Tectnoics Flashcards
How many tectonic plates are there in total?
52
Name the major tectonic plates
African
Antarctica
Eurasian
Indo Australia
North American
South American
Pacific
Name the minor tectonic plates
Caribbean
Cocos
Arabian
Juan de Fuca
Scotia
Indian
Nazca
Philippine 
Two examples of microplates
Nubian
Sunda plate
Where are earthquakes found
Collision, Conservative destructive, divergent

Where are volcanoes found?
Divergent and destructive
What are hotspots?
Places that are not on a plate Boundry yet have tectonic activities such as Hawaii
Where are tsunamis
Destructive plate along the coast
Describe oceanic lithosphere
Thickness density, rock type, age, formation, subduction 
Thin, 7 km
more dense 3.3 g/cm³
basaltic
youngest less than 200 million years
Formed at mid ocean ridges from seafloor spreading
subducts
Describe continental lithosphere
Thickness density, rock type, age,, subduction

Thicker up to 70 km
less dense 2.7 g/cm³
made of granites ,
oldest more than 1500 million years
does not subduction.
.
How is continental lithosphere formed?
Amalgamation of rock formed from volcano’s and hotspots as well as sedimentation
Pass through rock cycle, mountain building and erosion and metamorphism
Three ways mantle melts 
Addition of heat, mantle plumes and hotspots.
Addition of water, hydration, melting/slab dehydration at convergent plate, boundaries
less pressure, decompression, melting, divergent boundaries
How do convection currents occur
In upper mantle - asthenosphere partially melted - molten magma rises - convection currents occur
Describe ridge Push and Slab Pull
slap pull - weight of subducting wave pulling a plate in a certain direction
ridge push - force of magma forcing its way thro cracks btw plates and solidifying to form new crust pushing plates apart
Describe a Basaltic lava 
Temperature silica, content, gas, content viscosity, where it’s found  lava flow 
1000 to 1200°C
low silica content
Low gas content
low, viscosity
gentle effusive
divergent plate, boundaries, hotspot, and mental plumes 
Describe Andesitic Lava
Temperature silica, content, gas, content viscosity, where it’s found lava flow
800 to 1000°C
high silica content
more gaseous
high viscosity,
violent and moderately, explosive eruptions, convergent plate boundaries - hydration melting
Why Andesitic Lava more viscous
Do you hydration melting parts of crustless, lisopher and mantle melts together - release minerals 
What is an earth quake
Sudden release of energy that generates seismic waves 
Why do earthquakes occur? 
Along fault lines, plates become locked because of friction
opposing tectonic plates, buildup, pressure and strain
which eventually releases stored energy suddenly as a quake
What is the focus?
Focus point of rupture where the strain energy was released from 
What is the epicentre?
The point on Earth surface directly above the focus of the earthquake 
Describe the global distribution of seismic activity - PDA
distributed, unevenly belts along plate boundaries
examples of pacific ring of fire has the most seismic activity combo of convergent plate in conservative plate boundaries.
Hotspot volcanoes in centre of tectonic plates, intraplate earthquakes
Describes a global distribution of volcanicity 
Narrow linear belt along plate, boundaries
continental oceanic, convergence in Mount Saint Helens 
Hotspot working is there such as Hawaii or Yellowstone Deasa more scattered an individual often due to mantle plumes 
Describe global distribution of tsunamis
Occurs at the edges where o+o or c+o often caused by earthquakes causing a vertical displacement of water
2011 Japanese tsunami
Tsunamis can occur as a result of a volcanic of activity e.g Krakatau
Example of a divergent plate boundary
North American and Eurasian plates, moving away, causes the mid-Atlantic ridge
 How do mid ocean ridges occur
Manta rises, below surface,
pressures, lowered, decompression, melting
Rocks partially melt.
Plumes of magma, melt the crust above, crust expands on heating and up domes
split and volcanism begins convection currents in the way is the cost as a moves away from rift causes, lateral tension results in parallel faulting. Allow central section to subside into magma, creating a rift Valley
How is a new ocean formed?
plates move further magma cools form basaltic ocean crust, causes, seafloor, spreading and ocean.
Basin gets wider as rift continues. Seawater floods in to create an incipient sea
Evidence for seafloor spreading
Magnetic properties of the erupted basalt
earths magnetic field have been shown to flip occasionally so north and south pole swap
salts contains minute magnetic minerals and this changes directions depending on the earths magnetic field at the time of eruption 
magnetic stripes
Polarity reversal from rock formations at the, mid-Atlantic ridge 
Why do earthquakes occur at divergent plate boundary?
New Cross forms and spreads causes transform fault right angle two plate boundary
Move at different times. Friction causes plates to lock and buckle causing earthquakes. 
How do volcanos form?
as plates move apart - decompression melting - magma rises and starts melting the crust - and forms a volcano - usually oceanic crust = basaltic lava = shield volc
but nubia and somalian - continental so andisitic lava
descibe what a transformative / conservative plate is like
parallel movement of plates - differents speeds or/and directions - e.g. San Andreas Fault in Cali
describe the san andreas fault
btw N. Americ ad Pacific
1300 km
right lateral strike slip fault
fault system visible and cause 10,000 earthquakes a yr
why do earthquakes occur at conservatives
plates move sporadically and jerkily - frictional forces lock plates into eachotehr - friction builds up pressure strain and heat - suddenly releases energy - causes shallow focus earthquakes
Plate movements in o + c convergence
Denser, oceanic subducts
Tectonic processes in o + c convergent
Subduction and slab-pull
hydration melting
stoping (burning)
folding and faulting
friction and strain release
Landform o + c convergence
Composite volcanoes, ocean, trenches, fold mountains, volcanic arcs 
How do you trenches form - o + c convergence and example
As oceanic subducts, a deep V shaped depression is formed e.g. Mariana trench 
How do earthquakes form o + c
Subduction is not smooth + friction friction = strain = builds up pressure which is released when the plate slips releasing seismic waves.
What kind of earthquakes o+ c
Shallow to deep focus in the zone of earthquake foci - Wadatti-Benioff Zone
often high magnitude, 8 - 9 
How do you fold mountains occur? E.g
As oceanic subducts said, sediment accumulate on ocean floor - scraped off and forced onto the continental plate, due to obduction - forms in accretionary wedge - adds to size of continent
Collision —> Crustal shortening leads to vertical thickness and reducing the width of the lithosphere collision zone. fold and faulting rocks form in the fold mountains
E.g. the Andes
magma generation o + c
O subducts - when reach Benioff zone,
oceanic plate starts to crack and waters dragged out. This lowers the melting point of the magma (dehydration, melting) which generates magma.
How are volcanoes formed o + c
Magma rises up to Fischers and freeze doping till they reach the surface. They melt some of the continental plates on its way up, making making it silica rich, causing andesitic lava. - this causes composite volcanoes
When explode cause release pyroclastic, flow, ash and gas 
Describe andesitic lava
800 to 1000°C. High viscosity from is composite volcanoes. VEI 5-6
How do you tsunamis occur?
Earthquake magnitude greater than six call seafloor to uplift causes a vertical displacement of water. This causes a tsunami. Low lying wave until close to
shore, it starts to grow into a taller wave.
What happens in oceanic and oceanic convergence? E.g
Denser colder, oceanic plate subducts, this causes, submarine volcanoes, which, if grown, can cause volcanic arc. Lava can also produce island arcs.
E.g. Caribbean and South American plate
Landforms in oceanic and oceanic convergence
Composite volcano, ocean, trench island arc

Continental continental convergent
Two seas collide sediment exist between plates are pushed into each other and upwards, folding + faulting to make fold mountains
cause strain to build up when energy is released cause shallow, intermediate earthquakes, 6-8 magnitude 
Example of continental continental convergent
Eurasian, and Indian plate forms the Himalayan mountains
Geosyncline (basin) was sea of Tethys which eventually subducted and filled with sediments which was obducted
Describe the continent lithosphere 
Up to 70 km, thick, solid, less dense 2.8 g/cm³ Granite
O and S waves thro
Describe oceanic lithosphere
Up to 7 km, thick solid denser 3.3 g/cm³. Basalt, P and S waves pass through 
Describe the mantle
Solid but plastic with different densities made of periodite silica, rich Rock
P and S waves pass through a variable rates due to changes in density
Describe outer core
Liquid, dense, 12% sulphur, 88% iron only P-waves past thro high temperature
Describe inner core
Solid densest, hottest 20% nickel, 80% iron
only P waves reach the inner core and pass thro
What heats up the inner core?
Residual heat and radioactive decay
What is a P wave or S-wave shadow zone?
The area where the waves cannot be detected
What three mechanisms move plates?
Convection current slab, pull ridge push
How to convection currents occur
Core is hot and heats up surrounding magma which makes it less dense. This causes the rock or magma to rise as it rises it cools down, gets denser- as sinks it pushes against the plates, helping them move.
What is slab pull?
As a plate subducts its weight pulls, the rest of plate along - the more that is subducting the greater the force of the pull
What is ridge push?
As magma make its way to the surface and pushes through it separates and pushes against the surrounding plate
evidence for continental drift - biological
fossil remains across continents e.g. mesosaurus fresh water species fossil remains in south afric and brazil - can’t have swam across salt sea
evidence for continental drift -climatological
carboniferous limestone pennines and uk coal deposists need high temp and wet - fast decomp - suggests Eng was in tropics
evidence for continental drift - geological
mount ranges across continents - Appalachian (NA) and Caledonian (Scandenavia and UK)
what is the plate tectonic theory
earths surface is made up of plates which move relative to each other at diff speeds or directions. The boundaries btw plates are zone of tectonic activity like seismicity, vulcanity and mountain building
Wadatti Benioff
Date
Idea
Significance
1920
EQ at Wadatti Benioff due to subduction - zone where plates no longer exist
Explains EQs
Mantle Convection Current
