GENERAL GEOLOGY 1113-005 Fall 2008
Partial Examination IV – Study Guide
Dr. Glen S. Mattioli
Note that these are NOT questions, but rather are a list of topics that we have
covered either in class or are contained within the reading assignments. You should
use this list as a guide to help you review what topics are important for the exam.
Chapter 18: The Sea Floor
1) Methods to study the sea floor – what are they and how do they work?
a. Rock dredges
b. Sea-floor drilling
c. Submersibles
d. Echo sounding
e. Seismic profiling
f. Deep-sea cameras
g. Marine gravity surveys
h. Marine magnetic surveys
2) Different types of data acquired from each of the above techniques
a. Rock type (composition, mineralogy, etc.)
b. Sediment or rock ages (based on paleontologic or radiometric methods)
c. Bathymetry (i.e. sea floor topography)
d. Sub-surface geological structures
e. Sea-floor surface geological features
3) Primary features of the sea floor
a. “Average” profiles across prominent ocean features
i. Shelf, slope, rise
ii. Abyssal plain
iii. Oceanic trench
iv. Mid-oceanic ridges and rift valleys
v. Seamounts
b. Basic distinction between Active vs. Passive Continental Margins
c. Active Margin features
i. Trenches
ii. Waditi-Benioff Zones
iii. Accretionary prisms
iv. Volcanoes
d. Passive Margin features
i. Continental Shelves and Slopes – Dimensions and slope angles
ii. Relationship to mean sea level rise and fall
iii. Rifted continental crust and its relationship to shelf/slope
iv. Submarine Canyons
4)
5)
6)
7)
8)
1. Location
2. Dimensions
3. Processes
4. Abyssal Fans
v. Turbidity Currents
1. Features
2. How were they discovered?
3. Velocity and run out distances
vi. Contour Currents
Ridge crest features and processes
a. Creation of new oceanic lithosphere by basalt eruptions
b. High heat flow
c. Shallow focus, small earthquakes
d. Black Smokers and hydrothermal circulation
e. Biological activity and mineralization
Transform faults and Fracture Zones
a. Basic distinction between these features
b. Dimensions
c. Relative motion and difference in relief
d. Location of earthquakes
Seamounts, Guyots, and Aseismic Ridges
a. Definitions
b. Possible mechanisms for formation
c. Relationship to Hot Spots
d. Age and depth relations
e. Atolls and reefs
Sea floor sediments
a. Distinction between sediment source
i. Pelagic sediments
1. Composition and source
a. Siliceous
b. Carbonaceous
2. Thickness vs. distance from ridge crest
ii. Terrigenous sediments
1. Composition and source
2. Relationship to turbidity and contour currents
Oceanic crust structure and ophiolites
a. Structure and dimensions of each
b. Methods of study
Chapter 19: Plate Tectonics
1) Present plate distribution
a. Major vs. minor plates
b. Types of boundaries
2)
3)
4)
5)
6)
i. Divergent
ii. Convergent
iii. Transform
c. Relative motion and approximate plate velocities
Alfred Wegener’s case for Continental Drift
a. Plate reconstructions through geologic time
b. Definitions of super-continents
i. Pangaea
1. Laurasia
2. Gondwanaland
ii. Approximate time of super-continent separation and brake-up
c. Evidence supporting Continental Drift
i. Fossil distribution
ii. Glacial deposits and striae orientation
iii. Climate zones
d. Hypothesis of Polar Wander
i. Continental motion
ii. Polar motion
iii. Both
e. Arguments against Continental Drift
i. Continents pushing through ocean basins?
ii. Rock strength
iii. Strength of Driving forces
1. Centrifugal force
2. Tidal forces
Paleomagnetism
a. Definition of Curie point
b. Observed variation in magnetic inclination and declination in ancient
rocks
c. Apparent magnetic pole location in geological past
d. Magnetic polar wander paths
i. Interpretation of North American vs. European path difference
Recent evidence supporting Continental Drift
a. Fit of continents
b. Continuity of age and lithology of major rock units
c. Glacial striae orientation
Harry Hess and the proposal of Sea Floor Spreading
a. “Conveyor Belt” concept and the definition of “plates”
b. Proposal that the motion of the plates was driven by heat escape from a
convecting mantle
c. Evidence to support Sea Floor Spreading
i. Heat flow variations between ridges and trenches
ii. Deep vs, shallow earthquakes
iii. Young age of ocean basin rocks and sediments
Basic definition of plates and plate motion
a. Oceanic vs. Continental crust
b. Difference between crust and mantle
c. Definition of lithosphere and asthenosphere
d. Mohorovic discontinuity (Moho) and its relationship to seismic wave
velocity
7) Marine magnetic anomalies – Vine and Matthews hypothesis
a. Generally symmetrical pattern relative to ridge crest
b. Relationship of marine magnetic anomalies and polarity reversals on land
c. Theory for the generation of magnetic anomalies
d. Prediction of sea floor ages
e. Sea Floor Age map – NO oceanic crust older than 160 My.
f. Relationship of age pattern to spreading rate
8) Geometric and kinematic relations of Fracture Zones and Transform Faults
a. Euler poles (see web link) and the relationship of ridges and transforms to
great vs. small circles
b. Earthquake distribution
9) Current plate rates
a. Average rates: 1 to 10 cm/yr
b. Geological (geophysical methods) – 1-3 My rates
i. Orientations of Transforms and Ridges
ii. Convergent boundary slip vectors
iii. Magnetic anomalies
c. Direct measurements from satellite geodesy – 10-30 year rates
i. GPS methods and current global velocity field
10) Divergent plate boundaries
a. Models for early continental rifting
i. Horizontal tension
ii. Uplift from mantle upwelling (plume?)
iii. Passive vs. active upwelling
b. Consequences and sequences of rifting
i. Examples of stages
1. East African Rift (early)
2. Rea Sea Rift (intermediate)
3. Atlantic Ocean Basin (mature)
ii. Detailed structure of Rifted Passive Margin (eastern US example)
11) Transform boundaries
a. Basic types
i. Ridge-ridge
ii. Ridge-trench
iii. Trench-trench
b. San Andreas fault system
c. Oceanic vs. Continental difference in ridge-transform geometry
12) Convergent boundaries
a. Ocean-Ocean type (Examples: Lesser Antilles, Marianas)
i. Main features
1. Oceanic crust
2. Trench
3. Accretionary wedge (or prism)
4. Forearc basin
5. Volcanic Island Arc
6. Backarc basin
ii. Origin of convergent margin curvature
iii. Origin of Arc-Trench gap and its relationship to andesitic
volcanism
b. Ocean-Continent type (Examples: Andes, Cascades)
i. Main features
1. Oceanic crust
2. Trench
3. Accretionary wedge (or prism)
4. Forearc basin
5. Magmatic Arc (Mountain Belt)
a. Batholiths
b. Metamorphic rocks
6. Backarc thrust belt
7. Sedimentary Basin
8. Craton
c. Trench migration
i. Overlying plate “push”
ii. Subducting plate “pull”
d. Continent-Continent type (Examples: Himalaya, Appalachians)
i. Structure and sequence of events
1. Suture Zone
2. Opposing Trust Belt Zones
3. Basins on either side of high alpine zone
e. Backarc Spreading
i. Typical scenarios
ii. Probable causes
13) Dynamics of plate boundaries and sizes
14) Causes of plate motion
a. Ridge Push
b. Slab Pull (likely more important than ridge push)
i. Trench Suction
c. Relationship with deep mantle convection and circulation?
15) Mantle plumes and Hot Spots
a. Dynamic nature of plume head shape and its interaction of the crust
b. Global distribution of Hot Spots
c. Depth-Age relations of Hot Spot Tracks (e.g. Hawaiian chain)
d. Continental breakup driven by plumes
e. Triple junctions and failed rifts
16) Relationship of Ore Deposits and Plate Tectonics
a. Ridge crest environment
b. Arc environment
c. Convergent boundary environment
Chapter 20: Mountain Belts and the Continental Crust
1) Global Distribution of Major Mountain Belts
a. Distinction between mountain ranges and belts
2) Characteristics of Major Mountain Belts
a. Size and alignment
b. Ages and relationship to gross continental structure
c. Mountain belts of North America
i. The Cordillera and its ranges
d. Definition and characteristics of craton and Precambrian shield
e. Schematic cross-section through a mountain belt and craton/shield
f. Detailed schematic cross-section through a Cordilleran Fold and Thrust
Belt
g. Relative thickness and characteristics of cratonic rock sequences
h. Metamorphism and plutonism
i. Normal faulting in ancient mountain belts
3) Evolution of Mountain Belts
a. Accumulation Stage
i. Opening ocean basin
ii. Convergent margin
b. Orogenic Stage
i. Ocean-Continent convergence
1. Gravitational collapse and spreading
ii. Arc-Continent convergence
1. Accretion of “suspect” terranes (see below)
2. Subduction polarity reversal
iii. Continent-Continent convergence
1. The Wilson Cycle and the Evolution of the Southern
Appalachians
c. Uplift and Block Faulting Stage
i. Isostatic adjustment and its relationship to erosion
ii. Normal faulting
1. Related to mantle upwelling
2. Related to crustal extension
3. Related to delamination
iii. Delamination and thinning lithosphere models
4) Continental Growth
a. Definition of tectonostratigraphic terranes and its relationship to displaced
terranes
b. Suspect, accreted, and exotic terranes
c. Western North American example
d. Evolution of the Southern Pacific and accretion of crustal terranes in
Alaska