TYPES OF PLATE BOUNDARIES 1. Convergent 2. Divergent 3. Transform Plate tectonics

TYPES OF PLATE BOUNDARIES 1. Convergent 2. Divergent 3. Transform

Divergent  Plates move apart and new crust is formed   Heat from below rises  Under ridges, underlying rock melts, comes to surface and creates new crust  Mid-ocean ridges are long chains of volcanoes  Locations of shallow earthquakes PLATE BOUNDARIES

Divergent Sea-floor spreading (i.e. Atlantic ocean) at Mid-Ocean Ridges PLATE BOUNDARIES

Divergent On Continents: Continental rifting (i.e. African and Arabian plates to form Red Sea) Animation 1. sea floor spreading PLATE BOUNDARIES

Divergent On Continents: Continental rifting (i.e. African and Arabian plates to form Red Sea) PLATE BOUNDARIES

Divergent On Continents: Continental rifting (i.e. African and Arabian plates to form Red Sea) PLATE BOUNDARIES

Divergent Age of Ocean floor increases away from divergent boundary PLATE BOUNDARIES

Transform Plates move past each other (i.e. San Andreas fault) Ocean floor transform faults Evidence shallow earthquakes no volcanoes Geodetic rates across faults PLATE BOUNDARIES

Transform Plates move past each other (i.e. San Andreas fault) -shallow earthquakes -no volcanoes PLATE BOUNDARIES

Convergent Plates move toward each other -shallow, intermediate and deep earthquakes For example off the coast of Washington PLATE BOUNDARIES

Convergent a. Ocean & Continent (Juan de Fuca & N America) Ocean crust more dense compared to continental crust dives under continents Deep trenches created where the plates dive under continents Large earthquakes Volcanoes over the subducting slab on the overriding plate PLATE BOUNDARIES

Pacific-North America plate boundary 1) Convergent boundary in PNW 2) Divergent boundary between Juan de Fuca & Pacific plates 3) Transform boundary in California 4) Divergent boundary between Baja California and mainland Mexico

Convergent b. Ocean & Ocean (off the coast of the Aleutian Islands in Alaska) -denser plate subducts -deep trench -volcanoes created on overlying plate = island arcs PLATE BOUNDARIES

Convergent b. Ocean & Ocean (off the coast of the Aleutian Islands in Alaska) -denser plate subducts -deep trench -volcanoes created on overlying plate = island arcs PLATE BOUNDARIES

Convergent c. Continent & Continent— Thick and low density so neither subducts Collide into each other and create mountains Indian Plate collides into Eurasian Plate = Himalayas, PLATE BOUNDARIES

Convergent c. Continent & Continent— -Both quite thick and low density so neither subducts -They colide into each other and create mountains PLATE BOUNDARIES

TYPES OF PLATE BOUNDARIES 3 plate boundaries Divergent Transform Convergent continent-ocean ocean-ocean continent-continent

Need name, date and class. Neat handwriting Question of the week: Name the three types of plate boundaries.

The interior of the Earth The Earth’s crust The crust is relatively light & brittle. Most earthquakes occur within the crust.

The interior of the Earth Continental crust 1) Composed of mostly granitic rocks (high Si rocks) 2) These rocks are rich in quartz & feldspar 3) Continental rocks are relatively light & buoyant.

Oceanic crust 1) Composed of mostly basaltic rocks 2) These rocks are rich in feldspar & pyroxene 3) Oceanic rocks are heavier and less buoyant than crustal rocks. The interior of the Earth

Mantle 1) Located beneath the crust 2) Dense silicate rocks 3) More iron, magnesium, and calcium than the crust 1) Hotter and denser because temperature and pressure inside the Earth increase with depth 2) Solid on and strong on short- time scales 3) Convecting on long time- scales The interior of the Earth

Earth’s core The Earth's core consists of two parts: 1) 2,200 km-thick liquid outer core and 2) 1,250 km-thick solid inner core. As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field. The interior of the Earth

Summary Compositional layering Core: high density, iron and nickel. Mantle: medium density (3.3 g/cm 3, iron and magnesium plus silicon and oxygen-based rocks Crust: a) denser oceanic crust (3.0 g/cm 3 b) less dense continental crust (2.7 g/cm3) Contains silicon and oxygen-based rocks

Physical layering Defined by physical properties or rheology. The increase in temperature and pressure with depth affects the material physical properties The mechanical behavior of earth material may behave like: 1) brittle solid or 2) deform like putty or 3) melt to become a liquid.

1. Inner Core (core) radius 1216 km solid 2. Outer Core (core) 2270 km liquid 3. Lower Mantle (mantle) 2240 km rigid layer 4. Asthenosphere (upper mantle) 660 km soft, weak layer (silly putty) top is actually slightly melted, Asthenosphere is mechanically detached from the lithosphere Physical layering

5. Lithosphere Crust and uppermost mantle ~100 km thick, ranges from a few km up to ~400 km Thicker under continents Thinner under oceans, very thin at mid-ocean ridges Rigid layer, not connected below so can move. Physical layering

III. Internal Heat of the Earth A. Why is the Earth hot? 1.Initially hot from its formation, heat still being released compression  heat kinetic (moving) energy  thermal energy (heat) 2. Radioactive Decay— releases heat as radioactive substances “used up” Plate tectonics - Why?

B. Heat Transfer—Loss of heat from the Earth 1.Conduction—heat transfer through an object from atom to atom. -atoms become excited by heat and vibrate -then they collide with neighboring atoms sending them into motion Rocks are generally poor conductors of heat, so not a significant source of heat loss in the earth

2. Convection : movement of heat from place to place by a flowing medium -soup example—soup at bottom near flame heats up first -as it heats, its expands— becomes less dense and rises -at the surface it encountered cold air, it cools off (more dense) -then sinks back down *Unequal distribution of heat within Earth--convection cells created, heat rises under ridges, melts rock, creates new crust/lithosphere which moves away from ridges and cools and eventually subducts back into the mantle

3. Radiation— objects lose heat to their surroundings -heat from Earth radiates into the atmosphere -not significant for inside Earth Plate tectonics

Relative abundances of elements in the whole Earth and the Earth’s crust. 90% of the earth consists of only four elements. –Iron –Oxygen –Silicon –Magnesium 80% of the crust consists of: –Oxygen –Silicon –Aluminum

Compositional layering Core: high density, iron and nickel. Mantle: medium density (3.3 g/cm 3, iron and magnesium plus silicon and oxygen-based rocks Crust: a) denser oceanic crust (3.0 g/cm 3 b) less dense continental crust (2.7 g/cm3) Contains silicon and oxygen-based rocks