Oceanography Week Three
1. List three reasons to need to better understand the dynamics of subduction
zones?: Understanding the dynamics of subduction is particularly important for hazards such as earthquakes,
tsunamis, and volcanic eruptions.
2. What do they say provides most of the "power" for plate motion?: The sinking of
lithosphere in subduction zones provides most of the power for plate motions and is directly responsible for crustal
deformation and arc magmatism.
3. What two ways can convergent margins cause climate change?: Convergent margin
processes affect climate directly (volcanic gases) and indirectly (providing relief and stimulating weathering).
4. What factors do they say cause "along strike" variations along a subduction
zone?: A few of these factors are convergence rate and obliquity; age of incoming plate and the subduction zone
itself; physical, thermal, and chemical state of the subducting oceanic lithosphere; presence of seamounts and other
heterogeneities on the downgoing plate; the nature and thickness of subducting sediments; accretion versus erosion;
and the composition and structure of the upper plate.
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, 5. What is meant by Subduction erosion?: That most convergent margins loose material from the
upper plate and only a minority add material by growing accretionary prisms
6. How deep can continental crust be subducted?: 80-120km.
7. What happens to slab water content with depth (Figure 3)?: Subducting slabs lose
significant water when the slab comes into contact with the hot overlying mantle wedge.
8. What is an ophiolite and how are they used to understand subduction zone
processes?: An ophiolite is any of a group of rocks, especially mafic and ultramafic igneous rocks, thought to have
formed during crustal thinning at the mid-ocean ridge and to have been subsequently thrust onto continental crust.
9. Why do we worry so much about fluids in subductions zones?: Mass transport
capabilities, friction, melting and subduction mechanisms
10. What prevented newly formed crust from surviving during early earth?: Early
Earth was being bombarded by asteroids so the chance of any newly formed crust staying together while under this
level of destruction was extremely low.
11. What is special about granite and why was it important in early earth?: Early
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1. List three reasons to need to better understand the dynamics of subduction
zones?: Understanding the dynamics of subduction is particularly important for hazards such as earthquakes,
tsunamis, and volcanic eruptions.
2. What do they say provides most of the "power" for plate motion?: The sinking of
lithosphere in subduction zones provides most of the power for plate motions and is directly responsible for crustal
deformation and arc magmatism.
3. What two ways can convergent margins cause climate change?: Convergent margin
processes affect climate directly (volcanic gases) and indirectly (providing relief and stimulating weathering).
4. What factors do they say cause "along strike" variations along a subduction
zone?: A few of these factors are convergence rate and obliquity; age of incoming plate and the subduction zone
itself; physical, thermal, and chemical state of the subducting oceanic lithosphere; presence of seamounts and other
heterogeneities on the downgoing plate; the nature and thickness of subducting sediments; accretion versus erosion;
and the composition and structure of the upper plate.
1/2
, 5. What is meant by Subduction erosion?: That most convergent margins loose material from the
upper plate and only a minority add material by growing accretionary prisms
6. How deep can continental crust be subducted?: 80-120km.
7. What happens to slab water content with depth (Figure 3)?: Subducting slabs lose
significant water when the slab comes into contact with the hot overlying mantle wedge.
8. What is an ophiolite and how are they used to understand subduction zone
processes?: An ophiolite is any of a group of rocks, especially mafic and ultramafic igneous rocks, thought to have
formed during crustal thinning at the mid-ocean ridge and to have been subsequently thrust onto continental crust.
9. Why do we worry so much about fluids in subductions zones?: Mass transport
capabilities, friction, melting and subduction mechanisms
10. What prevented newly formed crust from surviving during early earth?: Early
Earth was being bombarded by asteroids so the chance of any newly formed crust staying together while under this
level of destruction was extremely low.
11. What is special about granite and why was it important in early earth?: Early
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