Volcanic activity sites along boundaries
description
Transcript of Volcanic activity sites along boundaries
![Page 1: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/1.jpg)
![Page 2: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/2.jpg)
Volcanic activity sites along boundaries
![Page 3: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/3.jpg)
![Page 4: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/4.jpg)
Where do volcanoes occur—and why?
• Divergent [MOR] boundaries – About 75% of erupted lava is found here– Basaltic magma; low viscosity, therefore it flows easily!– Oceanic crust ranges from about 2 km to 10 km thick
• Convergent plate boundaries– Forms about 10% of all erupted magma (on continents or ocean floor)– Ocean-continent or ocean-ocean plate collisions– Volcanoes contain mainly andesite, intermediate in composition
• Isolated hot spots– Under oceanic plates - Hawaii– Under continental plates – Yellowstone NP– At plate boundaries - Iceland
![Page 5: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/5.jpg)
Lithosphere and asthenosphere
![Page 6: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/6.jpg)
Volcanic features
• Composite volcano • Basaltic lava flow
![Page 7: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/7.jpg)
Volcanoes in Ring of Fire
![Page 8: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/8.jpg)
Hawaiian Islands and seamounts
![Page 9: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/9.jpg)
Distance vs age in Hawaiian Islands
![Page 10: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/10.jpg)
Products of volcanic activityMagma becomes lava and other products of eruption• Lava flows
– Basalt flows faster and farther– Higher silica content means slower flowing lava, such as rhyolites
• Pyroclastic debris– Due to high gas content of magma
• Volcanic gases– Many not-so-nice gases
![Page 11: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/11.jpg)
Components of Volcanic Eruptions
• Role of gases• Volcanic explosivity• Mineral composition– Role of silica content– Presence of different elements
![Page 12: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/12.jpg)
![Page 13: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/13.jpg)
Layers of basalt along Columbia River
![Page 14: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/14.jpg)
Mauna Loa, HI, shield volcano
![Page 15: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/15.jpg)
Cinder cone• General structure of cinder cone • Sunset Crater, AZ
![Page 16: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/16.jpg)
Composite or stratovolcano
![Page 17: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/17.jpg)
Domes
Elden Mt in Flagstaff Dome inside Mt St Helens
![Page 18: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/18.jpg)
Observe flow down hillside
![Page 19: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/19.jpg)
CalderaLake Atitlan in central Guatemala
![Page 20: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/20.jpg)
Types of Volcanic Hazards
• Gas emissions• Lava flows• Lahars• Pyroclastic flows• Directed blasts• Landslides and tsunami• Earthquakes
![Page 21: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/21.jpg)
Gas emissions
• Up to 9% of composition• Water vapor (ranges from 50 to >80%)• Carbon dioxide• Sulfur dioxide• Hydrogen sulfide• Lesser gases – HCl, HF, Cl• Creates vesicles when trapped in lava
![Page 22: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/22.jpg)
Fig. 7.05a
W. W. Norton Consider distribution offallout material away fromsource
![Page 23: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/23.jpg)
Lava flows
• Extruded magma creates lava• Movement controlled by composition and
temperature• More basaltic, greater flow due to simple
chemistry (most common type)• Can flow hundreds of kilometers
![Page 24: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/24.jpg)
Hawaii basalt lake
![Page 25: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/25.jpg)
Lahars due to snowmelt
Nevado del Ruiz, ColombiaToutle River, near Mt St Helens
![Page 26: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/26.jpg)
Pyroclastic flows
Combination of gases, ash and other debris
Up to 100s of meters thick
Can travel at >200 km per hour
![Page 27: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/27.jpg)
Mount Rainier, WA
![Page 28: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/28.jpg)
Activity around Mt Rainier, WA
![Page 29: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/29.jpg)
Directed blasts
![Page 30: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/30.jpg)
Landslides and tsunami
![Page 31: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/31.jpg)
Earthquakes
• Caused by rising magma• Usually small
magnitude events• Mostly shallow source
![Page 32: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/32.jpg)
Human toll through history
• Mount Vesuvius, Italy 79 AD• Mount Tambora, Indonesia 1815 (famine)• Krakatua, Indonesia 1883 (tsunami)• Mount St. Helens 1980 (last in continental US)• Lake Nyos 1986 – expulsion of carbon dioxide• Mount Pinatubo, Philippines 1991
Many others listed in Table 3.3 (p.72 of text)
![Page 33: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/33.jpg)
Events are Mt St HelensLook at the stages of development of the eruption
What were the precursors?
Relatively few died (about 60)
![Page 34: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/34.jpg)
Precursors to help mitigate damage
• Active, dormant, or extinct structures• Possible signals of eruptions– Seismic activity changes– Surface heat– Surface bulge– Gas emissions
![Page 35: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/35.jpg)
Type of volcano
Viscosity
(fluidity)
Volatiles(gas
content)
Volume Examples
Shield Low Low Large Hawaii
Flood basalt Low Low Very large Deccan, Columbia River
Scoria Medium Medium Small Paricutin, Stromboli
Stratovolcano (composite)
High High Large Vesuvius, Rainier,Fujiyama
Caldera High High Very large Crater Lake, OR, Krakatoa
Lava domes High Low Small In crater of Mt St Helens; Mt Elden
![Page 36: Volcanic activity sites along boundaries](https://reader036.fdocuments.net/reader036/viewer/2022062501/568163c6550346895dd4f907/html5/thumbnails/36.jpg)
• Sample Questions– Convection cells in the mantle rise and generate
what feature on the ocean floor above the cells? (a) continental plates, (b) active subduction, (c) convergent boundaries, (d) the mid-ocean ridge
– The concept of plate tectonics is classified as a(n): (a) theory, (b) hypothesis,(c) law or principle, (d) unaccepted idea.