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 Canyons1. 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 4) 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 5) Transform faults and Fracture Zones a. Basic distinction between these features b. Dimensions c. Relative motion and difference in relief d. Location of earthquakes 6) 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 7) 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 8) 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 boundariesi. Divergent ii. Convergent iii. Transform c. Relative motion and approximate plate velocities 2) 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 3) 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 4) Recent evidence supporting Continental Drift a. Fit of continents b. Continuity of age and lithology of major rock units c. Glacial striae orientation 5) 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 6) Basic definition of plates and plate motion a. Oceanic vs. Continental crustb. 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. Trench3. 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