Lecture 3: Plate Tectonics Flashcards
1858: Snider – existence of a great region of *
1890: Edward Suess – *
1915: Alfred Wegener – * {Challenge: not able to provide the mechanism on how continents drifted apart}
dry land before the Great Flood
breakup of supercontinent; Gondwanaland
Continental drift
- – existence of a great region of dry land before the Great Flood
- – breakup of supercontinent; Gondwanaland
- – Continental drift
1858: Snider
1890: Edward Suess
1915: Alfred Wegener
Challenge for continental drift
{Challenge: not able to provide the mechanism on how continents drifted apart}
All lands
Pangaea
All water
Panthalassa
Pangaea Breakup:
Laurasia {}
Gondwanaland {}
(North America, Europe, Asia)
South America, Africa, India, Australia, Antarctica
Evidence for Continental drift
- Global geography
- Rock sequences
- Fossil
- Paleoclimate
Clue from global geography
Continental fit
Coastlines of Africa + South America
{Challenge: coastlines are constantly modified by erosion and deposition}
What did Edward Buller use?
– used continental shelf
Clues from Rock Sequences
Mountain Ranges Appalachian Mountains (N America), British Isles, Caledonian Mountains (Scandinavia)
remains, trace, imprints of organisms that have been preserved in the Earth’s crust for 10,000 years +
Fossils
Fossil Distribution
- Mesosaurus – aquatic reptile; eastern South America and South Western Africa
- Lystrosaurus – strictly land-dwelling reptile; (Africa, Antarctica, Inda)
- Glossopteris “fossil seed fern” – too large to be carried by wind (Africa, Australia, India, South America)
aquatic reptile; eastern South America and South Western Africa
Mesosaurus
strictly land-dwelling reptile; (Africa, Antarctica, Inda)
Lystrosaurus
too large to be carried by wind (Africa, Australia, India, South America)
Glossopteris “fossil seed fern”
Glacial deposits – SA. Africa, India, Australia {tropical countries = rocks related to glaciers}; Coal fields in the northern hemisphere
Southern continents are joined together and located near the South Pole (Antarctica, Arctic}
Paleoclimate
Glacial deposits in
SA. Africa, India, Australia
Proponent of seafloor spreading
Harry Hess
Place of continuous generation of oceanic crust;
Mid-oceanic ridge:
ridge crest
7 major plates
African Plate Indo-Australian Plate Antarctic Plate Eurasian Plate North American Plate Pacific Plate South American Plate
MINOR PLATES
Somali Plate · Nazca Plate Philippine Sea Plate · Arabian Plate Caribbean Plate · Cocos Plate Caroline Plate · Scotia Plate Burma Plate · New Hebrides Plate
Elaborate Plate Tectonics:
Continental drift + seafloor spreading
*Earth is composed of lithospheric plates
Further Evidence of Plate Tectonics
- Hotspots
- Paleomagnetism
- Seismic Activity
area of high temperature
*Examples: Hawaii, Emperor Seamount chain
Hot spots
Hawaii, Emperor Seamount chain
* interacts with *
*Pacific Plate interacts with Eurasia
form magnetic stripes depending on Earth’s polarity. Record magnetic mineral; generate oceanic lithosphere.
Paleomagnetism
– temperature at which a mineral’s magnetism is lost
Curie point
Curie point of Magnetite
585 C
- deep earthquakes –> trenches
* shallow earthquakes –> boundaries of plate
Seismic Activity
Divergent plate boundary
centers, margin, where?
{Spreading centers}
*Constructive margin
Mid-oceanic ridge
Process involving divergent plate boundary
*Magma upwelling –> Rifting Event –> produce body of water
Convergent plate boundary
margin, where?
Destructive margin
- subduction zones – trenches
- orogenic belts – mountain
O-C Convergence
Float:
Sink:
Product:
Float: C
Sink: O
Product: Continental volcanic arc, trench
O-O Convergence
Sink:
Product:
Sink: Denser, older, faster
Product: Island Arcs
C-C Convergence
Product:
Product: Mountains
Collision of * to * forming the Himalayas
What type of convergent boundary?
India, Eurasia
C-C
Transform
Define, Margin, Example
Two plates slide past each other
Conservative margin
San Andreas Fault; East Pacific Rise
Driving mechanism of Plate Tectonics
Plate-Mantle Convection,
Slab pull and ridge push
- is the underlying driving force for plate movement
* models
Convective flow
(Plate-Mantle Convection)
TWO LAYER MANTLE CONVECTION MODEL
WHOLE MANTLE CONVECTION MODEL
Results from the sinking of a cold, dense slab of lithosphere
Slab pull
Gravity driven force that results from the elevated position of the ridge
where
Ridge push
oceanic ridge
Philippine Tectonics
seismically active island arc origin
- Philippine Mobile Belt
aseismic continental origin
- Palawan Microcontinental Block
Oceanic-Oceanic Convergence
West and East
{West}
1. Manila Trench
2. Negros Trench
3. Sulu Trench
4. Cotobato Trench
{East}
1. East Luzon Trough
2. Philippine TrenchMarginal Basins
- West Philippine Sea
- Sulu Sea
- Celebes Sea
- Philippine Sea
Oceanic Bathymetric Highs (emerged, elevated sea floor)
- Scarborough Seamounts
2. Philippine Rise
Another distinct feature of Philippine Tectonics
Philippine Fault Zone
The concept of a floating lithosphere in gravitational equilibrium with the Earth’s asthenosphere such that the tectonic plates “float” at an elevation which depends on their thickness and density.
Isostasy
Isostasy is the concept of a * in gravitational * with the Earth’s * such that the tectonic plates “*” at an elevation which depends on their thickness and density.
floating lithosphere, equilibrium, asthenosphere
float
Isostasy is the concept of a floating lithosphere in gravitational equilibrium with the Earth’s asthenosphere such that the tectonic plates “float” at an elevation which depends on their *
thickness and density.
Mountains have “roots” which extend down into
the mantle. Thus, elevation is proportional to
the depth of the underlying “root”.
Airy-Heiskanen Model
Elevation is inversely proportional to density.
Thus, the higher the mountain, the lower is its
density; that is, light rocks “float” higher.
Pratt-Hayford Model
the lithosphere acts as an elastic plate and its
inherent rigidity distributes local topographic
loads over a broad region by bending.
Vening Meinesz/Flexural Model
Height is proportional to depth
Airy-Heiskanen
Elevation is inversely proportional to density
Pratt-Hayford
Weight of the load bends or flexes the lithosphere/asthenosphere
Vening Meinesz/Felxural Model
concept that explains a floating crust in a gravitational balance
Isostasy
