geos 470r/570r volcanology l28, 4 may 2015 handing out powerpoint slides for today lecture final ...
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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 203Early offering: Monday, 11 May 2015, 1:00-3:00pm,
G-S 321Time 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 PerspectivesChapters 15 and 13
Last time: Extraterrestrial volcanism, II.
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 ash-flow 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
volcanoesSmall volcanoes and
fields of small shield volcanoes (colles)
Calderas (often, patera, irregular depressions)
Lava flows and channelsPlains lavasLava flow fields (fluctii)Unusual lava flowsLava channels (canali)
Magmatic structuresCoronaeArachnoidsRadial (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 steep-sided dome morphology near the summit
Crumpler and Aubele, 2000, Fig. 2
Intermediate volcanoes
Diameter 20 - 100 km Morphologic types
Radially patterned domesSteep-sided domesPancake domes (farra)Scalloped domesModified or fluted domesTholi
Volcano of intermediate size
A simple intermediate volcano20 km in diameter
Radial bright and dark lava flows
Summit caldera
Crumpler and Aubele, 2000, Fig. 3
Steep-sided dome
Steep-sided domeConvex 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 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 rightConvex profile~25 km in diameter
Deep central crater with inverted conical profile
Pancake-like steep-sided 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°ELocated 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
CoronaeAlmost unique to VenusBut 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
sidesCrumpler 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 arrangedHence the name: spiders along webs of linear
fracture belts
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 (1997-1998)
Mars Global Surveyor (1999-present)
Mars Odyssey (2002-present)
Mars Express (2003-present)
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 hillsSlopes 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 cratersScalloped edgesSurrounded by shallow flank slopes
Possibly have an important pyroclastic componentFlows or falls?Suggestive of increased volatile content of
magmas?
Paterae
Highland Paterae Irregular or complex
crater with scalloped edges that are surrounded by shallow flank slopes
Intensely eroded appearanceRemoval of friable
material?
Zimbelman, 2000, Fig. 4
Tyrrhena Patera (FOV ~ 120 km)
Volcanic plainsLava flow margins (FOV ~ 54 km)
Zimbelman, 2000, Fig. 1
Zimbelman, 2000, Fig. 6
Volcanic fields (white)
Volcanoes and ice on Mars Large amounts of water
iceBelieved to be present in
Martian subsurface Interaction of ice with
molten rock Produces distinct
landforms Features identified
recently includeRootless cones created by
phreatic explosions (e.g., Hamilton et al., 2010)
Lahars or debris flows
Images from Wikipedia Site, Volcanology of 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.
"Rootless Cones" on Mars – due to lava flows interacting with water (MRO, January 4, 2013)
Io Galilean satellites
(four largest satellites of Jupiter) 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 Most volcanically
active object in the solar system
Heat flow much higher than Earth’sSeveral volcanoes
erupt lavas that are hotter than any erupted on the Earth today
Lopes-Gautier, 2000, Fig. 1
Surface features Mountains Smooth plains Volcanic constructs
Absence of large volcanic edifices
Shield volcanoes are low Magmas of low viscosity?
Calderas 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 materialsEphemeral (lasting a few years?)Pyroclastic deposits—fall deposits from plumes?Associated with hot spots and plumes
Very dark depositsAlso associated with hot spots
Different colors may reflect different allotropes (crystal structures) of sulfurCooled rapidly from different temperatures
Cryovolcanism
DefinitionEruption 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 occurGeyser-like plumes of nitrogen were discovered on
Triton, a moon of Neptune, by Voyager 2 Indirect evidence that it has taken place
elsewhereMight 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 caldera-like 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 changeReview of atmospheric structure and processesEruptions and atmospheric anomaliesVolcanism and extinctionsVolcanic contributions to S and C fluxes
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 instabilityweather Precipitation causes rainout of particles within weeks
Mills, 2000, p. 933-934
Residence times in stratosphere
Fine ashResides 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
ClimateAverage weather conditions (temperature,
meteorological conditions) of a place over a period of years
WeatherDaily 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 worldTypically hemispheric spatial extentsTypically 1- to 2-year temporal effects
Ancient eruptions and atmospheric anomalies Santorini (Thera), Aegean Sea ~ 1620 BC
Atmospheric effects felt globallyChina: Floods, followed by 7 years of drought
Etna, Sicily ~42 BCCorrelates 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 year9 years of crop damage in Sweden and Germany
beginning in 1453Tree ring evidence for frost damage globally for
several years
More recent eruptions and atmospheric anomalies
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 Krakatau, 1883
Several years of brilliant sunsets
Laki fissure, Iceland
P. Kresan
Brilliant sunsets Major explosive eruptions
Produce smog-like silvery midday skies and colorful sunsets
Krakatau eruption (1883) impressed European observers Inspired a number of paintingsPerhaps 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 EnglandAnnual and
5-year running average
Sigurdsson, 2000, Fig. 5
ME
NH
MA
Extraordinarily large eruptions
Toba, IndonesiaEruption at 74,000 yr BPLargest eruption of last several hundred
thousand years (~280,000 km3)Ice core studies indicate that Toba aerosols
remained in stratosphere for ~6 yr
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
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 1-
μm 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
Temperature decreases correlate with sulfur yield of eruptions
Fisher et al., 1997, Fig. 9-1; adapted from Sigurdsson, 1990
Volcanism and extinctions Unclear relationship between volcanism and
extinctionsBest 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 atmosphereProportions 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
Building stone
IgnimbriteWelded tuffSillar
Lightweight Relatively high
strength
Ignimbrite column in Guadalajara, México
Fisher et al., 1997, Fig. 11-6; photo by G. Heiken
Building stoneBlocks 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 weatheredProducing clay mineralsReleasing 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 waysVolcanic soilsEffect of elevation
(2,000-3,000 m) on temperature and rainfall
Coffee finca (plantation) near Volcán Tecuamburro, southern Guatemala
Fisher et al., 1997, Fig. 13-5; photo by G. Heiken
Geothermal benefitsBlue Lagoon, Iceland: Bathers in foreground; geothermal power plant in background
Fisher et al., 1997, Frontispiece for Ch. 12; photo by G. E. Sigvaldason
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 1987Active 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 1962-1984
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
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
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
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 processesCan contribute to maturation of hydrocarbonsCan lead to overmaturation of hydrocarbonsDepends 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 sedimentTemperatures >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 reservoirsWhy?
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!