Study Guides (283,564)
AUS (7,769)
UniMelb (932)
EVSC10001 (1)
Final

EVSC10001 Final: Plate tectonics review

20 Pages
29 Views
Fall 2018

Department
Environmental Science
Course Code
EVSC10001
Professor
Dr. Jan-Hendrik May
Study Guide
Final

This preview shows pages 1-3. Sign up to view the full 20 pages of the document.
Tectonics:
Based on 3 concepts
Earth's lithosphere is divided into rigid segments - called plates
Plates are in motion relative to each other
Major structural features of Earth are formed at Plate Boundaries
-
Pacific plate
Largest plate
Made of mostly oceanic lithosphere
-
Lithospheric plates
7 major plates
-
Can include oceanic, continental crust or both
-
Plate motions
Driven by GRAVITY and linked to CONVECTION in the mantles
-
Plates slide across weak asthenosphere
-
Continents are carried along passively by plates
-
Plates are bounded below by asthenosphere and above by atmosphere and
oceans
Asthenosphere: weak layer below lithosphere that just started to melt
-
Mechanisms of plate tectonics
Follows convection currents in solid mantle
-
Slab-pull force: sinking/descending oceanic slabs at convergent boundaries
-
Ridge-push force: plates pushed apart at oceanic ridges (very weak)
-
Theory of Continental Drift
Proposed that continents had once been part of supercontinent - Pangea
-
Continents broke up and spread apart
Now known that continents carried passively by moving plates across
weak asthensophere
-
Evidence
Geometric fit of continents
Paleoclimate indicators in rocks - permian glacial deposits
Matching geology b/w continents
Distribution of fossils (plants and animals)
-
PLATE BOUNDARIES
DIVERGENT PLATE BOUNDARIES1)
New lithosphere created
-
Oceanic ridge system
Largest tectonic feature on Earth
Has a central RIFT VALLEY along crest - many earthquakes
Composed of basalt lavas with almost no sed on top
Many faults but no folds
High heat flow over ridge
Tensional forces + active volcanism
Deepest near continents
Mid-Atlantic ridge:
-
Volcanic activity on oceanic ridges
Almost entirely basalt lavas produced
Frequent eruption along central rift valleys
Nearly almost always submarine eruptions
Pillow basalts -indicative of underwater eruptions
§
Black smokers = submarine hot springs
Lavas produced from fissure eruptions
§
-
Rift valley
Eventually valley widens -> fills w/ sediment
-
Generation of magma at ridges
Asthenosphere rises beneath ridge axis
Decreased pressure triggers further partial melting (pressure makes it
harder to melt at greater depths)
Magmas produced are less dense -> rise
Partial melting of mantle -> BASALTS
-
SEA FLOOR SPREADING
Seafloor moves because of convection in mantle
-
Magnetism patterns were symmetrical about the ridge axis
Anomaly over ridge is always positive
Maps show stripes of positive anomalies in black and negative in white
Vine-matthews hypothesis:
Magnetic stripes due to bands of ocean crust magnetised in normal
and reverse directions
§
New BASALTIC MAGAMA injected along ridge axis -> records
magnetic filed at that time
§
Normal magnetised -> positive
§
Reversely magnetised -> negative
§
Sea floor spreading -> ocean crust acts as recorder of earths magnetic field
Confirming
Results from Deep Sea Drilling project confirmed
§
Age and thickness of sediment steadily increased away from ridge
crest - virtually no sediment on ridge
§
Elevation of ridge decreased away from ridge due to declining heat
flow
§
Upwelling of asthenosphere
Development of rifted margins
Extension produces stretching of crust
Decompression of upwelling material
Upper Earth's crust - cooler -> rocks fracture -> FAULTS
Lower part - heated -> don’t fracture -> stretched -> NECKING - thinning
Asthenosphere upwells -> decompression
-
-
TRANSFORM PLATE BOUNDARIES 2)
Strike-slip movement - 2 sides grind laterally
ZONE OF FAULTING where rocks are sheared
Line of ridges, cliffs and troughs
Faster spreading -> more upwelling -> 20% melting -> magma overflows in rift
valley
Both oceanic and continental crust
More common in OCEANIC - offset ridge axis
Sites of shallow EARTHQUAKE activity - not volcanic
Transform faults: large fault zones on ocean floor which cut across oceanic
ridges
Extend laterally into passive FRACTURE ZONES
Show vertical offset across due to diff. age crust on each side
Older -> colder -> sink -> lower
EARTHQUAKES:
Shallow earthquakes along transform faults and along median rift valley
Fracture zones are NOT seismically active - no relative movement
Continental transform boundaries
Eg. San Andreas Fault in California
Faults penetrate through lithosphere
VERY SEISMICALLY ACTIVE
Often follow old lines of weakness
Slight bends in direction of fault
Transforms often show bends that cause regions of TRANSPRESSION
(local compression - restraining bends - local fold mountains -
accompanied by crustal uplift and erosion) AND TRANSTENSION
(local tension - releasing bends - pull apart basins - local basins of
sedimentation)
Composition of oceanic crust
Ocean crust grows by continual igneous activity
Avg. 6km thick
-
-
VOLCANISM at oceanic islands
Coral atolls: separated from adjacent land mass - circular or oval with central
lagoon - can be built on volcanoes
Often occur in linear chains of islands / submarine mountains - seamounts
Made of basalts relatively richer in alkali elements than MORBS
-
Linear seamount and island chains
SEISMICALLY INACTIVE + much narrower than oceanic ridges
Usually have active volcanic island at one end
Eg. Hawaiian islands - Emperor seamount chain
Islands slowly subside + replaced by coral reefs
Coral atolls eventually give way to submerged seamounts
-
Mantle plumes
Hotspots/plumes: regions where columns of hot mantle material rise beneath
lithosphere
Ocean island chains - caused by lithosphere moving over hotspot magma
sources in mantle
On each plate, hotspot trails are parallel
Source is deep in lower mantle
-
CONVERGENT PLATE BOUNDARIES3)
2 lithospheric plats push together
-
3 types:
Convergence of 2 oceanic plates
Island arcs: eg. Marianas, Aleutians
§
Convergence of oceanic and continental plates
Andes in S. America
§
Convergence of 2 continental plates
Continental collision zones: Himalayas, alps
§
-
Island Arc Complexes produced by convergence b/w 2 oceanic plates + areas of
intense earthquake + volcanic activity
Curved chains of volcanic islands bounded on convex side by oceanic
trench
Active volcanoes found along the arc
Deep sea trenches occur along the ocean side
Typically andesite volcanoes
-
Subduction: process whereby oceanic plate bends downwards at ocean trench
and descends into mantle
Subduction begins at the trench
ONLY OCEANIC
Trench = site of subduction
Can occur beneath either oceanic or continental
Ocean sinks when old, cold, dense
Processes:
Igneous activity, sedimentation, metamorphism, crustal
deformation
§
EARTHQUAKES
Shallow, intermediate, and deep levels
§
Plane begins at trench and dips about 45 degrees beneath arc
Benioff Zone: dipping plane of earthquakes - upper surface of
descending oceanic slab, shallow earthquakes occur widely
§
Shallow also occur through the arc
§
IGNEOUS ACTIVITY:
Arc magmas: show range of compositions but most commonly
ANDESITE
§
Magmas originate mostly be wet partial melting by overlying mantle
§
Fluids driven off descending slab and trigger melting
§
Melting starts when slab descends to 100km depth
§
Over time, crust thickens + becomes more continental
§
-
Accretionary complex
Unconsolidated sed from ocean floor is scraped off descending plate
at trench
§
Accretionary wedge: zone of highly deformed sed and some ocean
floor volcanic rocks - above subduction zone
New material pushed beneath
§
Slices of oceanic crust may be included as OPHIOLITE BELTS
§
Metamorphism occurs in high-temp belts associated with magmatic arc +
high pressure belts associated with subduction zone (paired metamorphic
belts)
High temp-low pressure
Occurs in core of volcanic arcs
Abnormal heating of crust
Thermal effects of subduction-related magmatism
§
High pressure-low temp
In accretionary wedge
Cold rocks dragged to great depths and then upthrust again
§
-
Ocean-continent convergence
Edge of continent
Can be very long-lived
Similar features to Island Arcs
Earthquakes, volcanism, metamorphism
§
Thick crusts + high surface elevation
Ocean side: thick sequences of deformed marine sediments from
accretionary wedge
Inland side: fold + thrust belt of deformed sedimentary rocks
Eg. Andes, cascades
-
Closure of ocean basin
Ocean basin, rate of subduction can exceed rate of sea-floor spreading
Eventually oceanic ridge will be subducted -> ocean closes rapidly
Example: California transform margin
-
Continental collision zones - final stage of closure of ocean basin by subduction -
extreme deformation of crust
Closure of ocean brings 2 continents together
Suture: join b/w 2 formerly separate continents
§
Collision produces major MOUNTAIN RANGE within a larger continent
Very thick crust + high elevations
Examples: Himalayas, European alps, Appalachians
Himalayas - produced by collision of India with Eurasia
Continues today
Ophiolites along suture mark site of former ocean
Crust is of great thickness
§
-
Plate tectonics
Saturday, 2 June 2018
2:32 pm
Tectonics:
Based on 3 concepts
Earth's lithosphere is divided into rigid segments - called plates
Plates are in motion relative to each other
Major structural features of Earth are formed at Plate Boundaries
-
Pacific plate
Largest plate
Made of mostly oceanic lithosphere
-
Lithospheric plates
7 major plates
-
Can include oceanic, continental crust or both
-
Plate motions
Driven by GRAVITY and linked to CONVECTION in the mantles
-
Plates slide across weak asthenosphere
-
Continents are carried along passively by plates
-
Plates are bounded below by asthenosphere and above by atmosphere and
oceans
Asthenosphere: weak layer below lithosphere that just started to melt
-
Mechanisms of plate tectonics
Follows convection currents in solid mantle
-
Slab-pull force: sinking/descending oceanic slabs at convergent boundaries
-
Ridge-push force: plates pushed apart at oceanic ridges (very weak)
-
Theory of Continental Drift
Proposed that continents had once been part of supercontinent - Pangea
-
Continents broke up and spread apart
Now known that continents carried passively by moving plates across
weak asthensophere
-
Evidence
Geometric fit of continents
Paleoclimate indicators in rocks - permian glacial deposits
Matching geology b/w continents
Distribution of fossils (plants and animals)
-
PLATE BOUNDARIES
DIVERGENT PLATE BOUNDARIES1)
New lithosphere created
-
Oceanic ridge system
Largest tectonic feature on Earth
Has a central RIFT VALLEY along crest - many earthquakes
Composed of basalt lavas with almost no sed on top
Many faults but no folds
High heat flow over ridge
Tensional forces + active volcanism
Deepest near continents
Mid-Atlantic ridge:
-
Volcanic activity on oceanic ridges
Almost entirely basalt lavas produced
Frequent eruption along central rift valleys
Nearly almost always submarine eruptions
Pillow basalts -indicative of underwater eruptions
§
Black smokers = submarine hot springs
Lavas produced from fissure eruptions
§
-
Rift valley
Eventually valley widens -> fills w/ sediment
-
Generation of magma at ridges
Asthenosphere rises beneath ridge axis
Decreased pressure triggers further partial melting (pressure makes it
harder to melt at greater depths)
Magmas produced are less dense -> rise
Partial melting of mantle -> BASALTS
-
SEA FLOOR SPREADING
Seafloor moves because of convection in mantle
-
Magnetism patterns were symmetrical about the ridge axis
Anomaly over ridge is always positive
Maps show stripes of positive anomalies in black and negative in white
Vine-matthews hypothesis:
Magnetic stripes due to bands of ocean crust magnetised in normal
and reverse directions
§
New BASALTIC MAGAMA injected along ridge axis -> records
magnetic filed at that time
§
Normal magnetised -> positive
§
Reversely magnetised -> negative
§
Sea floor spreading -> ocean crust acts as recorder of earths magnetic field
Confirming
Results from Deep Sea Drilling project confirmed
§
Age and thickness of sediment steadily increased away from ridge
crest - virtually no sediment on ridge
§
Elevation of ridge decreased away from ridge due to declining heat
flow
§
Upwelling of asthenosphere
Development of rifted margins
Extension produces stretching of crust
Decompression of upwelling material
Upper Earth's crust - cooler -> rocks fracture -> FAULTS
Lower part - heated -> don’t fracture -> stretched -> NECKING - thinning
Asthenosphere upwells -> decompression
-
-
TRANSFORM PLATE BOUNDARIES 2)
Strike-slip movement - 2 sides grind laterally
ZONE OF FAULTING where rocks are sheared
Line of ridges, cliffs and troughs
Faster spreading -> more upwelling -> 20% melting -> magma overflows in rift
valley
Both oceanic and continental crust
More common in OCEANIC - offset ridge axis
Sites of shallow EARTHQUAKE activity - not volcanic
Transform faults: large fault zones on ocean floor which cut across oceanic
ridges
Extend laterally into passive FRACTURE ZONES
Show vertical offset across due to diff. age crust on each side
Older -> colder -> sink -> lower
EARTHQUAKES:
Shallow earthquakes along transform faults and along median rift valley
Fracture zones are NOT seismically active - no relative movement
Continental transform boundaries
Eg. San Andreas Fault in California
Faults penetrate through lithosphere
VERY SEISMICALLY ACTIVE
Often follow old lines of weakness
Slight bends in direction of fault
Transforms often show bends that cause regions of TRANSPRESSION
(local compression - restraining bends - local fold mountains -
accompanied by crustal uplift and erosion) AND TRANSTENSION
(local tension - releasing bends - pull apart basins - local basins of
sedimentation)
Composition of oceanic crust
Ocean crust grows by continual igneous activity
Avg. 6km thick
-
-
VOLCANISM at oceanic islands
Coral atolls: separated from adjacent land mass - circular or oval with central
lagoon - can be built on volcanoes
Often occur in linear chains of islands / submarine mountains - seamounts
Made of basalts relatively richer in alkali elements than MORBS
-
Linear seamount and island chains
SEISMICALLY INACTIVE + much narrower than oceanic ridges
Usually have active volcanic island at one end
Eg. Hawaiian islands - Emperor seamount chain
Islands slowly subside + replaced by coral reefs
Coral atolls eventually give way to submerged seamounts
-
Mantle plumes
Hotspots/plumes: regions where columns of hot mantle material rise beneath
lithosphere
Ocean island chains - caused by lithosphere moving over hotspot magma
sources in mantle
On each plate, hotspot trails are parallel
Source is deep in lower mantle
-
CONVERGENT PLATE BOUNDARIES3)
2 lithospheric plats push together
-
3 types:
Convergence of 2 oceanic plates
Island arcs: eg. Marianas, Aleutians
§
Convergence of oceanic and continental plates
Andes in S. America
§
Convergence of 2 continental plates
Continental collision zones: Himalayas, alps
§
-
Island Arc Complexes produced by convergence b/w 2 oceanic plates + areas of
intense earthquake + volcanic activity
Curved chains of volcanic islands bounded on convex side by oceanic
trench
Active volcanoes found along the arc
Deep sea trenches occur along the ocean side
Typically andesite volcanoes
-
Subduction: process whereby oceanic plate bends downwards at ocean trench
and descends into mantle
Subduction begins at the trench
ONLY OCEANIC
Trench = site of subduction
Can occur beneath either oceanic or continental
Ocean sinks when old, cold, dense
Processes:
Igneous activity, sedimentation, metamorphism, crustal
deformation
§
EARTHQUAKES
Shallow, intermediate, and deep levels
§
Plane begins at trench and dips about 45 degrees beneath arc
Benioff Zone: dipping plane of earthquakes - upper surface of
descending oceanic slab, shallow earthquakes occur widely
§
Shallow also occur through the arc
§
IGNEOUS ACTIVITY:
Arc magmas: show range of compositions but most commonly
ANDESITE
§
Magmas originate mostly be wet partial melting by overlying mantle
§
Fluids driven off descending slab and trigger melting
§
Melting starts when slab descends to 100km depth
§
Over time, crust thickens + becomes more continental
§
-
Accretionary complex
Unconsolidated sed from ocean floor is scraped off descending plate
at trench
§
Accretionary wedge: zone of highly deformed sed and some ocean
floor volcanic rocks - above subduction zone
New material pushed beneath
§
Slices of oceanic crust may be included as OPHIOLITE BELTS
§
Metamorphism occurs in high-temp belts associated with magmatic arc +
high pressure belts associated with subduction zone (paired metamorphic
belts)
High temp-low pressure
Occurs in core of volcanic arcs
Abnormal heating of crust
Thermal effects of subduction-related magmatism
§
High pressure-low temp
In accretionary wedge
Cold rocks dragged to great depths and then upthrust again
§
-
Ocean-continent convergence
Edge of continent
Can be very long-lived
Similar features to Island Arcs
Earthquakes, volcanism, metamorphism
§
Thick crusts + high surface elevation
Ocean side: thick sequences of deformed marine sediments from
accretionary wedge
Inland side: fold + thrust belt of deformed sedimentary rocks
Eg. Andes, cascades
-
Closure of ocean basin
Ocean basin, rate of subduction can exceed rate of sea-floor spreading
Eventually oceanic ridge will be subducted -> ocean closes rapidly
Example: California transform margin
-
Continental collision zones - final stage of closure of ocean basin by subduction -
extreme deformation of crust
Closure of ocean brings 2 continents together
Suture: join b/w 2 formerly separate continents
§
Collision produces major MOUNTAIN RANGE within a larger continent
Very thick crust + high elevations
Examples: Himalayas, European alps, Appalachians
Himalayas - produced by collision of India with Eurasia
Continues today
Ophiolites along suture mark site of former ocean
Crust is of great thickness
§
-
2:32 pm
Tectonics:
Based on 3 concepts
Earth's lithosphere is divided into rigid segments - called plates
Plates are in motion relative to each other
Major structural features of Earth are formed at Plate Boundaries
-
Pacific plate
Largest plate
Made of mostly oceanic lithosphere
-
Lithospheric plates
7 major plates
-
Can include oceanic, continental crust or both
-
Plate motions
Driven by GRAVITY and linked to CONVECTION in the mantles
-
Plates slide across weak asthenosphere
-
Continents are carried along passively by plates
-
Plates are bounded below by asthenosphere and above by atmosphere and
oceans
Asthenosphere: weak layer below lithosphere that just started to melt
-
Mechanisms of plate tectonics
Follows convection currents in solid mantle
-
Slab-pull force: sinking/descending oceanic slabs at convergent boundaries
-
Ridge-push force: plates pushed apart at oceanic ridges (very weak)
-
Theory of Continental Drift
Proposed that continents had once been part of supercontinent - Pangea
-
Continents broke up and spread apart
Now known that continents carried passively by moving plates across
weak asthensophere
-
Evidence
Geometric fit of continents
Paleoclimate indicators in rocks - permian glacial deposits
Matching geology b/w continents
Distribution of fossils (plants and animals)
-
PLATE BOUNDARIES
DIVERGENT PLATE BOUNDARIES
1)
New lithosphere created
-
Oceanic ridge system
Largest tectonic feature on Earth
Has a central RIFT VALLEY along crest - many earthquakes
Composed of basalt lavas with almost no sed on top
Many faults but no folds
High heat flow over ridge
Tensional forces + active volcanism
Deepest near continents
Mid-Atlantic ridge:
-
Volcanic activity on oceanic ridges
Almost entirely basalt lavas produced
Frequent eruption along central rift valleys
Nearly almost always submarine eruptions
Pillow basalts -indicative of underwater eruptions
§
Black smokers = submarine hot springs
Lavas produced from fissure eruptions
§
-
Rift valley
Eventually valley widens -> fills w/ sediment
-
Generation of magma at ridges
Asthenosphere rises beneath ridge axis
Decreased pressure triggers further partial melting (pressure makes it
harder to melt at greater depths)
Magmas produced are less dense -> rise
Partial melting of mantle -> BASALTS
-
SEA FLOOR SPREADING
Seafloor moves because of convection in mantle
-
Magnetism patterns were symmetrical about the ridge axis
Anomaly over ridge is always positive
Maps show stripes of positive anomalies in black and negative in white
Vine-matthews hypothesis:
Magnetic stripes due to bands of ocean crust magnetised in normal
and reverse directions
§
New BASALTIC MAGAMA injected along ridge axis -> records
magnetic filed at that time
§
Normal magnetised -> positive
§
Reversely magnetised -> negative
§
Sea floor spreading -> ocean crust acts as recorder of earths magnetic field
Confirming
Results from Deep Sea Drilling project confirmed
§
Age and thickness of sediment steadily increased away from ridge
crest - virtually no sediment on ridge
§
Elevation of ridge decreased away from ridge due to declining heat
flow
§
Upwelling of asthenosphere
Development of rifted margins
Extension produces stretching of crust
Decompression of upwelling material
Upper Earth's crust - cooler -> rocks fracture -> FAULTS
Lower part - heated -> don’t fracture -> stretched -> NECKING - thinning
Asthenosphere upwells -> decompression
-
-
TRANSFORM PLATE BOUNDARIES 2)
Strike-slip movement - 2 sides grind laterally
ZONE OF FAULTING where rocks are sheared
Line of ridges, cliffs and troughs
Faster spreading -> more upwelling -> 20% melting -> magma overflows in rift
valley
Both oceanic and continental crust
More common in OCEANIC - offset ridge axis
Sites of shallow EARTHQUAKE activity - not volcanic
Transform faults: large fault zones on ocean floor which cut across oceanic
ridges
Extend laterally into passive FRACTURE ZONES
Show vertical offset across due to diff. age crust on each side
Older -> colder -> sink -> lower
EARTHQUAKES:
Shallow earthquakes along transform faults and along median rift valley
Fracture zones are NOT seismically active - no relative movement
Continental transform boundaries
Eg. San Andreas Fault in California
Faults penetrate through lithosphere
VERY SEISMICALLY ACTIVE
Often follow old lines of weakness
Slight bends in direction of fault
Transforms often show bends that cause regions of TRANSPRESSION
(local compression - restraining bends - local fold mountains -
accompanied by crustal uplift and erosion) AND TRANSTENSION
(local tension - releasing bends - pull apart basins - local basins of
sedimentation)
Composition of oceanic crust
Ocean crust grows by continual igneous activity
Avg. 6km thick
-
-
VOLCANISM at oceanic islands
Coral atolls: separated from adjacent land mass - circular or oval with central
lagoon - can be built on volcanoes
Often occur in linear chains of islands / submarine mountains - seamounts
Made of basalts relatively richer in alkali elements than MORBS
-
Linear seamount and island chains
SEISMICALLY INACTIVE + much narrower than oceanic ridges
Usually have active volcanic island at one end
Eg. Hawaiian islands - Emperor seamount chain
Islands slowly subside + replaced by coral reefs
Coral atolls eventually give way to submerged seamounts
-
Mantle plumes
Hotspots/plumes: regions where columns of hot mantle material rise beneath
lithosphere
Ocean island chains - caused by lithosphere moving over hotspot magma
sources in mantle
On each plate, hotspot trails are parallel
Source is deep in lower mantle
-
CONVERGENT PLATE BOUNDARIES3)
2 lithospheric plats push together
-
3 types:
Convergence of 2 oceanic plates
Island arcs: eg. Marianas, Aleutians
§
Convergence of oceanic and continental plates
Andes in S. America
§
Convergence of 2 continental plates
Continental collision zones: Himalayas, alps
§
-
Island Arc Complexes produced by convergence b/w 2 oceanic plates + areas of
intense earthquake + volcanic activity
Curved chains of volcanic islands bounded on convex side by oceanic
trench
Active volcanoes found along the arc
Deep sea trenches occur along the ocean side
Typically andesite volcanoes
-
Subduction: process whereby oceanic plate bends downwards at ocean trench
and descends into mantle
Subduction begins at the trench
ONLY OCEANIC
Trench = site of subduction
Can occur beneath either oceanic or continental
Ocean sinks when old, cold, dense
Processes:
Igneous activity, sedimentation, metamorphism, crustal
deformation
§
EARTHQUAKES
Shallow, intermediate, and deep levels
§
Plane begins at trench and dips about 45 degrees beneath arc
Benioff Zone: dipping plane of earthquakes - upper surface of
descending oceanic slab, shallow earthquakes occur widely
§
Shallow also occur through the arc
§
IGNEOUS ACTIVITY:
Arc magmas: show range of compositions but most commonly
ANDESITE
§
Magmas originate mostly be wet partial melting by overlying mantle
§
Fluids driven off descending slab and trigger melting
§
Melting starts when slab descends to 100km depth
§
Over time, crust thickens + becomes more continental
§
-
Accretionary complex
Unconsolidated sed from ocean floor is scraped off descending plate
at trench
§
Accretionary wedge: zone of highly deformed sed and some ocean
floor volcanic rocks - above subduction zone
New material pushed beneath
§
Slices of oceanic crust may be included as OPHIOLITE BELTS
§
Metamorphism occurs in high-temp belts associated with magmatic arc +
high pressure belts associated with subduction zone (paired metamorphic
belts)
High temp-low pressure
Occurs in core of volcanic arcs
Abnormal heating of crust
Thermal effects of subduction-related magmatism
§
High pressure-low temp
In accretionary wedge
Cold rocks dragged to great depths and then upthrust again
§
-
Ocean-continent convergence
Edge of continent
Can be very long-lived
Similar features to Island Arcs
Earthquakes, volcanism, metamorphism
§
Thick crusts + high surface elevation
Ocean side: thick sequences of deformed marine sediments from
accretionary wedge
Inland side: fold + thrust belt of deformed sedimentary rocks
Eg. Andes, cascades
-
Closure of ocean basin
Ocean basin, rate of subduction can exceed rate of sea-floor spreading
Eventually oceanic ridge will be subducted -> ocean closes rapidly
Example: California transform margin
-
Continental collision zones - final stage of closure of ocean basin by subduction -
extreme deformation of crust
Closure of ocean brings 2 continents together
Suture: join b/w 2 formerly separate continents
§
Collision produces major MOUNTAIN RANGE within a larger continent
Very thick crust + high elevations
Examples: Himalayas, European alps, Appalachians
Himalayas - produced by collision of India with Eurasia
Continues today
Ophiolites along suture mark site of former ocean
Crust is of great thickness
§
-
Plate tectonics
Saturday, 2 June 2018 2:32 pm

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.

Leah — University of Toronto

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto
Saarim — University of Michigan

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan
Jenna — University of Wisconsin

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin
Anne — University of California

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
Plate tectonics Saturday, 2 June 2018 2:32 pm Tectonics: Based on 3 concepts Earths lithosphere is divided into rigid segments called plates Plates are in motion relative to each other Major structural features of Earth are formed at Plate Boundaries Pacific plate Largest plate Made of mostly oceanic lithosphere Lithospheric plates 7 major plates Can include oceanic, continental crust or both Plate motions Driven by GRAVITY and linked to CONVECTION in the mantles Plates slide across weak asthenosphere Continents are carried along passively by plates Plates are bounded below by asthenosphere and above by atmosphere and oceans Asthenosphere: weak layer below lithosphere that just started to melt Mechanisms of plate tectonics Follows convection currents in solid mantle Slabpull force: sinkingdescending oceanic slabs at convergent boundaries Ridgepush force: plates pushed apart at oceanic ridges (very weak) Theory of Continental Drift Proposed that continents had once been part of supercontinent Pangea Continents broke up and spread apart Now known that continents carried passively by moving plates across weak asthensophere Evidence Geometric fit of continents Paleoclimate indicators in rocks permian glacial deposits Matching geology bw continents Distribution of fossils (plants and animals)
More Less
Unlock Document

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

You've reached the limit of 4 previews this month

Create an account for unlimited previews.

Already have an account?

Log In


OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit