Plate Tectonics - The Engine That Drives the Rock Cycle
Jim Miller
Dept of Geological Sciences
Precambrian Research Center
University of MinnesotaDuluth
Earth
Materials
Geological
Processes
SEDIMENTARY
ROCKS
Melting 2
MAGMA
Compaction &
Cementation
Cooling &
Crystallization
VOLCANIC
ROCKS
Tectonic
Uplift
SEDIMENT
Erosion,
Transportation
& Deposition
INTRUSIVE
ROCKS
Weathering
Melting 1
METAMOPHIC
ROCKS
SOIL
Subduction
Heat &
Pressure
Precipitation
Rock Cycle
Limestone
Qtz Sandstone
Graywacke
Shale
Quartzite
Slate Marble
Quartz + Clay+Lithics
Clay+Lithics
Basalt
Rhyolite
Greenstone
Gabbro
Granite
Amphibolite
Felsic
Mafic
Schist
Migmatite
Gneiss
Overview of Plate Tectonics
Jim Miller
Plate Tectonic Theory
The Earth’s outer shell (lithosphere) is composed of rigid plates
that are moving relative to one another.
Physical and Chemical Structure of the Earth
Lithospheric Mantle
Compositional Components
of the Lithosphere
Continental Crust – ~62% SiO2, low
density rocks , “felsic”
Oceanic Crust - ~ 48% SiO2, high
density rocks , “mafic”
Lithospheric Mantle - ~ 40% SiO2,
very high density rocks , “ultramafic”
Chemical
Layers
Physical
Layers
Plate Tectonics drives 2 Stages of Crust-making
1. Mantle partially melts to make ocean crust
2. Ocean crust melts to make continental crust
What moves the Plates?
Slab Pull - densification of
subducted plate pulls the
plate into the mantle
Mantle Push - Upwelling of
the asthenospheric mantle
pushes the plates apart
Ridge Slide – Thermal
upwelling at ridges causes
plates to separate by sliding
downhill (by gravity)
Problem - we are not sure how the mantle
is structured.
Types of Plate Boundaries
Divergent Plate Boundaries
Mid-ocean Ridges
Where Stage 1 Crust is Made
Youthful Oceanic Crust
200
100
0 Ma
Basalt –
Rock Type
of the
Oceanic
Crust
Remember:
Melting the Mantle
Makes Mafic Magma!!
Always
Continental
Rifting
The creation
of new ocean
basins
Continental Rifting
and
The Break-up
of Pangea
Convergent Boundaries
Making 2nd Stage Crust
Ancient
Continental
Crust
Convergent BoundariesWhere the Action Is!!
Ocean - Ocean
Earthquakes
OceanContinent
Volcanoes
Continent - Continent
Consequences of Convergence
Explosive Volcanism
Mt. St. Helens
May 18, 1980
Consequences of Convergence
Mountain Building and
Rock Deformation
Consequences of Convergence - Earthquakes
1326 Aftershocks
OROGENESIS
The Culmination
of Convergence
Transform
Boundaries
Connects other
Boundaries
San Francisco Earthquake
April 18, 1906 Mag 7.8
Mantle
Plumes
(Hotspots)
Creation of
overthickened
oceanic crust
Famous Hotspots
Yellowstone
Hawaii
Iceland
Plate Tectonics - The Engine That Drives the Rock Cycle
Use
Illustrations
as Rock Cycle
Story Starters