Important for test info on tectonics Flashcards
What are the 7 major plates from largest to smallest?
- Pacific
- Eurasia
- North America
- South America
- Africa
- Antarctica
- Australian
How large is the pacific plate?
~14000km
What type of crust is the pacific plate made of?
Oceanic
What is the difference between plate and lithosphere?
A plate is a piece of lithosphere, which can have either continental or oceanic crust (or both) at its top. Continent is the emerged part of a plate
What is the position of the mid-Atlantic ridge between south America and Africa?
Symmetrically in the middle
What distance is the Mid-Atlantic ridge from South America and Africa?
Both ~2500km
Is the Mid-Atlantic ridge segmented or a straight boundary?
Segmented (by strike slip)
How long is the longest and shortest ridge segments of the Mid-Atlantic ridge?
Long =~1000km
Short =~50km
What is the maximum lateral offset of the Mid-Atlantic ridge?
870km
What is an example of where a spreading ridge occurs above sea level?
Iceland
What is the bathymetric profile along the south mid-Atlantic ridge?
Ridge is large elevated areas in centre of the ocean.
Coast to coast, the depth increases up to a maximum of -5500km and decreases again where the ridge starts
Where is the highest elevation along the Mid-Atlantic ridge?
In the centre at the divergent margin
What is the total height of the Mid-Atlantic ridge?
Around 3000m
How wide is the Mid-Atlantic ridge?
~2900km
Why is the Mid-Atlantic ridge so wide/ what controls this?
elevated area (ridge) is hotter than other oceanic rocks and therefore more buoyant. Temperature decreases from the ridge towards the ocean-continent boundary and so does the elevation (colder = less buoyant = deeper)
What is the age distribution of oceanic crust in the Atlantic ocean like?
Symmetric
What was the initial opening age of the mid-Atlantic ridge between NW Africa and the USA?
175-180 Ma
What is the spreading rate of the Mid-Atlantic ridge between NW Africa and USA?
3.2cm/year
What is the sequence of opening and age of the North, central and south Mid-Atlantic ridge?
North Atlantic = 130 Ma (southern part); Central Atlantic = 180 Ma;
South Atlantic = 130 Ma.
How old is the oldest oceanic crust?
~280 Ma
What has the spreading rate been like in the Central Atlantic?
Relatively constant
What does the difference between the age of oceanic and continental crust?
Oceans are continuously recycled during the various Wilson cycles, while continents are not
How many types of convergent plate boundary are there?
Ocean-ocean,
ocean-continent,
continent-continent.
What is the main large scale product of intra-continental and ocean-continent subductions?
orogenesys
What is the main large scale product of intra-oceanic convergent boundaries?
Island arc
Is the convergence of the Juan de Fuca plate perpendicular to the trench direction?
Subduction can be oblique to the trench, as for the Nazca plate.
What is the overall shape of the down-going plate?
From the abyssal plain, depths increase towards the trench, reaching a maximum depth at the trench where lithosphere inflects downward into the subduction zone
What is the overall depth of the overriding plate compared with the down-going plate?
Always higher
Along which type of plate margin do volcanoes occur more often?
Convergent margins
Where can a large number of volcanoes that are not associated with a plate boundary?
East African rift valley (a new plate margin is developing there as this is a rift)
What is the topographic profile and alignment of volcanoes in the East African rift valley?
Are aligned within the rift valley, which is a topographic depression
What is the process responsible for the topographic profile and volcano alignment in the east African rift valley?
Continental rifting
What is the distance between some volcanoes and trenchs?
South America: 320 km
North America: 290 km
Japan: 300 km
What type of margin do large volcanoes occur?
Convergent
Is there a link between depth of
the earthquake and distance from the trench?
Yes - depth increases away from the trench
reflecting the shape of the subduction zone.
What is the distribution of earthquakes on the plate called?
Benioff zone
