Remember these?  Draw them!
Faults - Hanging Wall & Foot Wall, Normal, Reverse, Strike Slip, Thrust
Folds - Anticlines, Synclines, Monoclines
 
 
 
 

Continental Drift - continents are not fixed in one place, but have moved about through time....

- 1858 Antonio Snider-Pellagrini (France) - Creation and It's Mysteries Revealed - continents were together until the Great Flood separated them.
 

- 1885 Edward Suess - (Austria) - linked much of the geological evidence for a southern Supercontinent consisting of India, Antarctica, Australia, South Africa and South America (Gondwana).
 

- 1915 Alfred Wegener (German meteorologist, explorer) - published The Origin of the Continents and the Oceans
- established theory of continental drift
- named Pangaea as the supercontinent (Gondwana + Laurasia)
 

Other Supercontinent Names:
Laurentia: North America & Europe
Laurasia: North America, Europe, northern Asia

 Evidence supporting Continental Drift
1.  fit of the continents
2.  distinctive rock types on Gondwanan continents
3.  similarity of paleoclimatic conditions over much of the world, indicating past supercontinents
- distribution of coals containing Glossopteris (large seeds not transportable by wind across oceans)
- distribution of Mesosaurus, a fresh-water aquatic reptile
- distribution of warm water limestones (now at high latitudes, formerly where?)
- distribution of Permian evaporites (evidence of low latitude aridity)
- distribution of tillites
- Cenozoic mammalian faunas differ among the continents

*** Geophysicists (especially Harold Jeffries) said No! to Continental Drift.  It can't be done.  Period.  No mechanism. Phooey!  ***

Key Support for Drift: Paleomagnetism
What is Paleomagnetism? record of earth's magnetic field in the past.
- magnetism of earth is due to convection in the molten iron-nickel core
 

- igneous rocks freeze in a Remanent Magnetic Field when they cool.

- sedimentary rocks freeze in a very low strength magnetic field, especially in shales

- take rocks, measure this field in a sensitive room (magnetically shielded, kinda cool) to get the:
 - Declination (direction to the pole) and
 - Inclination (dip of the field), represents paleolatitude (low dips = low latitudes).
 
 
 

Paleomagicians, as we call them:  PALEOMAGNETISM = "NOT A SIMPLE GAME".
 
 

In the 1950's, geophysists found that paleomagnetism posed FOUR problems:
1)  rock magnetism didn't usually reflect the present earth's pole position (fig 7.7)
 

2)  rock magnetism was consistent within a continent, but not between continents (fig. 7.7)
 

3)  Magnetic reversals - flip flops in the earth's magnetic field direction (fig. 7.8)
 

4)  stripes of magnetic intensity on the sea floor (fig 7.10-7.11).

 Numbers 1 and 2 provided first geophysical support for Continental Drift.
 - either Poles had moved (#1),
 - or Continents had moved (#2).

Apparent Polar Wander (APW) Paths - path of a paleomagnetic pole through time.
- Why Apparent?
 

- Compare Europe & N.American APW.
 
 

- Conclusion?

 Sea Floor Spreading - Harry Hess, 1962.
- New ocean floor is created at mid-ocean ridges (show picture)
 
 
 
 
 
 
 

- continents move apart as on a conveyor belt away from the ridges

- amount of ocean floor is conserved :
=> produced at MOR - consumed at deep sea trenches.
 

- accounts for Benioff zones - dipping earthquake trends at deep sea trenches
 
 
 

- accounts for Ophiolite suites (to be continued)
 Ophiolites - suites of ultramafic-mafic igneous rocks and deep sea sediments - found in many mountain belts of the world.

Simple form: (from bottom to top)
Ultramafics => mafics => deep-sea sediments.
 
 
 

A Perfect Ophiolite Suite:
1.  Siliceous ooze and mud- radiolarians, diatoms, plus minor clay (eolian - wind storms)
2.  Calcareous ooze - forams, nannofossils
3.  Pillow basalts - erupted underwater
4.  "Sheeted" dikes - layer of nearly 100% dikes - no host rock left
5.  Massive gabbro - intrusive mafic rocks
6.  Olivine cumulates - fractional crystallization and gravity settling
7.  Mantle peridotite - olivine + pyroxene + garnet.

Where do Ophiolites Form?
 
 
 
 

 "Subduction Leads To Orogeny" (Five types of orogenies - not a comprehensive listing)
1)  Divergent boundaries
2)  Ocean-Ocean subduction
3)  Oceanic subduction beneath Continent
4)  Continent-continent collision
5)  Terrane Accretion - or Microplate tectonics
 

1)  Divergent boundaries - most start in continents (weaker) then evolve into oceanic divergence.
*** Maybe Do "Human Divergent Boundary" ***

A.  Continental divergence (Rift zones) - Extension
- Early: normal faults, basaltic volcanism, Basin & Range topography - Rio Grande Rift
- Middle: oceanic crust begins to be produced, continents separate - Red Sea
- Late: continental margins subside (thermal contraction) - Atlantic passive margins

B. Oceanic divergence: mid-ocean ridges with transform faults connect spreading segments
                       <= || => _______
                                                  <= || =>
 2)  Ocean-Ocean subduction - creates volcanic Island Arcs - Japan, Aleutians
- accretionary wedge - (or subduction complex)
 - composed of mélange: low-int grade metamorphics, blueschist facies, deep sea sediments, ophiolite fragments
 - blueschist rocks: only from High P, Low T metamorphism =>

- volcanic arc - andesitic and basaltic volcanism and plutonism
- back-arc spreading

3)  Oceanic subduction beneath Continent - ex. Andes.
- accretionary wedge - mélange
- continental arc - andesitic to felsic volcanism and plutonism
- Fold-Thrust Belt and Foreland basin (FTB-FB)
 - thrust faults and folds, provenance from FTB amd continental arc: detrital seds fill FBasin.

 4) Continent-continent collision - ex. Himalayas, Appalachians (Late Paleozoic).

- FTB-FB : provenance from M&P belt

- Metamorphic and Plutonic Belt
 - int to high grade, regional metamorphism
 - includes Suture Zone - ophiolites marking boundary between two continents.

- FTB-FB : provenance from M&P belt
 

5)  Terrane Accretion - "Microplate tectonics" - jigsaw puzzle model for building orogenic belts

- Terrane - a 3-D block of crust containing a distinctive assemblage of rocks.
- Displaced terrane is a terrane on oceanic lithosphere that travels the world until colliding with a continent at a subduction zone, where it slides around until it gets stuck (accretion).
- Suspect Terrane is a terrane, within an orogenic belt, bounded by strike slip faults.

- examples of Displaced Terranes:
 - continental - Madagascar, Seychelles, Britain
 - oceanic - Hawaii, Iceland, 90 East Ridge
- examples of Suspect Terranes:
 - western U.S. and Canada (Fig 15.28)
 

Wilson (Supercontinent) Cycles:
 Rift => Drift => Subduction => Collision
- supercontinents undergo cyclic plate behavior involving:

(1) Rifting apart
(2) Drifting with Sea Floor Spreading
(3) Subduction of ocean (closure)
 and ultimately
(4) Collision with another continent.