Earthquakes & a case study of the Great Hanshin Earthquake (Kobe)  By Jasmine and Melody 310 ‘06
Kobe: The Story <ul><li>Formally known as the  South Hyogo Earthquake </li></ul><ul><ul><li>Other names include  Hyogo-ken...
Why?  (Investigation of Cause) <ul><li>Japan’s precarious position upon  3 plates , formed by molten magma from the Philli...
Why? (Geological Conditions) <ul><li>Kobe was located slightly off the Median Tectonic line, a zone of  strike-slip  fault...
Why?  (Human Conditions) <ul><li>Kobe was an  older  city with residential infrastructure built with wood on the bottom an...
1.1 1.2 1.3
Why? (Cont’d) & Effects.. <ul><li>Older reinforced concrete structures </li></ul><ul><ul><li>Vertical steel rods were  una...
2.1 2.2 2.3 2.4
Ouch!  (Some More Serious Effects) <ul><li>300,000 made homeless, requiring shelter </li></ul><ul><ul><li>People squeezed ...
So What Next? (Coping With Problems) <ul><li>Water, gas, electricity were restored within  half a year </li></ul><ul><li>R...
What is an earthquake? <ul><li>A  </li></ul><ul><li>Sudden, </li></ul><ul><li>Violent, </li></ul><ul><li>& (sometimes)  Ca...
Causes of Earthquakes <ul><li>Rocks in earth are elastic, may store  mechanical energy  same way a spring does </li></ul><...
Causes of Earthquakes (cont’d) <ul><li>At it’s source (or  focus ), movement may be over in a few seconds </li></ul><ul><l...
Causes of Earthquakes (cont’d) <ul><li>These rocks are held in place as a result of  friction  acting on the rough surface...
Seismic Gap theory <ul><li>A  theory  that was developed to explain the regular occurrence of earthquakes in certain place...
Effects of Earthquakes <ul><li>Varies  from earthquake to earthquake </li></ul><ul><li>Mainly includes the ground shaking,...
Primary Effects <ul><li>Formation of  fault-scarps </li></ul><ul><li>Collapse of existing structures, both natural and man...
Secondary Effects <ul><li>Landslides </li></ul><ul><li>Changes in the level of the land </li></ul><ul><li>Flooding; whereb...
Measuring Earthquakes <ul><li>The Richter Scale </li></ul><ul><ul><li>Based on the size, or  amplitude of the waves  trace...
Measuring Earthquakes (cont’d) <ul><li>The Mercalli Scale: the intensity of an earthquake is assessed by subjective and qu...
Measuring Earthquakes (cont’d) <ul><li>Other factors that affect intensity of the damage includes distance of the settleme...
Volcanoes & a case study of Fuji-san By Jasmine and Melody 310 ‘06
Fujiyama: The Story <ul><li>Actually made up of three different volcanoes;  Ko-mitake ,  Ko-Fuji  (Older Fuji Volcano) and...
Fujiyama: The Story (cont’d) <ul><li>Studded  with more than 100 parasitic cones and flank openings although most of them ...
Fujiyama: The 1707 eruption <ul><li>Latest Eruption: 1707-1708, where 0.8 cubic km of ash, blocks, and bombs was ejected <...
What is a Volcano? <ul><li>In basic terms, a volcano is a  hole  in the earth’s  crust , on land or on the sea floor, from...
What is a Volcano? (cont’d) <ul><li>These ( pyroclastic ) ‘materials’ may include hot lava, cinders, blocks, ash or pumice...
The Mafic Cone (ooh, runny!) <ul><li>Low silica content (~50%) </li></ul><ul><li>High Fe and Mg content </li></ul><ul><li>...
The Felsic Cone (look at the gas!) <ul><li>High silica content (~70%) </li></ul><ul><li>Low Fe and Mg content </li></ul><u...
Formation of a Volcano <ul><li>Generated by eruption of magma through a planet's surface; molten rock welling up from the ...
Formation (types of plate boundaries) <ul><li>Constructive </li></ul><ul><ul><li>The most common </li></ul></ul><ul><ul><l...
Formation (types of plate boundaries) <ul><li>Destructive </li></ul><ul><ul><li>The most visible and well-known </li></ul>...
Formation (Hotspots) <ul><li>Originally generalization for volcanoes that didn't fit into one of the above two categories ...
Primary Effects <ul><li>Phreatic  eruptions (steam-generated eruptions)  </li></ul><ul><li>Explosive eruption of high-sili...
Secondary Effects <ul><li>Earthquakes </li></ul><ul><li>Hot springs </li></ul><ul><li>Fumaroles </li></ul><ul><li>Mud pots...
Measuring Volcanoes <ul><li>Volcanologists  monitor the following phenomena to help forecast eruptions: </li></ul><ul><li>...
Measuring Volcanoes <ul><li>Ground Deformation </li></ul><ul><ul><li>Swelling of volcano signals magma has accumulated nea...
Eruption Styles <ul><li>Four main eruption styles: Hawaiian, Strombolian, Vulcanian and Pelean, after best known volcanoes...
Eruption Style (Hawaiian) <ul><li>Magma rises in a  central vent </li></ul><ul><li>Thin flows of basalt emerges and spread...
Eruption Style (Strombolian) <ul><li>Constant, but usually short lived moderate activity </li></ul><ul><li>Usually cinder ...
Eruption Style (Vulcanian) <ul><li>Vigorous  eruptions </li></ul><ul><ul><li>More explosive than moderate eruptions as the...
Eruption Style (Pelean) <ul><li>Viscous, silicic magma rises </li></ul><ul><li>Gases in magma separate into bubbles and, n...
Bibliography <ul><li>Kobe Earthquake </li></ul><ul><ul><li>http://www.vibrationdata.com/earthquakes/kobe.htm   </li></ul><...
AND HAHA BYEBYE SEE YOU! BE CAREFUL OF EARTHQUAKES! And volcanoes too, heh.
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Earthquakes & Volcanic Studies (Kobe! Fuji!)

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Earthquakes & Volcanic Studies (Kobe! Fuji!)

  1. 1. Earthquakes & a case study of the Great Hanshin Earthquake (Kobe) By Jasmine and Melody 310 ‘06
  2. 2. Kobe: The Story <ul><li>Formally known as the South Hyogo Earthquake </li></ul><ul><ul><li>Other names include Hyogo-ken Nanbu & Kobe </li></ul></ul><ul><li>Struck western Japan at 0546 hours, January 17, 1995 </li></ul><ul><li>Lasted about 20 seconds </li></ul><ul><li>Devastation was the worst in the port city of Kobe </li></ul><ul><li>7.2 magnitude quake toppled roadways, wrecked docks, severed communication lines and left the city in flames into the next day </li></ul><ul><li>killed almost 6500 people </li></ul>
  3. 3. Why? (Investigation of Cause) <ul><li>Japan’s precarious position upon 3 plates , formed by molten magma from the Phillipines plate </li></ul><ul><ul><li>Subducting Phillipines sea plate </li></ul></ul><ul><ul><li>Subducting Pacific plate </li></ul></ul><ul><ul><li> Under Eurasian continental plate </li></ul></ul><ul><li>Friction resulting from colliding on destructive margin </li></ul><ul><li>Seismic energy from collisions </li></ul><ul><li>is eventually released through </li></ul><ul><li>earthquakes </li></ul><ul><li>Subduction happening about </li></ul><ul><li>10 cm per year </li></ul>
  4. 4. Why? (Geological Conditions) <ul><li>Kobe was located slightly off the Median Tectonic line, a zone of strike-slip faults </li></ul><ul><li>Focus was 16km below Awaji-shima, an island in the Japan Inland Sea, close to Kobe </li></ul><ul><li>Shallow focus and probable surface ruptures </li></ul><ul><li>Kobe, a low-lying port city, was situated on soft, wet ground </li></ul><ul><li>Constructed on 2 artificial islands of water-saturated loose fill </li></ul><ul><li>High potential of ground liquefying, suspending & loosening sand, with ground unable to bear weight & buildings collapsing </li></ul>
  5. 5. Why? (Human Conditions) <ul><li>Kobe was an older city with residential infrastructure built with wood on the bottom and heavy tiles as roofs </li></ul><ul><ul><li>Created more shear force than frame could resist (1.1, 1.2) </li></ul></ul><ul><li>Old infrastructure codes allowed weaker superstructures at 5 th floor </li></ul><ul><ul><li>Thus some buildings sunk in at 5 th floor (1.3) </li></ul></ul><ul><li>Most infrastructure were old & built before strict seismic codes in 1980s </li></ul><ul><li>Lifelines constructed in the 60s and 70s, before modern construction practices </li></ul><ul><ul><li>Debris choked streets & rescue work was delayed. Fires were widespread, making it more deadly </li></ul></ul>
  6. 6. 1.1 1.2 1.3
  7. 7. Why? (Cont’d) & Effects.. <ul><li>Older reinforced concrete structures </li></ul><ul><ul><li>Vertical steel rods were unable to preserve structure from horizontal shaking forces (2.1) </li></ul></ul><ul><li>The Hanshin Expressway fell on its side (2.2) </li></ul><ul><ul><li>Soft soil, bad infrastructure? </li></ul></ul><ul><li>Subways sunk in, luckily as it was early morning so nobody was killed (2.3) </li></ul><ul><ul><li>Soft, saturated soil [liquefaction] </li></ul></ul><ul><li>Broken gas lines </li></ul><ul><ul><li>Fires ensued, killing those who survived the quake & slowed rescue work (2.4) </li></ul></ul>
  8. 8. 2.1 2.2 2.3 2.4
  9. 9. Ouch! (Some More Serious Effects) <ul><li>300,000 made homeless, requiring shelter </li></ul><ul><ul><li>People squeezed into public buildings like schools and town halls </li></ul></ul><ul><ul><li>Overcrowded, unsanitary </li></ul></ul><ul><ul><li>Lack of food, clean water & medical supplies </li></ul></ul><ul><li>Jan 17 th – cold winter , at temp. of -2 degrees Celsius </li></ul><ul><li>Hanshin Expressway closed, 130 km of subway closed </li></ul><ul><ul><li>Transport impaired, interrupting trade and commerce </li></ul></ul><ul><ul><li>Disrupted school, unemployment, etc </li></ul></ul><ul><li>120 out of 150 cranes at shipyard fell, destroying goods and ships </li></ul><ul><li>3-5% of Japan’s economy located near/at Kobe </li></ul><ul><ul><li>Shipbuilding, steelworks are just some that got affected </li></ul></ul>
  10. 10. So What Next? (Coping With Problems) <ul><li>Water, gas, electricity were restored within half a year </li></ul><ul><li>Railways back in service by August </li></ul><ul><li>134,000 housing units constructed, although some people still lived in temporary accommodation </li></ul><ul><li>New laws passed to make buildings more earthquake-proof </li></ul><ul><li>More instruments installed in area to monitor earthquake movements </li></ul><ul><li>However, Japanese government was heavily criticized </li></ul><ul><ul><li>WE ARE POLITICALLY CORRECT & DIPLOMATIC HAHA </li></ul></ul><ul><ul><li>(slow, uncoordinated, badly equipped, refused foreign relief) </li></ul></ul>
  11. 11. What is an earthquake? <ul><li>A </li></ul><ul><li>Sudden, </li></ul><ul><li>Violent, </li></ul><ul><li>& (sometimes) Catastrophic </li></ul><ul><li>movement of a part of the Earth's surface </li></ul>
  12. 12. Causes of Earthquakes <ul><li>Rocks in earth are elastic, may store mechanical energy same way a spring does </li></ul><ul><li>Rock gives way, cracks when forces are applied strong enough that they exceed the strength of the weakest part of the solid rock </li></ul><ul><li>These forces include convectional currents that cause our plate movements </li></ul><ul><li>Strain energy is relieved, forces are accommodated by sudden dislocation of rocks on either side of crack </li></ul><ul><li>Releasing of energy and dislocation of rocks is called ‘elastic rebound’ </li></ul>
  13. 13. Causes of Earthquakes (cont’d) <ul><li>At it’s source (or focus ), movement may be over in a few seconds </li></ul><ul><li>However, resulting huge amount of energy released travels through rocks of the crust in seismic waves </li></ul><ul><li>The crack marking the dislocation is known as a fault . </li></ul><ul><li>Following an earthquake (the displacement of the rocks), the rocks on either side come to rest in new positions </li></ul>
  14. 14. Causes of Earthquakes (cont’d) <ul><li>These rocks are held in place as a result of friction acting on the rough surfaces of the rocks as well as other forces exerted upon them from the crust </li></ul><ul><li>The stresses and strains that caused the original earthquake continue, and eventually break the ‘frictional lock’ to cause another earthquake </li></ul>
  15. 15. Seismic Gap theory <ul><li>A theory that was developed to explain the regular occurrence of earthquakes in certain places </li></ul><ul><li>For example, Parkfield, which has produced magnitude 6 earthquakes every 20-30 years </li></ul><ul><li>Idea – since plates are moving all the time at a steady rate, and since that is what causes the earthquakes; </li></ul><ul><li>… we should be able to predict the occurrence of earthquakes based on when and where they have occurred in the past. </li></ul>
  16. 16. Effects of Earthquakes <ul><li>Varies from earthquake to earthquake </li></ul><ul><li>Mainly includes the ground shaking, and in more serious cases damage to and destruction of infrastructure </li></ul><ul><li>As well as tsunamis in port cities </li></ul><ul><li>Fires as a result of the collapse of buildings & broken gas pipes </li></ul><ul><li>Loss of life; especially in large cities </li></ul><ul><li>Divided into Primary & Secondary, </li></ul><ul><ul><li>Primary ones - deformation of ground near the fault (immediate collapse of buildings, roads) </li></ul></ul><ul><ul><li>Secondary ones - result from seismic waves away from fault rupture (fire, aftershocks, homelessness) </li></ul></ul>
  17. 17. Primary Effects <ul><li>Formation of fault-scarps </li></ul><ul><li>Collapse of existing structures, both natural and man-made </li></ul><ul><li>Formation of ‘ sand boils’ , different types of shock wave vibrations can cause sand and water to spurt out in little cones that look like miniature volcanoes and may reach up to 30cm high </li></ul><ul><ul><li>In rare cases, streams diverted (due to fault scarps) </li></ul></ul><ul><li>Liquefaction –shaking increases underground water pressure and water invades all interstices on the sandy silt. </li></ul><ul><ul><li>Buildings often sink </li></ul></ul><ul><ul><li>Common cause to countless lives lost in devastating earthquakes, e.g. San Francisco, Messina and Reggio di Calabria as well as Kobe. </li></ul></ul>
  18. 18. Secondary Effects <ul><li>Landslides </li></ul><ul><li>Changes in the level of the land </li></ul><ul><li>Flooding; whereby the debris blocks up drainage systems </li></ul><ul><li>Water-borne diseases as a result of flooding </li></ul><ul><ul><li>Cholera, typhoid, dengue </li></ul></ul><ul><li>Lack of basic necessities such as food, potable water and basic sanitary needs </li></ul><ul><li>Holdups in transport and communications </li></ul><ul><ul><li>Leads to more deaths as it delays the rescue of people trapped in the debris </li></ul></ul>
  19. 19. Measuring Earthquakes <ul><li>The Richter Scale </li></ul><ul><ul><li>Based on the size, or amplitude of the waves traced by the pen on a seismograph </li></ul></ul><ul><li>Seismographs had to be standardized to allow for a fair comparison </li></ul><ul><li>Based on complex mathematical formulas </li></ul><ul><li>However it tells us little about the effect of earthquakes on human lives </li></ul>
  20. 20. Measuring Earthquakes (cont’d) <ul><li>The Mercalli Scale: the intensity of an earthquake is assessed by subjective and qualitative observations of the landscape and environment </li></ul><ul><li>Unlike the Richter scale; not based on mathematical calculations </li></ul><ul><li>Calculates the degree of damage done (in a scale of I-XII) based on timing and site of occurrence </li></ul><ul><li>E.g. An earthquake of magnitude 8.4 (Richter) may cause relatively little damage in a sparsely populated area as compared to an earthquake of magnitude 5.8 that occurs in a town </li></ul>
  21. 21. Measuring Earthquakes (cont’d) <ul><li>Other factors that affect intensity of the damage includes distance of the settlement in question to the epicenter </li></ul><ul><li>Settlements built on reclaimed land , or soft, water-saturated materials such as silt , would also be at higher risk as silt magnifies ground motion by as much as 75 times </li></ul>
  22. 22. Volcanoes & a case study of Fuji-san By Jasmine and Melody 310 ‘06
  23. 23. Fujiyama: The Story <ul><li>Actually made up of three different volcanoes; Ko-mitake , Ko-Fuji (Older Fuji Volcano) and the present Shin-Fuji (Younger Fuji Volcano) which lie one upon the other. </li></ul><ul><ul><li>Ko-Mitake – has been dormant since 100 thousand years ago. </li></ul></ul><ul><ul><li>Ko-Fuji – which formed the </li></ul></ul><ul><ul><li>base of the current Mount Fuji, </li></ul></ul><ul><ul><li>was active between 100,000 & </li></ul></ul><ul><ul><li>10,000 years ago. </li></ul></ul><ul><ul><li>Shin-Fuji – which is responsible for the mountain’s current shape, started to erupt about 10 thousand years ago continued erupting repeatedly over 100 times during a period of about 10 thousand years. </li></ul></ul>!!!! Flank resulted from last eruption. Fuji isn’t TOTALLY symmetrical.
  24. 24. Fujiyama: The Story (cont’d) <ul><li>Studded with more than 100 parasitic cones and flank openings although most of them are too small to be seen. </li></ul><ul><li>Dimensions: about 3776 m above sea level, 50 km across the base with a circular crater of about 500m across </li></ul><ul><li>Archetype of the stratovolcano </li></ul><ul><ul><li>Also known as composite volcanoes composed of lava flows & lahar in alternate layers. </li></ul></ul><ul><li>Fuji erupted at least 16 times since 781 AD. Most of these eruptions were moderate to moderate-large in size </li></ul><ul><li>Two largest eruptions to date were in 1050 and 930 BC </li></ul>
  25. 25. Fujiyama: The 1707 eruption <ul><li>Latest Eruption: 1707-1708, where 0.8 cubic km of ash, blocks, and bombs was ejected </li></ul><ul><li>Eruption started December 16 and ended about February 24, 1708 </li></ul><ul><li>This flank eruption was explosive and generated mudflows </li></ul><ul><li>It caused damage, but according to </li></ul><ul><li>‘Volcanoes of the World’, there were </li></ul><ul><li>no fatalities. </li></ul>
  26. 26. What is a Volcano? <ul><li>In basic terms, a volcano is a hole in the earth’s crust , on land or on the sea floor, from which materials are expelled naturally from below. </li></ul>
  27. 27. What is a Volcano? (cont’d) <ul><li>These ( pyroclastic ) ‘materials’ may include hot lava, cinders, blocks, ash or pumice, cold rock fragments of all sizes, aerosols, steam and water. </li></ul><ul><li>Some materials cool and pile up around the hole, or chimney, and often form a cone shaped hill ( composite ) </li></ul><ul><li>Other fine materials ( lahar ) can be blasted into the stratosphere, carried around the world, and may remain as aerosols that veil the sun for several years. ( Mt. Krakatoa ) </li></ul>
  28. 28. The Mafic Cone (ooh, runny!) <ul><li>Low silica content (~50%) </li></ul><ul><li>High Fe and Mg content </li></ul><ul><li>Relatively less viscous (hence the runny-ness) </li></ul><ul><ul><li>Travels relatively faster, able to cover distance of 150km before stopping to solidify </li></ul></ul><ul><li>Low-level of explosivity </li></ul><ul><ul><li>Because less gas escapes and hence, little vesiculation </li></ul></ul><ul><li>Low gradient due to slow drying of lava </li></ul>
  29. 29. The Felsic Cone (look at the gas!) <ul><li>High silica content (~70%) </li></ul><ul><li>Low Fe and Mg content </li></ul><ul><li>Relatively more viscous </li></ul><ul><ul><li>Hence moves at slower speeds </li></ul></ul><ul><li>Often explodes violently, producing large amounts of aerosols and fahar </li></ul><ul><ul><li>Gas escapes; causes viscosity to increase </li></ul></ul><ul><ul><li>Vesiculation is initiated; may trigger an explosive volcanic eruption </li></ul></ul><ul><li>Steep gradient due to viscosity </li></ul>
  30. 30. Formation of a Volcano <ul><li>Generated by eruption of magma through a planet's surface; molten rock welling up from the planet's interior </li></ul><ul><li>Magma wells up due to tectonic activity in the plates – e.g. when plates converge or diverge – causing either constructive , destructive or transform plate boundaries. </li></ul>
  31. 31. Formation (types of plate boundaries) <ul><li>Constructive </li></ul><ul><ul><li>The most common </li></ul></ul><ul><ul><li>The least visible (usually occur at considerable depths underwater) </li></ul></ul><ul><ul><li>Cause the formation of a mid-ocean ridge </li></ul></ul><ul><ul><li>E.g. the Mid-Atlantic Rift </li></ul></ul><ul><ul><li>May sometimes lead to volcanoes reaching the surface – e.g. St. Helena </li></ul></ul>
  32. 32. Formation (types of plate boundaries) <ul><li>Destructive </li></ul><ul><ul><li>The most visible and well-known </li></ul></ul><ul><ul><li>Form above the subduction zones, where oceanic plates subduct under the lighter continental plates </li></ul></ul><ul><ul><li>Cause the formation of subduction volcanoes </li></ul></ul><ul><ul><li>E.g. the Nazca plate diving under the South-American plate caused the formation of the Andes range </li></ul></ul>
  33. 33. Formation (Hotspots) <ul><li>Originally generalization for volcanoes that didn't fit into one of the above two categories </li></ul><ul><li>Refers to more specific circumstance today - where an isolated plume of hot mantle material hits the underside of the crust . </li></ul><ul><ul><li>Mantle plume can lead to volcanic center that’s not obviously connected with a plate margin </li></ul></ul><ul><li>E.g. Hawaiian Islands </li></ul><ul><ul><li>Generated by a hotspot underneath the oceanic crust of the Pacific </li></ul></ul><ul><li>E.g. 2: Yellowstone </li></ul><ul><ul><li>In this case involves continental crust </li></ul></ul><ul><ul><li>(Iceland may also be considered, but the coincidence of a hotspot intersecting a oceanic ridge constructive margin complicates things. ) </li></ul></ul>
  34. 34. Primary Effects <ul><li>Phreatic eruptions (steam-generated eruptions) </li></ul><ul><li>Explosive eruption of high-silica lava (e.g., dacite & rhyolite) </li></ul><ul><li>Effusive eruption of low-silica lava (e.g., basalt) </li></ul><ul><li>Pyroclastic flows </li></ul><ul><li>Lahars (debris flow) </li></ul><ul><li>Fumarolic activity (gaseous emissions, e.g. H20, C02, S02, mainly, with lesser toxic gases HCl, HF, H2SO4, H2S) </li></ul>
  35. 35. Secondary Effects <ul><li>Earthquakes </li></ul><ul><li>Hot springs </li></ul><ul><li>Fumaroles </li></ul><ul><li>Mud pots </li></ul><ul><li>Geysers </li></ul><ul><li>*Low-magnitude earthquakes often precede eruptions. </li></ul><ul><li>(that’s like Mother Nature’s forewarning) </li></ul>
  36. 36. Measuring Volcanoes <ul><li>Volcanologists monitor the following phenomena to help forecast eruptions: </li></ul><ul><li>Seismicity </li></ul><ul><ul><li>Seismic activity – or earthquakes etc, is observed </li></ul></ul><ul><li>Gas Emissions </li></ul><ul><ul><li>Magma nears surface, </li></ul></ul><ul><ul><li>pressure decreases, gas escapes </li></ul></ul><ul><ul><li>Sulphur dioxide (main </li></ul></ul><ul><ul><li>component of volcanic gases, increasing amounts of it herald arrival of increasing amounts of magma near surface) </li></ul></ul>Sampling volcanic gases in an evacuated flask.
  37. 37. Measuring Volcanoes <ul><li>Ground Deformation </li></ul><ul><ul><li>Swelling of volcano signals magma has accumulated near surface. </li></ul></ul><ul><ul><li>Tilt of volcanoes’ slope </li></ul></ul><ul><ul><ul><li>Mapped, rate of swelling tracked in order to help predict eruptions </li></ul></ul></ul><ul><ul><ul><li>Increased rate of swelling, accompanied by increase in sulphur dioxide emissions & harmonic tremors is a high probability sign of eruption </li></ul></ul></ul><ul><ul><ul><li>Deformation of Mount St. Helens prior to the May 18, 1980 eruption is another classic example of deformation </li></ul></ul></ul><ul><ul><li>Most cases of ground deformation are usually detectable only by sophisicated equipment used by scientists  </li></ul></ul>
  38. 38. Eruption Styles <ul><li>Four main eruption styles: Hawaiian, Strombolian, Vulcanian and Pelean, after best known volcanoes of each group </li></ul><ul><li>Mild eruptions </li></ul><ul><ul><li>Limited to emissions of gas, steam, hot water, sulphurous fumes and bubbling mud from geysers, hissing holes and fissures. </li></ul></ul><ul><ul><li>May be common on dormant or dying volcanoes </li></ul></ul><ul><li>Moderate eruptions </li></ul><ul><ul><li>Expel lava and some gas – lava usually basic, basaltic </li></ul></ul><ul><ul><li>Occur on fissures </li></ul></ul><ul><ul><li>Most common kind of eruption – not usually very dangerous </li></ul></ul>
  39. 39. Eruption Style (Hawaiian) <ul><li>Magma rises in a central vent </li></ul><ul><li>Thin flows of basalt emerges and spreads over a wide area </li></ul><ul><li>Volcano ‘grows’ as each eruption piles on a new layer </li></ul><ul><ul><li>Lava flows may also emerge from vents on either side of the summit, in flank eruptions (Fuji!) </li></ul></ul><ul><li>Characteristically broad-based shape – ‘shield volcano’ </li></ul><ul><li>Erupts relatively often </li></ul><ul><li>Usually non-explosive in nature </li></ul><ul><li>Destructive but slow-moving flows </li></ul>
  40. 40. Eruption Style (Strombolian) <ul><li>Constant, but usually short lived moderate activity </li></ul><ul><li>Usually cinder cones with a shallow, bowl-shaped crater </li></ul><ul><ul><li>Cinder cones : molten fragments settle on cones and embers cool – eventually many layers are created after constant repeating of this process </li></ul></ul><ul><li>Dust and ash released into atmosphere ( lahar ) </li></ul><ul><li>Lava flows are initially fast-moving, but eventually slow down </li></ul>
  41. 41. Eruption Style (Vulcanian) <ul><li>Vigorous eruptions </li></ul><ul><ul><li>More explosive than moderate eruptions as they often contain a strong element of gas or steam </li></ul></ul><ul><li>Gases escape from rising magmas that are viscous and silicic – large black cloud of ash and steam </li></ul><ul><li>Sudden eruptions – quick successions of explosions shatter fragments off the volcano, shooting them from the chimney </li></ul><ul><ul><li>May be followed by several days of total calm until eruptive spasm is over </li></ul></ul><ul><li>Although mostly basaltic, lava flows are often viscous </li></ul><ul><li>Larger cinder cones than strombolian counterparts </li></ul><ul><ul><li>Craters are large and deep </li></ul></ul>
  42. 42. Eruption Style (Pelean) <ul><li>Viscous, silicic magma rises </li></ul><ul><li>Gases in magma separate into bubbles and, near the top of the chimney, blow the magma into smithereens, forcing a lot of volcanic material of all sizes to be blown out </li></ul><ul><li>Whole mass may be as hot as 700 degrees Celsius </li></ul><ul><li>Nuees ardentes – incandescent clouds – are formed </li></ul><ul><ul><li>Made up of gases and fine ash mixed with larger fragments as it rolls down slope, picking up more as it goes along </li></ul></ul><ul><li>Eruptions may be short (2-3mins) but lethal as a result of the nuees ardentes </li></ul><ul><li>At same time, magma surges up forming a lava dome – usually able to withstand minor gas explosions </li></ul><ul><ul><li>However may crumble as a result of poor support, and form small blasts of nuees ardentes </li></ul></ul>
  43. 43. Bibliography <ul><li>Kobe Earthquake </li></ul><ul><ul><li>http://www.vibrationdata.com/earthquakes/kobe.htm </li></ul></ul><ul><ul><li>http://www.ce.washington.edu/~liquefaction/html/quakes/kobe/kobe.html </li></ul></ul><ul><ul><li>http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html </li></ul></ul><ul><li>Earthquakes </li></ul><ul><ul><li>http://wikipedia.org </li></ul></ul><ul><ul><li>http://eqseis.geosc.psu.edu/~ cammon /HTML/Classes/ IntroQuakes /Notes/earthquake_effects.html </li></ul></ul><ul><li>Mt. Fuji </li></ul><ul><ul><li>http://www.sacredland.org/world_sites_pages/Fuji.html </li></ul></ul><ul><ul><li>http://volcano.und.nodak.edu/vwdocs/volc_images/img_fuji.html </li></ul></ul><ul><ul><li>http://staff.aist.go.jp/a-takada/Fujiproject-e.html </li></ul></ul><ul><ul><li>http://staff.aist.go.jp/a-takada/recentpresent-e.html </li></ul></ul><ul><li>Volcanoes </li></ul><ul><ul><li>http://www.geology.sdsu.edu/how_volcanoes_work/Controls.html </li></ul></ul><ul><ul><li>http://piru.alexandria.ucsb.edu/~tierney/lectures/geology.htm </li></ul></ul><ul><ul><li>http://www2.umt.edu/Geology/faculty/hendrix/g100/L6A.html </li></ul></ul><ul><li>Savage Earth </li></ul>
  44. 44. AND HAHA BYEBYE SEE YOU! BE CAREFUL OF EARTHQUAKES! And volcanoes too, heh.

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