DESTRUCTIVE CONVERGENT PLATE MARGINS: SUBDUCTION
INTRODUCTION
G14 1
What is the process where oceanic plates descend into the mantle
called?
G14
2
What major topographic feature marks the junction between the
descending oceanic plate and the over –riding plate?
G178 3
E512
What topographic features develop above the subduction zone in:
a)
Oceanic – Oceanic collision
b)
Oceanic – Continental collision
G179 4
Describe and explain the gravity anomalies associated with subduction
Zones
G14
Describe and explain the presence of Benioff Zones
5
G179 6
Why are there no earthquake foci below 700km?
IGNEOUS PROCESSES AT SUBDUCTION ZONES
G63
1
What material is subducted with the oceanic crust?
G63 2
GS179
Explain 5 reasons why partial melting and the generation of magmas
occurs in subduction zones.
E512 3
At what depth are magmas generated in the subduction zone?
G63
Why do magmas produced at subduction zones not have the same
compositions the original basaltic rocks of the oceanic crust?
4
G179 5
What sequence of magma compositions is found after initial
subduction and why?
G63-4 6
What is the relative sense of movement between subducting and overriding plates?
G64
7
How and why does the composition of magmas generated at
subduction zones change with time?
G64
8
What rock type is characteristic of volcanic island arcs parallel to
oceanic trenches?
G64
9
Why are andesites described as an ‘irreversible addition to continental
crust’?
G64
10
How long does continental crust take to form?
G64
11
Why is volcanism above subduction zones usually explosive?
G64
12
What are volcaniclastic / pyroclastic / tephra rocks?
G64
13
What shape / type of volcano do pyroclastics form?
14
How does the size of pyroclastic material change with increasing
distance from the vent?
G64
15
What are nuess ardentes / pyroclastic flows and what deposits do the
produce?
G65
16
Copy fig 4.16
METAMORPHIC PROCESSES AT SUBDUCTION ZONES
G134 1
E512
Paired metamorphic belts are typical l associated with subduction
Zones. Describe the temperature and pressure conditions and
metamorphic facies that are produced in the metamorphic belt close to
the oceanic trench.
E512 2
How does blueschist facies metamorphism lead to further magma
genberation above the subduction zone?
E512 3
Describe the temperature and pressure conditions and 3 metamorphic
facies associated with rising magma causing metamorphism of igneous
rocks above subduction zones
E513 4
Describe the paired metamorphic belts found on the Californian coast
and Sierra Nevada and explain their interpretation.
SEDIMENTARY PROCESSES AT SUBDUCTION ZONES
E289 1
What type of deposition is typical of deep ocean trenches?
E512 2
Why are these sediments often intensely deformed?
E281 3
Copy fig 11.33
E512 4
What term is used to describe the intensely deformed sediments found
at subduction zones?
CONVERGENT PLATE BOUNDARIES
CONTINENT –CONTINENT COLLISION: OROGENY
G142 1
What happens to sediments on the continental shelf in continentcontinent collision?
G142 2
Give an example of where this has happened
G144 3
regions
What type of deformation is dominant at shallow depths in these
and why?
G144 4
What type of deformation is dominant at greater depths in these
regions and why?
G144 5
What grade of metamorphism is commonly associated with nappes?
E515 6
Describe the Wilson cycle of plate tectonics