ESC1000 Earth Science Summer 2016

ESC1000 Earth Science Summer 2016 As a scientifically literate citizen, what 3 questions would you ask about this volcano if you moved to the city in the foreground (Tacoma, Washington)? Volcanoes (Chapter 6) 1

Volcanoes As a scientifically literate citizen, what 3 questions would you ask about this volcano if you moved to the city in the foreground (Tacoma, Washington)? Also, lava can do many things: https://www.youtube.com/ watch?v=i5mdnkv8dza 2

500 million people live near 1500 active volcanoes worldwide. Fewer than 200 volcanoes have instruments to assess potential for eruption A third have records of previous eruptions 2 or 3 eruptions per decade are major disasters 3

Chapter 6: Volcanoes and Other Mountains 1. The Volcano Commandos 2. Magma Viscosity 3. Magma Sources and Magma Composition 4. The Mount St. Helens Eruption 5. Products of Volcanic Eruptions 6. Volcanoes and Volcanic Landforms 7. Mountains: Why are They There? 8. The Rise and Fall of Mountains and Temperatures Copyright McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 4

Volcanoes: Learning Goals Why (and where) are there different types of volcanoes? How are the types of volcanoes related to: Plate boundaries Hot spots Shield volcanoes, stratovolcanoes, cinder cones Why (and where) are there different types of volcanic lava? How are the types of lava related to: Plate boundaries Hot spots Basaltic, rhyolitic, andesitic Viscosity Silica content?? 5

Products of Volcanic Eruptions Major products of volcanic eruptions: Airborne lateral blast, tephra, volcanic gases Flows on land lava, pyroclastic flows, lahars 6

Products of Volcanic Eruptions Eruption of Mount St. Helens reduced height of volcano by 400 meters Features near volcano were blown over or carried away by products of eruption Geologist David Johnston (right) died at this site (Johnston s Ridge) located 10 km from the volcano. 7

Airborne Products of Volcanic Eruptions Tephra represents particles blasted into air by eruption Volcanic bombs and ash are found near and far from eruption source, respectively Blobs of magma solidify to form lava bombs Wind can transport fine volcanic ash for hundreds of kilometers downwind 8

Products of Volcanic Eruptions on Land Low viscosity lava can flow up to 50 km from its source Lava transported to front of lava flows in long lava tubes Lava flows build up in a series of layers Viscosity: resistance to flow 9

Products of Volcanic Eruptions on Land Low viscosity lava can flow up to 50 km from its source Lava transported to front of lava flows in long lava tubes Lava flows build up in a series of layers Walter s Kalapana store, Hawai i, was buried in lava within a few weeks in 1990 10

Products of Volcanic Eruptions on Land Pyroclastic flow dense cloud formed from combination of tephra and volcanic gases Fast moving, up to 700 C 11

Part A: During lecture: In-Class Activity 3 Kilauea Nyiragongo Mont Pelée Mt St Helens Describe one of the volcanoes discussed in class, in terms of - whether it s found at a divergent plate boundary, a convergent plate boundary, a transform plate boundary, or a hot spot - the type of magma or lava you d expect to find there - type of volcano (shield, stratovolcano, cinder cone) Part B: At the end of class: Evaluate the scientific evidence (if any) presented in the video about the Yellowstone Super Volcano: https://www.youtube.com/watch?v=epn4llrnqry (more information will be given about Part B when we get to that point) 12

Most active volcanoes are found near convergent plate boundaries. Active volcanoes Convergent plate boundaries (How can you tell?) 13

Most active volcanoes are located at the convergent boundaries around the Ring of Fire. Ring of fire??? Oceanic trenches are a major feature of convergent boundaries. Remember from Plate Tectonics class: Global distribution of active volcanoes One group noticed volcanoes in East Africa and suggested there was a plate boundary there. 14 The Good Earth/Chapter 4: Plate Tectonics

Volcanoes also occur at divergent boundaries and hot spots. Iceland East Africa Hawai i 15

Volcanoes also occur at divergent boundaries and hot spots. Iceland 1 East Africa Hawai i 16

Volcanoes also occur at divergent boundaries and hot spots. Iceland East Africa Hawai i 1 17

Types of Rocks One definition of rocks is that they have crystals. These don t. Questions we ll answer next week: - What are these? - How are they related to volcanoes? - Why are they different? (ARE they different?) 18

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Oceanic and continental crust are different. How is oceanic crust formed? (You should be able to answer this.) How is continental crust formed? The genesis and evolution of continental crust is one of the fundamental questions that remains unresolved in the geosciences. Models that have been proposed for crustal growth include: early extraction of all the crust from the mantle. (Carleton College website) 20

Viscosity: resistance to flow Viscosity of materials decreases with increasing temperature Viscosity varies with composition Magma molten rock below the surface Lava molten rock at the surface 21

Magma Sources and Magma Composition Silica content is controlled by partial melting of rocks at magma source Partial melting occurs when some minerals in a rock melt while others remain solid Minerals with lowest melting temperatures will melt first Silica-rich minerals have lowest melting temperatures Partial melting generates a more silica-rich magma than the parent rock These volcanic products have high silica content. 22

Volcanoes and Other Mountains Conceptest Place the following 4 materials maple syrup, milk, peanut butter, frozen yogurt in the correct positions (A, B, C, D) for their relative viscosity. 23

Different plate locations make magma from melting different rocks. Types of Magma: 1. Basaltic 2. Rhyolitic 3. Andesitic 1 2 3 Types of magma: Basalt: oceanic mantle rocks melt Rhyolite: continental crust melts Andesite: mantle rocks melt 24

1. Basaltic Magma partial melting of parts of asthenosphere below oceanic ridge or hot spots 1 25

2. Rhyolitic Magma melting of parts of continental crust 2 26

3. Andesitic Magma partial melting of mantle rocks (with water) at subduction zone 3 27

Examples of different magma types, at different volcanoes. Oceanic Hot spot Basaltic magma Divergent Boundary Continental Rift Basaltic & Rhyolitic magma Convergent Boundary Oceanic Trench/ Subduction Zone Andesitic magma 28

Other examples of volcanoes: think about what features you might expect them to have. Mount St. Helens Mount Pelée 29

Types of Volcanoes 30

Volcanoes and Volcanic Landforms Three types of volcanoes Shield, stratovolcanoes, cinder cone Composed of different materials Volcano type and eruption style varies with plate setting Different sizes (note size of trees on volcano slopes) Shield volcano Stratovolcano Cinder cone volcano 31

Volcanoes and Volcanic Landforms Shield volcanoes (e.g., Hawaiian Islands) Broad, gentle slopes Built from many low viscosity lava flows (basalt) Relatively mild eruptions associated with hot spots, divergent plate boundaries 32

Volcanoes and Volcanic Landforms Stratovolcanoes (e.g., Osorno, Chile) Most common volcano type Steeper slopes built from alternating layers of tephra and medium viscosity lava (andesite) Form on plates overriding subduction zones at convergent plate boundaries 33

Volcanoes and Volcanic Landforms Cinder cone volcanoes Smallest volcanoes, up to 400 meters elevation Built from more viscous magma products (coarse tephra) May form on slopes of shield or stratovolcanoes Sunset Crater volcano, Arizona 34

Past volcanic eruptions have altered large parts of the Earth s landscape. Other Volcanic Landforms Lava Plateau Hundreds of low viscosity lava flows stack up to on top of each other Individual layers of basalt 10-20 meters thick Plateau thousands of meters thick Form from some of the largest volcanic eruptions e.g., Columbia River plateau 35

Volcanoes and Volcanic Landforms Geysers, Hot Springs, Mud Volcanoes, Fumeroles Form when water circulates near magma chamber Geyser water heated under pressure with volcanic gases Hot spring heated groundwater rises to surface Mud volcano chemical reactions convert rock to clay Fumerole volcanic gases escape in absence of water Geyser Hot Spring Mud volcano Fumerole 36

In-Class Activity 3 Examples of Volcanic Formations and Eruptions Part A: During lecture: Kilauea Nyiragongo Mont Pelée Mt St Helens Describe one of the volcanoes discussed in class, in terms of - whether it s found at a divergent plate boundary, a convergent plate boundary, a transform plate boundary, or a hot spot - the type of magma or lava you d expect to find there - type of volcano (shield, stratovolcano, cinder cone) 37

Examples of Volcanic Formations and Eruptions 38

How do volcanoes (and islands) form at hot spots? 1. Kaua i formed 5,000,000 years ago 2. Kaua i has moved 600 km (600,000 meters) since its formation 3. Kaua i moved 600,000/5,000,000 meters per year = 0.12 m/yr = 12 cm/yr Animation: http://highered.mheducation.com/sites/ 0073524107/student_view0/chapter6/f ormation_of_hawaiian_island_chain_b y_hotspot_volcanism.html 600 km Hawaiian islands form over a hot spot in Pacific Ocean 39 The Good Earth/Chapter 4: Plate Tectonics

Kilauea: Most active volcano in the hot spot of the Hawaiian Islands (one eruption every 4 years) 2014 Pahoa Flow 6 min (UH-Hilo): https://www.youtube.com/watch?v=ddzu-rkzkf0 40

Nyiragongo: Volcano at a divergent plate boundary 2002 eruption of Nyiragongo volcano (2002) Lava flowed through the nearby city of Goma (450,000 residents) Fortunately, toxic volcanic gases trapped in Like Kivu were not released Distribution of older lava flows gave scientists some idea of the potential eruption products of Nyiragongo. 41

Another possible impact is the release of deadly gases from nearby lakes. Poisonous volcanic gases from Lake Nyos, Cameroon, killed 1,700 people in surrounding villages (1986) 42

In the 2002 eruption of Nyiragongo, lava was several meters thick. Lava burned and destroyed buildings in Goma Mt Nyiragongo (DR Congo) Carsten Peter 15 min https://www.youtube.com/watch?v=tliocrycg-g 43

Mont Pelée, Martinique Before 1902 eruption: https://www.youtube.com/watch? v=b58v2zesmvi&list=plsr2pq V04jSqBL1ZaBx65YrUMRYkY0p PS&index=6 After 1902 eruption: https://www.youtube.com/watch?v=9kftxxuor1u&list=plsr2pqv04jsq BL1ZaBx65YrUMRYkY0pPS&index=3 Documentary (intro is from 1991 eruption in Japan that killed volcanologists Maurice and Katia Krafft) https://www.youtube.com/watch?v=- XejSECLqVQ&list=PLsR2PqV04jSqBL1ZaBx65YrUMRYkY0pPS&index=2 https://www.youtube.com/watch?v=c5cayariw8s 44

The Mount St. Helens Eruption Cascade Mountains volcanic arc in Pacific Northwest Major cities within 100 km of active volcanoes Mount St. Helens eruption of May 18, 1980 45

The Mount St. Helens Eruption Prior Activity Early (March) unrest featured Minor eruptions Earthquakes Release of volcanic gases Followed by change in shape of cone (bulge on North flank) Increasing frequency of earthquakes 46

The Mount St. Helens Eruption Mt St Helens 7 min (USGS): https://www.youtube.com/watch?v=xp2dreoi8gi Cascade Mountains Volcanoes formed above subduction zone where Juan de Fuca plate slides beneath North America Mount St. Helens is most active volcano in conterminous US 47

In-Class Activity 3, Part B 48

In-Class Activity 3, Part B Evaluate the scientific evidence (if any) presented in the video about the Yellowstone Super Volcano: https://www.youtube.com/watch?v=epn4llrnqry 1. What does this video tell you about how volcanoes erupt? 2. Do you think that a super volcano is likely to erupt in Yellowstone National Park, in your lifetime? Why or why not?? 3. How does the Yellowstone Super Volcano compare to one of the other volcanoes you learned about today? 49