Chapter 14Chapter 14

The Internal ProcessesThe Internal Processes

The Internal ProcessesThe Internal Processes

• Rigid Earth to Plate Tectonics

• Plate Tectonics

• Vulcanism

• Folding and Faulting

• Earthquakes

Rigid Earth to Plate TectonicsRigid Earth to Plate Tectonics

• Questioning Theories of Rigid Earth

• Isostasy

• Continental Drift

Theories of Rigid EarthTheories of Rigid Earth

• For billions of years Earth has been shaped and reshaped by internal processes

• Crust is folded, bent, lowered, raised

• Until 1950’s it was believed that Earth was “rigid” or static

• Now established that continents drift – plate tectonics

Igneous Rock FormationIgneous Rock Formation

• Igneous rocks form in two layers

• Sima = silica+magnesium; oceanic; denser

• Sial = silica+aluminum; continental; less dense

• Because sima is denser than sial, it subducts the continental plate at convergence i.e., it slides under the less dense plate.

Isostasy – Isostatic ReboundIsostasy – Isostatic Rebound• Crust “floats” on denser, deformable mantle

• Addition of considerable weight/mass causes crust to sink

• Removal of weight allows crust to rise

• Example: Glacial and Interglacial periodsAccumulated iceCrust depressed

Ice meltsWeight removed

Crustrebounds

Continental Continental DriftDrift

Over millions of years, the shapes and positions of the continents have changed.

•450 million years ago, there was only one land mass, Pangaea

•250 million years ago, something happened to cause the plates to separate

•The separation has been ongoing to the present day

Continental Drift: PangaeaContinental Drift: Pangaea• Continental drift is the movement of continents

over the Earth's surface, and their change in position relative to each other.

Original land mass with continental boundaries

Plate TectonicsPlate Tectonics

• Seafloor Spreading

• 3 types of Plate movement 1. Divergent

2. Convergent

3. Transform

• Continental Rearrangement

• Accreted Terranes and Hot Spots

Plates - SeafloorPlates - SeafloorThe Mid-Atlantic Ridge is an underwater mountain range that runs from Iceland to Antarctica.

It is the longest mountain range on Earth.

The ridge was discovered by Bruce Heezen in the 1950s. The discovery of this ridge led to the theory of seafloor spreading and general acceptance of Wegener’s theory of continental drift.

The ridge runs along a divergent boundary.

Mid-Atlantic Ridge

PlatesPlates

• Earth's surface is broken into seven large and many small moving plates

• Each plate is about 50 miles thick• Each plate moves relative to one another an

average of a few inches a year• Three types of movement are recognized at

the boundaries between plates: convergent, divergent and transform-fault.

7 Major Plates7 Major Plates

1. Eurasion plate (which is covers Asia and Europe)

2. North American plate (North America)

3. South American plate (South America)

4. Pacific plate

5. African plate (Africa and Middle East)

6. Australian plate

7. Antarctic plate

For the most part, each major plate represents one of the seven continents.

Major and Minor PlatesMajor and Minor Plates

Plates with TopographyPlates with Topography

Plate Plate BoundariesBoundaries

(a) Oceanic-Continental

(b) Oceanic-Oceanic

(c) Continental-Continental

Be familiar with terms circled in red!

Convergent BoundariesConvergent Boundaries• Plates move toward each other and collide• Where an oceanic plate collides with a continental

plate, the oceanic plate tips down and slides beneath the continental plate forming a deep ocean trench (long, narrow, deep basin.)

• This is called subduction• Subduction, occurs at the boundary between the

oceanic Nazca Plate and the continental South American Plate.

• Where continental plates collide, they form major mountain systems such as the Himalayas.

SubductionSubduction

Be familiar with terms circled in red!

Divergent Plate BoundariesDivergent Plate Boundaries• Plates move away from each other, as at the

East African Rift

• Where plates diverge, hot, molten rock rises and cools adding new material to the edges of the oceanic plates

• This process is known as a rift valley

Be familiar with terms circled in red!

Figure 14-5

Seafloor Spreading

Be familiar with terms circled in red!

• Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges

• And, the movement of the crust away from the mid-ocean ridges.

Seafloor Seafloor SpreadingSpreading

Divergent Movement of Plates

Transform Plate BoundariesTransform Plate Boundaries

• Plates move horizontally past each other

• Since the plates are sliding past each other, and not tearing or crunching, they lack the spectacular features found at convergent and divergent boundaries

• They are marked in some places by linear valleys along the boundary where rock has been ground up by the sliding

• In other places, they are marked by stream beds that have been split in half

Transform Plate BoundariesTransform Plate Boundaries

• For example, the San Andreas Fault zone

• The Pacific Plate, on which Los Angeles sits, ismoving slowly northwestward relative to the North American Plate, on which San Francisco sits.

Formation of Accreted TerraneFormation of Accreted Terrane• Small to medium mass of lithosphere

carried a long distance by a moving plate

• Eventually converges with another plate

• Too buoyant to be subducted; it joins – accretes

• Often fragments in process

Accreted

Fragmented

Accreted TerranesAccreted Terranes added to western added to western

North America over North America over the past 200 million the past 200 million

yearsyears

Formation of Hot SpotFormation of Hot Spot• Magma comes to or close to surface at interior

plate location – not near plate boundary

• Hot spots are relatively stationary for 10-100 million years

• Create volcanoes or hydrothermal vents at surface

The Hawaiian Hot SpotThe Hawaiian Hot Spot• A mantle plume here for millions of years• As Pacific plate moved NW, volcanoes created

and died, as source of magma shut off

VulcanismVulcanism

• Volcanism• Distribution of Active Volcanoes• Volcanic Hazards• Intrusive Vulcanism

VulcanismVulcanism

• All phenomena connected with the origin and movement of molten rock

• Includes volcanic eruptions and solidification of molten material below the surface

VolcanismVolcanism

• Volcanism is the expelling of magma onto Earth’s surface

• The magma is then called lava• Pyroclasic material consists of: lava, rock

fragments, solidified blobs of lava, ashes, dust, gas and steam

• Pyroclastic material is hurled upward and can be carried in the atmosphere for thousands of miles and over many years

Distribution of Active VolcanoesDistribution of Active VolcanoesThe heaviest distribution of volcanoes is

the Pacific Ring of Fire

CalderasCalderas

• Produced when a volcano explodes, collapses or both

• Result is an immense basin shaped depression – usually circular

• Depression is many times larger than original volcanic vent

Kilauea, HawaiiThe summit area of Kilauea

volcano is dominated by collapse features.

Kilauea caldera is a large collapse structure caused by rapid draining of magma between 1460-1500.

Genovesa, Gallapogos Is.The island consists of a single

volcano, which emerges only 200 feet above sea level

A breached caldera on the south side of the island forms Darwin Bay

A small lake-filled crater is located in the center of the island.

Volcanic Volcanic HazardsHazards

• Volcanic gases

• Lava flows

• Eruption column & cloud

• Pyroclastic flows

• Volcanic mudflow

Intrusive VulcanismIntrusive Vulcanism•Magma solidifies beneath Earth’s surface and produces igneous rock

•Rock pushed up into crust, before or after solidification, is called igneous intrusion

Shiprock, NM

DiastrophismDiastrophism

• Deformation of Earth’s crust by folding or faulting

• Term implies that material is solid and not molten

• Rocks bent or broken from extreme pressure in mantle or crust

Folding and FaultingFolding and Faulting

• Types of Folds– Monoclines, Anticlines, and Synclines– Overturned and Overthrust Folds

• Types of Faults– Normal– Reverse– Strike-Slip– Thrust

• Faulted Landforms

FoldingFoldingCrustal rocks are bent and folded by forces, such

as lateral compression

Types of FoldsTypes of Folds

• Monocline

• Anticline

• Syncline

• Overturned fold

• Overthrust fold

Syncline FoldSyncline Fold

FaultingFaulting

• The breaking apart of rock material from crustal stress

• The crust on one or both sides of the break must move

• The movement can be vertical or horizontal or both

• Usually takes place in a fault zone• Intersection of fault zone with Earth’s

surface is called fault line

Types of FaultsTypes of Faults

Normal

Over thrust

Reverse

Strike slip

California Fault LineCalifornia Fault LineCalaveras Fault, Hollister CA

•Strike slip fault in the San Andreas fault system

Rift ValleyRift ValleyNorthern section of the Great Rift Valley. The Sinai peninsula is in center and the Dead Sea and Jordan River valley above

Rift valley Africa

EarthquakesEarthquakes

• Earthquake Movement (waves)

• Magnitude and Shaking Intensity

• Hazards

• Prediction

Seismic WavesSeismic Waves

Collision of India with EurasiaCollision of India with Eurasia

Earthquake WavesEarthquake Waves

FaultingFaulting

Transform FaultsTransform Faults

FoldingFolding

SeismographsSeismographs

Breakup of PangaeaBreakup of Pangaea

Formation of Crater LakeFormation of Crater Lake

Igneous FeaturesIgneous Features

Seafloor Spreading and Plate Seafloor Spreading and Plate BoundariesBoundaries

Tectonic Settings of Volcanic Tectonic Settings of Volcanic ActivityActivity

Terrane FormationTerrane Formation

AnimationsAnimations

• http://www.pbs.org/wnet/savageearth/animations/index.html

• http://iri.columbia.edu/~lareef/tsunami/#Tsunami_Animation:_National_Institute_of

• http://www.geophys.washington.edu/tsunami/general/physics/characteristics.html

• http://esminfo.prenhall.com/science/geoanimations/animations/86_Tsunami.html