• Like
Volcanism
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

Published

 

Published in Technology , Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
809
On SlideShare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
14
Comments
0
Likes
1

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Volcanism By Hans Ulrich Schmincke Presented By Mahmuda Afrin Badhan Mount Holyoke College ‘11 Volcanism By Hans Ulrich Schmincke http://www.fukubonsai.com/images3/VolcanoFlowAug2002.jpg
  • 2. The motivation to study volcanoes comes from wanting to know what happens beneath volcanoes and why they erupt the way they do --- as well as the processes leading to it and how they behave afterwards. Details of recent eruptions are available at www.volcano.si.edu/gvp . (The Global Volcanism Network of the Smithsonian Institution and the US Geological Survey) A VOLCANO is not made on purpose to frighten superstitious people into fits of piety and devotion, nor to overwhelm devoted cities with destruction; a volcano should be considered as a spiracle to the subterranean furnace, in order to prevent the unnecessary elevation of land, and fatal effects of earthquakes; and we may rest assured, that they, in general, wisely answer the end of their intention, without being in themselves an end, for which nature had exerted such amazing power and excellent contrivance. - James Hutton, Theory of the Earth, Codicote, 1795 http://www.photopumpkin.com/wp-content/uploads/volcanoes-1.jpg
  • 3.
    • Myths about demons and gods in the interior of the Earth… ‘Fire from hell’.
    • Beneficial properties of volcanic eruptions: Prometheus provided the basis for human existence by presenting the fire he had stolen from Hephaestus from the interior of the Earth.
    • *Scientific theories* included the idea of heat panned by winds beneath volcanic valves and sulfur or some organic substance causing the fire.
    • Mt. Shasta in N California – believed to be home of ‘exotic communities and bizarre creatures’.
    • Neptunists thought basalt columns were crystal-
    • lized out of water at low temperature.
    • In 1765, Nicolas Desmarest, a French geologist,
    • made findings in Auvergne (France)
    • that lead him to conclude they were formed by
    • solidification of lava on the Earth’s surface.
    • Volcanoes were commonly thought of as super-
    • ficial features which formed not so long ago.
    • Then Plutonists placed the roots of volcanoes
    • much deeper in the Earth, which proved to be
    • right.
    Early Perception of Volcanoes and Volcanic Activities. http://www.bhargavaz.net/rashi/volcano.jpg http://giantcrystals.strahlen.org/europe/basalt1.jpg
  • 4. The First Text…
    • Volcanology became a subdiscipline of Earth Science in the first quarter of the 19th century --- Leopold von Buch, Alexander von Humboldt and Poulett Scrope wrote first textbook on volcanology.
    http://www.bicolbusinessdirectory.com/mayon-volcano-2006-eruption/mayon-volcano01.jpg
  • 5.
    • Why do volcanoes exist and erupt?
    • So that volcanologists have something to do.
    • Prove that the Earth is alive and is in good health.
    • Prove that our planet is very hot and dynamic inside.
    • Feed materials to the Earth’s surface and atmosphere
    • (which was generated by the degassing of volcanoes in the first place).
    • Shows the flux of matter and energy from the
    • Earth’s interior to the surface.
    http://www.stacey.peak-media.co.uk/Year10/B6ManagingHazards/B6ManagingHazards-Tectonics/B6ManagingHazards-Volcano/volcano_7big_montserrat_eruption.jpg
  • 6.
    • How do Volcanoes work?
    • The Volcano-Magma System is divided into four zones for simplicity purposes.
    • Root zones – magma generated by partial melting of pre-existing older rocks.
    • Processes in the root zones explain why a volcano forms at a particular place on the Earth and not somewhere else at any given time, the characteristic magma composition, the way it erupts, i.e. quietly, gushy, highly explosive.
    • The intensity of the eruption depends on:
    • Composition
    • Viscosity of the magma and rise speed
    • Interaction with external water
    • Expansion and bursting of bubbles formed when the magma saturates with volatile compounds.
    http://www.nysm.nysed.gov/services/starks/images/volcano.jpg
  • 7. Also… All volcanoes emit gases, sometimes tens of thousands of tons without erupting explosively. For example, The Merapi volcano is a lava dome oozing out slowly over time and it appears to have lost most of it’s volatility by the time the magma reaches the surface. On the other hand, some volcanoes have ejecta rising as high as 40 km into the atmosphere and gases that rise even higher.
  • 8. The Global Framework of Volcanism
    • Volcanic eruptions created our first crust 4.6 billion years ago.
    • The crust then modified over time due to erosion, covering by sediments, mountain-building and transformed through metamorphism.
    • Crust formation occurs on a day by day scale.
  • 9. Plate Tectonics
    • The volumes, heights and forms of volcanoes fundamentally depend on the physical and chemical properties of the magma.
    • In other words, they depend on the processes in the root zones of the volcanoes whose dynamics is determined by their plate tectonic setting.
    • Because of the motion due to plate tectonics, a single volcano does not tell much about its local origin.
    • Morphology and architecture does not tell the type of tectonic setting; e.g. caldera volcanoes (an irregular to subspherical collapse feature several km to tens of kilometers in diameter within a volcano – formed by roof subsidence over an evacuated magma chamber) form in very different types of tectonic environments.
    • Some volcanoes have forms governed by near-surface processes (e.g. interaction of magma and water) hence unsuitable to associate with any particular tectonic setting.
    • Most volcanoes on Earth form either along convergent or divergent plate margins or in the continental or oceanic plate interiors.
    • The magmas of volcanoes in each of these settings are characterized by specific chemical compositions.
    • The volatile contents are well reflected in the mode of eruption.
    • For example, volcanoes over subduction zones are highly explosive because there the water-rich sediments and oceanic crust are dehydrated at depth and the processes of magma formation are strongly governed by fluid release from the subducted slab.
    • Magma composition and volcanic morphology show more complex characteristics in hybrid plate tectonic settings.
    http://lh3.google.com/_aomLKq12Qmc/RyX7UTZQCpI/AAAAAAAAAeg/0juTvBrpUtE/s800/CIMG1670.JPG
  • 10. Magma
    • What is magma?
    • Silicon is the main constituent of most minerals and rocks in the Earth’s crust and mantle.
    • Magma is molten matter of silicate composition.
    • Most dominant volcanic rocks on Earth are basaltic lavas – like those in the oceanic crust.
    • They are 50% silicon dioxide (SiO 2 ) by weight.
    • For granites, this is 70-75% by weight.
    • Carbonatite is an example of a non-silicate type of magma (which are unusual).
    http://shisa.ukzn.ac.za/pictures/Magma.jpg
  • 11.
    • Where and how are magmas generated?
    • Most magmas have basaltic composition and eruption temperatures of 1100 to 1250 degrees celcius, which is too high for them to have generated in the crust (where the temperature is about 500 degrees celcius).
    • Magma is generated by partial melting of rocks in the Earth’s mantle or, in much smaller amounts, in the lower crust. Volcanoes are basically features on the surface where the magma can erupt.
    • --------
    • Why do magmas rise?
    • They rise because of their lower density compared to the surrounding rocks.
    • They also rise because of dynamic triggers, like the pressure due to rising mantle plumes.
    http://ems.anu.edu.au/projs/pictures/Kavachi.jpg
  • 12. Also…
    • Magmas have varying degrees of differentiation during rise and cooling as well as variable degrees of contamination.
    • There are three melting mechanisms: addition of heat, decrease in pressure and addition of fluid phases to source rock.
    • Primary magma is melt in equilibrium with source rock. It’s composition depends on that of the source rock and degree of melt. The magmas that rise to the Earth’s surface are usually not primary.
    • Basalt magmas are generated in the Earth’s mantle mostly by decompression.
    • Granite magmas are formed mainly by partial melting of lower crust.
    • The magmas that rise to the surface have differentiated and mixed to varying degrees.
    • The most common but least understood magma chambers exist below mid-ocean ridges.
    • The formation of many ore deposits is connected with differentiation of magmas.
  • 13.
    • Temperature, viscosity and gas content of magma can be determined by the chemical composition of a rock, analysis of its mineral components and glass inclusions in the mineral phases.
    • The data framework allows us to predict the behavior of the magma.
    • CO 2 and H 2 0 are the most important magmatic volatiles.
    • In magmas with bubble content <1% by volume, CO 2 is the main gas phase.
    • At ratio H 2 0/C0 2 >1, H 2 0 is the main phase contributing to internal pressure of a degassing magma.
    • Gases such as SO 2 , H 2 S and the halogens, although found in magma, do not contribute much towards the triggering of explosive eruptions because of their low abundancy.
    • The noble gases and N 2 do not play a big role in the pressure build-up in a magma system because they occur in such small amounts.
  • 14.
    • How do Volcanologists work and why do they work on volcanoes?
    • passion for working on volcanoes;
    • recruited by universities and research institutes;
    • motivated by ‘I want to save the world’ (i.e. prevent disasters);
    • strong interest in the ‘most visible manifestation of visible earth’;
    • Morphology of a volcano tells us a lot about the magma and processes
    • involved in the particular eruption.
    • Planetary volcanology has developed a lot from studies made from the
    • active volcanism on Io, a moon of Venus, and also from Volcanic features
    • on Mars and the Moon.
    • Major revolutions in the understanding of how volcanoes work often come from large and well-studied eruptions, some producing greatly underestimated physical effects. For example,
    http://volcanoes.usgs.gov/Imgs/Jpg/Monitoring/Gas/dds24-Gas0004_large.jpg
  • 15.
    • Eruption of Mt. Pelee (Martinique, 1902) – Nuees Ardentes - A French term applied to a highly heated mass of gas-charged ash which is expelled with explosive force and moves at hurricane speed down the mountainside.
    • (Definition from http://volcano.und.edu/vwdocs/glossary.html )
    • Eruption of Taal Volcano (Philippines, 1965) – magma-water contact, base surges.
    • Eruption of Mt. St. Helens (Washington, USA, 18 May 1860) – lasted six years; sector collapse, lateral blasts, eruption forecast.
    • Eruption of El Chichon (Mexico, 1982) – sulphuric acid aerosols, climate impact.
    • Eruption of Pinatubo (Philippines, 19 June 1991) – another milestone in eruption prediction and effective mitigation and understanding volcanic climate forcing.
    • Montserrat (Lesser Antilles, 1995 – present) – mechanisms of dome growth, pyroclastic density currents.
    • Mt. Usu (Japan, March 31 – August 2000) – Phreatic eruptions and major ground deformation)
    • Miyakejima (Japan, July-August, 2000) – lateral magma withdrawal, caldera collapse and ensuing phreatomagmatic eruption
    http://www.montserratreporter.org/Volcano%20Dome%20Jan2199.jpg
  • 16.
    • The Kilauea volcano on the island of Hawaii is know to exhibit more activity than any other volcano on Earth.
    • Its study has lead into more new insights into the architecture and dynamics of active volcanoes, flow and crystallization of lava and gas evolution than any other volcano.
    • Modern analytic instruments used to study volcanoes include mass spectrometers, electron microprobe, broad-band seismometers, remote sensing, GPS, high resolution aerial laser scanning and computer power.
    • Newer methods are the use of ion-probe, single crystal dating, and analytic probing into crystals to determine trace element, isotopic composition, and focused study of gas and fluid intrusion. They also help us look into the origins of magma and their evolution prior to eruption.
    • Observations that help us to detect, quantify and predict processes and eruptions include tracking of airborne ash clouds, deformational evolution of volcanic edifices by radar, infrared radiation of higher temperature areas on active volcanoes, quantitative detection of gas emissions – especially S0 2 (using total ozone mapping spectrometer), mapping aerosol clouds resulting from major Plinian eruptions, and mapping the surface of volcanoes with spatial resolution of better than 10m.
    • Volcanoes are best studied in interdisciplinary fields, although this has proven to be very difficult.
    http://www.wvdhsem.gov/WV_Disaster_Library/Library/Volcano/Mt%20St%20Helens_files/image055.jpg
  • 17. The Impact of Volcanic Activity on the Environment and on Society.
    • Media tends to only report volcanic activity when people or buildings have been harmed, usually because of the social and political problems arising and need of evacuation.
    • People are being informed fully of the potential natural hazards in advance where applicable so that they can prepare themselves for a possible crisis. This is quite a revolution because traditionally the responsible authorities retained such info in order to prevent panic amongst the population.
    • One major task of hazard-focused work is assembling hazard maps which is particularly analysis and mapping of
      • Products of previous volcanic eruptions.
      • Modern theoretical insight into transport mechanisms.
      • Energy involved in the eruption and transport mechanisms.
      • Forecasting likely energies released.
      • Pathways based on analysis of older deposits.
    • Public education has helped increase awareness of the importance of advanced preparation for such a crisis.
    • Most people are reluctant to evacuate unless given strict orders or convinced by widespread gossips.
    • Volcanologists are often consulted about the impact on climate from eruptions. We have the global warming and greenhouse effect issues but are climatic changes also caused by volcanic eruptions? Scientists study the volcanic forcing of climate to get the answers.
  • 18. Man and Volcanoes: The Benefits
    • We’ve benefited more from volcanoes than
    • we’ve suffered because volcanic eruptions
    • have produced:
    • geothermal energy;
    • ore deposits;
    • volcanic soils;
    • volcanic raw materials and their…
    http://www.inhabitat.com/images/steamystuff2.jpg
  • 19. Beauty! http://www.smh.com.au/ffximage/2006/03/01/maunaloa_wideweb__430x322,2.jpg
  • 20.
    • Works Cited
    • Alexander von Humboldt picture:
    • http://en.wikipedia.org/wiki/Image:Alexander_von_Humboldt-selfportrait.jpg
    • Christian Leopold von Buch picture:
    • http://portrait.kaar.at/Deutschsprachige%20Teil%203/images/leopold_von_buch.jpg
    • George Julius Poulett Scrope picture:
    • http://www.eumed.net/cursecon/dic/dent/s/SCROPE.gif
    • Other images (volcanoes, lava, etc.)
    • http://emd.wa.gov/hazards/images/Volcano2.jpg
    • http://www.son.washington.edu/safety/images/volcano.jpg
    • http://www.destinbradwell.com/images/HawaiiVolc102sm.jpg
    • http://www.earthmountainview.com/volcano_cleveland_plume.jpg
    • http://asapblogs.typepad.com/news/images/2007/06/20/7bd693a649a38f47f1bd69e9a838a5ed9a7.jpg
    • http://newsfromrussia.com/img/idb/photo/1-977.jpg
    • Schimincke, Hans-Ulrich. Volcanism . Springer; 1st ed. 2004. Corr. 2nd printing edition, 2005.