plate tectonics. plate tectonics is a theory that describes the formation, movements, and...
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Plate TectonicsPlate Tectonics
Plate TectonicsPlate Tectonics is a is a theory that describes theory that describes
the formation, the formation, movements, and movements, and
interactions of Earth’s interactions of Earth’s plates.plates.
Alfred Wegener, a Alfred Wegener, a German meteorologist, German meteorologist, proposed a hypothesis proposed a hypothesis called called Continental DriftContinental Drift
in 1912.in 1912.
Continental DriftContinental Drift supposed that the supposed that the
continents have moved, continents have moved, or drifted, from one or drifted, from one
location to another over location to another over long periodslong periods of time. of time.
Continental DriftContinental Drift supposed that the supposed that the continents have continents have
moved, or driftedmoved, or drifted, from , from one location to another one location to another
over long periodsover long periods of of time.time.
Wegener based his idea Wegener based his idea on the following on the following observations:observations:
The continents had similar shapes.
The same fossils were found in South America and Africa.
Similar rock formations were found in South America and Africa.
Climate Change: Areas once covered in glaciers are now in warmer climate zones.
Wegener’s idea could not explain how the continents moved.
The Theory of Plate Tectonics suggests that the continents are part of the
lithospheric plates.
Evidence for this:
Volcano, Earthquake, and Mountain Belts are located
along plate boundaries.
The ocean floor gets older away from a mid-ocean
ridge.
The rock record shows that the magnetic field of the
Earth has reversed many times.
Types of Plate Boundaries
Divergent Boundary
Rift Valleys and Mid-Ocean Ridges
Convergent Boundary
Deep Sea Trenches, Subduction Zones, and Mountain Ranges
Convergent (2 Types)
Convergent Subduction
More Dense (Oceanic Crust)
Less Dense (Continental or Oceanic Crust)
Convergent Collision
Equal Density Continental Crust
Transform (Strike-Slip) Boundary
San Andreas FaultDivision between North American
and Pacific Plates
San Andreas FaultDivision between North American
and Pacific Plates
North American Plate
Pacific Plate
Pacifi
c Pl
ate
North
Am
erican
Pla
te
Types of Plate Boundaries
Causes of Plate Causes of Plate MovementMovement
3 Hypotheses3 HypothesesMantle ConvectionMantle Convection
Ridge PushRidge PushSlab PullSlab Pull
Mantle Convection: The mantle moves Mantle Convection: The mantle moves the plates along as it convects (heats the plates along as it convects (heats
from below). Mantle Convection from below). Mantle Convection Animation #2Animation #2
Ridge PushRidge Push: The : The accumulating magma at a accumulating magma at a mid-ocean ridge “pushes” mid-ocean ridge “pushes”
material away.material away.
Slab PullSlab Pull: When a plate : When a plate subducts, it pulls the rest of subducts, it pulls the rest of
the plate with it.the plate with it.