Earth History GEOL 2110 Theory of Plate Tectonics Part 2: Elements of Plate Tectonics

Major Concepts Plate Tectonic theory posits that the earth outer layer (lithosphere) is composed of rigid plates that are moving relative to each other; Plates are composed of either thin oceanic crust or thick continental crust overlying upper mantle Plate boundaries that are diverging are where new oceanic crust is being created as the mantle upwells, decompresses and partially melts. Plate boundaries that are converging involve one oceanic crust plate subducting beneath another or a continental edge. This triggers earthquakes and explosive volcanism resulting from partial melting of a hydrated mantle wedge Orogensis occurs when continental crust encounters continental crust

Plate Tectonic Theory The Earth’s outer shell (lithosphere) is composed of rigid plates that are moving relative to one another.

Internal Structure of the Earth Compositional Layers Physical Layers

Plate Tectonics Drives Two Stages Crust-making A. Mantle partially melts to make ocean crust B. Ocean crust partially melts to make continental crust

What Moves the Plates? Mantle Push Ridge Slide SlabPull

Types of Plate Boundaries

Divergent Plate Boundaries Mid-ocean Ridges Where Stage 1 Crust is Made

Basalt Rock Type of the Ocean Crust Pillow Lavas Remember: Melting the mantle makes mafic magma!! Always

Hydrothermal Alteration of Ocean Crust Preparing it for Stage 2 Melting “Black Smokers”- metal-rich hydrothermal waters venting into the ocean floor

Continental Rifting The creation of new ocean basins

Continental Rifting and The Break-up of Pangea

Age of the Atlantic Ocean Crust Recording the Break-up Beginning the Break-up 225 Ma

Youthful Oceanic Crust

Convergent Boundaries Making 2 nd Stage Crust AncientContinentalCrust

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 Banda Ache, Dec. 26, 2004

OROGENESIS The Culmination of Convergence

Ancient Orogens Looking into the Roots of Mountain Belts Penokean Orogen St. CloudJay Cooke

Transform Fault Plate Boundaries

San Francisco Earthquake April 18, 1906 Mag 7.8 The San Andreas Fault

MantlePlumes/Hotspots

Mantle Hotspots in the Oceans Sites of overthickene d crust and the formation of ocean islands and plateaus

Famous Hotspots Hawaii Yellowstone Iceland

Sedimentary Basins and Plate Tectonics Evolution of Sedimentation during Arc-Continent Collision

The Grand Unifying Theory of the Earth

FRIDAY Midterm Exam 1 Chapters 1 to 7