Earthquakes and Plate Tectonics Our Violent Earth.

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Earthquakes Earthquakes and Plate and Plate Tectonics Tectonics Our Violent Earth Our Violent Earth

Transcript of Earthquakes and Plate Tectonics Our Violent Earth.

Page 1: Earthquakes and Plate Tectonics Our Violent Earth.

Earthquakes Earthquakes and Plate and Plate TectonicsTectonics

Our Violent EarthOur Violent Earth

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The Earth’s Changing CrustThe Earth’s Changing Crust

►Todays evidence: EQ’s, volcanic Todays evidence: EQ’s, volcanic eruptions, mountain growth, moving eruptions, mountain growth, moving landmasses.landmasses.

►Past movements based on the concept Past movements based on the concept of ORIGINAL HORIZONTALITY: Assumes of ORIGINAL HORIZONTALITY: Assumes that sed. Rocks and some extrusive that sed. Rocks and some extrusive igneous. Rock form in horizontal layers igneous. Rock form in horizontal layers parallel to the earths surface.parallel to the earths surface.

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Past evidence of crustal Past evidence of crustal movementmovement

►Deformed rock layers such as folded Deformed rock layers such as folded rock, faulted rock, tilted rock, uplifted rock, faulted rock, tilted rock, uplifted rock (with displaced fossils.)rock (with displaced fossils.)

See page 214 of book.See page 214 of book.

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Crustal Change in depthCrustal Change in depth► Folds:Folds: bends in crust caused by compressional bends in crust caused by compressional

stressesstresses Anticlines:Anticlines: up-turned folds: Hills up-turned folds: Hills Synclines:Synclines: down-turned folds: valley down-turned folds: valley Tilts are just eroded sections of the above.Tilts are just eroded sections of the above.

► Faults:Faults: Breaks in the crust where movement Breaks in the crust where movement occursoccurs Normal:Normal: hanging wall moves down hanging wall moves down Reverse:Reverse: hanging wall moves upward hanging wall moves upward Strike-slip:Strike-slip: one block slides past the other laterally one block slides past the other laterally

► Mountains (uplift):Mountains (uplift): up-thrust crust material at up-thrust crust material at high elevationhigh elevation

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EarthquakesEarthquakes

►The natural, rapid shaking of the The natural, rapid shaking of the lithosphere caused by release of lithosphere caused by release of energy stored in rocksenergy stored in rocks

►Most earthquakes are caused by: Most earthquakes are caused by: FAULTINGFAULTING The grinding of pieces of crust past one The grinding of pieces of crust past one

anotheranother

►Some are causes by the Some are causes by the movement movement of magmaof magma within the lithosphere within the lithosphere under volcanoesunder volcanoes

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Earthquake TerminologyEarthquake Terminology► Seismic Waves:Seismic Waves:

The shock waves of a quakeThe shock waves of a quake► P-Waves:P-Waves:

Primary waves; fastest wave, first to be Primary waves; fastest wave, first to be recorded; particles vibrate in the direction of recorded; particles vibrate in the direction of movement, like a sound wave; movement, like a sound wave; travel through travel through solids and liquidssolids and liquids

► S-Waves:S-Waves: Secondary waves; second to be recorded; Secondary waves; second to be recorded;

particles vibrate at right angles to the direction particles vibrate at right angles to the direction of movement, like a water wave; of movement, like a water wave; travel travel through solids onlythrough solids only

► Focus:Focus: Point below earth’s surface where the energy is

released► Epicenter:Epicenter:

Point on earth’s surfacePoint on earth’s surface above the focus; most above the focus; most damage is done heredamage is done here

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Why Study EarthquakesWhy Study Earthquakes

►Develop an “early warning” or Develop an “early warning” or “prediction system”“prediction system”

►Seismic waves give scientists Seismic waves give scientists information on the inner layers and information on the inner layers and composition of the Earthcomposition of the Earth Different materials allow seismic waves to Different materials allow seismic waves to

act differentlyact differently

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VELOCITY OF SEISMIC WAVESVELOCITY OF SEISMIC WAVES

►Velocity depends on the material they Velocity depends on the material they are passing throughare passing through

a.a. Increase density and pressure – Increase density and pressure – greater the velocity greater the velocity

b.b.Waves are refracted or bent as waves Waves are refracted or bent as waves pass through material with different pass through material with different densitiesdensities

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EARTHQUAKEEARTHQUAKE SHADOW SHADOW ZONESZONES

►At an angle of 103° (distance 11,000 At an angle of 103° (distance 11,000 kms) from the epicenter both P and S kms) from the epicenter both P and S waves disappearwaves disappear

►P waves can again be detected at P waves can again be detected at l42° (16,000 kms.) l42° (16,000 kms.)

NO S WAVES EVER APPEAR AGAINNO S WAVES EVER APPEAR AGAIN

►THIS BAND OF 39° IN WHICH NO THIS BAND OF 39° IN WHICH NO WAVE ARE OBSERVED IS CALLED WAVE ARE OBSERVED IS CALLED THE THE EARTHQUAKE’S SHADOW ZONEEARTHQUAKE’S SHADOW ZONE

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EARTHQUAKE SHADOW ZONES

P WAVES DISAPPEAR FROM 105º -140º

S WAVES DISAPPEAR FROM 105º NEVER TO APPEAR AGAIN

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ANALYSIS OF SEISMIC WAVES HAVE RESULTED IN THE INFERENCE ABOUT EARTH’S INTERIOR

S WAVES CANNOT PASS THROUGH THE LIQUID OUTER CORE

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Earthquake MagnitudeEarthquake Magnitude

►The strength of an earthquakeThe strength of an earthquake►Measured on an intensity scaleMeasured on an intensity scale►Ex: Richter ScaleEx: Richter Scale

Seismograph needle and readout; shows P and S Waves being recorded

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Earthquake Magnitude ScaleEarthquake Magnitude Scale

Japanese Magnitude Scale

from 0 - 7

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SeismographSeismograph

March 28, 2005, near Northern Sumatra, Indonesia. This 8.7 magnitude earthquake came only three months after the devastating magnitude 9.0 earthquake of December 26, 2004, which caused the Tsunami.

Traditional Mechanical Seismograph

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Locating the Epicenter of an Locating the Epicenter of an Earthquake (Steps)Earthquake (Steps)

1.1. Acquire P and S wave data from at least 3 Acquire P and S wave data from at least 3 monitoring stations.monitoring stations.

2.2. Calculate the difference in arrival times Calculate the difference in arrival times between the P and S waves for each between the P and S waves for each station.station.

3.3. Use your reference tables to determine Use your reference tables to determine the distance that station is from the the distance that station is from the epicenter.epicenter.

4.4. Strike a circle with the scaled diameter of Strike a circle with the scaled diameter of the distance you just calculated.the distance you just calculated.

5.5. Do this 2 more times; where all 3 meet is Do this 2 more times; where all 3 meet is the location of the epicenter.the location of the epicenter.

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LOCATING EARTHQUAKE LOCATING EARTHQUAKE EPICENTEREPICENTER

MUST HAVE DISTANCE FROM 3 SEISMOGRAPH STATIONS TO DETERMINE EPICENTER

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Practice Using the P and S wave Practice Using the P and S wave Arrival Time ChartArrival Time Chart

1.1. If the P wave arrived at 02:00:00 and the If the P wave arrived at 02:00:00 and the S wave arrived at 02:04:00, find the S wave arrived at 02:04:00, find the distance the station is from the epicenter.distance the station is from the epicenter.

2.2. If the P wave arrived at 12:12:00 and the If the P wave arrived at 12:12:00 and the S wave arrived at 12:24:30, find the S wave arrived at 12:24:30, find the distance the station is from the epicenter.distance the station is from the epicenter.

3.3. If the P wave arrived at 09:15:30 and the If the P wave arrived at 09:15:30 and the S wave arrived at 09:18:50, find the S wave arrived at 09:18:50, find the distance to the station.distance to the station.

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Practice Using the P and S wave Practice Using the P and S wave Arrival Time ChartArrival Time Chart

4.4. If a monitoring station were 8200 km If a monitoring station were 8200 km from the epicenter of an earthquake. from the epicenter of an earthquake. If the P-wave arrived at 2:15 PM, find If the P-wave arrived at 2:15 PM, find the time the earthquake occurred.the time the earthquake occurred.

5.5. If a seismic station was 2600 km If a seismic station was 2600 km from the epicenter of a quake and it from the epicenter of a quake and it recorded an S-wave at 1:00 PM, find recorded an S-wave at 1:00 PM, find the time the quake occurred.the time the quake occurred.

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Practice Using the P and S wave Practice Using the P and S wave Arrival Time ChartArrival Time Chart

6.6. If an earthquake occurred at exactly If an earthquake occurred at exactly 7hr: 45 min: 00 sec. and the p-wave 7hr: 45 min: 00 sec. and the p-wave arrived at a station at 7 hr: 52 min: arrived at a station at 7 hr: 52 min: 00 sec, when did the s-wave arrive?00 sec, when did the s-wave arrive?

7.7. An earthquake exactly 8000 km away An earthquake exactly 8000 km away from a station occurred at 3 hr: 03 from a station occurred at 3 hr: 03 min: 00 sec. When did the P-waves min: 00 sec. When did the P-waves arrive? When did the S-waves arrive?arrive? When did the S-waves arrive?

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NORMAL FAULT

REVERSE FAULT

TRANSFORM FAULT

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Plate TectonicsPlate Tectonics

► The theory that suggests Earth’s lithosphere The theory that suggests Earth’s lithosphere is broken up into sections is broken up into sections (lithospheric (lithospheric plates or tectonic plates)plates or tectonic plates) and their and their movement and interactions produce major movement and interactions produce major changes in Earth’s surfacechanges in Earth’s surface

► At the plate boundaries you’ll find: At the plate boundaries you’ll find: Earthquakes, volcanoes, trenches, Earthquakes, volcanoes, trenches, mountains and mid-ocean ridges-Zones of mountains and mid-ocean ridges-Zones of frequent crustal activity!!! Ex: Pacific Ring of frequent crustal activity!!! Ex: Pacific Ring of FireFire

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Sea-Floor Spreading Sea-Floor Spreading

►Brand new ocean crust (basalt) is being Brand new ocean crust (basalt) is being made and is spreading out from the made and is spreading out from the ridge.ridge.

►Evidence: Evidence: ►Alternating zones of reversed magnetic Alternating zones of reversed magnetic

polarity at equal distances from the polarity at equal distances from the ridge.ridge.

►The age of the basaltic rock gets older The age of the basaltic rock gets older at equal distances from the ridge.at equal distances from the ridge.

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Continental DriftContinental Drift

►The movement of continents with The movement of continents with respect to one another.respect to one another.

►Evidence: Evidence: ►““Jig Saw Puzzle Effect”Jig Saw Puzzle Effect”►Similarities of rocks, minerals, fossils Similarities of rocks, minerals, fossils

and age at continental margins. and age at continental margins. ►Some mountain chains line up when Some mountain chains line up when

the continents are put back together.the continents are put back together.

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Driving Force Behind Plate Driving Force Behind Plate TectonicsTectonics

►Convection Currents in the mantle of EarthConvection Currents in the mantle of Earth►Convection currents work like tank tracks Convection currents work like tank tracks

and cause the plates to move by slowly and cause the plates to move by slowly dragging them around Earth’s surfacedragging them around Earth’s surface

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Earth’s Surface over timeEarth’s Surface over time►Reference tables: page 9; right Reference tables: page 9; right

columncolumn►The Location of the North America has The Location of the North America has

changed throughout geologic historychanged throughout geologic history►The continents have been connected 2 The continents have been connected 2

times throughout geologic time and times throughout geologic time and have subsequently broken up due to have subsequently broken up due to plate movementsplate movements

► If this process continues, we will be If this process continues, we will be part of a new super-continent in part of a new super-continent in another 250 million yearsanother 250 million years

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Plate BoundariesPlate Boundaries

►Divergent Plate Boundaries:Divergent Plate Boundaries: Crustal plates move apart (Ex. Mid-Crustal plates move apart (Ex. Mid-ocean Ridge)ocean Ridge)

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Plate BoundariesPlate Boundaries►Convergent Boundaries:Convergent Boundaries: crustal plates move crustal plates move

toward each other; cause collisionstoward each other; cause collisions►Ex. Ocean Trench Ex. Ocean Trench

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Plate BoundariesPlate Boundaries

►Transform Transform Boundaries:Boundaries: one plate slips one plate slips past another past another with no vertical with no vertical motion; San motion; San Andreas Fault, Andreas Fault, CaliforniaCalifornia

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NORTH

WEST

SOUTH

EAST

SAN ANDREAS FAULT

PACIFIC PLATE

WEST SIDE MOVES NORTH

NORTH AMERICAN PLATE

EAST SIDE MOVES SOUTH

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Test ReviewTest Review

►Test is coming!!!Test is coming!!!►Castle Learning ReviewCastle Learning Review►Earthquakes and Plate Earthquakes and Plate

Tectonics ReviewTectonics Review►Will help out with the Will help out with the

upcoming testupcoming test