Plate tectonics

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

TYPES OF PLATE BOUNDARIES

1. Convergent 2. Divergent 3. Transform

PLATE BOUNDARIES

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

PLATE BOUNDARIES

Transform

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

PLATE BOUNDARIES For example off the coast of Washington

Convergent

Plates move toward each other -shallow, intermediate and deep earthquakes

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

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

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 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

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.

The interior of the Earth

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.

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.

Physical layering

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.