Download OSU EARTHSC 1121 Summaries 2019

Name: __________________________________________
Regents Earth Science
Date: ___________
Per: ____________
Class Notes: Chapter 3: The Dynamic Earth (Completed Copy)
Measuring Earthquakes
Earthquake: A rapid shaking or rapid movement of Earth’s solid outer layers
→ Most earthquakes are caused by a movement along a fault where potential energy is given off as a seismic
wave
Where do Earthquakes Occur?
1.
2.
Along plate boundaries
Along fault lines
→ Normal
→ Reverse
→ Strike-slip (Transform)
__________________ Fault:
___________________ Fault:
Strike-Slip (___________________________) Fault: (San Andreas Fault!)
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 1
Epicenter: The location on Earth’s surface directly above the focus
Focus (Hypocenter): The point inside the Earth where the earthquake originates
Mercalli Scale: Scale that measures the intensity of an
earthquake based on the effects to Earth’s surface, humans, objects in nature, and other man-made structures
The values will differ based on the distance from the epicenter:
→ Highest intensities are closer
→ Lower intensities are farther away
Richter Scale: Logarithmic scale that measures the amount of energy released during an earthquake
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 2
Magnitude: A number to quantify the amount of seismic energy released from an earthquake
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The Richter Scale’s magnitude is determined from the following measurement:
→ Seismogram’s amplitude of waves
→ Distances from other seismographs
→ Epicenter distance
Seismometer: An instrument used to measure and record movements in the ground
Seismogram: Record of the seismometer
Primary Wave (P-wave)
→ P-waves are the fastest waves
→ Travels through solids, liquids, and gases
→ Compressional: particles travel in the direction of wave movement
Secondary Wave
→ S-waves are the slower and STRONGER wave
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 3
→ Travels through solids only
→ Shear particles travel in right angles to the direction of wave movement
Surface Wave (Rayleigh Wave)
→ The STRONGEST type of wave
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Epicenters are located using the velocity differences between the p-wave and s-wave
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Seismologists also want to find the origin time
Origin Time: The time at which the earthquake occurred at its epicenter
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In order to find the origin time, the P-Wave travel time must be known
Since p-waves travel faster than s-waves, as your distance increases from the earthquake’s epicenter
the arrival time between the two waves will be greater
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Distance to the epicenter is determined by comparing the arrival times and the E.S.R.T.
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 4
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After obtaining information from at least THREE seismic stations, the epicenter of the earthquake can
be pinpointed
Practice:
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 5
1.
2.
3.
What is the P and S Wave Arrival Time?
What is the time difference?
What is the epicenter distance?
Answers:
1.
What is the P and S Wave Arrival Time?
P Wave: 6:02:00 (In hours, minutes, seconds)
S Wave: 6:07:30
2. What is the time difference?
S-Wave - P-Wave
→
6:07:30 - 6:02:00 = 5:30 (5 hours, 30 minutes)
3. 3,800 km (page 11 of your ESRT)
Earth’s Layers
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Earth’s interior structures are known through the study of seismic waves
Seismic waves refract, reflect, change velocity, and are absorbed depending on the material they are
transmitted through
Lithosphere: Earth’s crust and outermost layer
Continental Crust: Thickest (100 km) and least dense (2.7 g/cm3) part of the lithosphere
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Granitic
Oceanic Crust: Thinnest (2-3 km) and most dense part of the lithosphere (3.0 g/cm3)
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Basaltic
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 6
Asthenosphere - Partially melted layer that flows slowly and is located below the lithosphere
MOHO (Mohorovicíc Discontinuity): Thin interface separating the lithosphere from the asthenosphere
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Speed of seismic waves suddenly increases here!
Mantle: Thickest part of Earth (80%) and is between the crust and the outer core
Outer Core: Liquid layer of Earth’s interior between the mantle and the inner core
Inner Core: The solid inner-most zone of Earth’s core composed of iron (Fe) and nickel (Ni)
Earthquake Shadow Zones
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Seismic waves radiate away from the focus
Shadow Zone - Area in which seismic waves are
not detected due to the liquid outer core
→ Waves do not pass through because the waves
refract (bend) due to density differences.
*NO WAVES PASS THROUGH THE SHADOW
ZONE*
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P-waves are refracted when they reach the
liquid outer core
S-waves are absorbed when they reach the outer core and are not transmitted through to the other side
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 7
Earthquakes & Volcanoes
“Ring of Fire:” Isolated belt around the Pacific Ocean where 90% of the world’s volcanoes exist and
earthquakes are extremely common
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Almost all of the world’s worst natural disasters have happened along the “Ring of Fire”
California, Washington, Oregon and Alaska are all located along the “Ring of Fire”
Tsunami: A series of large waves generated from an earthquake that occurred in or near oceans
→ Earthquakes that occurred under the ocean generate the largest tsunamis
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 8
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Earthquakes/Tsunamis/Volcanic Eruptions can cause…
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Power outages, Subsidence of the land (sinking), Liquefaction of the land, Damage to buildings
and bridges, Landslides, mudflows, lahars, Toxic ash clouds, Deaths, Etc...
Continental Drift
Continental Drift: The theory that Earth’s continents are moving atop a
liquid core
Pangaea - “All Earth” or name given to the supercontinent that existed 200
million years ago
Alfred Wegner, 1915 (Pronounced VEGnah)
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○
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German geologist and meteorologist
Proposed the theory of continental drift
Hypothesized a gigantic super continent
Evidence #1
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Similarities in the shape of Africa’s west coast and South America’s
east coast
→ Fits like a jigsaw piece
Evidence #2
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Fossil remains of the Mesosaurus were found in South America and
South Africa
Fossil remains of the Glossopteris were found throughout India,
South America, Africa, and Antarctica
Evidence #3
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Harry Hess (Oceanographer in the army)
discovered mid-ocean ridges (underwater
mountain range) underneath the Atlantic
Ocean.
Deep ocean fossils and and the analysis
of radioactive materials show the age of
the oceanic crust increases with
increasing distance from the mid-ocean ridges!
Harry Hess discovered that strips of dried-up molten rock had iron particles lined up with the poles
They swapped polarity every 780,000 years!
Scientists call it “reversed polarity” and gives us a rate of change for seafloor spreading
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 9
Plate Tectonics
Plate Tectonics - The study of the formation and movements of plates
Plates - Section of the lithosphere that moves around
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Earth’s surface consists of a dozen major plates and some minor ones
The plates are moving at rates close to 10 cm/year
Convection Currents - driving force of plate movement
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Magma heats up causing it to expand and rise
Magma cools down causing it to contract and sink
The plates (solid lithosphere) are moving on top of the asthenosphere (liquid magma) due to density
differences
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The idea of continental drift had been around since the early 1900’s, but lacked enough scientific
evidence to support the theory
New advancements after World War II help provide the evidences needed to validate the Theory of
Plate Tectonics
→ Harry Hess mapped the seafloor and helped to gather scientific evidence by accident.
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Scientist noticed that earthquakes do not occur at random locations, but run throughout the world along
isolated belts
When plotted on a map they outline the plate boundaries
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 10
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Occurs at plate boundaries where plates are interacting
Recall that over 90% of all volcanoes and a majority of earthquakes occur along The Ring of Fire!
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 11
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Sedimentary deposits and igneous lava flows are usually placed down in horizontal layers
Sometimes movement along boundaries causes these layers to tilt or fold
As plates collide they sometimes are pushed upward
Fossilized marine organisms can be found at these high altitudes in the rock
→ Example: Himalaya Mountains!
Plate Boundaries
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Tectonic plates are constantly moving and interacting
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As they move across the asthenosphere and form plate boundaries they interact in various ways
The types of plate boundaries are:
→ Divergent
→ Transform
→ Convergent
Convergent Boundary - boundary
where two lithospheric plates are
coming together
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Example: the India Plate
pushing upward into Eurasian
Plate and creating the
Himalayan Mountains
Three Types of Convergent
Boundaries:
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Ocean - Continental (a)
Ocean - Ocean (b)
Continental - Continental(c)
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Subduction - The process
where one plate is pushed
below another and consumed in
the mantle
Example: ___________________________________________________________________
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Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 12
Divergent Boundary - Boundary where two lithospheric plates are moving apart
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Example: ___________________________________________________________________
Sea Floor Spreading - the process where ocean
floor is extended when two plates move apart
Mid-Ocean Ridge - underwater mountain range
created from a divergent plate boundary
Mid-Atlantic Ridge - a mid-ocean ridge that runs
the length of the Atlantic Ocean
○
Separates the North and South American
Plates from the Eurasian and African Plates
Rift Valley - long narrow valley that runs the entire
length of a mid-ocean ridge system
Scientists dragged a magnetometer across the
ocean floor and discovered a unique magnetic
pattern where stripes of normal and reversed
polarity parallel the mid-ocean ridge flipping every
780,000 years
Rock samples of the deep ocean floor show that basaltic
oceanic crust becomes progressively younger as you approach
the mid-ocean ridge
Transform Boundary: Boundary where two lithospheric plates are
sliding past one another
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Example: The San Andreas Fault is 800 km long and runs
throughout California
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 13
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Hot Spot: Regions where the mantle is heating the crust.
→ Hot spots are NOT located along “The Ring of Fire”
→ Examples: Hawaiian Islands, the Galapagos Islands, Yellowstone, Iceland….etc.
→ As the plates move, hot spots are STATIONARY
=Symbol for Hot Spots on ESRT
Ms. LaCross: Earth Science Chapter 3: The Dynamic Earth: Page 14