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Chapter 9
The Wrath of Vulcan: Volcanic Eruptions
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
The Wrath of Vulcan: Volcanic Eruptions
Prepared by
Ronald Parker
Earlham College Department of Geosciences
Richmond, Indiana
Volcanic Eruptions

What is a volcano?
An erupting vent through which molten rock surfaces.
 A mountain built from magmatic eruptions.

Volcanoes are a clear result of tectonic activity.
 Volcanoes pose a number of hazards to humans.

Mexico City.
 Seattle, U.S.
 Naples, Italy.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Eruptions
In 79 C.E. Mt. Vesuvius erupted violently.
 Pyroclastic flows destroyed Pompeii, killing 20,000.
 A record of Roman life was preserved under ash.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Eruptions

Unpredictable, dangerous.
Build large mountains.
 Blow mountains to bits.


Eruptions can…
Provide highly productive
soils to feed a civilization.
 Can extinguish a civilization
in a matter of minutes.


Eruptions affect climate.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Materials

The products of volcanic eruption take three forms:
Lava flows – Molten rock that move over the ground.
 Pyroclastic debris – Fragments blown out of a volcano.
 Volcanic gases – Vapor and aerosols that exit a volcano.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Lava Flows
Lava can be thin and runny or thick and sticky.
 Flow type depends on viscosity via composition.
 Composition depends on silica (SiO2), Fe, and Mg.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Lava Compositions

Lavas with high silica / low Fe and Mg are called...


Lavas with low silica / high Fe and Mg are called…


Silicic, felsic, or rhyolitic.
Mafic or basaltic.
Lavas with moderate silica, Fe and Mg are called…

Intermediate or andesitic.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Basaltic Lava Flows
Mafic lava – Very hot, low silica, and low viscosity.
 Basalt flows are often thin and fluid.

They can flow rapidly (up to 100 km/hr).
 They can flow for long distances (up to several 100 km).

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Pahoehoe

Pahoehoe (pa-hoy-hoy) - a Hawaiian word
describing basalt with a glassy, ropy texture.
Pahoehoe forms when extremely hot basalt forms a skin.
 With flow, the skin is rolled into ropy ridges and furrows.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
A’a’

A’a’ (ah-ah) is a Hawaiian word describing basalt
that solidifies with a jagged, sharp, angular texture.
A’a’ forms when hot flowing basalt cools and thickens.
 With flow, lava crumbles into shards and fragments.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Lava Tubes
A cooled crust forms on top of a basalt flow.
 A conduit – a lava tube – develops in the flow.
 Tubes prevent cooling, facilitating flow for miles.
 Lava tubes become caves that can transmit water.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Columnar Jointing
Solidified flows may contract with vertical fractures
that are hexagonal in cross-section.
 Columnar jointing indicates lava.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Pillow Basalts
Underwater, basalt cools instantly; it cannot flow.
 It cools to form a rounded blob called a pillow.

The pillow surface is cracked, quenched glass.
 Lava pressure ruptures a pillow to form the next blob.
 The process repeats to form a mound of pillow basalts.


Common on the MOR.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Andesitic Lava Flows

Higher SiO2 content makes andesitic lavas viscous.
Unlike basalt, they do not flow rapidly.
 Instead, they mound around the vent and flow slowly.

The outer crust fractures, creating rubble.
 Andesitic lava flows remain close to the vent.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Rhyolitic Lava Flows
Rhyolite; the highest SiO2 – the most viscous lava.
 Rhyolitic lava rarely flows.
 Rather, lava plugs the vent as a lava dome.
 Sometimes, lava domes are blown to smithereens.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Pyroclastic Debris
Fragmental material ejected from a volcano.
 Glass shards, fragmented lava in a range of sizes.

Ash – Powdery glass shards.
 Lapilli – Pea- to plum-sized material.
 Blocks and bombs – Apple- to refrigerator-sized.

Blocks – Pre-existing rock torn from the volcano.
Bombs – Streamlined fragments of ejected lava.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Pyroclastic Debris

Tephra – Deposits of pyroclastic debris.
Volcanic agglomerate – Lapilli and bombs near the vent.
 Tuff – Lithified ash with or without lapilli.

Air-fall tuff – Accumulations of ash that fall like snow.
Welded tuff (ignimbrite) – Tuff that is deposited while hot.
Hot pyroclastic flow material that fuses before cooling.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Pyroclastic Flows

Pyroclastic flows (or, nuée ardentes - French):
200oC - 450oC avalanches of hot ash that race downslope.
 Moving up to 300 kph, they incinerate all in their path.
 Immediately deadly; they kill everything quickly.
 Many famous examples: Vesuvius, Mt. Pelée, Augustine.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Lahars
Tephra is readily moved by water as a debris flow.
 Known as lahars, these flows are often deadly.

Lahars move rapidly (up to 50 km/hr).
 They have the consistency of wet cement,.
 A distinct hazard to people living in volcanic valleys.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Gas

1 to 9% of magma may be gas.
Water (H2O) – Most abundant dissolved gas.
 Carbon dioxide (CO2) – Second in abundance.
 Sulfur dioxide (SO2) – Rotten egg smell.


Magma composition controls gas content.

Felsic magmas are gas-rich; Mafic magmas are less so.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Gas
Gases are expelled as magma rises (P drops).
 SO2 reacts with water to form aerosol sulfuric acid.
 Style of gas escape controls eruption violence.

Low viscosity (basalt) – Easy escape; mellow eruption.
 High viscosity (rhyolite) – Difficult escape; violent.


Gas bubbles in rock are
called vesicles.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Architecture

Volcanoes have characteristic features.
A magma chamber.
 Fissures and vents.
 Craters.
 Calderas.
 Distinctive profile.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Magma Chamber

Located in the upper crust.
Usually an open cavity or area of highly fractured rock.
 Contains a large quantity of magma.


Some magma cools here to form intrusive rock.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Magma Chamber
Some magma rises via a conduit to the surface.
 Magma may also erupt along a linear tear, a fissure.

Fissure eruptions may display a “curtain of fire.”
 Fissures evolve into discrete vents.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Vents
A vent is a lava outlet on a volcano.
 Vents can form anywhere on the volcano.

Summit vent – Located at the top of the volcano.
 Flank vent – Located on the side of a volcano.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Craters
Crater – A bowl-shaped depression atop a volcano.
 Craters are up to 500 m across; 200 m deep.
 Form as erupted lava piles up around the vent.
 Accentuated by summit collapse into conduit.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Caldera

A gigantic volcanic depression.
Much larger than a crater.
 1-10s of kilometers across.

Magma chamber empties.
 Volcano collapses into it.

Crater Lake, Oregon.
 Yellowstone National Park.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Crater Lake Caldera, Oregon
Shapes and Sizes
Magma type governs volcano shape and size.
 Categories:

Shield volcanoes – Largest.
 Cinder cones – Smallest.
 Stratovolcanoes – Intermediate in size.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcano Types

Shield volcanoes.
Broad, slightly domed-shaped (like an inverted shield).
 Lateral flow of low-viscosity basaltic lava.
 Have a low slope and cover large geographic areas.
 Mauna Loa on Hawaii is a good example.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcano Types

Cinder cone – Conical piles of tephra.
The smallest type of volcano.
 Built of ejected lapilli-sized fragments piled up at a vent.
 Slopes are at the angle of repose.
 Often symmetrical with a deep summit crater.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcano Types

Stratovolcanoes (composite volcanoes).
Large, cone-shaped volcano.
 Composed of alternating layers of lava and tephra.
 Often symmetric; can be odd shapes from landslides, etc.
 Examples include Mt. Fuji, Mt. Rainier, Mt. Vesuvius.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptive Style

Will it flow, or will it blow? Two dominant styles.
Effusive eruptions – Produce lava flows.
 Explosive eruptions – Blow up.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptive Style

Effusive eruptions – Produce lava flows.
Lava flows stream away from vents.
 Lava lakes can form around the vent.
 Can produce huge lava fountains.


Commonly basaltic, these eruptions create shields.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptive Style

Explosive eruptions – Produce pyroclastic flows.
Caused by gas pressure in the more viscous magma.
 Pressure is released explosively.
 Create stratovolcanoes.
 May create calderas.
 Blanket the landscape with tephra.


Andesitic and rhyolitic compositions.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptive Style

Phreatomagmatic eruptions – Less common style.
Volcanic eruption where magma interacts with water.
 Some phreatomagmatic eruptions can be cataclysmic.

A magma chamber breaches and admits water.
Water flashes to steam and blows the entire volcano apart.
Examples: Santorini, Krakatau.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Controls on Eruptive Style

Viscosity – Controls the ease of lava flow.
Basalt – Low-viscosity lava flows away from vent.
 Felsic – High-viscosity lava builds-up at the vent.


Gas Pressure – Greater P favors explosive style.
Basalt – Low-viscosity allows gas release.
 Felsic – High-viscosity prevents gas release.


Environment – Where eruption occurs important.
Subaerial lava flowing on land cools slower than…
 Submarine lava, which is quickly quenched.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptions to Remember

Mt. St. Helens – Erupted May 18, 1980, 8:32 A.M.
Earthquake-triggered landslide released pressure.
 Initial vertical blast followed by a much stronger lateral
blast that tore off the entire north side.
 396 m was blasted away.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Eruptions to Remember

Mt. St. Helens – Erupted May 18, 1980, 8:32 A.M.
The blast devastated 600 km2 and killed 61 people.
 Lahars plugged the Toutle River; closed the Columbia.
 Ash fell in North Dakota; highways and rail lines stopped.
 Destroyed timber valued at several $100 million.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Tectonic Settings
Plate motion is a dominant control on volcanism.
 Volcanic types are linked to tectonic settings


Hot spots - Where mantle plumes cut the lithosphere.
Oceanic hot spots.
Continental hot spots and flood basalts.
Mid-ocean ridges – Spreading axes.
 Convergent boundaries – Subduction zones.
 Continental rifts – Incipient ocean basins.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Hot Spot Eruptions

Oceanic hot spot – Plume under an oceanic plate.
Basalt erupts at the seafloor and forms a growing mound.
 A volcano builds above sea level to form an island.
 Then basalt will not quench and can flow long distances.
 Lava builds upward and outward and the island grows.
 Submarine slumps remove large masses of the volcano.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Hot Spot Eruptions

Continental hot spot – Cuts a continental plate.

Often erupts both basaltic and rhyolitic material.
Basaltic – Makes up the mantle plume.
Rhyolitic – Basalt melts the granitic crust it passes through.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Hot Spot Eruptions

Continental hot spots.

Yellowstone – Eruption 640 ka created a 100 km caldera.
1000 times more powerful than Mt. St. Helens.
Deposited 10s of m of ignimbrites.
Magma beneath the caldera still fuels geysers.
Heads a hot spot track.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Hot Spot Eruptions

Continental hot spots.

Flood basalts – Voluminous lava eruption above a plume.
Thinned lithosphere erupts magma from long fissures.
Lava spreads over large areas; great thicknesses stack up.
With time, a shrinking plume creates “normal” volcanoes.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
MOR Eruptions
Most lava erupts along the mid-ocean ridge (MOR).
 MOR-produced oceanic crust covers 70% of Earth.
 Basalt erupted from fissures quenches as pillows.
 Pillow mounds are pulled apart with plate motion.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Iceland

Iceland is a hot spot beneath the MOR.
Lava has built the hot spot/ridge above sea level.
 The island is being torn apart by plate motion.
 Volcanoes trace the MOR rift.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Convergent Boundaries

Most volcanoes form at convergent boundaries.
Volatiles from subducting plate initiate melting.
 Arc volcanoes develop on overriding plate.

May cut through oceanic or continental crust.

The “Ring of Fire” dominates Pacific margins.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Continental Rifts

Yield an array of volcano types reflecting...
Partial melting of the mantle (mafic magmas).
 Partial melting of the crust (felsic magmas).


Examples:
East African Rift.
 Basin and Range.
 Mid-continent Rift.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Volcanic eruptions cause great harm to humans.
Eruptions have profoundly influenced human history.
 In the past 2,000 years: an estimated 250,000 deaths.


Many populated areas ring active volcanoes.


More humans live in volcano hazard areas than ever.
Understanding volcanic
behavior is the best defense.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Lava flows – Lava threats are mostly from basalt.
Lava may completely destroy immovable objects.
 It is rare for lava flows to kill people.

Usually there is enough notice.
Lava rarely moves faster than people.
Sometimes people watching lava flows are killed.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Tephra – Ash and lapilli fall around the volcano.
Can completely bury landscapes, killing plants and crops.
 Tephra is heavy; it causes roof collapses.
 Tephra is gritty; it abrades car and airplane engines.
 Floodwaters easily move tephra as deadly lahars.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Pyroclastic flows – aka nuée ardente
Clouds of roiling ash and gas that race downslope.
 Ride over a carpet of superheated air.

Eases passage of the flow.
Permits high velocities.

Immediately deadly to anything living.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Blast – Rarely, explosions are ejected sideways.

Mt. St. Helens – Lateral blast tore off north side.
Destroyed over 600 km2 of forest.
Killed 61 people.

Blast hazard is uncommon; most eruption is vertical.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Landslides – Eruption-related slope failures.

Eruptions can trigger landslides.
Large masses of material are deposited rapidly near vent.
Earthquakes initiate failure of unstable slopes.

Mt. St. Helens.
The eruption immediately followed a 3 km3 slope failure.
Slide material moved more than 20 km from the peak.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Lahars – Mudflows result when water moves ash.
Like concrete, this material is more dense than water.
 It can carry away everything (people, houses, bridges).
 Nevada del Ruiz, Colombia, buried Armero +25,000 people.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Earthquakes – Moving magma causes earthquakes.
Although usually small in magnitude, they are frequent.
 Can cause slope failures and damage to structures.


Tsunamis – Water explosions create giant waves.

Tsunamis from Krakatau (1883) killed 36,000.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanic Hazards

Gas – Volcanic gases can be poisonous (H2S, CO2).

Lake Nyos, Cameroon, 1986.
Magmatic CO2 built up in the lake located in a crater.
The lake overturned (burped) and the CO2…
Moved down the valleys as a heavier-than-air underflow.
Killed 1,742 people; 6,000 cattle.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Active vs. Extinct

Recurrence interval – Average between eruptions.
Active – Erupting, recently erupted or likely to erupt.
 Dormant – Volcano that has not erupted in 100s to 1000s
of years (but could still do so).
 Extinct – No longer capable of erupting.

Tectonic changes can shut off the magma “fuel.”
 After extinction, erosion takes over.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Predicting Eruptions

Warning signs precede most eruptions.
Earthquake activity – Magma flow increases seismicity.
 Heat flow – Magma causes volcanoes to “heat-up.”
 Changes in shape – Magma causes expansion.
 Emission increases – Changes in gas mix and volume.

These signs indicate that an eruption is imminent.
 They cannot predict the exact timing or the style.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Mitigating Hazards

Danger assessment maps.

Delineate danger areas.
Pyroclastic flows.
Lahars.
Landslides.

Used for planning, zoning.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Mitigating Hazards

Evacuation – Moving those at high risk saves lives.
Mt. St. Helens – Timely evacuation saved 100s.
 Sometimes eruptions don’t occur, large expenses.


Diverting flows – Flowing lava can be diverted.
Explosives.
 Heavy equipment.
 Seawater.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanoes and Climate
Volcanic aerosols and fine-debris block sunlight.
 Examples of volcanism affecting climate

Mt. Tambora, Indonesia – 1815
 Pinatubo, Philippines – 1991


Makes for more
intense sunsets.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanoes and Civilization
Humans and volcanoes have coexisted for millenia.
 This coexistence has both bad and good facets.

Volcanic soils are highly fertile; excellent for crops.
 Civilizations have prospered and been erased.

Minoans - Santorini
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
Volcanoes on Other Planets

Volcanic activity evident on the Moon and planets.
Lunar maria (dark “seas”) are regions of flood basalts.
 Olympus Mons – Extinct Martian shield volcano.
 The Jovian moon Io has active volcanoes.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions
This concludes the
Chapter 9
The Wrath of Vulcan: Volcanic Eruptions
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions