PLATE TECTONICS: PLATE BOUNDARIES

LAYERS OF THE EARTH 1.Crust (brown/tan) 2.Mantle (light & dark orange) 3.Core (yellow & white) 1.Crust (brown/tan) 2.Mantle (light & dark orange) 3.Core (yellow & white)

LAYERS OF THE EARTH Crust and upper mantle make up the LITHOSPHERE  rigid plates (OCEANIC & CONTINENTAL plates)  low temperature & pressure Crust and upper mantle make up the LITHOSPHERE  rigid plates (OCEANIC & CONTINENTAL plates)  low temperature & pressure Lithosphere { Beneath the lithosphere is the ASTHENOSPHERE  plastic” mantle (flows, moves the plates)  higher temperature & pressure Beneath the lithosphere is the ASTHENOSPHERE  plastic” mantle (flows, moves the plates)  higher temperature & pressure

PLATE TECTONICS the surface of the Earth is made of rigid plates  Size and position of plates can change over time  PLATE BOUNDARIES Edges of plates, where two plates “float” side-by-side, is where geologic activity takes place  Plates movement is from convection currents deep in the mantle  Size and position of plates can change over time  PLATE BOUNDARIES Edges of plates, where two plates “float” side-by-side, is where geologic activity takes place  Plates movement is from convection currents deep in the mantle

EARTH’S MAJOR PLATES: Pacific, N. American, S. American, African, Eurasian, Indian, Antarctic

CONVECTION CURRENTS MOVE THE PLATES

This continual movement (called convection currents) causes the crust to move in plate tectonics.

CONVECTION CURRENTS MOVE THE PLATES  Material in the mantle is heated by the radioactive core  it floats to the surface next to the crust  as it cools, it moves back down towards the core  Material in the mantle is heated by the radioactive core  it floats to the surface next to the crust  as it cools, it moves back down towards the core 7c Movement of matter among reservoirs is driven by Earth’s internal and external sources of energy

PLATE BOUNDARIES Divergent boundaries  plates move apart Convergent boundaries  plates move together Transform boundaries plates slide past 

DIVERGENT BOUNDARIES Make new crust When two plates move apart and magma surfaces forming NEW crust (usually oceanic) continental rift zones (landmass splits into two or more segments) mid-ocean ridges (sea-floor is elevated)

DIVERGENT BOUNDARIES Make new crust Rift valley continent-continent

DIVERGENT BOUNDARIES Make new crust: Sea Floor Spreading Youngest rocks form at ridge Older rocks are further from ridge Oldest rocks are located at subduction zones

DIVERGENT BOUNDARIES Make new crust: Sea Floor Spreading  As magma rises and cools, iron and magnesium minerals align themselves to the Earth’s magnetic field  “Magnetic Stripes” are formed  The Earth’s magnetic field reverses polarity  Magnetic stripes are mirrored on each side of the mid-ocean ridge  As magma rises and cools, iron and magnesium minerals align themselves to the Earth’s magnetic field  “Magnetic Stripes” are formed  The Earth’s magnetic field reverses polarity  Magnetic stripes are mirrored on each side of the mid-ocean ridge Every ~20,000 years the polarity of the Earth changes. This is change is reflected in the rocks, whose polarity is fixed once the magma is cooled.

CONVERGENT BOUNDARIES plates colliding  Destroys old crust and forms new mountains  Three types of convergent boundaries  Destroys old crust and forms new mountains  Three types of convergent boundaries

CONVERGENT BOUNDARIES plates colliding Continent-continent convergence: Folded mountains Continent-continent convergence: Folded mountains Ex Himalayas Eurasian/Indian plates

CONVERGENT BOUNDARIES plates colliding: Subduction Zones Subduction Zones: where ocean plates slide under another plate Creates magma which moves upward, pushing up the land above it. Magma/lava solidifies into intrusive/extrusive igneous rock Heat from the magma can change the rock around it. Rock that recrystallizes without melting becomes metamorphic rock.. Denser oceanic plates always subduct beneath less dense continental plates

CONVERGENT BOUNDARIES plates colliding Ocean-continent convergence: Trench & Coastal Volcanoes Ocean-continent convergence: Trench & Coastal Volcanoes Andes Mountains Nazca & S.American plates

CONVERGENT BOUNDARIES plates colliding Ocean-ocean convergence: Trench & Island arc Ocean-ocean convergence: Trench & Island arc

TRANSFORM BOUNDARIES When two plates slide past each other  no tearing or crushing - no damage occurs to the lithosphere  Faults –San Andreas Fault  Cause most earthquake damage  no tearing or crushing - no damage occurs to the lithosphere  Faults –San Andreas Fault  Cause most earthquake damage

Summary of Plate Movements Convection currents