Austin Mills6th Period

Mrs. Turner

Plate Tectonics

Continental Drift

• Wegner’s Theory - hypothesized that the continents were slowly drifting around the Earth

• Evidence - There are different continents now, which we’re connected in Pangaea, also fossil evidence on continents being similar to other continents

• Problems – Geophysicist argued the ocean floor was not strong enough to hold the continents

Supercontinent Theory

• Supercontinent Cycle - geologic cycle in which the Earth's continents alternatively merge into a single supercontinent

• Pangaea and Panthalassa – Pangaea was the Supercontinent, and Panthalassa was the surrounding ocean

• Accretion - process by which water vapor in clouds forms water droplets

Supercontinent Theory Continued

• Rifting - linear zone where the Earth's crust and lithosphere are being pulled apart

• Plate Movement Affecting Climate – By changing Ocean Currents– Example

• Japan’s Coastline moving 13 feet

Theory of Plate Tectonics

• Lithosphere – comprises of the crust and the portion of the upper mantle

• Asthenosphere - comprises the crust and the portion of the upper mantle

• How Plates Move – Convection moves the plates around

• Three Types of Plate Boundaries - Divergent boundaries; Convergent boundaries; and Transform boundaries

Theory of Plate Tectonics Cont.

• Isostasty - Equilibrium in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses

• Isostatic Adjustment – Earth can move up or down

• Stress – Produces the Earthquakes and Volcanoes

Divergent Boundary• Sea Floor Spreading - extend the crust in a

direction perpendicular to the fault trace.• Landforms – Mid-Ocean Ridges - Equilibrium

in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses– Example – Off South America Coast in Pacific

Ocean

Paleomagnetism

• Magnetic Reversals - North pole is transformed into a South pole and the South pole becomes a North pole.

• Magnetic Symmetry - presence of identical parallel lines on each side of the Mid-Atlantic Ridge

Normal Faults

• Normal Faults - Extend the crust in a direction perpendicular to the fault trace.

• Related Landforms – Landforms with perfect faults in them where the plates are joining– Example – Great Rift Valley

Convergent BoundarySubduction Zones

• Continental & Oceanic Crust - Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental.

• Mt Fuji – Japan• Mt. Osorno

• Magma - mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth.

• 3 Conditions magma forms– 1. Decrease in Pressure 2. Increase in Pressure 3. increase in the amount of water in the

asthenosphere

Volcanoes

• Lava - molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling

• Volcano - opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber.– Common Locations – Where Tectonic Plates smash

into eachother.– Pacific Ring of Fire – Ring of active volcanoes

encircling the Pacific Ocean

Pyroclastic Material

• a cloud of ash, lava fragments carried through the air, and vapor.– Viscosity - measure of the resistance of a fluid

which is being deformed by either shear stress or tensile stress.

– How magma contents produce explosive eruptions• Explosive eruption occurs, from the magma building up

inside, until it fills so much it finally explodes from being under pressure.

Types of Volcanoes• Shield - usually built almost entirely of fluid lava

flows. They are named for their large size and low profile

• Cinder Cones - bowl-shaped crater at the summit and only grow to about a thousand feet.

• Composite - crater at the summit which contains a central vent or a clustered group of vents.

• Caldera - most powerful and catastrophic types of volcanoes in a category by themselves.

Oceanic & Oceanic Crust

• Outermost layer of Earth's lithosphere that is found under the oceans and formed at spreading centers on oceanic ridges

Landforms Produced

• Pacific Ocean

Collision Zones

• Continental & Continental crust - When two oceanic plates collide, the younger of the two plates, because it is less dense, it will ride over the edge of the older plate.

• Compression and uplift – Plates compressing and uplifting from one another

• Landforms Produced– Himalayas– Cape Fold Mountains

Transform Boundary

• Reverse Faults - Convergent zones are thrust or reverse faults, and divergent zones are normal faults

• Strike-slip Faults - Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally.

• Tension - two plates move against each other, building up tension, then releasing the tension

• Sheer Stress - Shear stress causes two planes of material to slide past each other. This is the most common stress found at transform plate boundaries.

• Related Landforms– Fault Block Mountains

• Pennsylvania Appalachians• Utah

– Grabens• Owens Valley

Earthquakes

• Elastic Rebound - The release of strain energy by the abrupt movement of a fault with a resultant earthquake.

• Seismology - branch of science concerned with earthquakes and related phenomena– Seismograph - instrument that measures and records

details of earthquakes, such as force and duration.• Focus – The focus of an earthquake is the point in

the earth where the earthquake rupture or fault movement actually occurred.

• Epicenter -point on the earth's surface vertically above the hypocenter

• Seismic Waves - waves of energy that travel through the core of the earth or other elastic bodies– Body Waves - waves of energy that travel through

the core of the earth or other elastic bodies• Example : Longitudinal or Compression Waves

• P Waves - move through material by squeezing and stretching the material in the same direction as the wave – Example – Compressional Waves

• S Waves - moves as a shear or transverse wave, so motion is perpendicular to the direction of wave propagation– Example- Shear Waves

• Surface Waves - a seismic wave that is trapped near the surface of the earth.– Ex. – Any wave trapped at the surface

• Earthquakes not from movement wat plate boundaries - An intraplate earthquake is an earthquake that occurs in the interior of a tectonic plate, whereas an interplate earthquake is one that occurs at a plate boundary. – Ex. Missouri & Tennessee

Magnitude

• The magnitude is a number that characterizes the relative size of an earthquake.– Example – Measuring on Richter’s Scale.

Intensity• The intensity is a number (written as a Roman

numeral) describing the severity of an earthquake in terms of its effects on the earth's surface– The Mercalli intensity scale is a seismic scale

used for measuring the intensity of an earthquake.

Tsunami

• series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake– Ex. Japan March, 2011

Other Related Landforms

• Hot Spots– Hawaii

• Dome Mountains – Castle Dome Mountains– Black Dome Mountain