volcanoes and earthquake

8/12/2019 Volcanoes and Earthquake

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VOLCANOES ANDEARTHQUAKES

Caribbean Studies


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Objectives

To explain what are earthquakes and

volcanoes

To identify major area of earthquake and

volcanic activity.

To assess the positive and negative effects of

earthquakes and volcanoes.


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What are Earthquakes?

The shaking or trembling caused by the

sudden release of energy

Usually associated with faulting or breaking of

rocks

Continuing adjustment of position results in

aftershocks


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Anatomy of an Earthquake

Focus(or hypocentre): the center of energy

release.

Epicentre: the point on the ground surface

immediately above the focus (closest point onthe surface to the focus).


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wo n s o waves romearthquakes

P waves (compressional) 68 km/s.

Parallel to direction of movement (slinky), also

called primary waves. Similar to sound waves.

S waves (shear) 4

5 km/s. Perpendicular to

direction of movement (rope); also called

secondary waves. Result from the shear

Strength of materials. Does not pass throughliquids.


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Tectonic activity in the

Caribbean


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The amount of damage created by an

earthquake depends on several factors.

The earthquakes strength

The kind of rock and soil that underlie an area

The population of the area

The kind of buildings in the area

The time at which the earthquake occurs


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Seismologists

Seismologists study earthquakes. They can

determine the strength of an earthquake by the

height of the wavy line recorded on the paper.

The seismograph record of waves is called aseismogram.

The Richter scale is used to calculate the

strength of an earthquake.

I i d M i d f


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Intensity and Magnitude of

Earthquakes

Magnitude

Often measured using the Richter scale

Based on the amplitude of the largest

seismic wave

Each unit of Richter magnitude equates to

roughly a 32-fold energy increase


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Intensity and Magnitude of

Earthquakes

Intensity

A measure of the degree of earthquake shaking

at a given locale based on the amount of

damage

Most often measured by the Modified Mercalli

Intensity Scale


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What arevolcanoes?


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What is a Volcano?

A volcano is a weak spot in the crustwhere molten material comes to thesurface

Magma reaching the surface is calledlava.A volcanic eruption is the process

wherein volcanic materials such as lava,

fragmented rocks or gases are emitted orejected through a crater, vent or fissure onto the earth's surface to form newdeposits.


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Volcanic Terms

A volcano not known to have erupted within

modern history is classified as an extinct

volcano.

A volcano that has been known to erupt withinmodern times but is now inactive is classified

as a dormant volcano.

An active volcano is one that erupts withercontinually or periodically


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Structure of volcano


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Where do volcanoes occur?

Volcanoes occur most frequently at plate

boundaries.

Some volcanoes, like those that form the

Hawaiian Islands, occur in the interior of platesat areas called hot spots .

The greatest number of volcanoes occur on the

ocean floor along spreading ridges.

Over 80% of those on land occur at edges of

continents, or subduction zones, where one

plate dives, or subducts, under another plate.


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Why do volcanoes occur?

Temperatures in the mantle arehot enough to melt rock into

magma magma.

Less dense than the solid rock

around it, magma rises and

some of it collects in magma

chambers magma chambers.

As the magma rises, pressuredecreases allowing trapped

gasses to expand and propel

the magma through openings in

the Earths surface causing an


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What causes volcanoes?


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What causes volcanoes?

Hot Spots


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Types of VolcanoesShield volcano

Cinder cone volcano

Composite volcano


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What Erupts from a

Volcano?Pyroclastic materialRockfragments created by eruptions

magma explodes from volcano and solidifies in the air

existing rock is shattered by powerful eruptions

Volcanic blocks

Volcanic bombs

Lapilli

Volcanic ash


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Volcanoes in the Caribbean


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QUESTIONS

volcanoes and earthquake

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