Tectonics Flashcards
What is enquiry question 1?
Why are some locations more at risk from tectonic hazards?
What is the distribution of tectonic hazards?
concentrated along plate boundaries
Ring of fire in pacific
intraplate hazards
What percentage of volcanoes happen in the ring of fire?
75%
What are the four plate boundaries?
Convergent
Collision
Divergent
Conservative
What is the structure of the earth?
lithosphere (solid, rigid)
Asthenosphere(plastic-putty texture- partially molten)
Mantle (solid, plastic)
Outer core (liquid)
Inner core (solid nickel and iron)
How hot is the earths inner core?
6000 degrees
What is slab pull?
suggests plates are pulled down into mantle through gravity and sliding
What is ridge push?
Occurs at mis ocean ridges which becomes thicker and denser as it cools causing its weight to increase and the plate is pushed down my gravity
Which plate is the convergent boundary?
When oceanic meets continental crust and one becomes subducted
Which plate is the collision boundary?
Two plates meet and push upwards
Which plate is the divergent boundary?
two plates are moving apart
Which plate is the conservative boundary?
two plates sliding past each other
What forms at a convergent plate boundary?
deep ocean trenches
fold mountains due to subduction
Underwater volcanoes (oceanic meets oceanic)
Island arcs
composite volcanoes
deep earthquakes
What forms at a divergent plate boundary?
formation of new crust
mid ocean ridges
submarine volcanoes
rift valleys
shield volcanoes
What forms at a collision plate boundary?
Fold mountains
What forms at a conservative plate boundary?
powerful earthquakes (strong and shallow)
What are intraplate boundaries related to?
associated with ancient faults such as Rhine rift valley
Solid crust cracking over millions of years
associated with smaller magnitude earthquakes
What causes volcanic hotspots?
mantle plumes (a stationary upswelling of abnormally hot rock within earths magma)
Examples: yellow stone and Hawaii
How many major tectonic plates are there?
7
How many minor plates are there?
10
How many microplates are there?
50
How do microplates cause earthquakes and tsunamis?
numerous microplates moving in different direction and at different speeds
What did tomography reveal?
revealed ‘torn’ slabs of oceanic plates as well as ‘detached’ which were suspended in the mantle
What does seismic tomography use?
P-waves and S-waves to produce a 2D and 3D image of the earth’s interior
What is mantle drag?
slow creep motion of convection currents
How fast are convection currents?
very slow, around 20mm per year with a slow creep
What is the study of palaeomagnetism?
Study of the earths ancient magnetic field, north and south pole pull the continents and crusts apart
What was the name of the super continent?
pangea
What is sea floor spreading?
where tectonic plates split apart from each other, occurs at mid ocean ridges which changes size of sea floor. Driven by mantle convections
What are the four components of the anatomy of the earthquake?
focus-point beneath earths crust where earthquake originates
epicentre-point above crust directly above focus
seismic waves-waves that transmit energy released
fault-fracture in rocks that make up earths crust
What are the primary effects of an earthquake?
ground shaking
buildings collapes
What are the secondary impacts of an earthquake?
tsunamis
liquefaction
landslides
What is liquefaction?
When the ground shaking causes rocks to become more liquid than solid
Describe P waves
longitudinal
travels the fastest
solids+liquids
Describe S waves
secondary waves
transverse
displace the ground perpendicular to the direction of propagation
Describe L waves
shake side to side
slowest travelling
focuses all it’s energy on earths surface
Describe R waves
travel along surface of a solid causing elliptical motion of the particles
responsible for damage during earthquake
What did Harry Hess do?
mapped out ocean floor across the pacific
What did Wegner use to support theory of super continent?
Jigsaw fit
geological fit
tectonic fit
glacial deposition
What did Wegner discover?
continental drift
(used fossils for evidence)
What did Dan Mackenzie add to Wegner’s idea?
applied his knowledge of thermo dynamics of how plates move, suggesting two layered mantle
What did Kiyoo Wadati discover?
patterns of earthquakes descending at angled path from trenches
What determines eruption types?
crystals (how thick)
Gases
High temprature
What is the order of most destructive volcano types plus examples?
Icelandic eruption (Iceland)
Hawaiian eruption (Hawaii)
Strombolian eruption (volcano in Italy)
Vulcanian eruption (island of volcanoes)
Pelean eruptions (mount Pelé Philippines)
Plinian eruption (mount Vesuvius, Rome)
What are the three types of magma?
Basaltic, Andesitic, Rhyolitic
What is the scale of the volcanic explosivity index?
0 - 8
What kind of scale does the volcanic explosivity index use?
logarithmic (each number increases by factor of 10)
What three factors make up the volcanic explosivity index?
amount and height of volcanic material ejected
how long eruption lasts
qualitative descriptive terms (gentle, explosive, etc)
What does the VEI index stand for?
Volcanic Explosivity Index
What are the primary hazards of a volcanic hazard?
Lava flows
pyroclastic flow
ask fall
gas eruption
What are the secondary impacts of a volcanic hazard?
lahars (like mudflows but consist of heavy rain + ask)
jokulhlaup (glacier on top of volcano so when volcano erupts it melts causing flash floods of water + ash so more viscous)
What does the higher the gas content mean?
More explosive the volcano
What are the three types of magma?
basaltic
Andesitic
rhyolitic
what are the characteristics of basaltic magma?
low viscosity, 1-2% silica content, 50% gas content, shield volcanoes
what are the characteristics of andesitic magma?
medium viscosity, 3-4% silica, 60% gas content, medium explosivity, composite volcano
what are the characteristics of rhyolitic magma?
high viscosity, 4-6% silica content, 70% gas content, greatest explosivity, cinder cone volcano
In spearman’s rank what does n stand mean in the equation?
number of places/ranks
In spearman’s rank what does d stand for in the equation?
difference between the two ranks
What is spearman’s rank used for?
used to see the correlation between two variables
When would you reject the null hypothesis in spearman’s rank?
if it’s more than the critical value
How does a tsunami form?
two overlapping plates become stuck, seismic energy begins to accumulate and the continental plate become distorted, stuck area ruptures releasing seismic energy causing a water column to be displaced, tsunami wave spreads and the waves arrive in a sequence
What are some facts about tsunamis?
waves arrive in sequence with the 4th and 5th wave being the largest
can be reflected and refracted by land
travels in two directions
What were the impacts of the 2004 Indian ocean tsunami?
coastal settlements devastated, infrastructure destroyed, economies devastated, destroyed tourism +fishing + agriculture jobs, cost of $10 billion
impacts of tsunamis?
can travel at 7 mph- sweeping away trees, buildings, bridges and people
washes away soil undermining foundation of buildings and destroying farmlands
can completely change landscapes
What is enquiry question 2 of tectonics?
why do some tectonic hazards develop into disasters?
