Volcanoes and Earthquakes

DAY 1• Objective:Objective:–I can explain how a volcano is

structured

What is a Volcano?

• A mountain formed of lava and/or pyroclastic material

Anatomy of a Volcano• Vent– Opening in the crust

• Crater– Steep-walled depression at the

top

• Magma Chamber–Where the molten rock waits

• Magma Tube– Links the vent to the magma

chamber

Day 2

• ObjectiveObjective: –I can explain what happens when a

volcano erupts

Magma verse Lava

• Magma –Molten rock under

the surface of Earth

• Lava –Molten rock on

the surface of Earth

Factors Affecting Eruption

• Magma Composition

• Magma Temperature

• Amount of Dissolved Gases

Viscosity of Magma

• Substance’s resistance to flow

• Hotter the magma, more fluid and less viscous

• Directly related to its silica content–More silica, greater its

viscosity (slower movement)

Dissolved Gases

• Consist of water vapor and carbon dioxide

• More gases, the more violent the eruption

• Gases–70% water vapor

–15% carbon dioxide

–5% nitrogen

–5% sulfur

• Pyroclastic Material–Fragments ejected

during eruptions

–From very fine to several tons

–Ex:• Volcanic Ash

• Cinders (lapilli)

• Volcanic Bombs

Other Eruption Results

• Pyroclastic Flow– Consist of hot gases,

glowing ash, and large rock fragments

– Races down the steep slope

• Lahar– Mudflow that occurs

when volcanic debris becomes saturated with water and rapidly moves down steep volcanic slopes

DAY 3• Objective– I can describe the locations of volcanoes

and the relationship between volcanoes and plate tectonics

Plate Tectonics & Volcanoes

• Relationship–Plate movement

provided the mechanism by which mantle rock melts to generate magma

Ring of Fire

• Area around the pacific ocean with extreme volcanic activity

• This shows the Pacific Plate Boarder

Intraplate Activity

• Occurs with a plate, not a plate boundary

• Hot Spots– Small volcanic

region a few hundred kilometers across within a plate

– Ex: Hawaiian Islands

DAY 4• Objective:Objective:–I can explain what an earthquake is

–I can explain why earthquakes happen

What is an Earthquake?

• Vibration of Earth

• Produced by a sudden release of energy

• Movement along a fault line

Parts of an Earthquake

• Focus– Point within Earth where

the earthquake starts

• Epicenter– Location on the surface

directly above the focus

• Fault– Associated with

earthquakes activity where movement has occurred

Causes of Earthquakes

• Elastic Rebound Hypothesis– Release of built-up energy

–Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces

–When the strength of the rock exceeded, it suddenly breaks, causing the vibrations of an earthquake

Foreshock vs. Aftershock

• Foreshock–Small earthquakes

before the big quake

• Aftershock–Smaller

earthquakes after the big quake

Seismic Science

• Seismology– Study of earthquake

waves

• Seismograph– Instruments that

record earthquakes

• Seismogram– The record made by

a seismograph

Day 5• Objective:–I can explain how to locate origin of an

earthquake

–I can explain how to measure the strength of an earthquake

Earthquake Waves

• Two Main Types–Surface Waves

–Body Waves• P-waves

• S-waves

Surface Waves

• Seismic waves that travel along Earth’s outer layer

• Moves up & down and side to side

• Most destructive

• Last to arrive at the seismograph

Body Waves

• P-Waves (primary waves)– They push (compress) and pull

(expand) rocks in the direction the wave travels

– Can travel through solids, liquids and gases

– Fastest waves

– First to the seismograph

• S-Waves (secondary waves)–Shakes particles at right angles

to their travel

–Can only travel through solids

–2nd to the seismograph

Locating Earthquakes

• The difference in velocity of a P-Wave & S-Wave provides a way to locate the epicenter– Use a travel-time

curve graph

– Needs at least three seismograph station data

Strength of an Earthquake

• Two different types of measurements to describe the strength of an earthquake– Intensity

–Magnitude

Earthquake Intensity

• A measure of the amount of earthquake shaking at a given location based on the amount of damage

Earthquake Magnitude

• A measure of the size of seismic waves or the amount of energy released at the source of an earthquake

The Richter Scale

• Measures magnitude

• Based on the amplitude of the largest seismic wave

• A TEN-FOLD system

• Largest earthquake record= 9.6 (CHILE)

Moment Magnitude Scale

• More precise

• Amount of displacement that occurs along a fault zone

• Most widely used – Estimates energy

released by earthquakes

Mercalli Intensity Scale

• How much damage occurs

• Depends on:– Strength

– Distance from the epicenter

– Nature of the surface material

– Building design

DAY 6• Objective:–I can describe the dangers of an

Earthquake–I can explain how to make earthquake

predictions

Earthquake Hazards

• Seismic Vibrations–Damage to building

depends on several factors• Intensity of vibration

• Duration of vibration

• What type of material built on

• Design of the structure

• Liquefaction–Stable soil

turns into a liquid that is not able to support building or other structures

• Tsunami–Large ocean

wave created by an earthquake

• Landslides– Greatest damage to

structures

– Sinking of the ground triggered by the vibration

• Fires–Caused by

ruptured gas lines

Predicting Earthquakes

• Short Range–Measure uplift,

subsidence and strain in the rocks–Short-range

predictions have not been successful

• Long Range–Based on the idea

that earthquakes are repetitive

–Seismic Gap• An area along a

fault where there has not been any earthquake activity for a long period of time