2.2b earthquakes and volcanoes

Earthquakes Vocabulary• Focus – the area

along a fault at which slippage first occurs, initiating an earthquake.

• Epicenter – the point on Earth’s surface directly above the focus.

EarthquakesVocabulary• Seismic waves –

waves of energy that travels through the earth as a result of earthquakes, explosion or heavy impact on Earth.

• Kinds of Seismic Waves:• P waves• S waves• Surface waves

Earthquakes Vocabulary• P waves – Primary

Waves; the longitudinal waves generated by an earthquake.

• S waves – secondary waves; the transverse waves generated by an earthquake.

Earthquakes Vocabulary• Surface waves –

Surface waves are analogous to water waves and travel along the Earth's surface.

What Are Earthquakes

• Earthquake - A sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust or volcanic action.

What Are Earthquakes

• Occur mostly at the boundaries of tectonic plates when plates shift.

• Rocks along edges of tectonic plates experience immense pressure.

What Are Earthquakes

• Rocks break as stress becomes so great.• Energy is released as seismic waves when

rocks break along fault line.

What Are Earthquakes• The exact place

where the rocks first break where the earthquake originates is called the focus.

• The Point on the surface directly above the surface is called the epicenter.

Energy is transferred by waves• P waves also

known as longitudinal waves, move faster through rocks than other seismic waves.

• So they are the first waves experienced

Energy is transferred by waves• P waves travel

by compressing Earth’s crust in front of it and stretching the crust behind it.

Energy is transferred by waves• S waves are also

known as transverse waves.

• They move more slowly through Earth.

• Thus called secondary waves (S waves)

Energy is transferred by waves• S waves motion

is like that of a rope shaken up and down and/or side to side.

Earthquakes Vocabulary• Seismology – the

study of earthquakes and related phenomena.

• Seismologist – a person studying seismology

Earthquakes Vocabulary• Richter scale – a

scale that express the relative magnitude of earthquakes.

• Seismograph – a machine that records earthquake data.

17.2 Kind of Volcanoes• Shield Volcano Magma rich in iron and

magnesiumVery fluidLava flows great distances

Eruption mildEruption occur several timesLava produces gently sloping

mountain

17.2 Kinds of Volcanoes• Composite Volcano

Made up of alternating layers of ash, cinders and lava

Magma is thicker Gases are trapped in the

magma making explosive eruptions

Typically thousand meters high

Steeper cones than shield volcanoes

17.2 Kinds of Volcanoes• Cinder Cone

Smallest and most abundant volcanoes

Tend to be active for a short time then become dormant

Vast quantities of ash and lava fall around vent that form the cone

Gas-trapped magma – explosive eruption

17.2 Earthquakes and Volcanoes• Kinds of Volcanoes