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The Formation of the Earth

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Title: The Formation of the Earth


1
The Formation of the Earth
http//www.youtube.com/watch?v_mcC8kFacrk (format
ion of the earth video, 5 min)
  • The effects of gravity
  • as the planet reached a diameter of about 350 km,
    the force of gravity became greater than the
    strength of rock.
  • The center was crushed by gravity and the planet
    started to become round.

2
The Formation of the Earth
  • The effects of heat
  • The collision of other objects generated heat
  • Radioactive material generated heat
  • Soon the interior began to melt

3
How the Layers Formed
  • As rocks melted, denser materials sank to the
    center of the Earth and became the core.
  • Nickel, iron
  • Less dense material rose to the surface and
    became the crust
  • Oxygen, silicon, aluminum
  • The middle layer is the mantle.
  • Magnesium, iron
  • http//www.youtube.com/watch?vH6OuD877Rog
  • (formation of the Earth, 10 min)

4
Earths Interior
  • ODE Standard The composition and properties of
    Earths interior are identified by the behavior
    of seismic waves.

5
The Crust
  • A layer of solid rock that includes both dry land
    and the ocean floor.
  • Very thin compared to the other layers, like the
    skin of an apple.
  • Thickest under high mountains, thinnest under the
    ocean floor.
  • 5-100 km thick
  • Oceanic crust is denser than continental.

6
The Mantle
  • Made of very hot, solid rock.
  • Lithosphere uppermost part of mantle and the
    crust together. Divided into tectonic plates.
  • Asthenosphere less rigid (plastic). Softer
    part of the mantle, but still solid.
  • Mesosphere lower mantle made of solid material
    that extends to the core.

7
The Core
  • Outer core molten (liquid) metal. Movements in
    this part of the core causes Earths magnetic
    field.
  • Inner core dense ball of solid metal.
  • Both are made of iron and nickel, but the extreme
    pressure in the inner core keeps the metal from
    becoming liquid.

8
How do scientists know the structure of the Earth?
  • Rock samples (direct evidence)
  • Seismic waves (indirect evidence)
  • Vibrations that travel through Earth carrying
    energy released during an earthquake.
  • The speed and paths of waves reveal the structure
    of the planet.
  • We will learn more about these later.

9
Tectonic Plates
  • ODE Standard Earths crust consists of major
    and minor tectonic plates that move relative to
    each other.

10
A Giant Jigsaw Puzzle
  • The lithosphere is made of plates that fit
    together like a puzzle.
  • Vary in size and thickness.
  • Float on the asthenosphere like ice floats in
    water.

11
Wegeners Continental Drift Hypothesis
  • Early 1900s
  • Continental drift - continents once formed a
    single landmass, broke up, and drifted to their
    present locations.
  • Pangaea existed about 245 million years ago.

12
Sea Floor Spreading
  • The process by which new oceanic lithosphere
    forms as magma rises to the surface and
    solidifies
  • Evidence for continental drift
  • Mid-ocean ridges are located where there is sea
    floor spreading.
  • Example Mid-Atlantic Ridge

13
Tectonic Plate Boundaries
  • Three types
  • Convergent plates collide
  • Divergent where plates separate (mid-ocean
    ridges)
  • Transform plates slide horizontally past each
    other (San Andreas Fault)

14
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15
Causes of Tectonic Plate Motion
  • Changes in density within the athenosphere
  • Energy comes from center of Earth
  • Heated rock expands and rises (less dense)
  • Cool rock contracts and sinks (more dense)

16
How is it measured?
  • In centimeters per year
  • GPS (global positioning system) from satellites
  • Scientists record the time it takes for GPS
    ground stations to move a given distance
  • This allows them to measure the speed of the
    plates motion

17
Deforming the Earths Crust
  • Deformation the process by which the shape of a
    rock changes because of stress
  • Stress the amount of force per unit area
  • Compression stress caused by squeezing.
    Convergent boundary.
  • Tension stress caused by stretching. Divergent
    boundary.

18
Folding
  • Bending of rocks because of stress
  • Types
  • Anticlines upward arching folds
  • Synclines downward, trough-like folds
  • Monocline both ends are horizontal

19
Faulting
  • The surface along which rocks break and slide
    past each other
  • Types
  • Normal usually with tension
  • Reverse usually with compression
  • Strike-slip opposing forces cause the rock to
    break and move horizontally.

20
Earthquakes
  • Occur along faults
  • Caused by stressed rock during plate movement.
  • Elastic rebound releases energy (remember elastic
    potential energy?).
  • This energy travels as seismic waves.
  • These waves cause earthquakes.

21
Earthquake Zones
  • Along tectonic plate boundaries where a large
    number of faults are located
  • Example San Andreas Fault Zone in California

22
A Brief Introduction to waves
  • Parts of a wave
  • Crest
  • Trough
  • Amplitude
  • wavelength

23
Waves Transfer Energy
  • Transverse waves
  • Particles vibrate perpendicular to the motion of
    the wave.
  • Longitudinal waves
  • Particles vibrate parallel to the motion of the
    wave.

24
Behavior of Waves
  • Diffraction
  • Waves bend around an edge and spread out. Ex.
    Sound waves
  • Refraction
  • Waves bend as they pass from one medium to
    another because the speed changes. Ex. Straw in
    glass (light waves bending from air to water)

25
Behavior of Waves
  • Reflection
  • Waves hit an obstacle and bounce off. Ex.
    Mirror
  • Absorption
  • Waves enter into a material and lose energy. Ex.
    Dark colored materials (blacktop)

26
Behavior of Waves
  • Constructive and Destructive interference
  • Waves come together to create bigger or smaller
    waves.

27
Seismic Waves
  • P waves Pressure waves (or primary)
  • Fastest, so they travel ahead of other waves and
    are the first to be detected.
  • Can travel through all media (solid, liquid,
    gas).
  • Move back and forth, which causes compression and
    tension.

28
Seismic Waves
  • S Waves Shear waves (or secondary)
  • Second-fastest waves
  • Cannot travel through parts of Earth that are
    completely liquid.
  • Shear rock side to side as they travel forward.

29
Seismic Waves
  • Surface waves
  • Move along the Earths surface (in the upper few
    kilometers) of the earths crust.
  • Move the ground much like ocean waves.
  • Travel the slowest.
  • The most destructive.

30
  • S and P waves give scientists a picture of what
    is inside the Earth.
  • P waves refract as they go from one layer of the
    earth to another
  • S waves diffract when they hit something liquid
  • http//earthquake.usgs.gov/earthquakes/eqarchives/
    year/2002/2002_11_03_waveani.php
  • http//earthquake.usgs.gov/learn/animations/animat
    ion.php?flash_titleShadowZoneflash_fileshadowz
    oneflash_width220flash_height320
  • http//science.discovery.com/tv-shows/greatest-dis
    coveries/videos/100-greatest-discoveries-the-core-
    of-the-earth.htm

31
Earthquake Measurement
  • Seismologist - a person who studies earthquakes
  • Seismographs - instruments that record seismic
    waves
  • Seismogram - the picture that is created by the
    seismograph

32
Determining Time and Location
  • Seismologists look at the seismogram to note the
    difference in arrival times of P waves and S
    waves
  • Seismographs also help find the epicenter and
    focus

33
Measuring Strength and Intensity
  • Charles Richter created the Richter scale in the
    1930s.
  • Measures the ground motion recorded by
    seismograms at seismograph stations.
  • Magnitude - a measure of the strength of an
    earthquake
  • Each unit on the Richter scale represents motion
    that is 10 times larger than the previous unit.
  • A magnitude of 5 is ten times stronger than a 4.
  • A magnitude of 6 is 100 times stronger than a 4.

34
Modified Mercalli Intensity Scale
  • Intensity - a measure of the degree to which an
    earthquake is felt by people and the amount of
    damage caused
  • Uses Roman numerals I to XII
  • I not felt, XII total damage of an area
  • The number changes depending on where you are
    (highest number is close to the epicenter).

35
Earthquake Forecasting
  • Strength of earthquakes is related to their
    frequency (how often they occur)
  • Scientists use this to help predict the strength,
    location, and frequency of future earthquakes

36
Earthquake Forecasting
  • The Gap hypothesis
  • Sections of active faults that have had few
    earthquakes are likely to be sites of strong
    earthquakes in the future.
  • These sites are called seismic gaps

37
Earthquakes and Buildings
  • Retrofitting - making older buildings more
    earthquake resistant
  • Fasten it to its foundation
  • Technology that improves earthquake resistance
  • Mass damper
  • Active tendon system
  • Base isolators
  • Cross braces
  • Flexible pipes

38
Volcanoes
  • Types of volcanoes
  • Shield volcanoes
  • layers of lava released from nonexplosive
    eruptions.
  • Ex. Hawaiis Mauna Kea (the tallest mountain on
    Earth)

39
Types of Volcanoes
  • Cinder cone volcanoes
  • from moderately explosive eruptions.
  • Ex. Paricutin in Mexico

40
Types of Volcanoes
  • Composite volcanoes
  • most common
  • From explosive eruptions.
  • Ex. Japans Mount Fuji, Mount Rainier

41
Other Volcanic Landforms
Caldera
Crater
Lava plateau
42
Where Volcanoes Form
  • Over plate boundaries
  • Ex. Ring of Fire surrounding the Pacific Ocean
    (contains 75 of active volcanoes on land)
  • 80 (on land) where plates collide
  • 15 (on land) where plates separate

43
Where Volcanoes Form
  • Mid-Ocean Ridges
  • Lava flows out to make crust
  • Where most volcanic activity takes place
  • Convergent boundaries
  • During subduction, the temperature and pressure
    increase causing lava to form

44
Where Volcanoes Form
  • Hot spots
  • Not along boundaries
  • Above columns of rising magma, results of cracks
    in the crust
  • Ex. Hawaiian Islands

45
Predicting Eruptions
  • Dormant and Active (not extinct)
  • Monitoring earthquakes
  • Studying volume and composition of volcanic gases
    (ratio of sulfur dioxide to carbon dioxide)
  • Measuring slope and temperature
  • GPS measures slope, infrared satellite images
    show temperature
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