GEOS 470R/570R Volcanology
L28, 4 May 2015

Handing out
 PowerPoint slides for today

Lecture final
 Wednesday, 13 May 2015, 10:30-12:30pm, G-S 203
 Early offering: Monday, 11 May 2015, 1:00-3:00pm,
G-S 321
 Time of lecture review session? Friday afternoon?
“The reward of a thing well done, is to have done it.”
--Ralph Waldo Emerson
Readings from textbook

For L28 from Lockwood and Hazlett
(2010) Volcanoes—Global Perspectives
Chapters 15 and 13
Last time: Extraterrestrial
volcanism, II.



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
Venus
Mars
Io
Cryovolcanism
Comparative
planetology revisited
Press and Siever, 2001, Fig. 1.10
Venus

Size and density similar to Earth
 Diameter only 330 km less than Earth

Covered with dense atmosphere rich in carbon
dioxide
 Capped with clouds with sulfuric acid droplets
 Clouds circulate planet once every four days
 High winds aloft, but mostly calm at surface

Explored by
 Pioneer Venus radar
 Earth-based radar
 Soviet Venera 15-16 orbital imaging radar
 Soviet Venera and Vegas landers
 Magellan radar, altimetry, and gravity (1990-1994)
Lunar and Planetary Institute, 1997, Venus Slide Set, #2
Volcanologic implications of
atmospheric pressure and heat

High atmospheric surface pressure
 Everything else being equal, will inhibit vesiculation of magma,
leading to less explosive eruption (some ash suspected; no ashflow tuffs documented)
 Makes wind velocities very low (few dunes observed on Venus)

High ambient surface temperature
 Slow the rate of solidification of lavas
 Prevent water from existing on or below surface
 Everything else being equal, would diminish potential to form
maars, tuff rings, etc.
 Potentially could increase long term rates of geological strain in
areas of high, mountainous relief
Types of magmatic features on
Venus

Volcanoes
 Large volcanoes
 Intermediate
volcanoes
 Small volcanoes and
fields of small shield
volcanoes (colles)
 Calderas (often,
patera, irregular
depressions)

Lava flows and
channels
 Plains lavas
 Lava flow fields (fluctii)
 Unusual lava flows
 Lava channels (canali)

Magmatic structures
 Coronae
 Arachnoids
 Radial (stellate)
fracture centers
Large volcanoes

Chloris Mons
 Shield volcano
 300 km in diameter


Numerous light and
dark lava flows and
radiating fractures
Distal ends of flows are
radar bright
 Relatively rough and
blockier?

Several small
volcanoes with steepsided dome morphology
near the summit
Crumpler and Aubele, 2000, Fig. 2
Intermediate volcanoes
Diameter 20 - 100 km
 Morphologic types

Radially patterned domes
Steep-sided domes
Pancake domes (farra)
Scalloped domes
Modified or fluted domes
Tholi
Volcano of intermediate size

A simple intermediate
volcano
 20 km in diameter


Radial bright and
dark lava flows
Summit caldera
Crumpler and Aubele, 2000, Fig. 3
Steep-sided dome

Steep-sided dome
 Convex profile
 ~40 km in diameter

Located on set of
annular fractures
defining the margins
of a corona
Crumpler and Aubele, 2000, Fig. 4
Pancake domes (farra)

Steep sided domes that
are
 Broad and flat
 Very circular
 Steep along their
perimeter
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

Apparent emplacement
in a single episode of
volcanism
Seem to require highly
viscous, perhaps silicic
magma
Located just southeast
of Alpha Regio at 30°S,
12°E
Fluted dome

Fluted dome on right
 Convex profile
 ~25 km in diameter


Deep central crater
with inverted conical
profile
Pancake-like steepsided dome at left
 ~35 km in diameter
Crumpler and Aubele, 2000, Fig. 5
Tholi


Intermediate volcano in
which the flanks appear
steep relative to most
volcanoes on Venus
Mahuea Tholus
 Located at 37.3°S, 165.1°E
 The bright, ridged flows
stand about 600 m above
the surrounding plains
 Inner tier sits >1000 m high
 Thickness suggests that
they were unusually
viscous at time of
emplacement
Lunar and Planetary Institute, 1997,
Venus Slide Set, #25
Small volcanic field

“Shield field”
 Centered at
78.4°S, 43.0°E
 Located in the
volcanic plains
Lunar and Planetary Institute,
1997, Venus Slide Set, #26
Caldera


Circular caldera with
ring fractures
Radar altimetry
profile
 Demonstrating depth
of caldera of 1 km
Crumpler and Aubele, 2000, Fig. 7A, B
Types of magmatic structures

Coronae
Almost unique to Venus
But also observed on Miranda, a moon of
Uranus
Arachnoids
 Radial (stellate) fracture centers

Coronae

Dominantly circular to elliptical
structures
 May be associated with mantle
plumes or hot spots

Characteristics
 Annulus of concentric ridges or
fractures
 Interior that may be high or low
 Peripheral moat or trough
 Large and small volcanoes
frequently present within the
corona or on its margins
 But exhibit a variety of
topographic forms

Interpreted origin
 Rising plumes push the crust
upward into a dome
 Dome collapses in center
 Molten lava leaks out around
sides
Crumpler and Aubele, 2000, Fig. 10
Arachnoids


Similar to coronae, but with strongly developed
radial patterns
Annular structural patterns consisting of
 Concentric or circular pattern of fractures or ridges,
With
 Radial arrays of fractures or ridges extending
outward for several radii
 Interior flows and small shield volcanoes

Radial fractures frequently merge outward with
the linear patterns of the fracture belts on which
arachnoids are arranged
 Hence the name: spiders along webs of linear
fracture belts
Arachnoids
Crumpler and Aubele, 2000, Fig. 12A, B
Mars

Explored by
 Flybys of Mariner 4
(1965), Mariners 6 and 7
(1969), and Mariner 9
(1971)
 Viking 1 and 2 orbiters
and landers (1976)
 Mars Pathfinder and
Sojourner Rover (19971998)
 Mars Global Surveyor
(1999-present)
 Mars Odyssey (2002present)
 Mars Express (2003present)
 Mars Exploration Rovers
Spirit and Opportunity
(2004)
 Phoenix Lander (2008)
 Curiosity Rover (2012)
Press and Siever, 2001, Fig. 1.10
Volcanic features on Mars

Mons
Large isolated mountain

Tholus (pl. tholi)
Isolated domical small mountain or hill, with
slopes much steeper than that of a patera

Patera (pl. paterae)
Irregular or complex crater with scalloped
edges, surrounded by shallow flank slopes
Olympus Mons

A shield volcano on Mars the size of Arizona
 Diameter ~600 km
 Relief: 21 km above datum (akin to sea level)
Tholi


Isolated, domical
mountains or hills
Slopes much
steeper than that of
most paterae
Smaller than 200
km in diameter
Ceraunius Tholus
 Lava dome
 Elongate crater at top
created by oblique
impact at northern base
 Dimensions 150 X 100
km
 Lava channel flowed
into crater
Zimbelman, 2000, Fig. 3
Paterae

Irregular or complex craters
Scalloped edges
Surrounded by shallow flank slopes

Possibly have an important pyroclastic
component
Flows or falls?
Suggestive of increased volatile content of
magmas?
Paterae
Tyrrhena Patera (FOV ~ 120 km)

Highland Paterae
 Irregular or complex
crater with scalloped
edges that are
surrounded by shallow
flank slopes

Intensely eroded
appearance
 Removal of friable
material?
Zimbelman, 2000, Fig. 4
Volcanic fields (white)
Volcanic plains
Lava flow margins (FOV ~ 54 km)
Zimbelman, 2000, Fig. 1
Zimbelman, 2000, Fig. 6
Volcanoes and
ice on Mars

HiRISE image of possible rootless cones east
of Elysium region. Chains of rings interpreted
to be caused by steam explosions when lava
moved over ground that was rich in water ice.
Large amounts of water
ice
 Believed to be present in
Martian subsurface

Interaction of ice with
molten rock
 Produces distinct
landforms

Features identified
recently include
"Rootless Cones" on Mars – due to lava flows
interacting with water (MRO, January 4, 2013)
 Rootless cones created by
phreatic explosions (e.g.,
Hamilton et al., 2010)
 Lahars or debris flows
Images from Wikipedia Site, Volcanology of Mars
Io

Galilean satellites
(four largest
satellites of Jupiter)
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Io
Europa
Ganymede
Callisto
Io
 Innermost satellite of
Jupiter

Intense magmatism
on Io
 Driven not by
internal heat
 But by
gravitational
attractions of
Jupiter and
Europa
Io
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
Most volcanically
active object in the
solar system
Heat flow much higher
than Earth’s
 Several volcanoes
erupt lavas that are
hotter than any erupted
on the Earth today
Lopes-Gautier, 2000, Fig. 1
Surface features
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Mountains
Smooth plains
Volcanic constructs
 Absence of large volcanic
edifices


Shield volcanoes are low
Magmas of low viscosity?
 Calderas

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Steep walls and flat
floors
20 – 200 km in
diameter
As deep as 2 km
Lockwood and Hazlett, 2010, Fig. 12.21
Scalloped (possibly sapped) volcanic
tableland and compound caldera of
Tvashtar patera on Io; ongoing effusive
eruption on left)
Eruptive products

Red materials
 Ephemeral (lasting a few years?)
 Pyroclastic deposits—fall deposits from plumes?
 Associated with hot spots and plumes

Very dark deposits
 Also associated with hot spots

Different colors may reflect different allotropes
(crystal structures) of sulfur
 Cooled rapidly from different temperatures
Cryovolcanism

Definition
 Eruption of liquid or vapor phases (with or without
entrained solids) of water or other volatiles that would
be frozen solid at the normal temperature of an icy
satellite’s surface

Known to occur
 Geyser-like plumes of nitrogen were discovered on
Triton, a moon of Neptune, by Voyager 2

Indirect evidence that it has taken place
elsewhere
 Might be active today
South pole of Triton, Neptune’s
only planet-sized moon

Bright polar
cap
 Made up of
relatively
mobile N2
ice,
subliming
in the
summer
sunshine

Dark
streaks are
active or
recent
plumes
Geissler, 2000, Fig. 3
Cryovolcanic flows on Triton

Evidence of
extensive melting
 Perhaps when
moon was
gravitationally
captured into orbit
about Neptune

Two large calderalike lake features
near the equator
 Rimless pits to the
right of the impact
crater may be the
source of the
smooth materials
Geissler, 2000, Fig. 5
Summary: Extraterrestrial
volcanism, II.

Venus
 Volcanoes: Large volcanoes, intermediate volcanoes (various domes),
small volcanoes and fields of small shield volcanoes, calderas, lava
flows and channels
 Magmatic structures characterized by surface deformation associated
with large-scale subsurface magmatism: Coronae, arachnoids, radial
fracture centers

Mars
 Volcanically inactive planet with huge volcanoes

Io
 Vigorous volcanism driven by tidal forces; sulfur is an important product

Cryovolcanism
 May be common on outer planets and their satellites

Comparative planetology, revisited
 Many features are similar on various planetary bodies
Lecture 28: Societal applications

Volcanic contributions to climate change
 Review of atmospheric structure and processes
 Eruptions and atmospheric anomalies
 Volcanism and extinctions
 Volcanic contributions to S and C fluxes

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Volcanic materials for consumers
Volcanic contributions to soils
Geothermal systems and resources
Petroleum maturation and reservoirs
Definitions

Colloid
 Any finely divided substance (finer than clay size)
that does not occur in crystalline form
 Any fine-grained material in suspension

Sol
 Homogeneous suspension or dispersion of colloidal
matter in a fluid (liquid or gas)
 A sol is more fluid than a gel

Aerosol
 A sol in which the dispersion medium is a gas
(usually air) and the dispersed or colloidal phase
consists of solid or liquid droplets
 e.g., mist, haze, most smoke, and some fog
Homospheric portion of the atmosphere

Mesosphere
 T decreases with altitude to a minimum at the top (the
mesopause)

Stratosphere
 Temperature increases with altitude to a maximum at the top
(the stratopause, ~50 km altitude)
 Warm air is less dense than cold air, so is more stable than
troposphere because air enters stratosphere from convective
storms in tropics; particles not rained out
 Air leaves stratosphere only by infolding into troposphere at
midlatitudes (3/4; residence time two years) and by descending
toward surface at poles during winter (1/4)

Troposphere
 Region closest to Earth; “dirty”
 Temperature decreases with altitude to a minimum at the top
(the tropopause, ~18 km altitude at equator, ~8 km at poles)
 Absoption of solar radiation causes instabilityweather
 Precipitation causes rainout of particles within weeks
Mills, 2000, p. 933-934
Residence times in stratosphere

Fine ash
Resides in stratosphere for <3 months
because of its relatively large size

Sulfuric acid aerosol
Resides in stratosphere for several years
Consequences of atmospheric
structure

Volcanic eruptions have little chance to impact global
atmosphere unless volcanic plumes penetrate the
tropopause
 Only explosive eruptions will affect the stratosphere

Ash not of major concern regarding climate
 Short residence time


Sulfuric acid aerosols are important if injected into
stratosphere
Explosive, SO2-rich eruptions will have the greatest impact on
climate
 Mafic eruptions (especially if explosive, but are uncommonly
explosive) and eruptions of oxidized intermediate magmas

Eruptions in the tropics have the best chance to have a
global impact
 Better chance for eruptive products to reach both the northern and
southern hemispheres (because their air masses do little mixing)
 Famous global impacts of Tambora (1815), Krakatau (1883),
Pinatubo (1991 were all equatorial, highly explosive eruptions
More definitions

Climate
Average weather conditions (temperature,
meteorological conditions) of a place over a
period of years

Weather
Daily changes or weekly and monthly
patterns
“Climate is what you expect; weather is
what you get”
Climate and global change
Dust and especially gases (CO2, SO2,
H2S) from large eruptions have short-term
impacts on climate
 Numerous atmospheric anomalies
correlate with historic volcanic eruptions,
commonly in a different part of the world

Typically hemispheric spatial extents
Typically 1- to 2-year temporal effects
Ancient eruptions and atmospheric
anomalies

Santorini (Thera), Aegean Sea ~ 1620 BC
 Atmospheric effects felt globally
 China: Floods, followed by 7 years of drought

Etna, Sicily ~42 BC
 Correlates with anomalies in Rome, China,
Greenland

Kuwae, Vanuatu, S. Pacific, ~1453 AD
 Eclipse, hailstorm, dense fog in Constantinople
(Istanbul)
 Frost and snow in China same year
 9 years of crop damage in Sweden and Germany
beginning in 1453
 Tree ring evidence for frost damage globally for
several years
More recent eruptions and atmospheric
anomalies
Laki fissure, Iceland

Laki fissure eruption, Iceland, 1783
 Largest historic series of lava flows (~15
km3)
 Europe’s “dry fog” may have caused cold
winter in 1783-1784 and cold summer of
1784

Tambora, Sumbawa, Indonesia, Apr 1815
 Largest eruption in last 10,000 yrs (~100
km3)
 1816: “Year without a summer” because of
lower temperatures in New England and
Europe
 France: Famines and riots at end of
Napoleonic wars
 Ireland and British Isles: Famine and
typhus epidemic
 India: Crop failures, famine, cholera
P. Kresan

Krakatau, 1883
 Several years of brilliant sunsets
Brilliant sunsets

Major explosive eruptions
 Produce smog-like silvery
midday skies and colorful
sunsets

Krakatau eruption (1883)
impressed European observers
 Inspired a number of paintings
 Perhaps Edvard Munch’s The
Scream (1893)
Lockwood and Hazlett,
2010, Fig. 13.3
Lockwood and Hazlett, 2010, Fig. 13.4
Volcanic eruptions and short-term changes
in climate

Eruption of
Tambora,
Indonesia, in
1815
shortened
growing
season in
New England
 Annual and
5-year
running
average
ME
NH
Sigurdsson, 2000, Fig. 5
MA
Extraordinarily large eruptions

Toba, Indonesia
Eruption at 74,000 yr BP
Largest eruption of last several hundred
thousand years (~280,000 km3)
Ice core studies indicate that Toba aerosols
remained in stratosphere for ~6 yr
Fisher et al., 1997, Fig. 9-2; adapted from AGU Report, “Volcanism and Climate Change”
Fate and impact of volcanic SO2

Within one month SO2 is converted to H2SO4
 Combines with water vapor to form stratospheric sulfate aerosol

Volcanic aerosol
 May cool the Earth’s surface by reflecting solar energy back to
space
 May warm the stratosphere by absorbing infrared radiation
escaping the from the surface and troposphere

Chemical reactions between gaseous and aerosol
components activate anthropogenic halogens
 Amplifies ozone depletion at midlatitudes and poles

Aerosol eventually is taken up by clouds in troposphere
 May again increase planetary albedo by decreasing average
size of droplets in cirrus clouds, modifying their optical
properties
Mills, 2000, p. 935-936
Eruptive plume that penetrates the
stratosphere and forms aerosols
Mills, 2000, Fig. 1
SAGE II
Stratospheric aerosol and gas experiment
(SAGE)
 Satellite-borne instrument that monitors
distribution of stratospheric aerosol
 Observations of effects of Pinatubo
eruption of June 1991

Eruption of Pinatubo, June 1991

Aerosol initially
confined to tropics
 Increased the 1-μm
optical depth by two
orders of magnitude

Over 6 months spread
to higher latitudes
 Global increase in 1μm optical depth by
one order of
magnitude

Stratospheric aerosol
layer continued to be
dominated by steadily
decreasing volcanic
aerosol for 3 yr
Self et al., 1996, Fig. 6; from McCormick et al., 1995
Effects of El Chichón 1982 and
Pinatubo 1991
Self et al., 1996, Fig. 9
Variability in sulfur loading
Mills, 2000, Table 1
Temperature decreases correlate
with sulfur yield of eruptions
Fisher et al., 1997, Fig. 9-1; adapted from Sigurdsson, 1990
Laki fissure eruptions, Iceland, 1783-4
Rampino and Self, 2000, Fig. 3
Flood basalt provinces of last 250 Ma
Rampino and Self, 2000, Table I
Flood basalts and faunal events
Rampino and Self, 2000, Table II
Volcanism and extinctions

Unclear relationship between volcanism and
extinctions
 Best temporal correlation is with eruption of flood
basalts

Does a large extinction require
 Combination of bolide impact + eruption?


Does bolide impact somehow trigger eruption of
flood basalts?
Can short-term climate-changes associated with
volcanic event somehow trigger longer term
climate change
 Which may be required to cause massive
extinctions?
Outgassing of the Earth
Midocean ridge volcanism
 Intraplate volcanism
 Convergent margin (arc) volcanism
 Subduction zone and collision zone
metamorphism
 Volatile loss during burial diagenesis of
sediments

Volcanic contributions to global C and
S fluxes

Volcanic outgassing represents ~50% of the
total flux of CO2 to the atmosphere
 Proportions of CO2 flux assigned to various tectonic
settings of volcanism remain uncertain

Volcanic volatile sulfur flux from subaerial
volcanism amounts to 20 – 30% of
preanthropogenic riverine sulfur flux
 Impact of submarine volcanism is difficult to assess
because of uncertainties assigned to hydrothermal
sinks and sources
Volcanoes for consumers
Metals from mineral deposits formed in
volcanic settings
 Ski mountains
 Construction materials
 Volcanic soils
 Geothermal baths
 Geothermal energy
 Petroleum maturation and reservoir rocks

Properties of volcanic materials
Dehn and McNutt, 2000, Table 1
Building stone
Ignimbrite column in Guadalajara, México

Ignimbrite
 Welded tuff
 Sillar


Lightweight
Relatively high
strength
Fisher et al., 1997, Fig. 11-6;
photo by G. Heiken
Building stone
Blocks from ignimbrite quarry
near Naples, Italy
Church in central Naples,
constructed in 13th century out
of cut blocks of Campanian
Ignimbrite and yellow tuff
Fisher et al., 1997, Fig. 11-8A, B;
photos by R. V. Fisher
Cinders



Road construction
and surfacing
“Sand” for traction
on ice
Ornamental
stones and
pathways
Cinder cone at Little Lake, CA
Fisher et al., 1997, Ch. 11 Frontispiece;
photo by R. V. Fisher
Volcanic ash in soil


Volcanic ash is made predominantly of volcanic
glass
Glass is easily weathered
 Producing clay minerals
 Releasing elements not accommodated in clay
minerals


Clay minerals can provide base for roots, help
soil hold water, and exchange nutrients
Some elements released are nutrients for plant
growth (K, Ca, Na, trace elements)
Ash

Ashfall from Parícutin, México
 Where thin, it enriched soils if tilled in with a plow
 Where thick, nothing would grow; farms were abandoned
Fisher et al., 1997,
Fig. 13-3
Soils and more

Volcanoes
contribute to fine
coffees of
Guatemala in
several ways
Coffee finca (plantation) near Volcán
Tecuamburro, southern Guatemala
 Volcanic soils
 Effect of elevation
(2,000-3,000 m)
on temperature
and rainfall
Fisher et al., 1997, Fig. 13-5; photo by G. Heiken
Geothermal benefits
Blue Lagoon, Iceland: Bathers in foreground; geothermal
power plant in background
Fisher et al., 1997, Frontispiece for Ch. 12; photo by G. E. Sigvaldason
Volcanic lakes
Delmelle and Bernard, 2000, Fig. 3
Fumaroles

Fumaroles, boiling acid-sulfate springs, and
acid sublimates produced bleached “wasteland”
 Bumpass Hell, Lassen Volcanic National Park, CA
Goff and Janik, 2000,
Fig. 6A
Surface
manifestations
of geothermal
systems

Silica sinter mound
around boiling
spring
 Sumurup, Lempur,
central Sumatra,
Indonesia
Hochstein and Browne,
2000, Title Banner
Geothermal fluids Valles caldera,
Jemez Mountains, New Mexico

Well VC-2A, Sulphur
Springs,, May 1987
 Active geothermal
system with small
reservoir
 Wall rocks altered to
native sulfur and
kaolinite
 Well producing fluids
from a single fracture
in the Bandelier Tuff
 Uneconomic for
electricity when
explored from 19621984
Goff, 2010, Fig. 4
Geothermal fluids

Neutral-chloride water
erupts during flow test of
well VC-2B, Sulphur
Springs, Valles caldera,
Jemez Mountains, New
Mexico
 Mean T of fluid production
during test 250°C
 Bottom hole T 295°C
 Scale: Well head 2.2 m tall

Reservoir conditions
(adjusted for steam loss)
 pH = 6.2
 Cl- content = 3000 ppm
Goff and Janik, 2000, Fig. 6B
Volcanic-hydrothermal system

Conceptual model of a “volcanic-hydrothermal system” with
characteristic surface manifestations
 Based on Suretimeat system, Vanuatu
 Isotherms: T1 = ~150°C; T2 = ~350°C
Hochstein and
Browne, Fig. 2
Liquid-dominated, high-temp. system

Conceptual model of a liquid-dominated, high-temperature system
beneath a partially eroded, high-standing volcanic complex
 Exhibiting lateral zonation (downstream) of surface manifestations
 Large amount of heat discharged by concealed outflows that are
partially sealed by mineral deposition
 Based in part on Palinpinon system, Philippines
Hochstein and Browne, Fig. 3
High-temp., steaming ground system

Conceptual model of a high-temperature, steaming ground system
beneath a broad volcanic center
 Natural two-phase (L + V) reservoir
 Showing restricted variety of surface manifestations in a semi-arid
environment
 Based in part on Olkaria, Kenya, and others in East African rift valley
Hochstein and
Browne, Fig. 4
Vapor-dominated system

Conceptual model of a vapor-dominated system beneath a broad, high-standing
volcanic system
 Reservoir has a condensate layer on top
 Heat transferred within the reservoir is discharged at the surface by steam and hot
condensates (bicarbonate waters)
 Model similar to Kamojang system, Java, Indonesia
Hochstein and
Browne, Fig. 5
The Geysers, CA

A vapor-dominated geothermal system
P. Kresan
Liquid-dominated, high-temp. system

Conceptual model of a liquid-dominated system in rather flat
terrain
 Heat source is an extensive layer of hot crustal rocks that contains
some partial melts and intrusions
 Similar to Wairakei system, New Zealand
Hochstein and
Browne, Fig. 6
Geothermal resources
Fisher et al., 1997, Fig. 12-2
How much geothermal energy is available?


Global arc volcanism produces 2 km3 magma per year
U.S. electrical power consumption is roughly 500 watts
(joules / second) per person
 How do these compare?

Cooling 1 gram of magma 1˚C releases about 1 joule of heat
 What is a typical magma T in round numbers?






1000˚ to 0˚C releases 1000 joules / gram
Mass magma per year: 2.5 x 109 (t/km3) x 2 x 106 (g/t)
Thus, 5 x 1015 grams or 5 x 1018 joules per year
joules per sec (= watts) is 5 x 1018 / 3 x 107 = 2 x 1011 W
from global arc volcanism
US consumption is 500 x 300 x 106 = 1.5 x 1011 W
Shocking, isn’t it?
M. D. Barton
Reservoir defined by distribution of wet
vs. dry volcanic products

Hydrothermal
reservoir geometry
(dotted line)
defined by
geological
mapping of young
volcanic products
 Dry volcanic
products
(pumiceous)
 Wet volcanic
products
(phreatomagmatic)
Wohletz and Heiken, 1992, Fig. 2-42
Economic significance



Hypothetical water :
magma ratio (Rm) as a
function of near-vent
median grain sizes of
tephra
Finer grain sizes from
phreatomagmatic
eruptions
Why are the
phreatomagmatic
eruptions more
significant economically?
Wohletz and Heiken, 1992, Fig. 2-43
Power generation schemes
Goff and Janik, 2000, Fig. 8
Potential environmental and safety
issues






H2S pollution of
atmosphere
Brine pollution of
groundwater
Hydrothermal explosions
Landslides
Reservoir interference,
depletion, subsidence,
and induced seismicity
Earthquakes and
volcanic hazards
Goff and Janik, 2000, p. 933
P. Kresan
Hydrothermally generated oil

Heat from magmatic processes
 Can contribute to maturation of hydrocarbons
 Can lead to overmaturation of hydrocarbons
 Depends on prior thermal history and temperature +
time exposure to hydrothermal system

Oil generated by interaction with hydrothermal
fluids at modern mid-ocean ridges receiving
pelitic sediment
 Temperatures >300°C--twice those at top of “normal”
oil window, i.e., in amagmatic sedimentary basins

Oil commonly found in many paleohydrothermal
systems hosted by organic-rich sedimentary
rocks
Volcanic rocks as reservoirs

Volcanic rocks uncommon reservoirs
Why?

An important petroleum reservoir in
Railroad Valley, eastern Nevada, is
Tertiary ignimbrite
Summary

Volcanic contributions to climate change
 Review of atmospheric structure and processes
 Eruptions and atmospheric anomalies
 Volcanism and extinctions
 Volcanic contributions to S and C fluxes




Volcanic materials for consumers
Volcanic contributions to soils
Geothermal systems and resources
Petroleum maturation and reservoirs
Thanks for participating in Volcanology classes during
Spring of 2015!