What is the Earth’s interior like?

CRUST Where we live

State of matter: solid

Characteristics: Rocky, Hard

Rock Composition: mostly Aluminum and Silicon

Thickness: 0-25 miles thick

Two types of crust 2 types of crust

Oceanic crust:

below ocean

4 miles thick

Continental crust:

Below the continents,

mostly granite

18-25 miles thick,

MANTLE State of matter: Semi-solid

Characteristics: hot, dense, semi-solid

Pressure and temperature increase as you go deeper

Convection (heat) currents – cause plates to move

Rock Composition: mostly Iron and magnesium

Thickness: 1,800 miles

80% Of Earth’s volume

Three layers of Mantle Three layers:

Lithosphere – Uppermost layer – relatively cool, rigid rock –

Made up of 7 large moving pieces and some smaller moving pieces called tectonics plates

Asthenosphere- middle layer – softer, weaker rock, flows slow like taffy

Mesosphere – bottom layer – stiff rock

CORE State of matter:

Inner core – Solid

Outer core- Liquid

Characteristics:

very high pressure

Very hot - 5500 c

Rock composition: Iron and Nickel

Two layers of the core Two Layers

Outer Core =

hot liquid metal

1,430 miles thick

Rock - nickel and iron alloy

Inner core =

solid metal

745 miles thick

Rock - iron

http://www.youtube.com/watch?v=3MFr2cC3erk&feature=related

http://www.youtube.com/watch?v=Q9j1xGax

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Practice Quiz Question Can you label the following layers?

Why is the interior of the Earth so hot? There are three main sources of heat in the deep

earth: Heat from when the planet formed

Frictional heating- caused by denser core material sinking to the center of the planet

Heat from the decay of radioactive elements .

The interior contains radioactive isotopes. When these isotopes break apart, they release energy in the form of heat.

The Theory of Plate Tectonics

The idea of plate tectonics was first introduced by Alfred Wegener in the early 1900’s but it was not widely accepted until the 1960’s.

Plate tectonics is the theory that pieces of the Earth’s lithosphere, called plates, move about slowly on top of the asthenosphere.

Forces causing plate movement The physical force

driving these plates is not fully understood, however it appears that the lithosphere plates glide slowly on top of a semi-solid layer of the upper mantle known as the asthenosphere.

Convection currents, due to the temperature differences between the mantle and the crust, hot matter will rise to the surface and cool matter will drop, which causes the plates above it to move and shift.

Forces causing plate movement

The Plate tectonics theory explains: The continents were once

connected together in a large continent called Pangaea – meaning “all land”.

The continents have been and are still moving at a rate of 1-16 cm a year.

http://www.classzone.com/books/earth_science/terc/c

ontent/visualizations/es0806/es0806page01.cfm?chapter_no=visualization

Plate Tectonics

Movement of the Plates

http://www.montereyinstitute.org/noaa/lesson01.html

1. Matching Coastlines (puzzle)

Eastern coast of South America and Western coast of Africa fit together

Evidence of Plate movement

Gondwanaland: matching coastlines

Matching

Coastlines

Evidence of Plate tectonics

2. Shared Fossils:

Same kinds of animals lived on continents that are now oceans apart

Evidence of Plate tectonics 3. Paleomagnetism Iron materials on ocean

floor align themselves parallel to Earth’s magnetic poles. A permanent records of magnetism field.

Rocks retain “memory” of magnetic field when they cool

Polar Reversals - Different aged rocks show that the polarity of the magnetic pole has reversed many times in the past.

Earth’s magnetic poles helped to determine the plate boundaries

4.Matching Glaciers

Evidence of Plate tectonics

5. Rocks strata (layers) match

Evidence of Plate tectonics

6. Matching Mountain ranges

Appalachian Mountains , Greenland range, British Idles and Caledonian Mountains

Evidence of Plate tectonics

Mechanisms of Plate Tectonics Movement Patterns:

1. Move towards each other

2. Move away from each

other

3. Slide alongside each other

Plate move about 1-16 cm/year

Earth’s Tectonic Plates

Plate Boundaries There are three types

Divergent boundaries

Convergent Boundaries

Transform Boundaries

Divergent Boundaries Two plates move apart and

creates a gap of newly formed rock.

• In the ocean:

• Ridges are created as lava pushes its way up through the crust.

• Ex. Mid-Atlantic ridge

• Sea Floor spreading – process where new oceanic crust is made as magma rises and old crust moves away.

Divergent Boundary

Divergent Boundary

On the continent:

Rift Valley: When the plates move away, the land between drops and creates a valley

http://www.montereyinstitute.org/noaa/lesson02.html

Convergent Boundary Two plates move towards each other In the ocean:

Subduction: As seafloor spreading occurs old oceanic plates sink into the mantle and creates a trench

This destroys old oceanic crust

Trench : where a plate sinks creating a depression

Plate movements

• On the continent: Continental plates moving towards each other can form mountains Example: Himalayas

Convergent Boundary

Building the Himalayas

Boundaries Review: Divergent Boundaries Convergent Boundaries

Plates Move away from each other

Continent: Form Rift Valleys

Ocean: Mid ocean ridges

Plates move towards each other

Continent: Mountain ranges

Ocean: Trenches

Transform Fault

Plates slide horizontally in opposite directions.

Rock is neither created or displaced, just shifted.

Often creates earthquakes

San Andres Fault: Transform Fault

What is an Earthquake? Movement of the earth’s lithosphere that occurs

when rocks suddenly shift, releasing stored energy.

As plates move, the rocks along their edges experience immense pressure and eventually rocks are broken along the fault line. The energy is released as seismic waves.

A tsunami is a large sea wave created by an underwater earthquake, volcano or landslide.

Earthquake Terms Fault – Break in a mass of rock along

which movement occurs

Fold – Bending in the layers of rock

Focus – location beneath the earth’s surface where an earthquake starts

Epicenter – Location on the earth’s surface directly above the focus

Types of Stress

Compression - squeezes rock until it breaks.

Tension – pulls on the crust stretching rock

Shearing – pushes a mass of rock in two opposite directions

Types of Faults Normal Fault – One block

of rock lies above the fault and one block below it

Caused by tension

Reverse Fault – The bottom block slides up past the upper block

Caused by compression

Strike Slip – Rocks slide past each other

Caused by shearing

Waves Energy from earthquakes is transferred through the

Earth by waves

P waves - Longitudinal Waves

“Primary wave” - First wave to reach the recording station.

The fastest moving wave – through solid or liquid

The wave looks like a compressed spring and then you release the spring.

Waves S Wave = Transverse Waves

Secondary wave

Move more slowly through rock

Wave looks like a rope being shaken up and down

Light and electromagnetic radiation

Cannot travel through liquid

Waves Surface Waves

These waves move on the surface of the Earth.

Move slower than S and P waves but produce larger ground movements and greater damage.

They can move up and down, side to side, or like an ocean wave coming in.

Measuring an Earthquake Seismology: Study of earthquakes.

Seismograph is a tool used to record P waves, S waves, and Surface waves. Based on the recordings, we can determine how strong the earthquake was.

Seismology

Three seismographs are necessary to locate the epicenter of an earthquake

1. P waves: small zigzag lines

2. S waves: larger, more ragged lines

3. Surface waves: arrive last and make the largest lines

How do geologists use seismographs to investigate the Earth’s interior??

Certain waves move at different speeds and through

certain material. (S waves can not go through liquid.) Because of this, we have figured out part of the core is liquid, the mantle is semi-liquid, etc.

Rating Earthquakes Richter Scale: measures the magnitude of earthquakes

Moment Magnitude Scale – Measures the amount of energy released by earthquake – each unit represents 32X increase in the energy released.

Modified Mercalli scale – rates the type of damage and other effects noted by observers

Largest Ever recorded – 9.5 in Chile 1960

Modified Mercalli

Richter Scale

Example In Alaska, 1964, there was an earthquake with a

magnitude of 8.4.

An earthquake with a magnitude of 8 releases 810,000 times as much energy as an earthquake with a magnitude of 4.

Scale vs. Damage The scales cannot predict amount of damage. Damage

depends on:

Distance between populated areas and the epicenter.

The depth of the focus.

The physical properties of the surface rocks.

Compare the occurrence of earthquakes with the plate boundaries. Where are the earthquakes happening? (Look at the black, green and red dots.)

An opening in the Earth’s crust through which magma reaches Earth’s surface.

Volcanoes Can be very destructive

Have also been beneficial:

Atmospheric gases

Water

New land

Energy source

Information about the inside of the Earth

Structure of a volcano Magma chamber – where

magma collects Pipe – Where magma rises to

the surface Conduit/Vent – Tubelike

structure from below the surface emerging to the surface as a vent.

Crater – Connected to the conduit, it is the bowl shaped pit at the top of the volcano

Caldera – depression at top of volcano caused by a shell collapse

Lava Dome – protrusion from extra lava flows

a. caldera

Mount St. Helen’s

Lava dome

c. lava dome

Why volcanoes erupt Similar to shaking a pop bottle

Magma is under the surface is under a lot of pressure from dissolved gases (water vapor and CO2)

As it approaches the surface, the lowered pressure causes the gases to expand rapidly.

An eruption occurs when the gases bubble out through a crack in the crust.

Magma vs Lava What is the difference?

Magma Under the Earth’s

surface.

Forced upward through the vent

Lava When magma reaches

the surface

Magma cools and hardens to form lava fields

Eruptions Volcanoes erupt explosively or quietly depending on

the magma.

Explosive eruptions – lava and hot gases are hurled outward and lava solidifies quickly

Quiet eruptions – lava erupts in a stream of easily flowing lava

Pahoehoe Lava flow

Hot fast moving with ropelike surface

AA lava flow

Cooler, slow lava with a chunky, crumbly appearance

Pillow lava-

oozing lava

beneath the

water surface

Eruptions Tephra is what volcanoes throw into the

air – it is classified by size

Ash/Dust – smallest fragments of tephra

Blocks – Largest size pieces

Cinders – igneous rock similar to pumice

Pyroclastic Flow – Rapidly moving clouds of tephra with hot gas (up to 700 ) at speeds up to 80 mph

Types of Volcanoes Shield Volcanoes

Broad, gentle sloping shape

Quiet, mild eruptions

Largest volcanoes

Ex. Mauna Loa

Types of Volcanoes

Composite Volcanoes

Tall with steep sides

Built from alternating layers of ash, cinder and lava

Explosive eruptions

Often have secondary vents

Ex. Mt Fuji, Japan

Types of Volcanoes

Cinder Cone Smallest and most abundant

Steep sides

Explosive eruption is entirely of ash and cinders

Active only for a short time, then dormant

Ex. Paracutin, Mexico

Sunset crater, AZ

Mt. Pelée, Martinique

Locations of volcanoes Two places most volcanoes

reside

Plate boundaries

Hot spots

Hot spots – occur in the middle of plates - region where hot rock extends from deep within the mantle – (ex. Hawaii, Iceland)

80% of all volcanoes are located in the “Ring of Fire”

Active, dormant, extinct An active volcano is a volcano that has had at least

one eruption during the past 10,000 years.

An active volcano might be erupting or dormant.

An erupting volcano is an active volcano that is having an eruption.

A dormant volcano is an active volcano that is not erupting, but supposed to erupt again.

An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.

Mauna Loa 1984 (Photograph by Richard B. Moore)

Hekla, Iceland 1991, photo by Sigurgeir Jónasson

Hekla, Iceland 1991, photo by Ragnar Th. Sigurdsson

Mauna Loa (Peter Francis)

1,900-foot high fountain, Kilauea Iki,1959 (National Park Service

Photograph)

Stromboli, April 1996

Vulcano,Vulcanello, and Lipari (Peter Francis)

1980 eruption of Mount St. Helens (photo courtesy of J.M. Vallance)

Mt. St. Helens most recent eruption

Eyjafjallajökull – Iceland - 2010