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

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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

10. 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

11. 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)

12. 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

13. 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