poznań, 2019 encyklopedia of volcanoes · volcanology and geothermal energy, kenneth wohletz,...
TRANSCRIPT
Volcanology
dr Monika Nowak
Poznań, 2019
Encyklopedia of Volcanoes
Magma Formation and Migration
Fundamentals of physical volcanology
VOLCANIAN TYPE OF ERUPTION
https://www.youtube.com/watch?v=E4j-PGiSYQI
Type of
eruption
Commonly
observed
phenomena Lavas
Pyroclastic deposits
(Composition) Typical volcanic landforms
hawaiian
fire fountains >100 m
high, lava lake, lava
tubes
close to basalt in
composition
small amounts of Pele'
hair/tears
basaltic shield volcano,
fissure eruptions, summit
caledra, spatter cone, lava
flows (pahoehoe, a'a),
levees
strombolian
periodic explosions
emitting scorai/ash
clouds
basalts ora
basaltic andesites
- rarly more acid
composition well sorted scoria beds
scoria cone (bombs-bloks),
fissure eruptions
vulcanian
discrete expolsions,
short-lived eruption
column 5-10 km
high
composition
intermediate to
acid
thin beds of ash, bread-
crust bombs, lithics crater
sub-pilnian
sustained eruption
column 10-20 km
high, PDCs
usually dacite,
rholite or
phonolite
widsperad pumice fall
blanket
stratovolcano, crater
(caldera subsidence)
pilnian and
ultrapilnian
sustained eruption
column 20-50 km
high, umbrella PDCs
usually dacite,
rholite or
phonolite
pumiceous lapilli
tuff/ignimbrite
stratovolcano, crater -
caldera subsidence
hydrovolcanic
repeted expolsions,
"cock's tail" ash
cloud, expanding
base-surge cloud often basalts
thin beds of juvenile ash,
and/or country rocks
lithicks; cross-stratified
base-surge deposits
tuff or ash ring, crater or
maar
http://oceanexplorer.noaa.gov/explorations/02fire/background/plan/media/plate.html
Rocks
Volcanic rock chemical classifications
TAS – (total alkali silica)
37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Na 2
O +
K2O
[wt%
]
SiO2 [wt. %]
Rhyolite
Dacite
Trachyte
Trachydacite
Trachy-
andesite
AndesiteBasaltic
Andesite
Trachy-
basalt
Basaltic
Trachy-andesite
Basalt
Picro-
basalt
Tephrite
Basanite
Phonotephrite
Tephriphonolite
Phonolite
Foidite
Igneous Rocks A classyfication and Glossary of terms R.W. Le Maitre
https://wwwf.imperial.ac.uk/earthscienceandengineering/rocklibrary/viewrecord.php?cID=5403
Andesite - Viti Levu, Fiji
Pictures from Rock Library Imperial College
https://wwwf.imperial.ac.uk/earthscienceandengineering/rocklibrary
/viewrecord.php?cID=5403
LANDFORMS – TYPES OF
VOLCANOES
http://canarygeog.canaryzoo.com
https://www.youtube.com/watch?v
=PJeTY1Eg-0o
Movie:
www.qualityplanning.org
Lavas
(Lava domes)
Volcanic sucession – Cas, Wright 1992
Lava domes
Volcanic sucession – Cas, Wright 1992
Lava domes – classyfication after Blake 1999
Volcanoes Francis, P., Oppenheimer, C. 2004
Showa Sin-Zan Lava Dome, Japan -- The Showa Sin-Zan (New Roof
Mountain) grew as a single mass of lava that was pushed upward like a piston.
This upheaved plug rose steadily from January 1944 to November 1944.
Courtesy of Peter Francis.http://www.geology.sdsu.edu/
Upheaved plug
Volcanology and Geothermal Energy, Kenneth Wohletz, Grant Heiken 1992
Forms of endogenous and exogenous domes, showing various fracture foliations. (a) Upheaved,
exogenous dome similar to that illustrated in Fig. 5.1. (b) Peléean dome showing vent spines,
blocky fracture, and development of talus aprons. (c) Detail of vent spine of Mont Pelée
(from Lacroix, 1904)(d) Exogenous dome that discharges viscous flow lobes from a summit vent. (e)
Intrusive dome in which viscous magma body is emplaced just below the earth's
surface and maintains a carapace of upwarped strata.
(Adapted from Williams and McBirney, 1979.)
Cryptodome
Volcanic sucession – Cas, Wright 1992
Organy Wielisławskie
Coulées are a hybrid between a lava dome and a lava flow. In order to get the
thick and sticky lava to flow, this type of dome is generally erupted on steep
slopes which allow the lava to ooze slowly down the slope. Typically they do not
flow more than a few kilometers, though some larger examples have traveled well
over 10km. As a neat feature of coulées, huge pressure ridges, known as
Ogives, are often seen on the outer surface of the flow.
Coulées
http://volcano.oregonstate.edu/book/export/html/443
The most famous dacite lava flow – Chao, Chile
One of the best known examples of a coulée, and the largest
of its type in the world, is the Chao dacite (Figure M4, a&b),
occupying the saddle between Paniri and Léon volcanoes
(Guest & Sanchez, 1969; de Silva et al., 1988). 39Ar-40Ar
ages indicate it is less than 100,000 years old (Drake et al.,
unpub. data, 1989). It is a 14.5 km long coulée, with flow
fronts 350-400 m high and has a total erupted volume of ~26
km3. A characteristic feature of this body are the prominent
30 m high flow ridges or ogives on its surface, resulting from
folding during emplacement of surface layers with different
mechanical properties due to differential cooling of the lava.
Eruption of the huge coulée appears to have occurred in two
main stages; 1) explosive eruption of a small volume of
dacitic ignimbrites (<1 km3) followed by passive effusion of
the main mass of lava (Chao I and II) which constitutes 22
km3; and 2) explosive eruption of small rhyolitic airfall and
formation of a dense pumice cone followed by passive
effusion of Chao III (~3 km3). The lava is high-K, very
porphyritic, and thought to have erupted over a period of
100-150 years (de Silva et al., 1994).
http://volcano.oregonstate.edu/oldroot/CVZ/chao/
Guest, Schancez 1969
Guest, Schancez 1969
Volcanic sucession – Cas, Wright 1992
http://library.thinkquest.org/
Spine
Mount St. Helen
PeléeanNamed after the iconic lava dome formed on Mt. Pelee in 1902 (which eventually collapsed resulting
in the destruction of St. Pierre on Martinique), these lava domes are often the steepest sided of all
lava domes. They are typically circular similar to Tortas, but rather than having a flat top, they show
relatively smooth upper surfaces punctuated by tall vertical spines. These vertical spines give these
domes a craggy appearance and also frequently collapse causing talus slopes to frequently
surround these domes. This type of dome is most commonly found associated with larger composite
volcanoes.
http://volcano.oregonstate.edu/book/export/html/443
Spine
Low lava dome - Tortas
Named after their striking resemblance to cake or “Torta”, these domes are common
throughout the world, but especially so in the Andes mountains of South America. This
type of lava dome is generally erupted on mostly flat ground and as a result the lava is
able to push outwards, but not far. They typically are flat-topped and roughly circular.
The thickness and diameter of these domes can vary greatly from a few meters to
nearly a kilometer in thickness and several kilometers in diameter. These domes grow
by internal processes and lava fills in the center of the dome near the vent and pushes
older layers outwards, forming an onion-like internal structure.
http://volcano.oregonstate.edu/book/export/html/443
Pyroclastic deposits
Igneous Rocks A classyfication and Glossary of terms R.W. Le Maitre
What control the eruption column height?
http://www.greendiary.com/mexican-mountain-spits-ashes-rocks-endangering-18-million-people.html
Encyklopedia of Volcanoes
pyroclastic fall The rain
out of clasts through the
atmosphere from an
eruption jet or plume during
an explosive eruption.
Ht is the maximum height
attained by the plume and Hb
is the height at which the
plume density is equal to that
of the surrounding atmosphere
Fragmentation index (F). A parameter measuring the grain size of a pyroclastic
fall deposit, specifically the percentage of ash finer than 1 mm at the point on the
dispersal axis corresponding to 1/10 of the maximum thickness of the deposit.
Dispersal index (D) A measure of the extent of a pyroclastic fall deposit,
specifically the area enclosed by an isopach drawn at 1/100 of the maximum
extrapolated thickness of the deposit.
Thickness half-distance (bt) The ‘‘average’’ distance over which the thickness
of a pyroclastic deposit halves.
Grain size half-distance (bc). The ‘‘average’’ distance over which the maximum
clast size in a pyroclastic deposit halves.
Encyklopedia of Volcanoes
Isopach maps show maximum thickness of a pyroclastic
fall deposits.
Isopleth maps show average maximum pumice or scoria
and lithic size distribution.
Booth et al. (1978)
Encyklopedia of Volcanoes
Shock waves
• https://www.youtube.com/watch?v=E4j-PGiSYQI
https://www.youtube.com/watch?v=BUREX8aFbMs
Bread-crust bombs (panino)
Rounded or angular lumps with a smooth,
galssy crust broken by deep cracks and
fissures, exposing the forthy, vescicular core,
of the bomb, and reminiscent of a well-
baked, crusty loaf of bread.
https://www.youtube.com/watch?v=Nee6zg9azb0
Volcano – google maps
Isla di Vulcano - Wikipedia
Based on webcam data and satellite images, the Darwin VAAC reported that during 13-14 November an
ash plume from Sinabung rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted almost 150 km NW and
W. According to a news article, a pyroclastic flow traveled 1.2 km down the SE flank on 14 November,
prompting more evacuations from villages near the base of the volcano. The article noted that more than
7,000 people had been evacuated from 10 villages.
An explosion observed with the webcam on 18 November produced an ash plume that rose to an altitude
of 7.6 km (25,000 ft) a.s.l. About 30 minutes later an ash plume also visible in satellite images rose to an
altitude of 11.3 km (37,000 ft) a.s.l. and drifted 65 km W. Four hours later satellite images showed ash
plumes at an altitude of 9.1 km (30,000 ft) a.s.l. to the W of Sinabung and at an altitude of 4.6 km (15,000
ft) a.s.l. over the crater. On 19 November the webcam recorded an ash plume that rose to an altitude of
4.6 km (15,000 ft) a.s.l. over the crater. A news article stated that later that night that an ash plume rose to
an altitude of 10 km (32,800 ft) a.s.l.
A news article from 20 November noted that volcanologists updated the hazard map for Sinabung. The
second-tier disaster-prone area, previously defined as a radius of 2-3 km from Sinabung’s crater, was
expanded to 4-5 km.
http://volcano.si.edu/reports_weekly.cfm#vn_211060; http://www.bbc.co.uk/news/world-asia-24124361
Mount Sinabung - Indonesia