op ch09 lecture_earth3 -1, volcanoes
DESCRIPTION
A volcano is an opening, or rupture, in the surface or crust of the Earth or a planetary mass object, which allows hot lava, volcanic ash and gases to escape from the magma chamber below the surface. On Earth, volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are not usually created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of platesTRANSCRIPT
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
©2008 W. W. Norton & Company, Inc.
Portrait of a PlanetThird Edition
earthearth
LECTURE OUTLINE
Chapter 9The Wrath of Vulcan: Volcanic Eruptions
The Wrath of Vulcan: Volcanic EruptionsThe Wrath of Vulcan: Volcanic Eruptions
Prepared by
Ronald ParkerEarlham College Department of Geosciences
Richmond, Indiana
Prepared by
Ronald ParkerEarlham College Department of Geosciences
Richmond, Indiana
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic EruptionsVolcanic Eruptions What is a volcano?What is a volcano?
An erupting vent through which molten rock surfaces. An erupting vent through which molten rock surfaces. A mountain built from magmatic eruptions.A mountain built from magmatic eruptions.
Volcanoes are a clear result of tectonic activity.Volcanoes are a clear result of tectonic activity. Volcanoes pose a number of hazards to humans.Volcanoes pose a number of hazards to humans.
Mexico City.Mexico City. Seattle, U.S.Seattle, U.S. Naples, Italy.Naples, Italy.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
In 79 C.E. Mt. Vesuvius erupted violently.In 79 C.E. Mt. Vesuvius erupted violently. Pyroclastic flows destroyed Pompeii, killing 20,000. Pyroclastic flows destroyed Pompeii, killing 20,000. A record of Roman life was preserved under ash. A record of Roman life was preserved under ash.
Volcanic EruptionsVolcanic Eruptions
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic EruptionsVolcanic Eruptions Unpredictable, dangerous. Unpredictable, dangerous.
Build large mountains.Build large mountains. Blow mountains to bits.Blow mountains to bits.
Eruptions can…Eruptions can… Provide highly productive Provide highly productive
soils to feed a civilization.soils to feed a civilization. Can extinguish a civilization Can extinguish a civilization
in a matter of minutes.in a matter of minutes.
Eruptions affect climate. Eruptions affect climate.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic MaterialsVolcanic Materials The products of volcanic eruption take three forms: The products of volcanic eruption take three forms:
Lava flows – Molten rock that move over the ground. Lava flows – Molten rock that move over the ground. Pyroclastic debris – Fragments blown out of a volcano. Pyroclastic debris – Fragments blown out of a volcano. Volcanic gases – Vapor and aerosols that exit a volcano. Volcanic gases – Vapor and aerosols that exit a volcano.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Lava FlowsLava Flows Lava can be thin and runny or thick and sticky. Lava can be thin and runny or thick and sticky. Flow type depends on viscosity via composition.Flow type depends on viscosity via composition. Composition depends on silica (SiOComposition depends on silica (SiO22), Fe, and Mg. ), Fe, and Mg.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Lava CompositionsLava Compositions Lavas with high silica / low Fe and Mg are called...Lavas with high silica / low Fe and Mg are called...
Silicic, felsic, or rhyolitic.Silicic, felsic, or rhyolitic.
Lavas with low silica / high Fe and Mg are called…Lavas with low silica / high Fe and Mg are called… Mafic or basaltic.Mafic or basaltic.
Lavas with moderate silica, Fe and Mg are called…Lavas with moderate silica, Fe and Mg are called… Intermediate or andesitic.Intermediate or andesitic.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Basaltic Lava FlowsBasaltic Lava Flows Mafic lava – Very hot, low silica, and low viscosity. Mafic lava – Very hot, low silica, and low viscosity. Basalt flows are often thin and fluid.Basalt flows are often thin and fluid.
They can flow rapidly (up to 100 km/hr).They can flow rapidly (up to 100 km/hr). They can flow for long distances (up to several 100 km).They can flow for long distances (up to several 100 km).
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
PahoehoePahoehoe Pahoehoe (pa-hoy-hoy) - a Hawaiian word Pahoehoe (pa-hoy-hoy) - a Hawaiian word
describing basalt with a glassy, ropy texture.describing basalt with a glassy, ropy texture. Pahoehoe forms when extremely hot basalt forms a skin. Pahoehoe forms when extremely hot basalt forms a skin. With flow, the skin is rolled into ropy ridges and furrows. With flow, the skin is rolled into ropy ridges and furrows.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
A’a’A’a’ A’a’ (ah-ah) is a Hawaiian word describing basalt A’a’ (ah-ah) is a Hawaiian word describing basalt
that solidifies with a jagged, sharp, angular texture.that solidifies with a jagged, sharp, angular texture. A’a’ forms when hot flowing basalt cools and thickens.A’a’ forms when hot flowing basalt cools and thickens. With flow, lava crumbles into shards and fragments.With flow, lava crumbles into shards and fragments.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Lava TubesLava Tubes A cooled crust forms on top of a basalt flow.A cooled crust forms on top of a basalt flow. A conduit – a lava tube – develops in the flow. A conduit – a lava tube – develops in the flow. Tubes prevent cooling, facilitating flow for miles. Tubes prevent cooling, facilitating flow for miles. Lava tubes become caves that can transmit water. Lava tubes become caves that can transmit water.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Columnar JointingColumnar Jointing Solidified flows may contract with vertical fractures Solidified flows may contract with vertical fractures
that are hexagonal in cross-section. that are hexagonal in cross-section. Columnar jointing indicates lava. Columnar jointing indicates lava.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Pillow BasaltsPillow Basalts Underwater, basalt cools instantly; it cannot flow.Underwater, basalt cools instantly; it cannot flow. It cools to form a rounded blob called a pillow.It cools to form a rounded blob called a pillow.
The pillow surface is cracked, quenched glass.The pillow surface is cracked, quenched glass. Lava pressure ruptures a pillow to form the next blob.Lava pressure ruptures a pillow to form the next blob. The process repeats to form a mound of pillow basalts.The process repeats to form a mound of pillow basalts.
Common on the MOR.Common on the MOR.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Andesitic Lava FlowsAndesitic Lava Flows Higher SiOHigher SiO22 content makes andesitic lavas viscous. content makes andesitic lavas viscous.
Unlike basalt, they do not flow rapidly.Unlike basalt, they do not flow rapidly. Instead, they mound around the vent and flow slowly.Instead, they mound around the vent and flow slowly.
The outer crust fractures, creating rubble.The outer crust fractures, creating rubble. Andesitic lava flows remain close to the vent.Andesitic lava flows remain close to the vent.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Rhyolitic Lava FlowsRhyolitic Lava Flows Rhyolite; the highest SiORhyolite; the highest SiO22 – the most viscous lava. – the most viscous lava. Rhyolitic lava rarely flows.Rhyolitic lava rarely flows. Rather, lava plugs the vent as a lava dome.Rather, lava plugs the vent as a lava dome. Sometimes, lava domes are blown to smithereens. Sometimes, lava domes are blown to smithereens.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Pyroclastic DebrisPyroclastic Debris Fragmental material ejected from a volcano.Fragmental material ejected from a volcano. Glass shards, fragmented lava in a range of sizes. Glass shards, fragmented lava in a range of sizes.
Ash – Powdery glass shards. Ash – Powdery glass shards. Lapilli – Pea- to plum-sized material.Lapilli – Pea- to plum-sized material. Blocks and bombs – Apple- to refrigerator-sized. Blocks and bombs – Apple- to refrigerator-sized.
Blocks – Pre-existing rock torn from the volcano.Blocks – Pre-existing rock torn from the volcano.Bombs – Streamlined fragments of ejected lava.Bombs – Streamlined fragments of ejected lava.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Pyroclastic DebrisPyroclastic Debris Tephra – Deposits of pyroclastic debris. Tephra – Deposits of pyroclastic debris.
Volcanic agglomerate – Lapilli and bombs near the vent.Volcanic agglomerate – Lapilli and bombs near the vent. Tuff – Lithified ash with or without lapilli.Tuff – Lithified ash with or without lapilli.
Air-fall tuff – Accumulations of ash that fall like snow.Air-fall tuff – Accumulations of ash that fall like snow.Welded tuff (ignimbrite) – Tuff that is deposited while hot.Welded tuff (ignimbrite) – Tuff that is deposited while hot.
Hot pyroclastic flow material that fuses before cooling.Hot pyroclastic flow material that fuses before cooling.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Pyroclastic FlowsPyroclastic Flows Pyroclastic flows (or, Pyroclastic flows (or, nunuéée ardentes - Frenche ardentes - French):):
200200ooC - 450C - 450ooC avalanches of hot ash that race downslope.C avalanches of hot ash that race downslope. Moving up to 300 kph, they incinerate all in their path.Moving up to 300 kph, they incinerate all in their path. Immediately deadly; they kill everything quickly.Immediately deadly; they kill everything quickly. Many famous examples: Vesuvius, Mt. PelMany famous examples: Vesuvius, Mt. Peléée, Augustine.e, Augustine.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
LaharsLahars Tephra is readily moved by water as a debris flow.Tephra is readily moved by water as a debris flow. Known as lahars, these flows are often deadly.Known as lahars, these flows are often deadly.
Lahars move rapidly (up to 50 km/hr).Lahars move rapidly (up to 50 km/hr). They have the consistency of wet cement,.They have the consistency of wet cement,. A distinct hazard to people living in volcanic valleys.A distinct hazard to people living in volcanic valleys.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic Gas Volcanic Gas 1 to 9% of magma may be gas. 1 to 9% of magma may be gas.
Water (HWater (H22O) – Most abundant dissolved gas.O) – Most abundant dissolved gas.
Carbon dioxide (COCarbon dioxide (CO22) – Second in abundance.) – Second in abundance.
Sulfur dioxide (SOSulfur dioxide (SO22) – Rotten egg smell.) – Rotten egg smell.
Magma composition controls gas content. Magma composition controls gas content. Felsic magmas are gas-rich; Mafic magmas are less so. Felsic magmas are gas-rich; Mafic magmas are less so.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic Gas Volcanic Gas Gases are expelled as magma rises (P drops).Gases are expelled as magma rises (P drops). SOSO22 reacts with water to form aerosol sulfuric acid. reacts with water to form aerosol sulfuric acid. Style of gas escape controls eruption violence. Style of gas escape controls eruption violence.
Low viscosity (basalt) – Easy escape; mellow eruption.Low viscosity (basalt) – Easy escape; mellow eruption. High viscosity (rhyolite) – Difficult escape; violent.High viscosity (rhyolite) – Difficult escape; violent.
Gas bubbles in rock are Gas bubbles in rock are
called vesicles.called vesicles.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcanic ArchitectureVolcanic Architecture Volcanoes have characteristic features. Volcanoes have characteristic features.
A magma chamber.A magma chamber. Fissures and vents.Fissures and vents. Craters.Craters. Calderas.Calderas. Distinctive profile.Distinctive profile.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Magma ChamberMagma Chamber Located in the upper crust.Located in the upper crust.
Usually an open cavity or area of highly fractured rock.Usually an open cavity or area of highly fractured rock. Contains a large quantity of magma.Contains a large quantity of magma.
Some magma cools here to form intrusive rock.Some magma cools here to form intrusive rock.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Magma ChamberMagma Chamber Some magma rises via a conduit to the surface. Some magma rises via a conduit to the surface. Magma may also erupt along a linear tear, a fissure. Magma may also erupt along a linear tear, a fissure.
Fissure eruptions may display a “curtain of fire.”Fissure eruptions may display a “curtain of fire.” Fissures evolve into discrete vents.Fissures evolve into discrete vents.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
VentsVents A vent is a lava outlet on a volcano.A vent is a lava outlet on a volcano. Vents can form anywhere on the volcano.Vents can form anywhere on the volcano.
Summit vent – Located at the top of the volcano.Summit vent – Located at the top of the volcano. Flank vent – Located on the side of a volcano. Flank vent – Located on the side of a volcano.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
CratersCraters Crater – A bowl-shaped depression atop a volcano.Crater – A bowl-shaped depression atop a volcano. Craters are up to 500 m across; 200 m deep.Craters are up to 500 m across; 200 m deep. Form as erupted lava piles up around the vent.Form as erupted lava piles up around the vent. accentuate by summit collapse into conduit. accentuate by summit collapse into conduit.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
CalderaCaldera A gigantic volcanic depression. A gigantic volcanic depression.
Much larger than a crater.Much larger than a crater. 1-10s of kilometers across.1-10s of kilometers across.
Magma chamber empties.Magma chamber empties. Volcano collapses into it.Volcano collapses into it.
Crater Lake, Oregon.Crater Lake, Oregon. Yellowstone National Park.Yellowstone National Park.
Crater Lake Caldera, OregonCrater Lake Caldera, Oregon
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Shapes and SizesShapes and Sizes Magma type governs volcano shape and size.Magma type governs volcano shape and size. Categories:Categories:
Shield volcanoes – Largest.Shield volcanoes – Largest. Cinder cones – Smallest.Cinder cones – Smallest. Stratovolcanoes – Intermediate in size.Stratovolcanoes – Intermediate in size.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcano TypesVolcano Types Shield volcanoes.Shield volcanoes.
Broad, slightly domed-shaped (like an inverted shield).Broad, slightly domed-shaped (like an inverted shield). Lateral flow of low-viscosity basaltic lava. Lateral flow of low-viscosity basaltic lava. Have a low slope and cover large geographic areas.Have a low slope and cover large geographic areas. Mauna Loa on Hawaii is a good example.Mauna Loa on Hawaii is a good example.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcano TypesVolcano Types Cinder cone – Conical piles of tephra.Cinder cone – Conical piles of tephra.
The smallest type of volcano.The smallest type of volcano. Built of ejected lapilli-sized fragments piled up at a vent.Built of ejected lapilli-sized fragments piled up at a vent. Slopes are at the angle of repose. Slopes are at the angle of repose. Often symmetrical with a deep summit crater.Often symmetrical with a deep summit crater.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Volcano TypesVolcano Types Stratovolcanoes (composite volcanoes).Stratovolcanoes (composite volcanoes).
Large, cone-shaped volcano.Large, cone-shaped volcano. Composed of alternating layers of lava and tephra.Composed of alternating layers of lava and tephra. Often symmetric; can be odd shapes from landslides, etc.Often symmetric; can be odd shapes from landslides, etc. Examples include Mt. Fuji, Mt. Rainier, Mt. Vesuvius.Examples include Mt. Fuji, Mt. Rainier, Mt. Vesuvius.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Eruptive StyleEruptive Style Will it flow, or will it blow? Two dominant styles.Will it flow, or will it blow? Two dominant styles.
Effusive eruptions – Produce lava flows.Effusive eruptions – Produce lava flows. Explosive eruptions – Blow up.Explosive eruptions – Blow up.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Eruptive StyleEruptive Style Effusive eruptions – Produce lava flows.Effusive eruptions – Produce lava flows.
Lava flows stream away from vents.Lava flows stream away from vents. Lava lakes can form around the vent.Lava lakes can form around the vent. Can produce huge lava fountains.Can produce huge lava fountains.
Commonly basaltic, these eruptions create shields. Commonly basaltic, these eruptions create shields.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Eruptive StyleEruptive Style Explosive eruptions – Produce pyroclastic flows.Explosive eruptions – Produce pyroclastic flows.
Caused by gas pressure in the more viscous magma.Caused by gas pressure in the more viscous magma. Pressure is released explosively. Pressure is released explosively. Create stratovolcanoes.Create stratovolcanoes. May create calderas.May create calderas. Blanket the landscape with tephra.Blanket the landscape with tephra.
Andesitic and rhyolitic compositions.Andesitic and rhyolitic compositions.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Eruptive StyleEruptive Style Phreatomagmatic eruptions – Less common style.Phreatomagmatic eruptions – Less common style.
Volcanic eruption where magma interacts with water. Volcanic eruption where magma interacts with water. Some phreatomagmatic eruptions can be cataclysmic.Some phreatomagmatic eruptions can be cataclysmic.
A magma chamber breaches and admits water.A magma chamber breaches and admits water.Water flashes to steam and blows the entire volcano apart.Water flashes to steam and blows the entire volcano apart.Examples: Santorini, Krakatau.Examples: Santorini, Krakatau.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Controls on Eruptive StyleControls on Eruptive Style Viscosity – Controls the ease of lava flow.Viscosity – Controls the ease of lava flow.
Basalt – Low-viscosity lava flows away from vent.Basalt – Low-viscosity lava flows away from vent. Felsic – High-viscosity lava builds-up at the vent.Felsic – High-viscosity lava builds-up at the vent.
Gas Pressure – Greater P favors explosive style.Gas Pressure – Greater P favors explosive style. Basalt – Low-viscosity allows gas release.Basalt – Low-viscosity allows gas release. Felsic – High-viscosity prevents gas release.Felsic – High-viscosity prevents gas release.
Environment – Where eruption occurs important. Environment – Where eruption occurs important. Subaerial lava flowing on land cools slower than…Subaerial lava flowing on land cools slower than… Submarine lava, which is quickly quenched.Submarine lava, which is quickly quenched.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Tectonic SettingsTectonic Settings Plate motion is a dominant control on volcanism.Plate motion is a dominant control on volcanism. Volcanic types are linked to tectonic settingsVolcanic types are linked to tectonic settings
Hot spots - Where mantle plumes cut the lithosphere. Hot spots - Where mantle plumes cut the lithosphere. Oceanic hot spots.Oceanic hot spots.Continental hot spots and flood basalts.Continental hot spots and flood basalts.
Mid-ocean ridges – Spreading axes.Mid-ocean ridges – Spreading axes. Convergent boundaries – Subduction zones.Convergent boundaries – Subduction zones. Continental rifts – Incipient ocean basins.Continental rifts – Incipient ocean basins.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Hot Spot EruptionsHot Spot Eruptions Oceanic hot spot – Plume under an oceanic plate. Oceanic hot spot – Plume under an oceanic plate.
Basalt erupts at the seafloor and forms a growing mound. Basalt erupts at the seafloor and forms a growing mound. A volcano builds above sea level to form an island.A volcano builds above sea level to form an island. Then basalt will not quench and can flow long distances.Then basalt will not quench and can flow long distances. Lava builds upward and outward and the island grows. Lava builds upward and outward and the island grows. Submarine slumps remove large masses of the volcano. Submarine slumps remove large masses of the volcano.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Hot Spot EruptionsHot Spot Eruptions Continental hot spot – Cuts a continental plate. Continental hot spot – Cuts a continental plate.
Often erupts both basaltic and rhyolitic material.Often erupts both basaltic and rhyolitic material.Basaltic – Makes up the mantle plume. Basaltic – Makes up the mantle plume. Rhyolitic – Basalt melts the granitic crust it passes through.Rhyolitic – Basalt melts the granitic crust it passes through.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Hot Spot EruptionsHot Spot Eruptions Continental hot spots.Continental hot spots.
Flood basalts – Voluminous lava eruption above a plume.Flood basalts – Voluminous lava eruption above a plume.Thinned lithosphere erupts magma from long fissures. Thinned lithosphere erupts magma from long fissures. Lava spreads over large areas; great thicknesses stack up.Lava spreads over large areas; great thicknesses stack up.With time, a shrinking plume creates “normal” volcanoes.With time, a shrinking plume creates “normal” volcanoes.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
MOR EruptionsMOR Eruptions Most lava erupts along the mid-ocean ridge (MOR).Most lava erupts along the mid-ocean ridge (MOR). MOR-produced oceanic crust covers 70% of Earth.MOR-produced oceanic crust covers 70% of Earth. Basalt erupted from fissures quenches as pillows.Basalt erupted from fissures quenches as pillows. Pillow mounds are pulled apart with plate motion. Pillow mounds are pulled apart with plate motion.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Convergent BoundariesConvergent Boundaries Most volcanoes form at convergent boundaries. Most volcanoes form at convergent boundaries.
Volatiles from subducting plate initiate melting. Volatiles from subducting plate initiate melting. Arc volcanoes develop on overriding plate.Arc volcanoes develop on overriding plate.
May cut through oceanic or continental crust.May cut through oceanic or continental crust.
The “Ring of Fire” dominates Pacific margins.The “Ring of Fire” dominates Pacific margins.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Continental RiftsContinental Rifts Yield an array of volcano types reflecting...Yield an array of volcano types reflecting...
Partial melting of the mantle (mafic magmas).Partial melting of the mantle (mafic magmas). Partial melting of the crust (felsic magmas).Partial melting of the crust (felsic magmas).
Examples:Examples: East African Rift.East African Rift. Basin and Range.Basin and Range. Mid-continent Rift.Mid-continent Rift.
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
©2008 W. W. Norton & Company, Inc.
Portrait of a PlanetThird Edition
earthearth
LECTURE OUTLINE
Chapter 9The Wrath of Vulcan: Volcanic Eruptions
This concludes the