earth science kessel · 2019-07-06 · mountain ranges, such as the himalayas....
TRANSCRIPT
EARTH SCIENCE
KESSEL
Bell Ringer
List everything you KNOW about a volcano
(at least 3 things). Then list everything you
WANT to know about volcanoes (at least 2
things).
Bell Ringer
What evidence might you look for if you
think a volcanic eruption has occurred?
Bell Ringer
Explain how the idea of plate tectonics
influences earthquakes and volcanoes.
Bell Ringer
From what we have talked about previously,
what do you think the Earth’s interior is like?
Layers Defined by Composition
Plate Tectonics, Earthquakes, & Volcanoes
Earth’s interior
consists of three
major zones
defined by their
chemical
composition—the
crust, mantle, and
core.
Earth’s Layered Structure
Layers Defined by Composition
Plate Tectonics, Earthquakes, & Volcanoes
• Composed mainly of oxygen and silicon
Crust
• Varies in thickness
- About 7 km in
oceanic regions
- Continental crust
about 8-40 km
- Exceeds 70 km in
mountainous
regions
Layers Defined by Composition
Plate Tectonics, Earthquakes, & Volcanoes
Mantle
• Composed mainly of silicate rocks rich in
magnesium and iron
• About 2900km thick
- Contains lithosphere,
asthenosphere and
mesosphere.
Layers Defined by Composition
Plate Tectonics, Earthquakes, & Volcanoes
Outer Core
• Composed of nickel-iron alloy
• About 2180km thick
• Outer core is
liquid in
nature
Layers Defined by Composition
Plate Tectonics, Earthquakes, & Volcanoes
Inner Core
• Composed of iron
• About 1220km thick
• Inner core is
solid in nature
Earth’s Layered Structure
Layers Defined by Physical Properties
Plate Tectonics, Earthquakes, & Volcanoes
Lithosphere
• Made up of the crust and uppermost mantle
(about 100 km thick)
• Cool, rigid, solid layer that behaves like solid rock
Layers Defined by Physical Properties
Plate Tectonics, Earthquakes, & Volcanoes
Asthenosphere
• Beneath the lithosphere, above the mesosphere.
• Soft, weak layer that is easily deformed.
• About 700km thick
Bell Ringer
List the layers of Earth that you know of
AND then explain how you think scientists
know these layers.
An Idea Before Its Time
9.1 Continental Drift
Albert Wegener was a
German born polar
researcher, geophysicist and
meteorologist. He is famous
for his hypothesis of
continental drift.
An Idea Before Its Time
Plate Tectonics, Earthquakes, & Volcanoes
Wegener’s continental drift hypothesis
stated that the continents had once been
joined to form a single supercontinent,
Pangaea.
Pangaea
Breakup of Pangaea
An Idea Before Its Time
Plate Tectonics, Earthquakes, & Volcanoes
Evidence • Rock Types and Structures
- Evidence of continental drift exists in the form
of several mountain belts that end at one
coastline, only to reappear across the ocean.
Matching Mountain Ranges
An Idea Before Its Time
Plate Tectonics, Earthquakes, & Volcanoes
Evidence • The Continental Puzzle
An Idea Before Its Time
Plate Tectonics, Earthquakes, & Volcanoes
Evidence
• Matching Fossils
- Fossil evidence
for continental
drift includes
several fossil
organisms found
on different
landmasses.
Glacier Evidence
Rejecting the Hypothesis
Plate Tectonics, Earthquakes, & Volcanoes
A New Theory Emerges
• Wegener could not provide an explanation of
exactly what made the continents move. New
technology lead to findings which then lead to
a new theory called plate tectonics.
Earth’s Major Roles
Plate Tectonics, Earthquakes, & Volcanoes
A plate is one of numerous rigid sections of
the lithosphere that move as a unit over the
material of the asthenosphere.
Types of Plate Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Divergent boundaries are the places where
two plates move apart.
Types of Plate Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Convergent boundaries form where two
plates move together.
Types of Plate Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Transform fault boundaries are where two
plates grind past each other without the
production or destruction of the lithosphere.
Bell Ringer
Has Earth’s surface (the continents) always
looked the way it does now? Explain your
answer in 2-3 sentences.
Divergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Rift Valleys and Seafloor Spreading
• Rift valleys are deep
faulted structures
found along the axes
of divergent plate
boundaries.
Divergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Rift Valleys and Seafloor Spreading
• Seafloor
spreading
produces new
oceanic
lithosphere.
Convergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
A subduction zone occurs when one
oceanic plate is forced down into the
mantle beneath a second plate.
Convergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
• Denser oceanic slab sinks into the asthenosphere.
Oceanic-Continental
• Pockets of magma develop and rise.
• Continental volcanic arcs form by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent.
Oceanic-Continental
Convergent Boundary
Convergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
• Two oceanic slabs converge and one descends beneath the other.
Oceanic-Oceanic
• This kind of boundary often forms volcanoes on the ocean floor.
• Volcanic island arcs form as volcanoes emerge from the sea.
Oceanic-Oceanic
Convergent Boundary
Convergent Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
• When subducting plates contain continental material, two continents collide.
Continental-Continental
• This kind of boundary can produce new
mountain ranges, such as the Himalayas.
Continental-Continental
Convergent Boundary
Collision of India and Asia
Transform Fault Boundaries
Plate Tectonics, Earthquakes, & Volcanoes
Transform faults
• Most join two segments of a mid-ocean ridge.
• At the time of formation, they roughly parallel the direction of plate movement.
• They aid the movement of oceanic crustal material.
Transform Fault Boundary
Evidence for Plate Tectonics
Plate Tectonics, Earthquakes, & Volcanoes
Hot Spots
• A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth’s surface.
• Hot spot evidence supports that the plates move over the Earth’s surface.
Hot Spot
Causes of Plate Motion
Plate Tectonics, Earthquakes, & Volcanoes
The unequal distribution of heat within
Earth causes the thermal convection in the
mantle that ultimately drives plate motion.
• Convective flow is the motion of matter resulting from changes in temperature.
Bell Ringer
Explain, in your own words, how mountains
are formed.
Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
• Focus is the point
within Earth where the
earthquake starts.
• Epicenter is the
location on the surface
directly above the
focus.
An earthquake is the vibration of Earth
produced by the rapid release of energy
Focus and Epicenter
Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
• Faults are fractures in Earth where movement
has occurred.
Faults
Slippage Along a Fault
Cause of Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
Elastic Rebound Hypothesis
• Most earthquakes
are produced by the
rapid release of
elastic energy
stored in rock that
has been subjected
to great forces.
Elastic Rebound Hypothesis
Cause of Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
• An aftershock is a small earthquake that follows
the main earthquake.
• A foreshock is a small earthquake that often
precedes a major earthquake.
Aftershocks and Foreshocks
Cause of Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
Aftershocks and Foreshocks
Earthquake Tools
Plate Tectonics, Earthquakes, & Volcanoes
Seismographs
are
instruments
that record
earthquake
waves.
Earthquake Tools
Plate Tectonics, Earthquakes, & Volcanoes
Seismograms
are traces of
amplified,
electronically
recorded
ground motion
made by
seismographs.
Earthquake Waves
Plate Tectonics, Earthquakes, & Volcanoes
Surface waves
are seismic
waves that travel
along Earth’s
outer layer.
Earthquake Waves
Plate Tectonics, Earthquakes, & Volcanoes
Body Waves
• P waves
Have the greatest
velocity of all
earthquake waves
Travel through
solids, liquids, and
gases
Earthquake Waves
Plate Tectonics, Earthquakes, & Volcanoes
Body Waves
• S waves
Seismic waves that
travel along Earth’s
outer layer
Travel only through
solids
Measuring Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
Scientists have used two different types of
measurements to describe the size of an
earthquake: intensity and magnitude.
Richter Scale
• Based on the
amplitude of the
largest seismic
wave
Measuring Earthquakes
Plate Tectonics, Earthquakes, & Volcanoes
Momentum Magnitude • Most widely used measurement for earthquakes
because it estimates the energy released by earthquakes.
Earthquake Magnitudes
Bell Ringer
Earthquakes are caused by the Earth
shaking. Can you feel all earthquakes?
Explain.
Seismic Vibrations
Plate Tectonics, Earthquakes, & Volcanoes
The damage to buildings and other
structures from earthquake waves depends
on the intensity and duration of the
vibrations, the nature of the material on
which the structure is built, and the design
of the structure.
Earthquake Damage
Seismic Vibrations
Plate Tectonics, Earthquakes, & Volcanoes
Building Design
- The design of the structure
- Unreinforced stone or brick buildings are
the most serious safety threats
- Nature of the material upon which the
structure rests
• Factors that determine structural damage
- Intensity of the earthquake
Seismic Vibrations
Plate Tectonics, Earthquakes, & Volcanoes
Liquefaction
• Saturated material turns fluid
Tsunamis
Plate Tectonics, Earthquakes, & Volcanoes
A tsunami triggered by an earthquake
occurs where a slab of the ocean floor is
displaced vertically along a fault.
Tsunamis
Plate Tectonics, Earthquakes, & Volcanoes
• Large earthquakes are reported to Hawaii from
Pacific seismic stations.
Tsunami Warning System
• Although tsunamis travel quickly, there is
sufficient time to evacuate all but the area
closest to the epicenter.
Other Dangers
Plate Tectonics, Earthquakes, & Volcanoes
• With many earthquakes, the greatest damage
to structures is from landslides and ground
subsidence, or the sinking of the ground
triggered by vibrations.
Landslides
• In the San Francisco earthquake of 1906, most
of the destruction was caused by fires that
started when gas and electrical lines were cut.
Fire
Landslide Damage
Predicting Earthquakes
8.3 Destruction from Earthquakes
• So far, methods for short-range predictions of
earthquakes have not been successful.
Short-Range Predictions
• Scientists don’t yet understand enough about
how and where earthquakes will occur to make
accurate long-term predictions.
Long-Range Forecasts
• A seismic gap is an area along a fault where
there has not been any earthquake activity for a
long period of time.
Discovering Earth’s Layers
8.4 Earth’s Layered Structure
• Velocity of seismic waves increases abruptly below
50 km of depth
• Separates crust from underlying mantle
Shadow Zone
• Absence of P waves from about 105 degrees to
140 degrees around the globe from an earthquake
• Can be explained if Earth contains a core composed of materials unlike the overlying mantle
Moho
Earth’s Interior Showing
P and S Wave Paths
Seismic Waves Paths Through the Earth
Bell Ringer
Describe the similarities between an
earthquake and a tsunami.
Bell Ringer
Based off of your knowledge of plate
tectonics, how do you think volcanoes are
formed?
Anatomy of a Volcano
Plate Tectonics, Earthquakes, & Volcanoes
A volcano is a mountain formed of lava
and/or pyroclastic material
Anatomy of a Volcano
Plate Tectonics, Earthquakes, & Volcanoes
• A conduit, or pipe, carries gas-rich magma to the
surface.
• A crater is the depression at the summit of a
volcano.
Anatomy of a “Typical” Volcano
Types of Volcanoes
Plate Tectonics, Earthquakes, & Volcanoes
Shield Volcanoes
• Shield volcanoes are broad, gently sloping
volcanoes.
Types of Volcanoes
Plate Tectonics, Earthquakes, & Volcanoes
• Cinder cones are small volcanoes built primarily
of pyroclastic material ejected from a single vent.
Small in size; occur in groups
Cinder Cones
Cinder Cones
Types of Volcanoes
Plate Tectonics, Earthquakes, & Volcanoes
Composite Cones • Composite cones are volcanoes composed of
both lava flows and pyroclastic material.
Most are adjacent to the Pacific Ocean
Large size; most violent activity
Composite Cones
Mount St. Helens Before and
After the May 18, 1980, Eruption
Profiles of Volcanic Landforms
Volcanic Material
Plate Tectonics, Earthquakes, & Volcanoes
Pyroclastic Materials
• Pyroclastic
materials is the
term given to
particles
produced in
volcanic
eruptions.
Volcanic Material
Plate Tectonics, Earthquakes, & Volcanoes
Pyroclastic Materials
• The fragments
ejected during
eruptions range
in size from very
fine dust and
volcanic ash to
pieces that weigh
several tons.
Pyroclastic Materials
Volcanic Material
Plate Tectonics, Earthquakes, & Volcanoes
Pyroclastic Materials • Types of pyroclastic material
- Ash and dust—fine, glassy fragments
- Pumice—frothy, air-filled lava
- Lapilli—walnut-sized particles
- Cinders—pea-sized particles
• Particles larger than lapilli
- Blocks—hardened lava
- Bombs—ejected as hot lava
Factors Affecting Eruptions
Plate Tectonics, Earthquakes, & Volcanoes
Viscosity
• Factors affecting viscosity
Temperature (hotter magmas are less viscous)
Composition (silica content)
• Viscosity is the measure of a material's
resistance to flow.
Factors Affecting Eruptions
Plate Tectonics, Earthquakes, & Volcanoes
Dissolved gases
• Mainly water vapor and carbon dioxide
• Violence of an eruption is related to how easily
gases escape from magma
Gases escape easily from fluid magma.
Viscous magma produces a more violent
eruption.
Convergent Plate Boundaries The basic connection between plate
tectonics and volcanism is that plate
motions provide the mechanisms by which
mantle rocks melt to generate magma.
10.3 Plate Tectonics and Igneous Activity
• Rising magma can form continental volcanic arcs
(Andes Mountains).
Ocean-Ocean
Ocean-Continent
• Rising magma can form volcanic island arcs in
an ocean (Aleutian Islands).
Convergent Boundary Volcano
Divergent Plate Boundaries
The greatest volume of volcanic rock is
produced along the oceanic ridge system.
10.3 Plate Tectonics and Igneous Activity
• Lithosphere pulls apart, partial melting occurs, and large quantities of fluid basaltic magma are produced.
Intraplate Igneous Activity
Intraplate volcanism is igneous activity
that occurs within a tectonic plate away
from plate boundaries.
10.3 Plate Tectonics and Igneous Activity
• The activity forms localized volcanic regions called hot spots.
• Most intraplate volcanism occurs where a mass of hotter than normal mantle material called a mantle plume rises toward the surface.
• Examples include the Hawaiian Islands and the Columbia Plateau.
Kilauea, an Intraplate Volcano