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Lecture notes for Geology 11 subject. Topics include earth, minerals, big bang theory, etc. Useful infos.

Lecture notes for Geology 11 subject. Topics include earth, minerals, big bang theory, etc. Useful infos.

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    Lecture notes 1 Lecture notes 1 Document Transcript

    • Lecture 1: Introduction Geology - the study of the Earth, the processes that shape it, and the resources that could be obtained from it. Main branches Physical Geology - deals with the materials that comprise the Earth and the processes that affect it (e.g., Volcanology, Seismology, Environmental Geology, Engineering Geology, Mining Geology, Petroleum Geology, Mineralogy, Petrology, Geomorphology, Geophysics, Geochemistry, Planetary Geology) Historical Geology - the study of the origin and evolution of the Earth through time (e.g., Paleontology, Stratigraphy, Geochronology) Basic Concepts Catastrophism – proposed by Georges Cuvier; advocates the idea that sudden, worldwide catastrophes are the agents of change that alter the physical features of the Earth over time and that the latter remains unchanged in between these periods of upheavals; widely accepted by theologians in the early 1800s due to similarity with Biblical events such as Noah’s Flood (James Ussher, mid-1600s) Uniformitarianism - proposed by James Hutton (late 1700s, “The Father of Modern Geology”), modernized by Charles Lyell (mid1800s); “The present is the key to the past”; advocates the idea that the Earth is continuously modified by geologic processes that have always operated throughout time (at different rates), and that by studying them we can understand how the Earth has evolved through time Relevance to daily life Everything we use comes from the Earth Particularly in the form of natural resources provided through application of geologic knowledge. Construction - cement, concrete and asphalt Fuel, light and heat - oil, gas and coal Water Prediction and avoidance of hazards, earthquakes, floods, volcanoes, landslides, erosion. Lecture 2: The Planet Earth Cosmology: study of the universe and its origins and processes Formation of the Universe: Big Bang Theory Formation of the Solar System: Nebular Hypothesis The Big Bang Theory: proposed by the Belgian priest Georges Lemaître in the 1920s ; contends that the Universe originated from a cosmic explosion that hurled matter in all directions 15 and 20 billion years ago; Edwin Hubble justified Lemaître’s theory through observations that the Universe is continuously expanding; galaxies are moving away from each other
    • Evidence of Big Bang: red shift and cosmic background microwave radiation metric expansion of space Nebular Hypothesis: proposed by Emaneuel Swedenborg, Immanuel Kant and Pierre Simon de Laplace in the 18th century; the solar system originated from a single rotating cloud of gas and dust, starting 4.6 billion years ago, which contracted due to gravity 1. The Big Bang produced enormous amount of matter: rotating cloud of gas and dust. 2. The rotating gas-dust cloud began to contract due to gravity. Most of the mass became concentrated at the center, forming the Sun. 3. The remaining matter condensed to form the planets. The Sun: a middle-aged star; mostly made up of hydrogen, the principal product of the Big Bang; sun’s center became compressed enough to initiate nuclear reactions, consequently emitting light and energy (sun became a star) The Planets: composition depended on distance from the sun; planets nearest the sun contained high-temp minerals (e.g. iron) while those that are far away contained lower-temp materials (e.g. methane and ammonia, and some that contained water locked in their structures) Mercury, Venus, Earth, Mars: inner or terrestrial planets (nearest the sun); rocky composition: largely silicate rocks and metals (Si, Fe, O) Jupiter, Saturn, Uranus, Neptune: giant or Jovian planets (outer planets; far from the sun); lack solid surfaces: in gaseous or liquid form; composition: light elements (H, He, Ar, C, O, Ni) The Earth: started as a “dust ball” from the nebular gas and dust brought together by gravity (accretion), which was heated (heating) and eventually segregated into layers (differentiation) as it cooled; when cooling set in, the denser elements (e.g., iron) sank while the lighter ones floated out into the surface, creating a differentiated Earth The Moon: said to have been formed by a Mars-sized impactor that collided the flanks of the Earth during its early stages (not yet differentiated) removing a significant chunk of the still-molten Earth (Giant Impact Hypothesis) Earth’s Chemical Composition by mass: 34.6% Iron, 29.5% Oxygen, 15.2% Silicon, 12.7% Magnesium Circumference was popularly computed by Eratosthenes Shape: oblate spheroid Equatorial Radius = 6378 km Polar Radius = 6357 km Equatorial Circumference = 40076 km Polar Circumference = 40008 km Volume = 260,000,000,000 cu. miles Density = 5.52 g/cm3 Age: 4.6 billion years
    • Earth’s Large Scale Features Continents (prominent features: mountains mountains; mountain belts – mountain ranges that run across a vast area) Ocean basins (prominent features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains) Internal Structure of the Earth Geochemical layering: based on chemical composition of rocks Geophysical layering: based on the physical characteristics of materials/rocks Crust 1. Oceanic: basaltic composition (SiMa); 3 to 15 km thick; density: ~3.0 g/cm 2. Continental: granitic composition (SiAl); 20 to 60 km thick; density: ~2.7 g/cm3 Mantle: extends to a depth of ~2900 km (Fe, Mg) 1. Upper mantle – extends from the base of the crust 2. Mesosphere – lower mantle; from 660 km depth to the core-mantle boundary Core: iron-rich sphere with small amounts of Ni and other elements 1. Outer core – 2270 km thick; liquid 2. Inner core – solid sphere with a radius of Discontinuities/boundaries: determined from the study of earthquakes transmission of energy; passes through solid and liquid and S of energy; passes through solid only) 1. Mohorovicic (Moho) discontinuity 2. Gutenberg discontinuity – core 3. Lehmann discontinuity – outer core Mechanical layers: layers that move 1. Lithosphere a. Upper crust – brittle; 4 b. Lower crust/uppermost mantle 2. Asthenosphere – weak sphere; beneath the lithosphere and within the upper mantle 3. Mesosphere – solid, rocky layer Isostasy: from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain (prominent features: mountains – elevated features of continents; mountain ranges mountain ranges that run across a vast area) nt features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains) based on chemical composition of rocks based on the physical characteristics of materials/rocks : basaltic composition (SiMa); 3 to 15 km thick; density: ~3.0 g/cm3 : granitic composition (SiAl); 20 to 60 km thick; density: ~2.7 : extends to a depth of ~2900 km (Fe, extends from the base lower mantle; from 660 mantle boundary rich sphere with small amounts of Ni and other elements 2270 km thick; liquid solid sphere with a radius of 1216 km : determined from the study of earthquakes (P-waves: primary waves; parallel transmission of energy; passes through solid and liquid and S-waves: secondary waves; normal transmission of energy; passes through solid only) (Moho) discontinuity – crust – mantle core – mantle outer core – inner core layers that move brittle; 4-15 km depth Lower crust/uppermost mantle – ductile; 15 to 100 or 200 km depth weak sphere; beneath the lithosphere and within the upper mantle solid, rocky layer : from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain elevated features of continents; mountain ranges – chains of nt features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains) waves: primary waves; parallel waves: secondary waves; normal transmission ductile; 15 to 100 or 200 km depth weak sphere; beneath the lithosphere and within the upper mantle : from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain
    • regions causes the lithosphere to make adjustments until isostatic equilibrium (i.e., neither rising or sinking) is reached Pratt’s theory: regional scale; elevation is inversely proportional to density. Thus, the higher the mountain, the lower is its density; that is, light rocks “float” higher. Airy’s theory: regional scale; Mountains have “roots” which extend down into the mantle. Thus, elevation is proportional to the depth of the underlying “root”. Vening Meinesz’ Theory: local scale; a.k.a. flexure theory; lithosphere is flexible; redistributes loads by bending, like in Hawaii Isostatic rebound in Ferroscandian region, Canada and Utah How old is the earth? Cooling through conduction and radiation (Lord Kelvin, 1897): ~24 – 40 m.y. Rate of delivery of salt to oceans (John Joly, 1901): ~90 – 100 m.y. Thickness of total sedimentary record divided by average sedimentation rates (1910): ~1.6 b.y. Amount of evolution of marine mollusks (Charles Lyell, 1800s): ~80 m.y. for the Cenozoic Radioactivity (Henri Becquerel, 1896): ~500 m.y. Radiometric dating: 4.5 – 4.6 b.y. Oldest dated Earth rocks: 3.4 to 4.03 b.y. Meteorites and moon rocks: ~4.5 b.y. Lecture 3: The Restless Earth Continental Drift Theory: introduced by Alfred L. Wegener in his book “The Origin of Continents and Oceans” in 1915 Supercontinents: Vaalbara, Kenorland, Columbia/Nuna, Rodinia (1.1 Ga-750 Ma); Pangaea (Laurasia and Gondwanaland) (300-200 Ma) Evidence for Continental Drift Theory 1. “Jigsaw puzzle” fit: e.g. Africa and South America 2. Fossils: Lystrosaurus, Cynognathus, Mesosaurus and Glossopteris 3. Rock type and structural similarities: rocks found in one continent closely match (in age and type) those rocks found in the matching continent, e.g. glacier tillites, coal deposits, evaporates, mountain belts like Appalachians in east coast of North America and Western Europe and Cape Fold Belt in South America and Africa 4. Paleoclimatic evidence a. Glaciers in South America, Africa, India and Australia b. Coal in Antarctica
    • Sea Floor Spreading Hypothesis: introduced by Harry Hess (1960s); ocean floor around 130Ma while continental rocks 4.6Ga; new material formed at mid-oceanic ridges Wilson Cycle: from John Tuzo Wilson; explains life of an oceanic basin from sea-floor spreading hypothesis Paleomagnetism and Continental Drift: Magnetic minerals (e.g. magnetite) in rocks align themselves in the direction of the existing magnetic field at the time they were formed; rocks formed at the same time = record of magnetic field should be the same; Positions of ancient magnetic poles for continents do not coincide, therefore continents moved! Magnetic reversals: Earth’s true (geographic) north coincides with magnetic north (normal polarity) and Earth’s true (geographic) north coincides with magnetic south (reversed polarity); due to periodic fluctuations in the inner core Continental drift + Sea floor spreading + Paleomagnetism > Plate Tectonics Plate Tectonics: Unifying theory of geology; all geological features and processes are related; concepts were drawn together in 1968; lithosphere is made up moderately rigid plates (may consist of oceanic or continental lithosphere; 7 major plates + several smaller plates) Plate Boundaries 1. Convergent Plate Boundary: “crashing”; places where plates crash into each other; destruction of crust a. Oceanic-continental: subduction of oceanic crust beneath continental crust, formation of volcanic arcs, e.g. Andes (from Nazca plate under South American Plate) and trenches b. Continental-continental: collision and deformation of continental crust, formation of mountain belts and ranges, e.g. Everest (from Indian Plate - Eurasian Plate collision) and Appalachians (from North American Plate – Eurasian Plate collision) c. Oceanic-oceanic: subduction of faster and/or denser oceanic crust, formation of island arcs and deeper trenches, e.g. e.g. Marianas Trench (from Pacific Plate subduction to Philippine Sea Plate) 2. Divergent Plate Boundary: “pulling apart”; places where plates are being pulled away from each other, forms mid-ocean ridges, e.g. Mid-Atlantic Ridge, rift basins, e.g. Great Rift Valley in Syria to Mozambique (African Plate and Arabian Plate) and islands, e.g. Iceland (North American plate and Eurasian Plate); creation of crust 3. Transform Plate Boundary: “sliding”; places where plates slide past each other, e.g. San Andreas fault in North American and Pacific Plates Plate Boundaries associated with volcanism and earthquakes Driving Mechanism Convection Currents: Hot materials rise, cold materials sink 1. Two-layer convection – separated at depth of 660 kilometers 2. Whole-mantle convection – entire 2900-km mantle “Slab-pull” Evidence
    • 1. Hot-spots: provide a frame of reference for tracing the direction of plate motion; relatively small, long- lasting, and exceptionally hot regions which exist below the plates; provide localized sources of high heat energy (thermal plumes) to sustain volcanism, e.g. Hawaii 2. Global Positioning System Philippine Tectonics 1. Manila Trench 2. Negros Trench 3. Sulu Trench 4. Cotabato Trench 5. Philippine Trench 6. East Luzon Trough 7. Philippine Fault Zone Plate Boundaries associated with volcanism and earthquakes, even in the Philippines! Lecture 4. Minerals Naturally occurring Inorganic Homogeneous solid Definite chemical composition Ordered internal structure Mineraloid: naturally occurring, inorganic material that is amorphous (ex. glass, opal) Polymorphism: ability of a specific chemical substance to crystallize in more than one configuration, which is dependent upon changes in temperature, pressure, or both (ex. FeS2: pyrite and marcasite, graphite and diamond) Physical Characteristics of Minerals Color: caused by the absorption, or lack of absorption, of various wavelengths of light Streak: the color of a mineral in powdered form; not always identical to the color Hardness: resistance of mineral to abrasion or scratching Mohs’ Scale of Hardness 1. Talc 2. Gypsum 2.5. Fingernail 3. Calcite 3.5. Copper coin 4. Fluorite 5. Apatite, Steel Nail 5.5. Glass 6. Orthoclase 6.5. Streak Plate 7. Quartz 8. Topaz 9. Corundum 10. Diamond
    • Crystal Form: the shapes and aggregates that a certain mineral is likely to form Cleavage: the tendency of a mineral to break in particular directions due to zones of weakness in the crystal structure Fractures or irregular breakages occur when bond strengths in a crystal structure is equal in all directions. Luster: the ability of minerals to reflect light Specific Gravity: Ratio of volume of a substance and the weight of the same volume of water Other properties: 1. Magnetism – ex. magnetite 2. Fluorescence – ex. fluorite 3. Reaction to acid – ex. calcite 4. Taste – ex. halite, borax 5. Odor – ex. sulphur 6. Feel – ex. graphite, talc Classification of minerals: Silicates and non-silicates Bases of classification Composition: 1. Single element (e.g. Cu, Au, S) 2. 2 elements (e.g. halite, pyrite) 3. Greater number of different kinds of atoms (e.g. KAl3Si3O10(OH)2) Crystal Structure The Silicates: largest group of minerals; compounds containing silicon and oxygen; building block: silicon tetrahedron (SiO4)-4 Silicate Group Silicate Structure Mineral Group Cleavage Example Associated rock Nesosilicate "island" Olivine Group none olivine ferromagnesian rocks Inosilicate "single- chain" Pyroxene Group 2 directions at 90 degrees pyroxene ferromagnesian rocks "double- chain" Amphibole Group 2 directions at 60-120 degrees amphibole mostly ferromagnesian rocks Phyllosilicate "sheet" Mica Group 1 direction biotite, muscovite, clay minerals felsic rocks Tectosilicate "3D network" Feldspar Group 2 directions at 90 degrees plagioclase feldspar, orthoclase feldspar both ferromagnesian and felsic rocks
    • Quartz Group no cleavage quartz felsic rocks Sorosilicate "sister" Epidote Group 1 direction epidote metamorphic rocks Cyclosilicate "ring" Beryl Group no cleavage emerald, aquamarine metamorphic rocks The Non-silicates Mineral Group Characteristics Examples Native Elements Single elements Gold (Au), Diamond (C), Silver (Ag) Oxides Metallic ion and oxygen Hematite (Fe2O3), Magnetite (Fe3O4) Sulfides Sulfur and a metallic ion Galena (PbS), Realgar (AsS) Sulfates Metallic ion, sulfur & oxygen Barite (BaSO4), Gypsum (CaSO4) Carbonates Metallic ion and carbon and oxygen (CO3) Calcite (CaCO3), Rhodocrosite (MnCO3) Phosphates Metallic ion and phosphate and oxygen (PO4) Apatite (Ca5(PO4)3(F,Cl,OH)) Halides Metallic ion and a halogen (F, Cl, Br, I and At) Halite (NaCl), Fluorite (CaF2) Common rock-forming minerals: Feldspar, Quartz, Olivine, Pyroxene, Amphibole, Mica (Biotite and Muscovite), Clay, Calcite Non-renewable resource – processes that create the resources are so slow (takes millions of years to accumulate) Ores – useful metallic (and some nonmetallic) minerals that can be extracted and which contain useful substances Economic Importance: 1. Mineral resources – sources of metals and other materials 2. Gemstones Gold and copper associated with volcanism in the Philippines.
    • Lecture 5: Igneous Rocks The Rock Cycle Rocks: naturally-occurring aggregate of minerals, mineraloids, organic components and rock fragments; classification based on mineral, texture and formational processes Common rock-forming minerals • quartz: glassy-looking, transparent or translucent mineral which varies in colour from white and grey to smoky; hard (H=7), durable and no cleavage; most common mineral on the Earth’s crust • potassium feldspar (orthoclase): generally dull to opaque with a porcelain-like appearance; color varies from red, pink, white and buff gray; all have 2 cleavages at approximately 90° and a hardness of 6; occurs in well shaped prismatic and tabular crystals, which are sometimes striated • plagioclase feldspar: may have striations (very fine "razor-cut" grooves on selected cleavage faces), but not always; color varies from green, gray, white; all have 2 cleavages at approximately 90° and a hardness of 6; crystals are usually flat and bladed, and commonly in compact groupings • muscovite: most common of the mica minerals; typically found as massively crystalline colorless, white, pearly material in "books”; has the characteristic of peeling into many thin flat smooth sheets or flakes; has a 1 direction perfect cleavage • biotite: crystals are in thick flakes; similar to muscovite but in darker in color • amphibole: mostly black, forms long, slender crystals with 2 cleavages at 60° and 120°; most common member: hornblende • pyroxene: usually dark-green or black minerals with hardness of 5 or 6 and two good cleavages at right angles (square cleavages) • olivine: olive green to black, translucent, with a conchoidal fracture, sugar-like appearance • calcite: a very common mineral in sedimentary rocks; commonly white to grey, sometimes clear and transparent; hardness = 3 • clay minerals: very fine grained and difficult to tell apart in the field; vary in colour from white to grey, brown, red, dark green and black Igneous rocks formed from solidification of magma (intrusive) or lava which flows out from depths (extrusive) Magma: Molten material which may contain suspended crystals and dissolved volatiles (gases, such as water vapor, CO2, SO2); composed of mobile ions of the 8 most abundant elements in the Earth’s crust: Si, O, Al, K, Ca, Na, Fe, Mg Formation of magma: Increase temperature, decrease pressure, add volatiles (i.e. water, carbon dioxide, etc.) Sources of heat • original heat of the earth at the time of formation • heat produced from radioactive decay • heat transfer by conduction from a nearby body of magma • hot mantle plumes • frictional heat caused by rocks grinding past each other
    • Magma forms at Mid-Oceanic Ridges (MOR), Subduction Zones, Hot spots Classification based on: Silica content - amount of SiO2 Viscosity - resistance to flow Temperature - temperature of melt formation Basaltic magma • High density • Low viscosity • Relatively low silica content • “Dry” • Crystallizes at high temperatures (~1000 - 1200ºC) Granitic magma • Low density • High viscosity • Relatively high silica content • Gaseous • Crystallizes at ~600°C
    • Kinds of igneous rocks • Extrusive (volcanic) – molten rock solidified at the surface (ex., basalt, andesite, rhyolite) • Intrusive (plutonic) – igneous rocks formed at depth (ex., gabbro, diorite, granite) Intrusive Igneous bodies • Stock – small discordant pluton • Batholith – more than 100 sq. km. in outcrop area • Dike – tabular body cutting across bedding (=discordant) • Sill – concordant (= parallel to beds) tabular body • Laccolith – blister-shaped sill • Lopolith – bowl-shaped sill Textures • Aphanitic – very fine-grained (<2mm in diameter) as a result of rapid cooling at the surface; minerals too small to be seen by the naked eye • Phaneritic – coarse-grained (>5 mm) mineral sizes due to slow magma cooling at depth. • Porphyritic – very large crystals (phenocrysts) embedded in smaller crystals (groundmass) • Vesicular – contains tiny holes called vesicles which formed due to gas bubbles in the lava or magma • Glassy – molten rock quenched quickly as it was ejected into the atmosphere or contact with water. • Pegmatitic – interlocking crystals greater than 1 cm • Pyroclastic – formed when volcanic materials are extruded violently. Pyroclastic Rock Identification (based on dominant fragment size) • Ash – <2 mm in diameter • Lapilli – 2-64 mm in diameter • Block or bomb – >64 mm; block is extruded in a solid state (thus angular)while bomb is partially or wholly molten (thus rounded or spiniform [football-shaped]) Cooling history based on crystal face geometry • Euhedral – well-defined crystal faces • Subhedral – intermediate faces • Anhedral – no well-formed crystal faces *suggests rate of cooling undergone by the magma (longer cooling period, more well-formed crystal faces)
    • Classification of Igneous Rocks based on mineral assemblage and other characteristics Source of magma Partial melting of mantle Variation in magma composition due to: • Assimilation: melting of overlying rocks and incorporation of melted rock material • Magmatic differentiation, including: • Fractional Crystallization • Differential Settling: lighter minerals float, denser minerals sink • Magma mixing: mixing of at least two chemically distinct melts Classification (based chemical composition) Felsic, Silicic or acidic: >63% SiO2 • Intermediate: 52-63% SiO2 • Mafic or basic: 45-52% SiO2 • Ultramafic or ultrabasic: <45% SiO Viscosity • ↑ temperature, ↓ viscosity • ↑ SiO2, ↑ viscosity • ↑ dissolved H2O, ↓ viscosity Density • heavier oceanic crust mafic rocks • lighter continental crust felsic rocks Lecture 6: Volcanism Volcano: place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and pyroclastic debris erupt through the earth's crust Eruption due to decompression (magma is lighter than surrounding rock) Types of volcanoes • Cinder Cones: relatively small (<300 m high); steep slopes (30 • Composite Volcanoes: layered structure (tephra and lava flows) • Shield Volcanoes: slopes are gentle (15 ground; made up of successive lava flows • Lava Domes: formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent Rocks based on mineral assemblage and other characteristics Variation in magma composition due to: : melting of overlying rocks and incorporation of melted rock material including: Fractional Crystallization: minerals have different crystallization temperatures : lighter minerals float, denser minerals sink : mixing of at least two chemically distinct melts composition) <45% SiO2 ↓ viscosity mafic rocks felsic rocks : place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and pyroclastic debris erupt through the earth's crust (magma is lighter than surrounding rock) relatively small (<300 m high); steep slopes (30 – 40o ); made up of pyroclastic material layered structure (tephra and lava flows) slopes are gentle (15o or less); shape resembles a Roman shield ground; made up of successive lava flows formed by relatively small, bulbous masses of lava too viscous to flow any great extrusion, the lava piles over and around its vent Rocks based on mineral assemblage and other characteristics : melting of overlying rocks and incorporation of melted rock material : minerals have different crystallization temperatures : place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and ); made up of pyroclastic material shield lying on the formed by relatively small, bulbous masses of lava too viscous to flow any great
    • Distribution of volcanoes • Pacific Ring of Fire • Hot spots • Spreading centers Volcanic Eruption Styles Volcanic Explosivity Index or VEI - based on a number of things (e.g. plume height, volume, etc.) that can be observed during an eruption • Magmatic eruption: purely magmatic eruption, lavas and pyroclastic material only • Hawaiian: calm eruptions where lava flows • Strombolian: short-lived, explosive outbursts of pasty lava ejected a few tens or hundreds of meters into the air • Vulcanian: occur as a series of discrete, cannon-like explosions that are short-lived • Pelean: mainly pyroclastic with nuee ardente (“glowing cloud”; hot glowing ash avalanche) • Plinian: generate sustained eruptive columns; very destructive (Ultra-Plinian) • Phreatomagmatic eruption: generated by the intereaction of magma with either groundwater or surface water • Surtseyan: volcanic eruptions that have come into contact with encroaching seawater • Submarine: underwater eruptions • Subglacial: under glaciers • Phreatic eruption: steam and some rock fragments only, lava is unusual Monitoring Volcanic Activity • Remote Sensing • Ground Deformation • Seismicity • Geophysical Measurements • Gas • Hydrology Volcanic Hazard Pyroclastic Flows: explosive eruptive phenomenon of fluidized masses of rock fragments and gases; gravity- driven, which means that they flow down slopes. Lahar: specific kind of mudflow made up of volcanic debris, remobilized pyroclastic deposits; can cause fatalities years after an actual eruption Volcanic Gases: can be directly harmful to humans, animals, plants, agricultural crops, and property (e.g. CO2, SO2, HCl, H2S, F2, HF, etc.) Lava Flow Tephra: ejected material such as rock fragments Benefits Fertile lands New islands Pumice can be used as an abrasive Porous volcanic rock can create fresh water aquifers Tourism Weather balance Source of geothermal energy – benign source of electricity Resources • metallic resources, such as gold, copper, silver, platinum o hydrothermal solution precipitates • construction/ building materials • tiles and countertops • gravestones • abrasive materials (for cosmetics) • minerals