Tectonic Plates

By: Andrew ThomasEarth Systems

5th

Wegner’s theory of Continental Drift & the Supercontinent Theory

Wegner’s Theory explains: Stated that Earth's continents were once joined in a single landmass and gradually moved or drifted apart. i.e. Pangaea

Evidence of Wegener’s Theory He provided evidence that the same

fossils and plants are evident on all continents before being separated; Many people during his time didn't believe him. Just after his death in 1930 did people begin to accept the theory of continental drift.

Supercontinent theory

Describes the quasi-periodic aggregation and dispersal of Earth’s Continental crust. There are varying opinions as to whether the amount of continental crust is increasing, decreasing, or staying about the same, but it is agreed that the Earth's crust is constantly being reconfigured. One complete supercontinent cycle is said to take 300 to 500 million years.

Pangaea & Panthalassa

Pangaea- Was a supercontinent that existed during the late Paleozoic and early Mesozoic eras, forming about 300 million years ago

Panthalassa- A.K.A. Panthalassic Ocean was the vast global ocean surrounding Pangaea during the Mesozoic and Paleozoic

Accretion A process by which material is added to a

tectonic plate or a landmass Examples of the material would be either

sediment or igneous such as volcanic arcs, seamounts.

Continental Rifting (Rifting)

Continental rifts are locations of continental crustal divergence, crustal thinning, sedimentary basin formation, and often thermal and igneous activity. As indicated, they are diverse, complex and polygenetic. Continental crust can only be thinned so far and at some point and in some way seafloor spreading takes over.

How plate movements alter climate and evolution

Climate: Plate tectonics gives the basic setting for Earth's climate.  The only effect that plate tectonics has on climate is through volcanic emissions; Radioactivity in the Earth’s mantle moving the crustal plates on the surface. For example the

Evolution: When plate tectonics shift, the animals above the tectonic plates also shift causing them have to adapt to wherever they are taken. Sometimes destroying species.

Theory of Plate Tectonics

The Lithosphere The rigid outermost shell on Earth  It comprises the crust and the portion

of the upper mantle 

The Asthenosphere The highly viscous and mechanically

weak region Comprises of the upper mantle of the

Earth

How do plates move? Convection of heat causes the

movement of lithospheric plates. Although plate movements do occur

because of when the Asthenosphere heats there is enough Lithostatic pressure to prevent it’s melting.

3 types of plate boundaries Convergent boundaries Divergent boundaries Transform boundaries

Isostasy Equilibrium in the Earth’s crust such

that the forces tending to elevate landmasses balance the forces tending to depress landmasses.

Isostatic adjustments (Glacial Isostatic Adjustments)

The rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period

Via Isostasy

Stress A.K.A. Tension. Refers to a stress which

stretches rocks in two opposite directions

In relative it is also found in tectonic regions of divergent boundaries

DIVERGENT BOUNDARY

SEA-FLOOR SPREADING A process that occurs at mid-ocean ridges,

where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

For example a Mid-ocean ridge; The Juan de Fuca Ridge is a tectonic spreading center off the coast of Washington State. The Explorer Ridge is a divergent tectonic plate boundary located about 241 km west of Vancouver Island, British Columbia, Canada

PALEOMAGNETISMThe study of the record of the Earth's

magnetic field in rocks

Magnetic Reversals: Is the change in the Earth’s magnetic field such that the positions of magnetic north and magnetic south are interchanged

Magnetic Symmetry: Puzzling magnetic patterns in the sea-floor

NORMAL FAULTSA normal fault occurs when the

crust is extended, can also be called an extensional fault.

Wasatch Fault is an example of a normal fault

Sierra Nevada Fault is also an example of a normal fault

Convergent PlateBoundary

Subduction Zones

Volcanoes

Magma

A mixture of Molten Rock that is found beneath the surface of the Earth

Conditions of Magma Formation

An increase in temperature can cause materials in the asthenosphere to melt. Such as the increase that occurs at a hot-spot.

Lava

Refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling

Volcano

An opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface.

Common Locations

• Nazca Plate• Eurasian Plate• Pacific Ring of Fire*• North American Plate• Pacific Plate• Arabian Plate

• *DENOTES MOST ACTIVE LOCATION FOR VOLCANOES

Major zone of Volcanoes in the Pacific

Is called the Pacific “Ring of Fire”, where a large number of Earthquakes and Volcanic eruptions in the Pacific

Horseshoe shape 452 volcanoes in total and 90% of the World’s

earthquakes occur in the Pacific Ring of Fire

Pyroclastic Material

Solid fragments of rock ejected during a volcanic eruption

Viscosity of Pyroclastic Material

It is likely to form at a high viscosity according to history as studies on a volcano in Japan at Mount Unzen show

How magma contents produce explosive eruptions

Because felsic magma has a higher gas content than mafic magma

Types of Volcanoes

ShieldCinder ConeComposite

Shield volcano

A type of volcano usually built almost entirely of fluid lava flows.

They are named for their large size and low visibility, resembling a battle shield

Ex: is Puʻu ʻŌʻō on Kīlauea, in Hawaii. Also the Snake River in Idaho and the Columbia River in Washington and Oregon

Cinder Cone volcano

Cinder cone volcanoes are the most common kind of volcanoes.

They are steep sided cones of basaltic fragments and are smaller and simpler than composite volcanoes.

Streaming gases carry liquid lava blobs into the atmosphere that fall back to earth around a single vent to form the cone.

Ex: Paricutin in Mexico and in Iceland, Surter I.

Composite Volcano

A tall, conical volcano built up by many layers of hardened lava, pumice, and volcanic ash.

Unlike shield volcanoes, Composite volcanoes are characterized by a steep profile and periodic explosive eruptions and quiet eruptions.

The lava that flows from Composite volcanoes typically cools and hardens before spreading far due to high viscosity.

The magma forming this lava is (most of the time) felsic

Ex: Mount Fuji in Japan, Mount Tavurvur in Papau New Guinea

Caldera

Comes from the latin root word Caldaria, literally means “cooking pot”, because of it’s positioning on the volcano.

Ex: Mount Fogo, Cape Verde. Off the coast of Africa. Mount Pinatubo, Phillipines

Animated Representation of Calderas’

Continental Crust

The layer of igneous, sedimentary, and metamorphic rocks which forms the continents and the areas of shallow seabed close to their shores

Oceanic Crust

Is the part of Earth's lithosphere that surfaces in the ocean basins

Composed of Mafic rock

Types of Oceanic Crust

Trenches and Undersea Mountains

Types of Continental Crust

Normal Faults and Mid-ocean ridges

Collision Zones

A phenomenon of the plate tectonics of Earth that occurs at convergent boundaries where the subduction zone is destroyed, mountains produced, and two continents push together

Compression & (Tectonic) Uplift

Uplift is a geological process often caused by plate tectonics

Landforms Produced

Folded Mountains, Plateaus, Dome Mountains. Plateau:  is an area of highland, usually consisting of

relatively flat terrain. Folded Mountains: When one or a stack of originally flat

and planar surfaces, such as sedimentary, are bent or curved as a result of permanent deformation

Dome Mountains: A deformational feature consisting of symmetrically-dipping anticlines

Types of Folded Mountains: Anticline, Syncline, Antiform, Synform, Dome, Basin, etc.

Types of Dome Mountains: Anticline, Basin, Granite Dome, Petroleum Reservoir, Resurgent Dome, Salt Dome

Types of Plateaus: Tibetan Plateau, Antarctic Plateau, Columbia Plateau. Are some of the most iconic

Plateaus Example (Mt. Roraima, Venezuela)

Folded Mountains Example (Mt. Zagros, Iran)

Dome Mountains Example ( Navajo Mountains, Utah)

Transform Boundary

EARTHQUAKES

ELASTIC REBOUND

An explanation for how energy is spread during earthquakes. As rocks on opposite sides of a fault are subjected to force and shift

SEISMOLOGY

The scientific study of earthquakes and the

propagation of elastic waves through the Earth

or through other planet-like bodies

Seismograph- Are instruments that measure

motions in the ground, including those of

seismic waves generated by earthquakes,

volcanic eruptions, and other seismic sources.

FOCUS

The location within Earth along a fault at which the

first motion of an earthquake occurs

EPICENTER

The point on the Earth’s surface that is directly

above the hypocenter or focus, the point where an

earthquake originates

SEISMIC WAVES

Waves of energy that travel through the Earth, and

are a result of an earthquake, explosion, or a

volcano.

BODY WAVES

Waves that travel through Earth’s

interior

TYPES OF BODY WAVES

P (Primary) waves- Compressional waves that

travel faster than any other waves through the

earth, hence the name “Primary”; Longitudinal

S (Secondary) waves- Shear waves that arrive

at seismograph stations after the faster moving

P waves during an earthquake; Transverse

SURFACE WAVES

Seismic waves that travel along the surface of the

Earth

TYPES OF SURFACE WAVES

L(Love) waves- Named after A. E. H. Love, waves

that travel along the Earth's surface-travel slower

than body waves-Because of their low frequency,

long duration, and large amplitude, they can be the

most destructive type of seismic wave

Rayleigh Waves- Named after Lord Rayleigh,

waves that travel near the surface of solids. include

both longitudinal and transverse motions that

decrease exponentially in amplitude as distance from

the surface increases

HOW SEISMIC WAVES LED TO DETERMINATION OF

EARTH’S INTERIOR

Seismic waves, which are generated naturally

by earthquakes, by volcanoes, and by impacts,

and may be produced artificially by explosions

and mechanical devices, tell us about the

interior in several general ways.

Firstly, Seismic waves have their direction of

motion changed by variations in the interior

density.

EARTHQUAKES NOT RESULTING FROM

MOVEMENT ALONG PLATE BOUNDARIES

MAGNITUDE

In correlation to Earthquakes, it is the

measurement of the “size” or amplitude of the

seismic waves generated by an earthquake source

and recorded by seismographs.

INTENSITY

A measure of the size of an earthquake based on

observation of the effects of the shock at the Earth's

surface.

MERCALLI SCALE

a seismic scale used for measuring the intensity of

an earthquake, it measures the effects of an

earthquake.

Example: The Earthquake in Haiti had a Mercalli

Scale of 10

TSUNAMI

Japanese Pseudonym, A long high sea wave caused

by an earthquake or other amphibious disturbance

Example: The most prevalent (brought up in

conversation) and most recently was the devastating

Tsunami that obliterated Japan back in January of

2011 and also the Chilean Tsunami of 2010.

Reverse faults

A.K.A. extensional fault, occurs when the crust is extended

Strike-slip Faults

A fault surface that is usually near vertical and the footwall moves either left or right or laterally with very little vertical motion

Tension

Refers to a stretch which stretches rocks in two opposite directions

Shear stress

Distortion of a body by pushing a body in opposite directions

Works Cited page

http://maps.unomaha.edu/maher/plate/week3/contrift.html

http://en.wikipedia.org/wiki/Panthalassa http://en.wikipedia.org/wiki/Pangaea www.Google.com www.thefreedictionary.com http://en.wikipedia.org/wiki/Tectonic_uplift http://en.wikipedia.org/wiki/Explorer_Ridge http://en.wikipedia.org/wiki/Juan_de_Fuca_Plate http://en.wikipedia.org/wiki/Augustus_Edward_Hough

_Love http://wiki.answers.com/Q/How_are_seismic_waves_u

sed_to_provide_evidence_about_Earth%27s_interior www.tulane.edu/~sanelson/eens1110/volcanoes.htm