EARTHQUAKES

Earthquake Facts

• An earthquake is the shaking and trembling that results from sudden movement of the earth’s crust.

• They occur along plate boundaries where tension builds between rock layers.

• There are over 150,000 earthquakes every year, however only about 75 of these are significantly strong enough to be felt by people.

Map of earthquakes in the past three days (Jan, 2002)

Map of earthquakes in the past week.

Map of earthquakes in the past month, Dec15-Jan15, 2002.

Focus / Epicenter

• Focus - The point below the earth’s surface where the rock breaks.

• Epicenter - point on the surface directly above the focus.

• In general, a shallow focus earthquake causes more damage than a deep focus earthquake.

The Seismograph

P S and Surface Waves

• P Waves arrive first and go through solid and liquid. These are compression waves.

• S Waves arrive second and only go though solid. They travel at right angles to the shock wave.

• Surface waves arrive last and do most of the damage. They are similar to waves on the surface of a lake or ocean.

Earth’s Interior

• P & S waves act like a probe revealing the earth’s interior.

• Remember that P-waves travel through both liquid and solid while S-waves travel only through solids.

If the earth had a solid core this would represent the S/P waves.

The outer core is liquid

• Because earth has a liquid outer core there is an S-wave shadow zone on the opposite side of the world.

Distribution of Earthquakes

Tsunami

• An underwater disturbance such as an earthquake or volcano can cause a Tsunami.

1946, a man stands before a wall of water about to engulf him in Hilo, Hawaii

Tsunami damage in Hawaii from the 1960 Chilean quake.

The Richter Scale

A photo gallery of famous quakes

Orange Trees Displaced along the San Andreas Fault

North Ridge California, 1994

North Ridge California, 1994

Mexico City 1985 Liquefaction

Mexico City, 1985

Tangshan China 1976

San Francisco 1906

San Francisco

Chili 1960 Mag 9.5!

Alaska 1964

Peru 1970

San Francisco 1989

Kobe Japan, 1995

San Fernando California 1971

Some famous earthquakes

• New Madrid Missouri 1811&1812

• San Francisco 1906 (fire damage)

• Alaska 1964 (Good Friday quake)

• 1970 Peru (deadliest in South America)

• Tangshan China 1976 (deadliest this cent.)

• Mexico City 1985 (liquefaction damage)

• Chili 1960 (Most powerful Earthquake)

New Madrid Missouri 1811&12

• In 1811 & 1812 there were three major earthquakes that rocked the central U.S.

• The New Madrid fault line is an old plate boundary.

• The Mississippi River changed its course after these powerful earthquakes.

San Francisco 1906

• This 8.3 magnitude earthquake ruptured many gas lines and destroyed the city.

• 1500 people died many from the resulting fires.

• The San Andreas fault line shifted 21 feet!

Peru 1970

• 66,000 people died making it the deadliest earthquake in South America.

• The 7.8 magnitude quake had a high death toll because many of the adobe houses collapsed and there were massive landslides in the Andes.

Alaska 1964

• This 8.7 magnitude earthquake was one of the most powerful in modern times.

• The quake lasted four minutes however the death toll was only 130.

Tangshan China, 1976

• At 3:40 in the morning on July 28th 1976 a 7.8 magnitude quake obliterated the city of Tangshan China.

• Approximately 500,000 people died making it the deadliest quake in the twentieth century.

Strange Phenomena in Tangshan

• Well water rose & fell three times the day before the quake occurred.

• Chickens refused to eat and mice were seen running around looking for hiding places.

• The night before, people saw strange lights and loud sounds in the sky. (A similar phenomena occurred in Mexico city, 1985.)

Mexico City 1985

• Over 9,000 people died from an 8.1 magnitude earthquake.

• Liquefaction - caused much of the damage.

• Liquefaction is when once stable soil turns into a fluid and cannot support buildings.

End of part I: EarthquakesContinue for part II: Volcanoes

Volcanoes

Presentation Outline

• 1. Cinder Cone Volcanoes

• 2. Shield Volcanoes

• 3. Stratovolcano or composite cone

• 4. Flood Basalts

• 5. Volcanic features

• 6. Volcano vocabulary

Basic Facts on Volcanoes

• There are over 600 active volcanoes. 2/3 of these are found along the ring of fire tectonic plate boundary.

• There are three basic types of volcanoes:

• 1. Shield Volcanoes.

• 2. Stratovolcano or composite cone.

• 3. Cinder Cone Volcanoes.

Location of earthquakes & volcanoes

The three types of Volcanoes

Cinder Cone Volcanoes

• These are generally small volcanoes that build up from ejected lava and rock fragments.

Sunset Carter in Arizona is a typical cinder cone volcano

Sunset crater

Paracutin: Cinder Cone

• In 1943 a cinder cone volcano grew in a farmer’s corn field west of Mexico City.

• In one day the cone grew grew over 130 feet.

Paracutin 1943, Mexico

Paracutin

Paracutin

Church near Paracutin

Capulin Cinder Cone Volcano, New Mexico

Capulin New Mexico

Shield Volcanoes

• Shield Volcanoes have a very broad base and gentle slope.

• The Hawaiian Islands are classic shield volcanoes.

• Shield Volcanoes generally have gentle liquid lava eruptions.

• Mauna Loa is the largest volcano on Earth!

Shield volcanoes

The Hawaiian Shield Volcanoes

Mauna Loa, from its base to summit is 30,000 feet!

Two types of Lava

• Pahoehoe is smooth rope like lava

• AA lava is rough and angular

• Both types of lava are associated with shield volcanoes.

Pahoehoe & AA Lava

Stratovolcano or composite cone

• The stratovolcano or composite cone represents your “typical” volcano.

• These Volcanoes are cones made of alternating layers of lava and pyroclastic rock layers.

The Stratovolcano

Stratovolcano

Indonesia, Where 67% of all volcanic related deaths occur.

Tambora Indonesia

The Tambora Eruption 1815

• This was the most powerful eruption in recorded history and had the highest death toll.

• Over 92,000 died from this eruption mostly from starvation. 1815 was known around the world as “the year without a summer.”

• Ash from Tambora block sunlight causing massive starvation around the world.

Krakatoa Indonesia before & after 1883

Krakatoa 1883

• When Krakatoa erupted it blew away 2/3 of the uninhabited island.

• The Tsunami that resulted killed over 36,000 people on the nearby island of Java.

• The explosion was so powerful it was heard 3,000 miles away in Australia!

Krakatoa today

Krakatoa

Mt. Vesuvius & Pompii Italy

• For over 16 years earthquakes shook the Roman city of Pompii Italy.

• In 79 AD Mt. Vesuvius finally exploded causing hot ash and sulfur gases to bury the city of Pompii.

• Over 20,000 Romans were fossilized from the explosion of Mt. Vesuvius.

Mt Vesuvius & Italy

A fossilized dog from Pompii

A Roman Soldier

A recent 1944 eruption ofMt. Vesuvius

Mt. Pelee & the city of Martinque

• In 1902 Mt. Pelee erupted destroying the Caribbean city Martinque.

• 29,000 people died. The only survivor was a prisoner in an underground jail.

• Nuee ardent is a hot ash flow and caused most of the destruction.

Mt. Pelee today

Mt. Pelee in 1902

Mt. Pelee

The destruction of Martinque

The Cascade Mountain Range

• The Cascade Mountain range is located in the North West United States and contains some of the most famous volcanoes.

• These include: Mt. St. Helens, Crater lake, Mt. Ranier, Mt. Baker, Mt. Hood, Mt. Shasta, Mt. Hood, to name a few.

Crater Lake Oregon

• About 6,000 years ago Mt. Mazama in Oregon blew its top creating a large caldera.

• This caldera filled in with water creating the 6 mile wide Crater Lake National Park.

How Crater Lake formed

Crater Lake Oregon

Crater Lake & Wizard Island

Crater Lake & Wizard Island

Mt. St. Helens 1980

• On May 18, the dormant volcano Mt. St. Helens in Washington state erupted.

• The top 1,300 feet of the mountain disappeared in a few minutes.

Mt. St. Helens, May 1980

The ash fall-out from Mt. St. Helens

Diagram of the eruption

Mt. St. Helens after 1980

Mt. St. Helens today

Volcanic flood basalts

• Liquid lava comes up from cracks or fissures in the earth’s crust. This lava can cover many square miles of earth.

• The dark mare on the moon are flood basalts.

Deccan India

• Deccan India is the worlds largest flood basalt.

• The region in west central India is called the Deccan traps.

• The Deccan traps are composed of black basalt 6,500 feet thick.

Deccan India

Deccan traps, India

The Columbia River flood Basalts

• A large region of the U.S. extending from Yellowstone Wyoming to the Columbia River in Washington is composed of flood basalt.

Flood Basalts in North West U.S.

Arial view of flood basalts

Columbia River Flood Basalt

Columbia River flood basalt

El Malpais National Monument

• A flood basalt igneous rock region extends from New Mexico to Arizona and includes the El Malpais (bad land) national monument.

El Malpais New Mexico

Arial view of flood basalt in New Mexico

El Malpais New Mexico

Lava tube in El Malpais

Volcanic Necks

• When erosion removes the softer rock around a volcano the more resistant volcanic neck is exposed.

• Ship rock New Mexico and Devil’s Tower are two examples of an exposed volcanic neck.

The volcanic neck

Erosion exposes the neck

Devil’s Tower Wyoming

Devil’s Tower

Formation of a Volcanic Neck

Ship Rock New Mexico

Ship Rock New Mexico

Volcanic Vocabulary

• Nuee ardente is a fiery cloud of hot gas.

• Lahar mudslides that result from a volcanic eruption.

Nuee Ardente

Lahar

Three levels of volcanic activity

• 1. Extinct - has not erupted in recorded history.

• 2. Dormant - has erupted in recorded history but is currently “sleeping.”

• 3. Active - means it is currently erupting.

The End