The Dynamic Earth

ESSC 1010 The Dynamic Earth Prof. Kennet E. Flores Visualizing Geology

3rd Edition Barbara W. Murck Brian J. Skinner

Chapter 6 Volcanoes and Igneous Rocks 1. Volcanoes and Volcanic Hazards 2. How, Why, and Where Rock Melts 3. Cooling and Crystallization 4. Plutons and Plutonism Copyright © 2012 by John Wiley & Sons, Inc. Volcanoes and Volcanic Hazards Volcanoes

Volcano •A vent through which lava, solid rock debris, volcanic ash, and gasses erupt from Earth’s crust to its surface Volcanoes

Volcano •Can be explosive or nonexplosive Volcanoes

Volcano •The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit.

• This describes just one of many types of volcano, and the features of volcanoes are much more complicated http://video.nationalgeographic.com/video/news/150 220-volcano-drones-vin?source=relatedvideo Volcanoes

Volcanic materials •Lava, fragments of rock, and glassy volcanic ash Volcanoes

Lava •Molten rock that reaches Earth’s surface Volcanoes

Pyroclast • Fragment of rock ejected during volcanic eruptions Volcanoes

Tephra • All the pyroclas ejecta from a volcano • It range from car-size rocks (blocks) to ultrafine volcanic ash Volcanoes

Bishop Tuff, Long Valley Caldera (California)

Clast size Pyroclast Tephra Pyroclastic rock (mainly unconsolidated (mainly consolidated) <0.063 mm Fine ash Fine ash Fine tuff <2 mm Coarse ash Coarse ash Corse tuff <64 mm Lapillus Layer of lapilli or lapilli tephra Lapilli tuff or lapillistone >64 mm Block, bomb Agglomerate Pyroclastic breccia Volcanoes

Mt. Etna, Sicily Santorini, Greece Clast size Pyroclast Tephra Pyroclastic rock (mainly unconsolidated (mainly consolidated) <0.063 mm Fine ash Fine ash Fine tuff <2 mm Coarse ash Coarse ash Corse tuff <64 mm Lapillus Layer of lapilli or lapilli tephra Lapilli tuff or lapillistone >64 mm Block, bomb Agglomerate Pyroclastic breccia Volcanoes

Clast size Pyroclast Tephra Pyroclastic rock (mainly unconsolidated (mainly consolidated) <0.063 mm Fine ash Fine ash Fine tuff <2 mm Coarse ash Coarse ash Corse tuff <64 mm Lapillus Layer of lapilli or lapilli tephra Lapilli tuff or lapillistone >64 mm Block, bomb Agglomerate Pyroclastic breccia Volcanoes

The different kinds of eruptions and the volcanoes they build have much to do with the physical properties of the magma that lies at their source Volcanoes

Magma •Molten rock, which may include fragments of rock, volcanic glass and ash, or gas Eruptions, Landforms, and Materials Volcanoes and eruptions

VEI Plume height Eruption type Frequency Example

0 <100 m (330 ft) Hawaiiann Continuous Kilauea

100–1,000 m Hawaiian/Strombo 1 Months Stromboli (300–3,300 ft) liann

Strombolian/Vulca 2 1–5 km (1–3 mi) Months Galeras(1992) nian

Nevado de 3 3–15 km (2–9 mi) Vulcanian Yearly Ruiz (1985)

10–25 km (6– Eyjafjallajökull 4 Vulcanian/Peléan Few years 16 mi) (2010)

Mount St. 5 >25 km (16 mi) Plinian 5–10 years Helens (1980)

Plinian/Ultra Krakatoa 6 >25 km (16 mi) 1,000 years Plinian (1883) Tambora 7 >25 km (16 mi) Ultra Plinian 10,000 years (1815) Lake Toba (74 8 >25 km (16 mi) Ultra Plinian 100,000 years ka)

VEI: Volcanic Explosivity Index Eruptions, Landforms, and Materials Volcanoes and eruptions

Eruption types It depends of two factors (a) Viscosity of the magma and (b) amount of gas dissolved in it

Eruptions, Landforms, and Materials Volcanoes and eruptions

Viscosity • Degree to which a substance resists flow. • A less viscous liquid is runny, whereas a more viscous liquid is thick.

Eruptions, Landforms, and Materials Volcanoes and eruptions

Volcanic Gases • Water vapor, carbon dioxide, sulfur dioxide, etc. • They can cause a volcano to explode Eruptions, Landforms, and Materials Volcanoes and eruptions

Hawaiian eruptions https://www.youtube.com/watch?v=6VfsKoH-ScA •Consist of very runny lava that flows easily •These flows gradually build shield volcanoes Eruptions, Landforms, and Materials Volcanoes and eruptions

• Shield volcanoes are broad, flat volcanoes with gently sloping sides, built of successive lava flows Eruptions, Landforms, and Materials Volcanoes and eruptions

• Tallest mountains in Earth (10 Km from b.s.l. to a.s.l.)

Eruptions, Landforms, and Materials Volcanoes and eruptions

• In shield volcanoes sometimes the lava rises to the surface through long fissures rather than central craters Eruptions, Landforms, and Materials Volcanoes and eruptions

• These fissures produce flood basalts or basalt plateaus Eruptions, Landforms, and Materials Volcanoes and eruptions

The classic volcano profile of a shield volcano Eruptions, Landforms, and Materials Volcanoes and eruptions

https://www.youtube.com/watch?v=6I5rC-ibqi4 Strombolian eruptions •More explosive than Hawaiian •Create loose volcanic rock called spatter cones or cinder cones Eruptions, Landforms, and Materials Volcanoes and eruptions

https://www.youtube.com/watch?v=mIX43uy4Zvg Vulcanian eruptions • More explosive than Strombolian and, as a result, can generate billowing clouds of ash up to 10 km. Eruptions, Landforms, and Materials Volcanoes and eruptions

Pyroclastic flows are hot volcanic fragments (tephra), buoyed by heat and volcanic gases, flow very rapidly

Vulcanian eruptions https://www.youtube.com/watch?v=Cvjwt9nnwXY • Produce pyroclastic flows Eruptions, Landforms, and Materials Volcanoes and eruptions

https://www.youtube.com/watch?v=CCujnt68bVg Plinian eruptions • Named after Pliny the Elder, who died during eruption of Mount Vesuvius Eruptions, Landforms, and Materials Volcanoes and eruptions

Plinian eruptions • Most violent eruptions, generating ash columns that can exceed 20 kilometers Eruptions, Landforms, and Materials Volcanoes and eruptions

Plinian eruptions • Produce steep-sided volcanoes, called stratovolcanoes Eruptions, Landforms, and Materials Volcanoes and eruptions

• Stratovolcanoes are composed of solidified lava flows interlayered with pyroclastic material. • Steep sides curve upward Eruptions, Landforms, and Materials

The classic volcano profile of a stratovolcano Eruptions, Landforms, and Materials

Other volcanic features • Craters Eruptions, Landforms, and Materials

Other volcanic features • Resurgent dome

Eruptions, Landforms, and Materials

Other volcanic features • Thermal spring

Eruptions, Landforms, and Materials

Other volcanic features • Geysers

Eruptions, Landforms, and Materials

Other volcanic features • Fumaroles

Volcanic Hazards Volcanic Hazards

Deadly eruptions Volcanic Hazards Primary effects •Lava flows •Pyroclastic flows •Volcanic gases

Secondary effects •Related to, but not a direct result of, volcanic activity • Fires • Flooding • Mudslides • Debris Kalapana, Hawaii avalanche Volcanic Hazards Primary effects •Lava flows •Pyroclastic flows •Volcanic gases

Secondary effects •Related to, but not a direct result of, volcanic activity • Fires • Flooding • Mudslides • Debris Pompeii, Mt. Vesuvious avalanche Volcanic Hazards Primary effects •Lava flows •Pyroclastic flows •Volcanic gases

Secondary effects •Related to, but not a direct result of, volcanic activity • Fires • Flooding • Mudslides • Debris Ijen, East Java avalanche Volcanic Hazards Primary effects •Lava flows •Pyroclastic flows •Volcanic gases

Secondary effects •Related to, but not a direct result of, volcanic activity • Fires • Flooding • Mudslides • Debris Lahar from Mount St Helens avalanche Volcanic Hazards

Tertiary and beneficial effects

•Change a landscape

•Affect climate on regional and global scale

•Renew mineral content and replenish fertility

•Geothermal energy

•Provide mineral deposits Volcanic Hazards

Tertiary and beneficial effects

•Change a landscape

•Affect climate on regional and global scale

•Renew mineral content and replenish fertility

•Geothermal energy

•Provide mineral deposits Volcanic Hazards

Tertiary and beneficial effects

•Change a landscape

•Affect climate on regional and global scale

•Renew mineral content and replenish fertility

•Geothermal energy

•Provide mineral deposits Volcanic Hazards

Tertiary and beneficial effects

•Change a landscape

•Affect climate on regional and global scale

•Renew mineral content and replenish fertility

•Geothermal energy

•Provide mineral deposits Volcanic Hazards

Tertiary and beneficial effects

•Change a landscape

•Affect climate on regional and global scale

•Renew mineral content and replenish fertility

•Geothermal energy

•Provide mineral deposits Predicting Eruptions

Volcano monitoring from the ground Predicting Eruptions Predicting Eruptions

Establishing a volcano’s history •Active •Dormant

Monitoring changes and anomalies •Earthquakes •Shape or elevation •Volcanic gases •Ground temperature •Composition of water

Monitoring volcanoes from orbit How, Why, and Where Rocks Melt How, Why, and Where Rocks Melt

Geothermal gradient

Heat and pressure inside Earth: • Continental crust: temperature rises 30°C/km, then about 6.7°C/km. • Ocean crust: temperature rises twice as rapid. How, Why, and Where Rocks Melt Effect of temperature and pressure on melting How, Why, and Where Rocks Melt Heat and Pressure Inside Earth

Fractional melt •A mixture of molten and solid rock How, Why, and Where Rocks Melt Heat and Pressure Inside Earth

Fractionation •Separation of melted materials from the remaining solid material during the course of melting How, Why, and Where Rocks Melt Magma and Lava

Magma •Molten rock below surface

Lava •Magma when it reaches the surface

•Differs in composition, temperature, and viscosity

Two types of lava flows How, Why, and Where Rocks Melt Magma and Lava

Composition •45% to 75% of magma by weight is silica. •Water vapor and carbon dioxide are usually present. Temperature •Lavas vary in temperature between 750°C and 1200°C.

•Magmas with high H2O contents melt at lower temperatures. Viscosity •Lavas vary in their ability to flow. •Influenced by silica content and temperature. How, Why, and Where Rocks Melt Magma and Lava

Three types of magma Basaltic •45% to 50% of magma by weight is silica •Little dissolved gas •Oceanic crust How, Why, and Where Rocks Melt Magma and Lava

Three types of magma Andesitic •60% of magma by weight is silica. • 2-4% dissolved gas (mainly water vapor) •Subduction zones How, Why, and Where Rocks Melt Magma and Lava

Three types of magma Rhyolitic • 70-75% of magma by weight is silica. •3- 8% dissolved gas (mainly water vapor) •Continents How, Why, and Where Rocks Melt Tectonic setting and volcanism How, Why, and Where Rocks Melt Tectonic setting and volcanism Oceanic, divergent margins • Lava is thin with a steep geothermal gradient.

Midocean ridge: submarine basaltic pillow lavas How, Why, and Where Rocks Melt Tectonic setting and volcanism Continental divergent margins • Lava is high in silica.

Continental rift: rhyolitic and lavas with unusual composition How, Why, and Where Rocks Melt Tectonic setting and volcanism Subduction zones •Typically have high water content and melt at lower temperatures.

Ocean-ocean subduction zone

Ocean-continent subduction zone How, Why, and Where Rocks Melt Tectonic setting and volcanism Hot spots • Lava tends to be hot and basaltic and build giant shield volcanoes

Shield volcano Cooling and Crystallization Cooling and Crystallization

Crystallization •The process whereby mineral grains form and grow in a cooling magma (or lava) •Classified as: • Volcanic • Plutonic

Cooling and Crystallization Rate of Cooling

Rapid cooling: Volcanic rocks and textures

•Volcanic rock • An igneous rock formed from lava • Glassy • Aphanitic • Porphyritic • Pumice

• Vesicular basalt Glassy texture Cooling and Crystallization Rate of Cooling

Rapid cooling: Volcanic rocks and textures

•Volcanic rock • An igneous rock formed from lava • Glassy • Aphanitic • Porphyritic • Pumice

• Vesicular basalt Aphanitic texture Cooling and Crystallization Rate of Cooling

Rapid cooling: Volcanic rocks and textures

•Volcanic rock • An igneous rock formed from lava • Glassy • Aphanitic • Porphyritic • Pumice

• Vesicular basalt Porphyritic texture Cooling and Crystallization Rate of Cooling

Slow cooling: Plutonic rocks and textures

•Plutonic rock • An igneous rock formed underground from magma • Phaneritic: A coarse-grained texture • Can have Plutonic rock textures exceptionally large grains Cooling and Crystallization Chemical Composition Igneous rocks subdivided into three categories based on silica content: •Mafic, Intermediate, and Felsic

Cooling and Crystallization Fractional crystallization a) Filter pressing

b) Crystal settling c) Crystal flotation

•Separation of crystals from liquids during crystallization Bowen’s reaction series •Predictable melting and cooling of minerals Cooling and Crystallization Fractional crystallization

•Separation of crystals from liquids during crystallization Bowen’s reaction series •Predictable melting and cooling of minerals Plutons and Plutonism Plutons and Plutonism

Plutons •Any body of intrusive igneous rock, regardless of size or shape Plutons and Plutonism Plutonic features

Batholith A large, irregularly shaped pluton that cuts across the layering of the rock into which it intrudes

Stock Is a smaller version of a batholith, only 10km or so its maximum dimensions

Laccolith A mushroom-shaped pluton between pre-existing layers

Plutons and Plutonism

Batholiths are so huge that map views give us the best perspective. Plutons and Plutonism

Xenoliths A foreign rock (preexisting rocks) Plutons and Plutonism Plutonic features

Dike A tabular pluton that runs perpendicular to pre- existing layers They form when magma squeezes into a cross- cutting fracture and solidifies Plutons and Plutonism Plutonic features

Dike Plutons and Plutonism Plutonic features

Sill A sheet-like pluton that is parallel to pre- existing layers They form when magma intrudes between two layers and is parallel to them.

Plutons and Plutonism Plutonic features

Sill

Plutons and Plutonism Plutonic features

Volcanic neck Remnant of a volcanic pipe that once fed the magma to the volcanic vent

Plutons and Plutonism Plutonic features

Devil’s Tower, Wyoming