Earth Science

Layers of the Earth

The The Earth’sEarth’s LayersLayers

Lithosphere

• The top part of the layer is the Earth’s crust.

• The outermost layer of the earth known as the “rock sphere” that we live on.

• It is divided into pieces called tectonic plates

Asthenosphere

• The soft layer of the mantle below the lithoshphere.

• Tectonic plates move above this layer.

                                                                               

                                                                                                           

Outer Core

• The liquid layer below the earth’s mantle.

• This layer surrounds the inner core.

Inner Core

• The solid, dense center of our planet.

• It is about 6,374 km. beneath the earth’s surface.

“Plate tectonics” Theory:

explains motion/behavior of Earth’s lithosphere

Moves a few centimeters a year

explains volcanoes, mountain building and earthquakes

stiff lithosphere floats on top of weak asthenosphere

Plate tectonics about a dozen or so plates

Modernmeasurements

Supporting evidenceSupporting evidenceSupporting evidenceSupporting evidence

What drives the plate movement?

EARTH is a Heat EngineEARTH is a Heat Engine

Tectonic Plates

• The place where two tectonic plates meet is called a plate boundary.

Plate BoundariesPlate Boundaries

divergent boundaries

convergent boundaries

transform fault boundaries

3 types

• http://www.wwnorton.com/college/geo/earth2/content/chapter_4/animations.asp

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

Divergent boundaries

Mostly mid-ocean ridges (seafloor spreading)

Typical spreading rates ~ 5 cm/year

As oceanic moves away from ridge, it cools, & becomes denser

Also found where continents break apart

Example: Red Sea and East African Rift

Mid Ocean Ridges

http://earthquake.usgs.gov/learning/animations/

Continents Break Apart – Rift Valley

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

Divergent boundaries

Also found where continents break apartExample: Red Sea

http://www.wwnorton.com/college/geo/animations/sea_floor_spreading.htm

Red Sea (looking southeast)

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

Divergent boundariesContinents breaking apart Example: East African Rift

Red triangles show the active volcanoes and the Afar Triangle (shaded, center)

Divergent Plate BoundariesDivergent Plate Boundaries

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

Convergent boundaries

Subduction zones

ocean-continent

ocean-ocean

continent-continent

- VolcanoesExamples: Mount St. Helens

- Volcanic island arcs Examples: Marianas, Aleutians, Hawaii

- Mountain BuildingExamples: Himalayas, Alps, Appalachians

ConvergentConvergent Plate boundariesPlate boundaries

continental crust and continental crust

• Mountain building

Oceanic and oceanic crust• DEEPEST Trenches and Island Arcs

Oceanic crustOceanic crust

Continental Crust and Oceanic Crust• Trenches and explosive volcanoes

Molten rock

Oceanic crust Continental crust

volcano

SUBDUCTION ZONE

• Mountains

• Volcanoes, trenches & earthquakes

Transform fault boundaries

Strike-slip faulting

Plates slide past each other: no production/destructionof material

2) Plate boundaries2) Plate boundariesPLATEPLATETECTONICSTECTONICS

STRESS• Stress occurs at plate boundaries. Stress

causes rock to change shape or deform (deformation)

Types of Stress: Type of boundary

– Compression

– Tension

– Shearing

convergent

divergent

transform

Stress Causes Deformation

Deformation Bends and Breaks Rock

If you bump your bike into a large rock two things can happen.

The metal can either bend or snap.

Stress Cause - CompressionEffect: Folding

• Folding- When rock layers bend because of stress on the earth’s crust.

The types of folding are:

Folding

• Anticline- Arch shape folds in the earths’ crust.

• Syncline- Trough shaped fold in a rock.

pushing

pushing

Monocline

• Monocline – simplest - involves a slight bend on one side

Anticline

Anticline

Anticline

Folding

• Syncline- Trough shaped fold in a rock.

Syncline

Syncline

Syncline

Syncline

Syncline

Monocline

• Monocline – simplest - involves a slight bend on one side

Monocline

Monocline

Monocline

Monocline

Monocline

Tectonic Plates

• The place where two tectonic plates meet is called a plate boundary. (When there is enough pressure that builds up on the rocks’ edges and earthquakes can occur).

• Earthquake Facts

Earthquake Animation

Tectonic Forces• Faulting- Stress that causes rocks to

break

• Faults slide past each other.

• The types of faulting are:

- normal fault

- reverse fault

- strike-slip fault

Fault Type #1: Normal Fault Cause: Tension/ Divergent movement

Normal Faults- Effect: The hanging wall moves down, relative

to the footwall. Normal because of the

pull of gravity.

Normal Fault

NormalFault

Normal Fault

Fault Type #2: Reverse Fault

Cause: Compression/ Convergent MovementReverse Fault-

Effect: The hanging wall moves up relative to the

footwall.

Reverse Fault

Reverse Fault

Reverse Fault

Reverse Fault

Strike-Slip FaultCause: shearing/ crosswise movement

Strike-slip Faults-

Effect: When opposing forces cause rock to

break and move horizontally.

Strike Slip FaultStrike Slip Fault

Strike Slip FaultStrike Slip Fault

Strike Slip FaultSan Andreas Fault

Mountain BuildingCause: CompressionEffect: Uplift – crust is raised to higher

elevation

• US Geological Survey scientist Chris Newhall attaches a tape measure to a cliff on Bubuin Island. Activity from nearby Volcano Island has lifted Bubuin by 15 centimeters

Grand Canyon

Folded Mountains• In a folded mountain range, the rock layers are

folded up.

Folded Mountains

• Fault-Block

• Folded

• Volcanic

Folded Mountains

Sierra Nevada

Folded Mountains

Appalachian

Folded MountainsAppalachian Mountains

Fault-BlockMountains

• Fault-Block

Fault- Block Mountians

• Rock layers are tilted up and can have sharp jagged peaks.

Fault-Block MountainsGrand Tetons from Jackson Lake Lodge (WY)

are examples of fault block mountains.

Fault Block Mountain

Fault-Block Mountains

• Big Bend Texas

Volcanic Mountains

• Volcanic mountains are often cone shaped, and form along convergent boundaries.

• Also forms along the divergent sea floor spreading

Volcanic Mountains

Volcanic Mountains• Mt. Ranier, Washington

Volcanic MountainsMt. St. Helens, Washington

Volcanic Mountains

Mt. Shasta, California

Volcanic Mountains• Volcanic mountains of Guatemala make up

part of the Pacific's "Ring of Fire".

Popocatepetl, Mexico. December 12, 2007 this volcano spewed lava and ash two miles high.

Volcanic Mountains• Mt. St. Helens- Live

• On May 18, 1980, Mount St. Helens violently erupted. For 2 months the volcano showed signs that it was waking up from its 123-year sleep.

• Earthquakes beneath the mountain increased. Steam and ash erupted.

• And a "bulge" grew on the mountain's steep north side. All these warning signs signaled that magma was moving upward inside the volcano.

US Volcanoes

• Cascade Range Volcanoes

• Major West Coast Volcanoes

• Hawaii Volcano Map