EARTH SCIENCE KESSEL · 2019-07-06 · mountain ranges, such as the Himalayas. Continental-Continental Convergent Boundary . Collision of India and Asia . Transform Fault Boundaries

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



• 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



Mantle

• Composed mainly of silicate rocks rich in

magnesium and iron

• About 2900km thick

- Contains lithosphere,

asthenosphere and

mesosphere.



Outer Core

• Composed of nickel-iron alloy


• Outer core is

liquid in

nature



Inner Core

• Composed of iron


• Inner core is

solid in nature

Earth’s Layered Structure

Layers Defined by Physical Properties


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


Asthenosphere

• Beneath the lithosphere, above the mesosphere.

• Soft, weak layer that is easily deformed.


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.



Wegener’s continental drift hypothesis

stated that the continents had once been

joined to form a single supercontinent,

Pangaea.

Pangaea

Breakup of Pangaea



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



Evidence • The Continental Puzzle



Evidence

• Matching Fossils

- Fossil evidence

for continental

drift includes

several fossil

organisms found

on different

landmasses.

Glacier Evidence

Rejecting the Hypothesis


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


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


Divergent boundaries are the places where

two plates move apart.



Convergent boundaries form where two

plates move together.



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


Rift Valleys and Seafloor Spreading

• Rift valleys are deep

faulted structures

found along the axes

of divergent plate

boundaries.

Divergent Boundaries


Rift Valleys and Seafloor Spreading

• Seafloor

spreading

produces new

oceanic

lithosphere.

Convergent Boundaries


A subduction zone occurs when one

oceanic plate is forced down into the

mantle beneath a second plate.



• 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



• 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



• 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


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


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


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


• 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


• Faults are fractures in Earth where movement

has occurred.

Faults

Slippage Along a Fault

Cause of Earthquakes


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



• 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



Aftershocks and Foreshocks

Earthquake Tools


Seismographs

are

instruments

that record

earthquake

waves.

Earthquake Tools


Seismograms

are traces of

amplified,

electronically

recorded

ground motion

made by

seismographs.

Earthquake Waves


Surface waves

are seismic

waves that travel

along Earth’s

outer layer.

Earthquake Waves


Body Waves

• P waves

Have the greatest

velocity of all

earthquake waves

Travel through

solids, liquids, and

gases

Earthquake Waves


Body Waves

• S waves

Seismic waves that

travel along Earth’s

outer layer

Travel only through

solids

Measuring Earthquakes


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


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


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


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


Liquefaction

• Saturated material turns fluid

Tsunamis


A tsunami triggered by an earthquake

occurs where a slab of the ocean floor is

displaced vertically along a fault.

Tsunamis


• 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


• 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


A volcano is a mountain formed of lava

and/or pyroclastic material

Anatomy of a Volcano


• 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


Shield Volcanoes

• Shield volcanoes are broad, gently sloping

volcanoes.

Types of 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


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


Pyroclastic Materials

• Pyroclastic

materials is the

term given to

particles

produced in

volcanic

eruptions.

Volcanic Material



• The fragments

ejected during

eruptions range

in size from very

fine dust and

volcanic ash to

pieces that weigh

several tons.


Volcanic Material


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


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


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.


• 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.


• 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

Documents

EARTH SCIENCE KESSEL · 2019-07-06 · mountain ranges, such as the Himalayas. Continental-Continental Convergent Boundary . Collision of India and Asia . Transform Fault Boundaries