PLATE TECTONICS

2 Theories for the Structure of the Earth’s Lithosphere

Lithosphere = Crust plus upper mantle

1. Continental Drift - Continents “float” on the mantle, and occasionally collide.
1. Jigsaw Fit
2. Lithologic Continuity
3. Faunal Continuity
4. Paleoclimatic Continuity


2. Plate Tectonics
5. Polar wandering curves
6. Symmetry in oceanic rock age and magnetism.


PLATE TECTONIC BOUNDARIES

1. Convergent Boundaries (Destructive)
A. Ocean-Ocean = Trench, Subduction Zones, volcanic island arcs,

Trench = Deep undersea valley formed with subduction zones

Subduction zones = Places where oceanic crust is sinking beneath another plate, eventually remelting causing volcanism.

Volcanic Island arcs - areas near subduction zones where remelted magma forms island volcanoes

B. Ocean-Continent = Trench, Subduction Zones, volcanic arc, fold belts

C. Continent-Continent= Orogenic (mountain-building) fold belts

2. Divergent Boundaries (Constructive)

A. Mid-Ocean Ridge - Place where new ocean floor is being produced
B. Rift Valley - area on continental plates where extension is occurring
C. Failed Arm (Aulacogen) - weakened crust from extension subsides forming a arge basin for sediments to be deposited




The three types are often found in combinations of the three types, in a structure called a triple junction.













3. Transform Boundaries (Conservative)
- plates are neither created nor destroyed

Transform faults ~ a strike-slip fault at a plate boundary


Hot Spots - a stationary plume of magma in the middle of a plate causing a volcanic island arc. e.g. Hawaii Islands