Plate Tectonics - The Engine That Drives the Rock Cycle Jim Miller Dept of Geological Sciences Precambrian Research Center University 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 SEDIMENTARY ROCKS MAGMA VOLCANIC ROCKS SEDIMENT INTRUSIVE ROCKS METAMOPHIC ROCKS SOIL

Rock Cycle Basalt Granite Mafic Quartz + Clay+Lithics Felsic Gabbro Rhyolite Clay+Lithics Graywacke Shale Slate Schist Gneiss Migmatite Qtz Sandstone Limestone Quartzite Marble 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 Lithosphere Compositional Components of the Lithosphere Continental Crust – ~62% SiO 2, low density rocks, “felsic” Oceanic Crust - ~ 48% SiO 2, high density rocks, “mafic” Lithospheric Mantle - ~ 40% SiO 2, very high density rocks, “ultramafic” Lithospheric Mantle

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 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 2 nd Stage Crust Ancient Continental Crust

Convergent Boundaries- Where the Action Is!! Ocean- Continent Continent - Continent Ocean - Ocean Earthquakes Volcanoes

Mt. St. Helens May 18, 1980 Consequences of Convergence Explosive Volcanism

Consequences of Convergence Mountain Building and Rock Deformation

Consequences of Convergence - Earthquakes 1326 Aftershocks

OROGENESIS The Culmination of Convergence

San Francisco Earthquake April 18, 1906 Mag 7.8 Transform Boundaries Connects 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