Nova in the Path of a Killer Volcano PDF

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Notes from movie re: Pinatubo Volcano eruption in the Philippines (the largest eruption in the world in the past 18 years): Movie available on Youtube: NOVA in the path of a killer volcano (1992) Predicting volcanic eruption: - Predict time, size and direction of eruption Precursors of volcanic eruption: - SO2 & CO2 discharge from molten material inside the mountain (measured by correlation spectrometer or corspec) - Micro cracks - Rising magma plume (i.e. steam) - Magma spine (glow) - Earthquakes Alert levels: - Level I: activity detected; eruption not eminent - Level II: activities intensify; eruption probable - Level III: eruption can occur within 2 weeks - Level IV: eruption will occur within 48 hours In 1986, in Columbia, Nevado del Ruiz erupted. Prior to that, scientists advised of no risk but the eruption occurred in the middle of the night, resulting in 22,000 death toll. In 1991, June 12 and June 15, Pinatubo erupted with only 500 death toll. Roofs caved in due to the weight of the rain-soaked ash exceeding the load capacity (rain created by the micro-climate (characterized by lightning and heavy rain). The surrounding areas were covered by ashes, described as monochromatic landscape. Volcanic eruptions can occur in: - Subduction zones - Sea floor spreading - Hot spots where magma from deeper athenosphere coming in contact with water table and aquifer (i.e. hot magma mixing with H2O)  geysers or natural spas (e.g. Greater Yellowstone National Park in the U.S.: Hot Spa, releasing a lot of Sulphur, 600 volcanoes are active out of 1300 in total. So, some are ecquiescent/dormant. An average of 50 eruptions occur in a year. Pinatubo was violent because: not only in ring of fire; dormancy for decades; blocked conduit trapping gases What was the causes: - Magma rising from earth crust - Tetonic stress due to shifting of crust Discharge from volcanic eruption: - Lava flows – rivers of molten rocks - Ash and rocks ejections into the air - Scorching mud flow

Volcanic setting: - A vent or conduit through which ash ^& magma can speu out of - Subduction zones - Under water where ash becomes sea floor spreading - Hot spot - Geysers -0-> greater Yellowston National Park US

Types of Volcanoes by features – intrusive vs. extrusive: 1. Batholith  solidified magma underground; aka Plutonic rock  formed inside earth 2. Laccolith  small pool of solidified magma, also formed inside earth Intrusive rock  rock formed inside the earth Extrusive rock  vice –versa Dyke  vertical column of magma, could be seen from outside Sill  angular column of magma; intrusive Dyke = vertical elongated tunnel for lava to come up. Sill = tunnel at an angle or horizontal Classification of volcanoes: 1. Cinder cones – relatively small ~600m wide a. Pyroplastic cone 2. Shield volcanoes – fluid lava deposits, wide 3. Composite volcanoes – angle 25-45 degrees; formed by two previious types of volcanoes

Slide 5 1. Stratovolcanoes - Lava symmetrical in shape - Steep sides or conical hill due to the high viscosity of magma or lava, not traveling far from the vent before it solidifies - Balanced explosion - e.g. Mt St. Helens in US, Pinatubo in the Philippines, Mt Rainier in the US - have different mineral composition - higher than 50% silica, thus sticky; Felsic material (ferrous material and silica material) 2. Caldera – Formed in composite volcanoes or explosive volcanoes; i.e. caldera is a composite volcano that has collapsed – Lake in the middle of the volcano – not safe due to eruption of CO2, unannounced, not healthy for humans – Lake Nyos, East Africa – e.g. In 1883, Mt Krakatoa destroyed twin cities of Sumatra and Java. – E.g. Mount Mazama of Oregon – E.g. Mount Ozone (sp???)

3. Shield volcanoes – E.g. Maona Lua and Maona Kea, and other in Hawaii – Gentle slopes, rising a few metres from surrounding landscape – Gentle because it has low viscosity and is highly fluid flowing considerable distances prior to solidification. – Rich in basaltic material or MAFIC, thus denser in weight and highly fluid 4. Hotspots volcanoes – rich in MAFIC, silica less than 50% – Formed within oceanic crust, esp when two oceanic crusts slide and sometimes slides part each other, with an opening in the oceanic crust allowing magma to spill out and solidifies when in touch with H2O – Such volcanoes can be completely submerged. In case where they come out of the surface of oceans they are subject to constant wave erosion (due to hydraulic pressure), then not lasting long, i.e. transient or short-lived volcanoes 5. Hot spring and geysers – Occur in subterranean water sources, esp where magma comes in contact with aquifers and water table. Water heated up gushes out like steam. Some may be rich in Sulphur, e.g. Old Faithful, Greater Yellowstone National Park, a hot steam geyser spilling from the ground. 6. Vulcanian Eruption – meaning Greek God of smoke – Characterized by high amount of smoke, ash and fire – E.g. Tavurvur volcano in Papua New Guinea, South East Asia, just above Australia.

VOLCANIC HAZARDS AND THEIR IMPACTS A. Eruptive-related hazards: 1. Lava flows - lava = elongated stream of molten rocks oozing non-explosively out of a volcanic vent) - two types of lava: (i) Aa: jagged, rugged, steep-side rocks, which are formed after lava solidifies or even when gases come out. When Aa is hard, the terrain looks spiky, causing pain to walk on. (ii) Pahoehoe: elongated stream of lava, which twists and turns as the lava flows. It looks like a rope (spinning a yarn). It is formed like that because the gases are contained and lava can flow slowly. It tends to contain thin crust that develops folds as the lava cools down. - The flow can be stopped by pouring water to get it to form a dam. 2. Pyroclastic flows and base surges - very hot (can be 1000oC); made of boulders and ash; often move very fast (roaring down); need to divert the course by creating a deep trench 3. Large tephra fall and ballistic fragments of stones, rocks, sand and ash material - very hot (can be 1000oC); can cause roof to collapse 4. Ash falls

– fine particles of sand, powdery in texture, very light – can be airborne or drifted by wind for considerable distances; problem is its light texture can despoti in machines, e.g. car causing damage; can fill lungs with gas particular causing silicosis; bad for asthma, amphyzema, respiratiory; known to affect eletroncis; can settle on leave surfaces, harming agricultural drops since photosynthesis can be prevented; so, farming in such locations is not advisable 5. Poisonous volcanic gases – e.g. CO2, SO2, CO (which can cause axyfication / suffocation) e.g. Mount Vesuvius in AD1879 in Pompeii and Herculaneum - hydrogen oxysulfide, nitrogen oxide, all very dangerous for inhalation

B. Non-eruptive hazards: 1. Large volume debris avalanches: - loose sediments from mountain tops, destroying landscape and structures in the affected areas 2. Landslides - land instability, resulting in subsidence or sinking; ground can cave in and develop sink holes, destroying constructions on and around it. - very common in mines where tunnels can collapse. So, need to steel to strength the support to prevent collapse of mines or to use robots - e.g. mines collapsed in Chile, but everyone saves 3. Lahars - e.g. Mt Pinatubo in the Philippines - red hot - one of the fastest-moving volcanic materials; so, don’t try to outrun it, but outsmart it - formed when volcanic material diluted by rainfall or in contact with streams; or formed when material melts on mountain top and turns into steam

BENEFITS OF VOLCANOES Benefits: - Lava rocks are used a lot for counter-tops - lava rocks are used to build roads, stones, support metals etc. - Soil fertilizer: volcanic ashes (not landed on leaves) are known to have rich ninerals, e.g. nitrogen. - Geothermal energy source (as long as the heat is not too hot to evaporize the water), e.g. Mokai in New Zealand – for electricity supply - Yukon geothermal project – renewal heat sources

REDUCING VOLCANIC HAZARDS -

Hazard assessment – based on past volcanic behavior and material spilled out (using methods like carbon-dating), we monitor current activities of mountains, esp. signs of eruption; predict future eruption based on known and analyzed info

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Volcanic monitoring and surveillance o

History of volcano

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Tephrochronology (tephro = stone, rock, sandy particles): study the date of sediments

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Volcanic precursors: SO2, magma plume, micro crack/vibration; earthquake

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Tiltmeters

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Thermal and magnetic measurements: examine the magnetism of magma; e.g. mineral composition, possible direction of lava flow

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Land use planning and regulations: zoning; identify areas of risk (e.g. mountain valley likely direction for lava flows)

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Relocation: esp. cities developed while volcanoes become dormant yet potentially active; raise awareness

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Economic protection: insurance protection; govt disaster funds to help people in time of needs

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Preparedness, contingency and disaster awareness: e.g. drills

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Hazard-specific counter measures: e.g. pour cold water if it is lava (but not on cryplastic material); try to divert magma by digging deep trenches; create a depression for magma deposit;

Weathering: physical, biological and chemical disintegration of rocks into smaller fragments Once montains are formed based on compression between plates, these mountains are subject to erosion by aging and denudation, due to rain water, glacial movement, wind erosion

Material formed in the weathering processes is called regolith or residual soil (i.e. remnants of rock disintegration)

Process of weathering -

Mechanical weathering o

Pressure-release fracturing: some rocks are extrusive – i.e. formed outside the earth; some are intrusive e.g. granite ???. The pressure is huge inside. When exposed due to erosion, the pressure is released  pressure-release fracturing.

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E.g. The Johnson’s Shut-Ins State Park in southwestern region of St. Francois Mountains, USA; in Newfoundland, Canada

Frost wedging: at the east ridge of Mt. Brewer (the easy way up), near the summit. This mountain, like most in the Sierra, is overed by a thick layer of sharp-edged boulders produced by frost wedging. Frost wedging is well-developed here because the temp cycles across the freezing point many days each year. We need to climb this moutn early in the morning when the ice can still hold the ice. 

When water freezes at night, ice accumulates within rock strata and expands the cavity by ~ 8%. Alternating contraction and expansion cause ….

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Frost wedging: splitting of rock thru pressure exerted when water freezes. Freezing water expands by 9.2%. Costal areas prone to frost wedging where temp oscillates around the freezing point.

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E.g. Frost Wedging of jointed and fractured rocks on a coasteal cliff in Torbay, Nfld and Labrador.

Abrasion – anytime they blast explosion and collision, causing rock surface to be scraped off. 

E.g. Rounded boulders in Joshua Tree National Monument in California. This park is famous for its rock climbing and its cactus forests. Rounded boulders like these reflect long-term erosion of granitic rocks by frost wedging and chemical weathering.

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After erosion, many modification of the rocks, which classified as ventifact, such as moon surface, where wind eddies curves the surface …

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Abrasion by glacier to scrape or striate the rock surface over which it moves. If the sediment is big enough, it can do glacial plucking – meaning taking out a big portion of the rock. It can make part of a rock smooth and other parts rugged.

Salt crystal growth 

Salt can settle within joitns and cavities, causing it to break down into fragments.

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Common in halite, which is a type of rock rich in NaCl.

Thermal expansion & contraction 

Due to daily changes in temp conditions. At night, rocks cool and contract. During daytime, rocks warm up and expand. Alternating expansion and contraction cause them to break into fragments.

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Chemical weathering

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Dissolution 

When running water, rainfall (which may have SO2, CO2, NO2) or acidic solution break down limestone rocks, such as calcium carbonate or halite rocks, into pits. They are dissolved and suspended in water.

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E.g. Lechuguilla Cave, New Mexico – limestone cavern – stalactite (hanging from ceiling) and stalagmite (protruding from ground) columns; can be dangerous due to

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e.g. lava tube in Hawaii

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Karst Topography

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Karst Croatian word – a landscape characterized by funnel-shaped depression or channel which causes surface H2O to disappear Conditions are necessary for karst formation: o

- easily soluble rock

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- enough rainfall in the area

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- subterranean aquifer

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- calcium carbonate rock / limestone rock

E.g. Krs Plateau in Solvenia Could feature a disappearing stream/river because the river goes into the funnel formed in the dissolution of … E.g. Ogallala in the US – aquifer surfacing many A sinkhole in Quatemala caused by removal of water from aquifer

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Soil Horizons Soil is mixrture of particles of signs???, minerals, microorganization, organic matters, gases, O horizon: organic rich upper layer, composed of litter, backs of trees, twigs, dead trees or snag, decomposed roots A horizon: composed of much organic matter and minerals, formed from complex biogeochemical processes. Ions and colloids of minerals, e.g. Ca, Mg, P, N, Cu, .. are washed away from the A horizon and deposited to B horizon. A horizon – Elluviation. B horizon – Illuviation C horizon – transition to subsoil – freshly weatherly material.

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Biological : the root of plant forces their way through rocks, esp through the fissure between rocks. As roots grow, they expand the rock and break the rock down into smaller pieces. Flying organisms, e.g. birds, spread seeds, which can drop on crack of rocks, forcing the rock surface to expand. Chemicals relezed from leave decay can decolour a car.

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Hydrolysis

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Oxidation

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Chemical and mechanical weathering sometimes act together

As rocks decompose, they may stay in same location or they may move, depending on salt particle size, angle of slope, or plate tetonic activity (e.g. earthquake), moisture, gravity, herd of animals. There is a difference in mass wasting and mass movement.

Slide FACTORS THAT INFLUENCE DOWNSLOPE MOVEMENT 1. Slope Angle (i.e. slope gradient), which can be run or rise a. Run is the movement parallel to the ground. Rise has an angle from the surface. Run and rise can occur together. (slide 4). Gravity pulls the boulder down. - Shear Stress: stress resulting from application of force parallel to a surface (force pulling the boulder/grain downslope (Shear stress: is caused by the gravity or frictional stress - Normal Stress: component of stress perpendicular to the Earth’s planar surface (force keeping the boulder/grain from moving) -

Balance between friction & gravity

2. Critical Angle of Repose 3. Material Strength 4. Cohesion & Water Saturation 1. Surface tension – cohesive force 2. Water pressure

Laminar: 3. When the bottom material moves, the upper material may be caused to move.

Solifuction: 4. Sometimes too much moisture in the soil, thus lubricating the soil to move Gelifluction – frost creep … creep is the lowest of the earth movement, ~ a few inches a year, very inperceptible. E.g. fence creeping on one side; a tree planted on the slope with the base bending down while the truck growing up, causing a J shape.

How to remove creeping: remove moisture from the hill or plant grass (if grass can stand the weight of creep) or use hollow structures to keep the sediments being washed.

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Mudflow is the rapid down slope movement of water-saturated soil. E.g. Pacific Palisades. 1. Mudflow - When soil satured with water, sediement drifts to low-lying area. As mud flows from various streams converge, slowing down …. 2. Debris flow – move in big mass

Landslide is different than mudflow – enough water to trigger a slide but not enough water to induce a flow. So, the sheet of …

Slumps – rotational slide along a concave plain, where …

Mitigating landslides: •

Perforated pipes: good to know the moisture content so that we can take out moisture; not good to use sprinkler system on mountain top. Toe drainage is used to dehydrate sediment at the bsae of a hill

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Geotextile fabric – a fabric like a mesh on slope surface allowing H2O to infiltrate the mesh while/ holding sediments

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Channel debris into basins – create a special channel to conform to general direction of debris movement

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Trap the debris by building check dams – use highly fortified structure to hold the weight of the sediement that may come down.

Rockfall -

The fastest, faster than mudflow

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Talus – protruding rock from the ….e.g. Upper Island Cover, Nfld and Labrador

Preventive measures for rock fall: •

Heavy wire nets or fences (but need to be strong enough)

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Barricades along roadsides shotcrete (cement mixture applied to restrict water access)

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Rockbolts

MITIGATION OF MASS MOVEMENT Hazard mapping Loss assessment Information systems application Training and guidelines Mitigative policies Awareness creation...