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Chapter 4 . ROCKS “The Mixture of Minerals”. Rock – a naturally occurring solid mixture of crystals of one or more minerals. Rock Cycle – the continual process by which new rock forms from old rock material. Rocks are always changing. The Rock Cycle.

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Chapter 4

Chapter 4

ROCKS “The Mixture of Minerals”


The rock cycle

The Rock Cycle


Weathering erosion and deposition

Weathering, Erosion, and Deposition


Types of weathering

  • Physical Weathering – Any process in which rocks are broken down by contact with the Earth’s atmosphere and water.

  • Chemical Weathering – Occurs when chemical reactions break down the bonds holding the rocks together.

    • Most common in areas that contain large amount of water.

Types of weathering


Weathering erosion and deposition1

Weathering, Erosion, and Deposition


Weathering erosion and deposition2

Weathering, Erosion, and Deposition


Heat and pressure

Heat and pressure may cause a rock to chemical change into a metamorphic rock.

If the rock gets too hot it will melt which eventually cools to form igneous rocks.

Heat and Pressure


Foliation

Foliation


Bedding

Bedding


Heat and pressure1

The relationship of heat and pressure: rocks as a result of flattening and stretching of mineral grains during metamorphism.

Heat and Pressure

  • ^Pressure ^ Heat

  • ^ Heat ^ Pressure


Mechanical energy

Gravitational Potential Energy – is the potential energy associated with gravitational forces, as work is required to elevate objects against Earth’s gravity.

Mechanical energy


How the cycle continues

How the Cycle Continues


Round and round it goes
Round and Round It Goes uplift and erosion.


A trip around the rock cycle

You are going to need your notebook for this activity. uplift and erosion.

In the output section record 10 rolls of the dice. (Write down what the dice said.)

You may never move from a station but continue to roll the dice at that station and write down what the dice said.

Once you have finished return to your seat.

A Trip around the rock cycle


Rock classification

  • Three main classes of rock: uplift and erosion.

    • Igneous

    • Sedimentary

    • Metamorphic

      In order to identify rocks scientist break the rocks up into two categories:

      Composition and Texture

Rock Classification


Composition

Composition


Texture

Texture


Texture1

Texture


Fine grained silkstone
Fine Grained “Silkstone” determines the texture of the rock.


Medium grained granite
Medium Grained “Granite” determines the texture of the rock.


Coarse grained conglomerate
Coarse Grained - conglomerate determines the texture of the rock.


Individual practice
INDIVIDUAL PRACTICE determines the texture of the rock.


Roger the rock

Your assignment: Create a children’s story, comic strip, or some other creative story about Roger the Rock.

Roger is a rock that has been a part of the rock cycle for millions of years. Your job is to tell Roger’s story. You must describe how Roger was “born” and at least three transitions that occurred during Roger’s life. (For example, changing from igneous to sedimentary, sedimentary to metamorphic, and metamorphic to igneous.)

Your grade will be based on in-class work, the accuracy of your information, creativity, and neatness/effort. This should be a story appropriate for a children’s story (think back to 2nd grade here!), including pictures.

To earn an “A”, you need to include many details-the names of specific rock types, descriptions about what causes the changes to occur, etc.

This project will be due on the day of Chapter 4 Test. These projects will be presented by you and your partner.

ROGER THE ROCK


End of section 4 1
End of Section 4.1 or some other creative story about Roger the Rock.


Mechanisms that drive lithospheric plates

Mechanisms that drive lithospheric plates


Mantle convection
Mantle Convection rocky mantle caused by convection currents carrying heat from the interior of the Earth to the surface.


Mechanisms that drive lithospheric plates1

Ridge Push – Gravitational force that causes a plate to move away from the crest of an ocean ridge, and into a subduction zone.

Mechanisms that drive lithospheric plates


Gravity pull

Gravity Pull


Wegener s continental drift hypothesis
Wegener’s Continental Drift Hypothesis a sub-ducting slab pulls the plate at the surface down.

  • Continental drift – the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations.

    • Alfred Wegener proposed the theory in the early 1900’s.


Wegener s continental drift hypothesis1
Wegener’s Continental Drift Hypothesis a sub-ducting slab pulls the plate at the surface down.

  • Supporting Evidence

    • Plates Fit together like a puzzle.

    • Fossil Evidence across continents.

    • Rocks matched across seas.

    • Glacial striations on rocks matched on Africa and South America proving a once super continent.

    • Coal on Antarctica proves that it was once warm.


Wegener s continental drift hypothesis2
Wegener’s Continental Drift Hypothesis a sub-ducting slab pulls the plate at the surface down.


Wegener s continental drift hypothesis3
Wegener’s Continental Drift Hypothesis a sub-ducting slab pulls the plate at the surface down.


Wegener s continental drift hypothesis4
Wegener’s Continental Drift Hypothesis a sub-ducting slab pulls the plate at the surface down.

  • Inconclusive Evidence

    • No credible evidence that explained why the continents moved.

      • Wegner thought that the continents just “plowed” through the rocks.

      • Many scientist concluded that the continents would have broken into several different pieces if this were to true.


The drifting continents
The Drifting Continents a sub-ducting slab pulls the plate at the surface down.

  • 245 million years ago

  • Pangaea (Means entire Earth) existed when some of the earliest dinosaurs were roaming the Earth.

  • Panthalassa (all sea) The ocean that once covered the Earth.


Pangaea
Pangaea a sub-ducting slab pulls the plate at the surface down.


The drifting continents1
The Drifting Continents a sub-ducting slab pulls the plate at the surface down.

  • 180 Million Years ago Pangaea gradually breaks up into two pieces.

    • Laurasia

    • Gondwana


The drifting continents2
The Drifting Continents a sub-ducting slab pulls the plate at the surface down.

  • 65 million years ago.

  • Dinosaurs became extinct and Laurasia and Gondwana split into two smaller pieces.


Mid ocean ridges and sea floor spreading
Mid-Ocean Ridges and Sea-Floor Spreading a sub-ducting slab pulls the plate at the surface down.

  • Sea-floor spreading – the process in which new oceanic lithosphere forms as magma rises toward the surface and solidifies.

    • A chain of submerged mountains runs through the center of the Atlantic Ocean.

      • Also known as Mid-ocean Ridges


Mid ocean ridges and sea floor spreading1
Mid-ocean ridges and Sea-Floor Spreading a sub-ducting slab pulls the plate at the surface down.

  • As tectonic plates move away from each other, the sea floor spreads apart and magma fills in the gap.

  • New crust forms, older crust gets pushed away from the mid-ocean ridge.


Mid ocean ridges and sea floor spreading2
Mid-ocean Ridges and Sea-Floor Spreading a sub-ducting slab pulls the plate at the surface down.


Evidence for sea floor spreading magnetic reversals
Evidence for Sea-Floor Spreading: Magnetic Reversals a sub-ducting slab pulls the plate at the surface down.

  • Biggest evidence comes from magnetic reversals recorded in the ocean floor.

    • North and South poles have changed places many times.

  • Magnetic Reversal – the process in which magnetic poles change places.


How magnetic reversal works
How magnetic reversal works. a sub-ducting slab pulls the plate at the surface down.

  • Tiny grains of magnetic minerals are found at the mid-ocean ridges.

  • Mineral grains contain iron and are like compasses.

  • They align with the magnetic field of the Earth.

  • When the rock cools, the record of theses tiny compasses remains in the rock.


Magnetic reversals and sea floor spreading
Magnetic Reversals and Sea-Floor Spreading a sub-ducting slab pulls the plate at the surface down.

  • Rock is slowly taken away from the spreading center of the ridge as sea-floor spreading occurs.


Evidence for sea floor spreading magnetic reversals1
Evidence for Sea-Floor Spreading: Magnetic reversals a sub-ducting slab pulls the plate at the surface down.


Seafloor spreading
Seafloor Spreading a sub-ducting slab pulls the plate at the surface down.

  • Activity on seafloor spreading.


The theory of plate tectonics
The Theory of Plate Tectonics a sub-ducting slab pulls the plate at the surface down.

  • Plate Tectonics – the theory that explains how large pieces of the Earth’s outermost layer called tectonic plates, move and change shape.


Tectonic plate boundaries
Tectonic Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • Boundary – a place where tectonic plates touch.

  • There are three different types of boundaries:

    • Convergent

    • Divergent

    • Transform


Convergent boundaries
Convergent Boundaries a sub-ducting slab pulls the plate at the surface down.

  • Convergent Boundary – the boundary formed by the collision of two lithospheric plates.

  • There are three different types of convergent boundaries:

    • Oceanic – Oceanic

    • Oceanic – Continental

    • Continental - Continental


Oceanic oceanic plate boundaries
Oceanic – Oceanic Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • http://geology.com/nsta/convergent-boundary-oceanic-oceanic.gif


Oceanic oceanic convergent boundary
Oceanic – Oceanic Convergent Boundary a sub-ducting slab pulls the plate at the surface down.

  • Normally one of the oceanic plates will subduct below the other.

    • The older plate is usually the one that gets pushed down because it has a greater density.

  • Eventually magma is formed because of the increased pressure causing volcanoes to form over the top of the layer.

    • Eventually the volcanoes will peak out of the water and if they continue to grow the will form island chains.

      • Ex. Japan


Oceanic oceanic plate boundary
Oceanic – Oceanic Plate Boundary a sub-ducting slab pulls the plate at the surface down.


Continental oceanic plate boundaries mt adams
Continental – Oceanic Plate Boundaries “Mt. Adams” a sub-ducting slab pulls the plate at the surface down.

  • http://geology.com/nsta/convergent-boundary-oceanic-continental.gif


Continental oceanic plate boundaries
Continental – Oceanic Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • When the two plates collide the less dense continental plate will rise up on top of the more dense oceanic plate.

    • The subducted plate will become molten due to the increase in temperatures.

    • The magma will then rise because it is less dense than the mantle that is surrounding it.

      • As the magma rise it will cause volcanic and earthquake activity.


Continental oceanic plate boundaries1
Continental – Oceanic Plate Boundaries a sub-ducting slab pulls the plate at the surface down.


Continental continental plate boundaries
Continental – Continental Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • http://geology.com/nsta/convergent-boundary.gif


Continental continental plate boundaries1
Continental – Continental Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • The process in which two land masses collide together. Normally the landmass that is the least dense will subduct only slightly below the other.

    • Mountains will form because the two colliding plates are very light in comparison to the mantle.


Divergent plate boundaries
Divergent Plate Boundaries a sub-ducting slab pulls the plate at the surface down.

  • Divergent Boundary – the boundary between two tectonic plates that are moving away from each other.

    • New Sea floor forms at divergent boundaries.

    • Mid-ocean ridges is the most common type of divergent boundary.


Divergent plate boundaries1
Divergent Plate Boundaries a sub-ducting slab pulls the plate at the surface down.


Transform boundaries
Transform Boundaries a sub-ducting slab pulls the plate at the surface down.

  • Transform Boundary – The Boundary between tectonic plates that are sliding past each other.

  • Ex. San Andreas Fault in California.

    • One of the few faults that can be visibly seen.

    • One of the major causes of Earthquakes.


Output pushing and pulling mountains
Output: Pushing and Pulling Mountains a sub-ducting slab pulls the plate at the surface down.

  • Draw an example of the five different plate boundaries.

  • Label and describe what happens at each different plate boundary.


Transform plate boundaries
Transform Plate Boundaries a sub-ducting slab pulls the plate at the surface down.


Plate summary
Plate Summary a sub-ducting slab pulls the plate at the surface down.


Possible causes of tectonic plate motion
Possible Causes of Tectonic Plate Motion a sub-ducting slab pulls the plate at the surface down.

  • Asthenosphere flows very slowly.

  • This movement occurs because of the change in density within the asthenosphere.

    • Density changes because of the outward flow of energy within the Earth.

      • Hot rock expands and rises.(Less Dense)

      • Cool rock contracts and sinks. (More Dense)


Possible causes of tectonic plate motion1
Possible Causes of Tectonic Plate Motion a sub-ducting slab pulls the plate at the surface down.


Tracking tectonic plate motion
Tracking Tectonic Plate Motion a sub-ducting slab pulls the plate at the surface down.

  • Tectonic plates move roughly 5cm per year.

    • The rate is so slow that it cannot be seen nor felt except during an Earthquake.

  • Plate movement is tracked by GPS.


Fall zone
Fall Zone a sub-ducting slab pulls the plate at the surface down.

  • The fall zone marks the geologic boundary of hard metamorphosed terrain and the sandy, relatively flat outwash plain of the upper continental shelf.

    • The transition from the harder metamorphosed rock to the softer sediment creates water falls.

  • Formed from the erosion of the mountain regions of NC to help form the Sandy coastal plain regions.


Volcanic eruptions
Volcanic Eruptions a sub-ducting slab pulls the plate at the surface down.

  • Volcanoes – are areas of Earth’s surface through which magma and volcanic gases pass.

    • Explosion of a volcanic eruption can turn an entire mountain into a billowing cloud of ash and rock in a matter of seconds causing global climate temperatures to drop.

    • Help form fertile land.

    • Create some of the largest mountains on earth.


Volcanic eruptions1
Volcanic Eruptions a sub-ducting slab pulls the plate at the surface down.

  • Magma – melted rock below the Earth’s surface.

  • Lava – Melted rock above the Earth’s surface.


Mt cleveland aleutian islands alaska
Mt. Cleveland- Aleutian Islands, Alaska a sub-ducting slab pulls the plate at the surface down.


Stromboli volcano sicily
Stromboli Volcano - Sicily a sub-ducting slab pulls the plate at the surface down.


Mount redoubt alaska
Mount Redoubt - Alaska a sub-ducting slab pulls the plate at the surface down.


Types of lava flows
Types of Lava Flows a sub-ducting slab pulls the plate at the surface down.

  • Pahoehoe lava flows – sheet like lava flows that result in continuous surfaces.

    • Flow smoothly

    • Move forwards in tongues or lobes and are characterized by a glassy, plastic skin.


Pahoehoe lava flow
Pahoehoe a sub-ducting slab pulls the plate at the surface down. Lava Flow


Types of lava flows1
Types of Lava Flows a sub-ducting slab pulls the plate at the surface down.

  • Aa – lava pours out quickly and forms a brittle crust.

    • The crust is torn into jagged pieces as molten lava continues to flow underneath.

    • Got its name because of the painful experience of walking barefoot across the jagged surfaces.

    • Associated with lava fountaining.


Aa lava flow
Aa a sub-ducting slab pulls the plate at the surface down. Lava Flow


Lava fountaining
Lava a sub-ducting slab pulls the plate at the surface down.Fountaining

  • Lava Fountaining – spraying of lava into the air pulsing with the pressure of escaping gases.


Types of lava flows2
Types of Lava Flows a sub-ducting slab pulls the plate at the surface down.

  • Pillow lava – forms when lava erupts underwater.

    • Lava forms rounded lumps that are the shape of pillows.


What erupts from a volcano
What erupts from a Volcano? a sub-ducting slab pulls the plate at the surface down.

  • Lava – liquid magma that flows from a volcanic vent.

  • Pyroclastic material - forms when magma is blasted into the air and hardens.

    • Nonexplosive eruptions produce mostly lava.

    • Explosive eruptions produce mostly pyroclastic material.

    • Volcano’s eruptions may alternate between lava and pyroclastic eruptions.


Pyroclastic material
Pyroclastic Material a sub-ducting slab pulls the plate at the surface down.


Volcanic bombs
Volcanic Bombs a sub-ducting slab pulls the plate at the surface down.

  • Volcanic Bombs – large blobs of magma that harden in the air.

    • The shape of the bomb was caused by the magma spinning through the air as it cooled.


Lapilli
Lapilli a sub-ducting slab pulls the plate at the surface down.

  • Lapilli – pebblelike bits of magma that hardened before they hit the ground.

    • Means “little stones”


Volcanic ash
Volcanic Ash a sub-ducting slab pulls the plate at the surface down.

  • Volcanic Ash – forms when the gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny, glasslike slivers.

    • Makes up most of the pyroclastic material in an eruption.


Volcanic ash1
Volcanic Ash a sub-ducting slab pulls the plate at the surface down.


Pyroclastic flows
Pyroclastic a sub-ducting slab pulls the plate at the surface down. Flows

  • Pyroclastic Flow – produced when enormous amounts of hot ash, dust, and gases are ejected from a volcano.

    • Can move downhill at 200km/h.

    • Center of the flow can exceed 700 C.


End of section 9 1
End of Section 9.1 a sub-ducting slab pulls the plate at the surface down.


Effects of volcanic eruptions
Effects of Volcanic Eruptions a sub-ducting slab pulls the plate at the surface down.

June 10, 1816 Connecticut

“Dear Diary, The clothes my wife had laid out to dry the day before had frozen during the night.”


Volcanic eruptions and climate change
Volcanic Eruptions and Climate Change a sub-ducting slab pulls the plate at the surface down.

  • 1815, Mount Tambora blanketed most of Indonesia in darkness for more than 3 days.

    • 12,000 people died directly from the explosion.

    • 80,000 people died from the resulting hunger and disease.


Mauna kea shield volcano
Mauna Kea - Shield Volcano a sub-ducting slab pulls the plate at the surface down.


Cinder cone volcanoes
Cinder Cone Volcanoes a sub-ducting slab pulls the plate at the surface down.


Mt st helens
Mt. St. Helens a sub-ducting slab pulls the plate at the surface down.


Mt st helens1
Mt. St Helens a sub-ducting slab pulls the plate at the surface down.


Mt fuji
Mt. Fuji a sub-ducting slab pulls the plate at the surface down.


Craters
Craters a sub-ducting slab pulls the plate at the surface down.

  • Crater – funnel-shaped pit found around the central vent at the top of many volcanoes.

    • When eruption stops, lava drains back underground making a larger collapsed crater.

    • Next eruption may blast it away creating a larger and deeper crater.


Kamchatka russia
Kamchatka, Russia a sub-ducting slab pulls the plate at the surface down.


Calderas
Calderas a sub-ducting slab pulls the plate at the surface down.

  • Caldera – a large, semicircular depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink.

    • Much larger than a crater.


Crater lake washington
Crater Lake, Washington a sub-ducting slab pulls the plate at the surface down.


Lava plateaus
Lava Plateaus a sub-ducting slab pulls the plate at the surface down.

  • Lava Plateau – a wide, flat landform that results from repeated nonexplosive eruptions of lava that spread over a larger area.

    • Formed from seepage of magma from long cracks or rifts.

    • Lava can pour out for millions of years and spread over huge areas.


Lahar mud flows
Lahar (mud) Flows a sub-ducting slab pulls the plate at the surface down.

  • A type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water.

    • Typically occurs along a river.

    • Has the density and consistancy of concrete.


Possible causes of a lahar
Possible Causes of a Lahar a sub-ducting slab pulls the plate at the surface down.

  • Melted glaciers

  • Mixture with wet soil to create a viscous material.

  • Water from a crater lake.


Columbia river plateau
Columbia River Plateau a sub-ducting slab pulls the plate at the surface down.


End of section 9 2
End of Section 9.2 a sub-ducting slab pulls the plate at the surface down.


Where volcanoes form
Where Volcanoes Form a sub-ducting slab pulls the plate at the surface down.

  • Most volcanoes are found directly on tectonic plate boundaries.

    • 80% of active volcanoes on land form where plates collide.

    • 15% form where plates separate.

  • Other rare and few volcanoes form far away from plate boundaries known as hotspots.


Ring of fire
Ring of Fire a sub-ducting slab pulls the plate at the surface down.

  • The location of the worlds most active volcanoes.

  • The ring is entirely located along plate boundaries in which many earthquakes occur as well.


Hotspots
Hotspots a sub-ducting slab pulls the plate at the surface down.

  • Hotspot – is a location on the Earth’s surface that has experienced active volcanism for a long period of time.

    • Often located in the middle of oceanic plates.

    • Hawaii is an example of an active hotspot.


When tectonic plates separate
When Tectonic Plates Separate a sub-ducting slab pulls the plate at the surface down.

  • Rift zone – an area of deep cracks that forms between tectonic plates that are pulling away from each other.

    • Mantle rock lifts up to fill the gap.

    • As mantle rises the pressure decreases allowing the rock to melt and form magma.


End of volcanoes
End of Volcanoes a sub-ducting slab pulls the plate at the surface down.


Earthquakes

Earthquakes a sub-ducting slab pulls the plate at the surface down.


What are earthquakes
What Are Earthquakes? a sub-ducting slab pulls the plate at the surface down.

  • Seismology – the study of earthquakes.

  • Seismologist – scientist who study Earthquakes.

  • Earthquake – the shaking of the Earth’s surface due to the movement of tectonic plates.


Where do earthquakes occur
Where Do Earthquakes Occur? a sub-ducting slab pulls the plate at the surface down.

  • Most if not close to all Earthquakes occur near the edges of tectonic plates.

    • Due to the movement of tectonic plates, numerous features called faults exist in the Earth’s crust.

  • Fault – is a break in the Earth’s crust along which blocks of the crust slide relative to one another.


Where do earthquakes occur1
Where Do Earthquakes Occur? a sub-ducting slab pulls the plate at the surface down.


What causes earthquakes
What Causes Earthquakes? a sub-ducting slab pulls the plate at the surface down.

  • Deformation – the bending, tilting, and breaking of the Earth’s crust; the change in the shape of rock in response to stress.

  • This process occurs in two ways:

    • Plastic deformation.

    • Elastic deformation.


Plastic deformation
Plastic Deformation a sub-ducting slab pulls the plate at the surface down.

  • Plastic Deformation – a rock that deforms in a stretching gentle manner.

    • Example: Pulling apart a piece of molded clay.


Elastic deformation
Elastic Deformation a sub-ducting slab pulls the plate at the surface down.

  • Elastic Deformation – rock is stretched until it can no longer stand the force in which the rock springs back to its original location.

    • Rock can stretch farther than steel without breaking.

  • Example: Stretched rubber band.


Elastic rebound
Elastic Rebound a sub-ducting slab pulls the plate at the surface down.

  • Elastic Rebound – the sudden return of elastically deformed rock to its undeformed shape.

    • Occurs when more stress is applied to the rock than the rock can stand.

  • Energy is released during the rebound.

    • Energy is released as seismic waves.


Visualizing elastic rebound
Visualizing Elastic Rebound a sub-ducting slab pulls the plate at the surface down.

  • http://projects.crustal.ucsb.edu/understanding/elastic/rebound.html


How do earthquake waves travel
How Do Earthquake Waves Travel? a sub-ducting slab pulls the plate at the surface down.

  • Seismic Wave – a wave of energy that travels through the Earth, away from an earthquake in all directions.

  • Body Waves – seismic waves that travel through the Earth’s interior.

  • Surface waves – seismic waves that travel along the Earth’s surface.


Types of waves
Types of Waves a sub-ducting slab pulls the plate at the surface down.

  • P-waves or Primary Waves – Types of seismic waves that move in a compression manner.

    • Ex. A slinky moving back and forth from end to end.

    • Has the ability to move through all materials.

    • Fastest moving wave.


Types of waves1
Types of Waves a sub-ducting slab pulls the plate at the surface down.

  • P-waves are always the first waves of an earthquake to be detected.


Types of waves2
Types of Waves a sub-ducting slab pulls the plate at the surface down.

  • S-Waves or Secondary waves – are waves that move up and down.

    • Ex. Stretching a slinky outward and then pulling down on the center so that it would bounce up and down.

    • Cannot move through a liquid.

    • Waves are very damaging to surface objects.


Types of waves3
Types of Waves a sub-ducting slab pulls the plate at the surface down.

  • S-waves are also known as shear waves because of the damage they cause to the Earth’s rocks at the surface.

  • S-waves cannot travel through parts of the Earth that are completely liquid.

  • S-waves are slower than P-waves and always arrive later than P-waves.


Surface waves
Surface Waves a sub-ducting slab pulls the plate at the surface down.

  • Surface Waves – are waves that move along the Earth’s surface and produce motion mostly in the upper few kilometers of Earth’s crust.

  • Two types:

  • Rayleigh Wave - Produces up, down, and around motion.

  • Love Waves - Back and forth motion much like S-waves.

    These waves are more destructive than body waves and move more slowly


Surface waves1
Surface Waves a sub-ducting slab pulls the plate at the surface down.


Locating earthquakes
Locating Earthquakes a sub-ducting slab pulls the plate at the surface down.

  • Seismographs – instruments located at or near the surface of the Earth that record seismic waves.

  • Seismogram – tracing of earthquake motion recorded by a seismograph.


Determining time and location of earthquakes
Determining Time and Location of Earthquakes a sub-ducting slab pulls the plate at the surface down.

  • Seismologists find an earthquake’s start time by comparing the differences in arrival times of P waves and S waves.


Determining time and location of earthquakes1
Determining Time and Location of Earthquakes a sub-ducting slab pulls the plate at the surface down.

  • Epicenter – the point on the Earth’s surface directly above an earthquake’s starting point

  • Focus – the point inside the Earth where an earthquake begins.


The s p time method
The S-P Time Method a sub-ducting slab pulls the plate at the surface down.

  • S-P time method – the way in which seismologists find an earthquake’s epicenter.

    • Collect several seismograms of the same earthquake from different locations.

    • Seismograms are placed on a time-distance graph.

    • By reading the horizontal axis the distance from the earthquake can be determined.


The s p time method1
The S-P Time Method a sub-ducting slab pulls the plate at the surface down.


The richter magnitude scale
The Richter Magnitude Scale a sub-ducting slab pulls the plate at the surface down.

  • Richter scale – a scale used to measure the strength of an earthquake.


Earthquake ground motion
Earthquake Ground Motion a sub-ducting slab pulls the plate at the surface down.

  • Magnitude – the strength of an earthquake.

  • Every time that the Richter scale increases by one it will produce 10x as much ground motion.

    • Ex. 5 on the scale will be 10x stronger than an earthquake that is a 4.


Modified mercalli intensity scale
Modified a sub-ducting slab pulls the plate at the surface down.Mercalli Intensity Scale

  • Intensity – a measure of how much damage caused by the earthquake.

    • The Scale uses roman numerals I-XII

    • Shows the type of damage caused by an earthquake.


Strength and frequency
Strength and Frequency a sub-ducting slab pulls the plate at the surface down.

  • Earthquakes vary in strength.

  • Earthquakes don’t occur on a set schedule.

    • But, the strength of an earthquake is related to how often they occur.


Strength and frequency1
Strength and Frequency a sub-ducting slab pulls the plate at the surface down.


The gap hypothesis
The Gap Hypothesis a sub-ducting slab pulls the plate at the surface down.

  • Gap hypothesis – a hypothesis that states that sections of active faults that have had relatively few earthquakes are likely to be the sites of strong earthquakes in the future.

  • Seismic Gap – areas along a fault where relatively few earthquakes have occurred.


What causes change in sea level
What causes change in sea-level? a sub-ducting slab pulls the plate at the surface down.


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