts in the middle.
Continental- Continental D PB
A rift valley has a central topographic depression, which is bounded by faults with uplifted shoulders .
Oceanic - Oceanic D PB
Mid-ocean ridges are 2000metres deep and this is where new ocean floor is formed
Mid-Atlantic ridge spreads by 3-5cm a year and has deep rift valleys
can have offsets from transform faults that cause segments in the ridges
Convergent plate boundary’s
what is it
name the three types
C PB is when plates converge towards each other, then the oceanic plate subducts underneath the continental plate in the lithosphere, creating a trench. In this subduction zone, the oceanic plate is melted in the asthenosphere, causing an upwelling of magma above this zone, where volcanic eruptions occur.
Oceanic-Continental
occurs at when an oceanic and continental plate collide, so volcanoes erupt causing a volcanic arc
Oceanic-Oceanic
occurs when two oceanic plate boundaries collide, so the volcanoes erupt on the ocean floor, creating Island arcs
Continental-Continental
Occurs when when 2 continental plates (Indian and Eurasian plates) collide as they have similar densities so neither subside so fold up, creating a collision zone where fold mountains form
Conservative Plate boundary
what is it
This is where two plates are going the same direction where one is moving faster than the other, or in opposite directions. No volcanoes are made as no crust is destroyed, but earthquakes are caused (San Andreas Fault). This is due to the built up stress energy whilst the plates grind past. Earthquake occurs when the stress energy is released, and sends shock waves through the earth’s crust.
list the 3 factors that influence global distribution of tectonic plates
- Plate boundaries
- Intra-plate hazards
- Distribution patterns
name three features of tectonic processes that links the factors that influence global distribution
1.The movement and interaction of lithospheric plates, links to plate boundaries because of subduction zones and faults
2. The accumulation of energy from the crust is released as a hazard which occurs in specific areas e.g a boundaries, so the hazards are concentrated more there
3.Heat and movement of material occurs in intra plate hazards because of mantle plumes below
Explain the tectonic processes that occur at a Continental-Continental divergent boundary
Includes: process, land form, what is happening, example
Process at a C-C DP is convection currents, this creates a Rift basin and graben formation
This happens due to a central topographic depression that occurs, in between the faults that have uplifted shoulders
e.g. East African ridge
Explain the tectonic processes that occur at a Oceanic-Oceanic divergent boundary
Includes: process, land form, what is happening, example
The process at a O-O DB is convections currents, where mid ocean ridges form when the plates move apart and magma wells up creating an eruption on the seafloor
e.g. Mid-Atlantic ridge
Explain the tectonic processes that occur at a Continental- Oceanic Convergent boundary
Includes: process, land form, what is happening, example
The process at a O-C CB occurs when there’s slab pull, creating deep trenches (seafloor) and volcanic arcs (on land)
e.g. Washington oregon coastline
Explain the tectonic processes that occur at a Oceanic-Oceanic Convergent boundary
Includes: process, land form, what is happening, example
The process at a O-O CB is slab pull will occur, creating a trench and volcano eruptions that creates an Island Arc when there’s repeated eruptions, which increased the landmass until it breaks through the ocean surface.
e.g. Canary Island
Explain the tectonic processes that occur at a C Continental-Continental boundary
Includes: process, land form, what is happening, example
The process at a C-C CB is convection currents, which creates fold mountains as the two plates have the same densities. Seismic activity also occurs here
e.g. Himalayan mountains
Explain the tectonic processes that occur at a Conservative boundary
Includes: process, land form, what is happening, example
At a conservative plate boundary, there is seismic activity that occurs, do to the built up stress energy which is released causing an earthquake, Due tot he plates grinding past each other
e.g. San Andreas Fault
what is meant by hazard profiles
hazard profiles are descriptive representations of the main characteristics of a tectonic hazard e.g. earthquake, volcano, tsunami
explain the one way, hazard profiles could be used in the analysis in a tectonic essay
Hazard profiles should be used when comparing different tectonic hazards at different plate boundaries
e.g. if discussing boundaries, could discuss the different hazard profiles at divergent and convergent boundaries to compare things such as magnitude and potential damage that the earthquakes and volcanoes
explain the other way hazard profiles could be used in the analysis in a tectonic essay
Hazard profiles can be used to compare case studies, as a way to integrate discussion between which event had more impact
explain how hazard profiles could be used tin evaluation in a tectonics essays
Hazard profiles can be used to discuss the effectiveness of management strategies at specific case studied events
list the 6 hazard profiles
Magnitude
Speed of onset
Frequency
Predictability
Duration
explain the 3 ways magnitude (a hazard profile) is measured for different tectonic hazards
The VEI- the volcanic explosivity index measures the total volume of products ejected 0-8
The Mercalli scale- measures earthquakes descriptively
The Richter scale- Measures earthquakes by amplitude on a seisogram 1-9
explain what speed of onset is
speed of onset is how fast the hazard occurs so earthquakes are immediate but volcanoes are slower, unless phreatic eruptions which are underwater
how would predictability help prepare people
A volcano is easier to predict due to monitoring but earthquakes are not
So people can evacuate for volcacanoes
explain how areal extent effects hazards
Earthquake damage may not be local of where it happens and volcanoes dependent of how explosive it is, so the lava is local damage but the plume of smoke could have a global effect
explain how frequency can have an effect on hazards
how often the event happens is important, as earthquakes could be repeated one after another, but the longer it hasn’t happened for the increased tension that builds. inverse relationship with magnitude
