Plate Tectonics - The Engine That Drives the Rock Cycle

Jim MillerDept of Geological Sciences

Precambrian Research CenterUniversity of Minnesota-

Duluth

Geological Processes

Melting 2

Compaction &Cementation

Cooling &Crystallization

Tectonic Uplift

Erosion, Transportation& Deposition

Weathering

Melting 1

Subduction

Heat & Pressure

Precipitation

Earth Materials

SEDIMENTARYROCKS

MAGMA

VOLCANIC ROCKS

SEDIMENT

INTRUSIVEROCKS

METAMOPHICROCKS

SOIL

Rock Cycle

Basalt

Granite

Mafic

Quartz + Clay+Lithics

Felsic

Gabbro

Rhyolite

Clay+Lithics

GraywackeShale

Slate

Schist

GneissMigmatite

Qtz SandstoneLimestone

QuartziteMarble

Greenstone

Amphibolite

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

Chemical Layers

Physical Layers

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”

Lithospheric Mantle

Plate Tectonics drives 2 Stages of Crust-making1. Mantle partially melts to make ocean crust2. 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 BoundariesMid-ocean Ridges

Where Stage 1 Crust is Made

Youthful Oceanic Crust

200 100 0 Ma

Basalt – Rock Typeof the OceanicCrust

Remember:Melting the Mantle Makes Mafic Magma!! Always

Continental Rifting The creationof new ocean basins

Continental Rifting and

The Break-up of Pangea

Convergent Boundaries Making 2nd Stage Crust

Ancient Continental Crust

Convergent Boundaries- Where the Action Is!!

Ocean-Continent

Continent - Continent

Ocean - Ocean

Earthquakes

Volcanoes

Mt. St. HelensMay 18, 1980

Consequences of ConvergenceExplosive Volcanism

Consequences of ConvergenceMountain Building and Rock Deformation

Consequences of Convergence - Earthquakes

1326 Aftershocks

OROGENESISThe Culmination of Convergence

San Francisco EarthquakeApril 18, 1906 Mag 7.8

Transform BoundariesConnects other Boundaries

Mantle

Plumes

(Hotspots)Creation of

overthickened oceanic crust

Famous Hotspots

Hawaii

Yellowstone

Iceland

Plate Tectonics - The Engine That Drives the Rock Cycle

Use Illustrations

as Rock Cycle Story Starters