Building Earth’s Surface
Download
1 / 60

- PowerPoint PPT Presentation


  • 130 Views
  • Updated On :

Building Earth’s Surface. An aerial view from the south of the eruption of Mount St. Helens volcano on May 18, 1980. Interpreting Earth’s Surface. Observations Today we noticed all kinds of aspects of Earth that seem to need an explanation.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '' - vaughan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript


Slide3 l.jpg


Slide4 l.jpg

  • Observations Helens volcano on May 18, 1980.

    • Today we noticed all kinds of aspects of Earth that seem to need an explanation.

    • Some have in the past thought that these aspects of the Earth had always been there

    • Others thought that they were a result of some catastrophic event in the Earths history, causing sudden change.


Slide5 l.jpg

  • Would you believe that this rock island has "always" existed where it is? Would you believe it was formed by a sudden, single event? What evidence would it take to convince you that the rock island formed ever so slowly, starting as a part of southern California and moving very slowly, at a rate of cm/yr, to its present location near the coast of Alaska?


Slide6 l.jpg

  • Principle of Uniformity where it is? Would you believe it was formed by a sudden, single event? What evidence would it take to convince you that the rock island formed ever so slowly, starting as a part of southern California and moving very slowly, at a rate of cm/yr, to its present location near the coast of Alaska?.

    • This is the frame of reference that is used today to understand changes in the Earth’s surface over time.

    • This principle helps us to understand what has shaped the Earth through those processes that are still occurring today.


Slide7 l.jpg

  • Diastrophism where it is? Would you believe it was formed by a sudden, single event? What evidence would it take to convince you that the rock island formed ever so slowly, starting as a part of southern California and moving very slowly, at a rate of cm/yr, to its present location near the coast of Alaska?


Slide8 l.jpg

  • Introduction where it is? Would you believe it was formed by a sudden, single event? What evidence would it take to convince you that the rock island formed ever so slowly, starting as a part of southern California and moving very slowly, at a rate of cm/yr, to its present location near the coast of Alaska?

    • Diastrophism describes all of the movements of the Earth’s plates.

      • Movement relative to other plates

      • Isostatic adjustment

      • Deforming and changing th Earth’s surface


Slide9 l.jpg

  • Stress and Strain where it is? Would you believe it was formed by a sudden, single event? What evidence would it take to convince you that the rock island formed ever so slowly, starting as a part of southern California and moving very slowly, at a rate of cm/yr, to its present location near the coast of Alaska?

    • Four events associated with increased pressure

      • As pressure begins to build up, the pressure is slight and nothing visible is happening to the surface.

      • As the pressure increases, eventually the surface will begin to deform into a concave surface

      • The concave shape builds up to the point where it is no longer able to return to its original shape.

      • The surface will rupture and begin to break at the point of the increasing pressure, releasing the pressure.


Slide10 l.jpg

  • A stress is some force that can compress, pull apart, or deform a rock and there are 3 basic types

    • Compressive stress is caused when two plates move together or when one moves and applies a force on another one that is not moving.

    • Tensional stress occurs when one part of a plate moves away from another part of a plate.

    • Shear stress occurs when two plates slide past one another


Slide11 l.jpg

  • The adjustment to stress is called strain and there are 3 basic types

    • Elastic strain occurs when rocks recover to their original shape.

    • Plastic strain occurs when rocks are molded or bent under the stress and do not return to their original shape.

    • Fracture strain is when the rocks crack or break under the stress.


Slide12 l.jpg


Slide13 l.jpg

  • How a rock responds to stress depends on 4 variables. rocks under high pressure (A) and cooler rocks near the surface (B). Breaking occurs when stress exceeds rupture strength.

    • Nature of the rock

    • Temperature of the rock

    • The period of time ever which the stress is applied to the rock

    • The confining pressure on the rock.


Slide14 l.jpg

  • Folding rocks under high pressure (A) and cooler rocks near the surface (B). Breaking occurs when stress exceeds rupture strength.

    • Sedimentary rock is usually buried as layers of rocks.

    • Stress on these layers of rocks usually uplift the layer together forming bends in the layer called folds.

    • Symmetrical up and down folds can be produced by widespread horizontal stress on sedimentary rock layers.

    • A dome can be produced when a vertical upward stress exerts on a rock layer

    • A basin can be produced when there is a dome produced

    • Anarch shaped fold is called an anticline

    • A trough shaped fold is called a syncline

      • A syncline of any great extent is called a geosyncline

    • When synclines and anticlines are not horizontal they are called plunging folds


Slide15 l.jpg


Slide16 l.jpg


Slide17 l.jpg


Slide18 l.jpg


Slide19 l.jpg


Slide20 l.jpg


Slide21 l.jpg


Slide22 l.jpg

  • Faulting left and right and a syncline in the center. (B) A photo of a plunging fold in Utah.

    • Cooler rocks near the surface of the earth do not always react to pressure by folding.

      • This is due to the fact that they are cooler and therefore more brittle.

    • These cooler more brittle rocks can react to pressure by faulting.

    • A joint is when there is a break in the rock, but the rock is not displaced on either side of the break

    • A fault is when there is a break in the rock and the rock on either side of the break is displaced.



Slide24 l.jpg


Slide25 l.jpg

  • The basalt cools. (A) Devil's Post Pile, San Joaquin River, California. (B) The Devil's Tower, Wyoming.fault plane is the movement of the rocks on one side of the fault relative to rocks on the other side of the fault.

  • We describe faults in terms of:

    • The steepness of the fault plane

    • Direction of the relative movement


Slide26 l.jpg

  • Three basic ways in which rocks can move basalt cools. (A) Devil's Post Pile, San Joaquin River, California. (B) The Devil's Tower, Wyoming.

    • Dip is the movement of rock up and down relative to the fault plane

    • Strike is the horizontal or sideways movement of rock relative to the fault plane.

    • Oblique is the movement of rock both up and down and sideways relative to the fault plane.


Slide27 l.jpg

  • When two rock planes move relative to one another one is called the footwall as it has dropped below and the other is called the hanging wall as it is above the plane

  • In a normal fault the hanging wall has moved down relative to the footwall

  • In a reverse fault the hanging wall has moved up relative to the footwall.

  • A reverse fault with a low angle fault plane is called a thrust fault.


Slide28 l.jpg




Slide31 l.jpg


Slide32 l.jpg

  • Causes of Earthquakes and (B) a thrust fault.

    • An earthquake is a quaking, shaking, vibrating, or upheaval of the ground.

      • They occur as a result of the sudden release of energy due to stress on rock that occurs beneath the Earth’s surface.

    • If the rock fractures as a result of the stress if produces waves or vibrations that move out from the source as seismic waves.

      • Seismic waves are produced when a mass of rock breaks and slides into a different position.


Slide33 l.jpg


Slide34 l.jpg

  • Most earthquakes occur along a fault plane and near the Earth’s surface since this is where the rocks are coolest and the most brittle.

  • Elastic rebound is when the stress causes the rock to break and snap into a new position.

    • The rocks are displaced to new positions and the released energy causes an earthquake.




Slide37 l.jpg

(C) Rock breaks suddenly, releasing energy, with rock movement along a fault. Horizontal motion is shown; rocks can also move vertically.


Slide38 l.jpg

(D) Horizontal offset of rows in a lettuce field, 1979, El Centro, California. (D) Photo by University of Colorado; courtesy National Geophysical Data Center, Boulder, Colorado.


Slide39 l.jpg

  • Locating and Measuring Earthquakes Centro, California. (D) Photo by University of Colorado; courtesy National Geophysical Data Center, Boulder, Colorado.

    • Focus

      • This is the place where the seismic waves originate below the surface of the Earth

    • Epicenter

      • The point on the surface of the Earth directly above the focus.

    • Seismograph

      • An instrument used to measure the seismic waves.


Slide40 l.jpg


Slide41 l.jpg


Slide42 l.jpg

  • P-wave The suspended mass remains motionless when the earth vibrates, and the motion detector moves with the seismic waves. The movements are recorded on a remote recording drum.

    • A compressional seismic wave that moves in a longitudinal fashion

  • S-wave

    • A shear seismic wave that moves in a transverse fashion.

  • Surface wave

    • A seismic wave that moves in an up and down fashion with crests and troughs.


Slide43 l.jpg


Slide44 l.jpg

  • Classification in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.

    • Shallow-focus

      • Occur within a depth of 70 km

    • Intermediate-focus

      • Occur in the upper part of the Earth’s mantle

    • Deep-focus

      • Occur in the lower part of the upper mantle

  • Most earthquakes are shallow-focus because:

    • The rocks at the surface are cooler and more brittle

    • There is the most resistance to movement of the plates at the surface of the Earth.


Slide45 l.jpg

  • Measuring Earthquake Strength in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.

    • Mercalli scale

      • Expresses relative intensities of earthquakes with intensities ranging from I to XII.

      • Level I is not felt by humans

      • Level VI is felt by all

      • Levels V through VII are concerned with levels of damage

      • Level XI means that few buildings are left standing

      • Level XII means total destruction with waves moving across the ground being visible to the eye.


Slide46 l.jpg

  • Richter scale in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.

    • Assigns numbers based on magnitude of the earthquake

    • Describe the severity of the vibrations and the energy released during the earthquake.


Slide47 l.jpg

  • Moment magnitude in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.

    • A logarithmic scale based on the size of the fault and the amount of movement along the fault.

  • Surface-wave magnitude

    • Based on the displacement of the Earth’s surface.


Slide48 l.jpg

  • Origin of Mountains in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.


Slide49 l.jpg

  • Folded and Faulted Mountains in times of first arrivals of P-waves and S-waves is a function of the distance from the focus. (B) Triangulation using data from several seismograph stations allows location of the earthquake.

    • The Earth’s surface is thickened in the areas where mountains occur due to the compressional forces that produce tight almost vertical folds.

    • The Appalachian Mountain range was produced by differential weathering which gives it its parallel features

    • The Rocky Mountains have almost upright beds produced by folding of sedimentary rock layers.

    • The Black Hills of South Dakota were produced by a broad folding arch called a dome.


Slide50 l.jpg


Slide51 l.jpg


Slide52 l.jpg


Slide53 l.jpg

  • Volcanic Mountains by weathering and erosion, is obvious in this Skylab photograph of the Virginia-Tennessee-Kentucky boundary area. The clouds are over the Blue Ridge Mountains.

    • As volcanic material builds up on the surface of the Earth, it can build to the point where it produces a mountain.

    • A volcano is a hill or mountain produced by the extrusion of lava or rock fragments from the magma below the Earth’s surface.



Slide55 l.jpg

  • 3 major types of volcanoes 1980 explosive eruption.

    • Shield volcanoes

      • Broad, gently sloping cones made as magma solidifies at the surface of the Earth.

      • These originate from low viscosity lava which spreads out quickly from the vent.

    • Cinder cone volcano

      • Made of cinders.

      • These cinders are rock fragments that have solidified from lava that cooled as it was thrown into the air.

    • Composite volcano

      • Built of alternating layers of cinder, ash, and lava.


Slide56 l.jpg


Slide57 l.jpg

  • (A)A schematic cross section of an idealized composite volcano, which is built up of alternating layers of cinders, ash, and lava flows. (B) A photo of Mount Shasta, a composite volcano in California. You can still see the shapes of former lava flows from Mount Shasta.



Slide59 l.jpg

  • Batholith Columbia Plateau Basalts.

    • A large amount of lave that has crystallized below the surface.

    • If part of the batholith protrudes above the surface it is called a stock.

  • Dike

    • An intrusion that flows into a joint or fault that cuts across rock bodies.

  • Sill

    • When the intrusion flowed into the plane of contact between sedimentary rock layers.

  • Laccolith

    • Similar to a sill, but with an arched top where the intrusion has raised the overlying rock into a blister-like uplift.