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1
Types of volcanoes
Christoph Breitkreuz,
TU Bergakademie Freiberg
Fig. 3.1 Types of volcaniclandforms. Vertical exaggeration 2 to 1 (polygenetic) and 4 to 1 (monogenetic). Relative sizes areonly approximate (From Orton1996, after Simkin et al., 1981).
Monogenetic and complex volcanoes
Scoria cones: most abundant volcanic land form- high viscosity, basaltic (high microlith content!)
Stromboli 2001
2
Mt. Tarawera, New Zealand
Typical eruption styles: - strombolian fallout- minor phreatomagmatic fallout and surge- small lava flows
Schmincke 1988
4 km
Typical horse shoe shape due to erosion by lava
3
Maar – tuff ring – tuff cone:typical land forms of phreatomagmatic eruptions of SiO2-poor magma
Ukinrek maar (formed 1977; Lorenz)
Malha Maar, Meidob Hills, NW Sudan
4
Lorenz 2004
Phreatic tuff breccia, Neogene, Eifel, W Germany
Southern Slovakia: Neogene Diatreme Field
5
Bedded diatreme facies
Unbedded diatreme facies
6
Urach diatreme field, Neogene SW Germany
Iceland 1995
7
Litoral cones, Myvatn, Iceland
Rootless phreatic land forms
Mt. St. Helens volcanic ring plain
Rootless phreatic craters in 1980 tuff deposit
Mt. Pelee, Martinique, 1902/3
SiO2-rich Lava flows and domes
8
Mt. St. Helens, 1980 - 82More about this in the next lecture…
Shield volcanoes:- low-viscosity
basaltic magma- longlasting magma
production at one place
Olympus Mons, Mars
Complex volcanoes
Isabela, Galapagos
9
SW Tenerife: cross section through a Cenozoic shield volcano:Lava pile cross cut by numerous dykes
SW Tenerife: cross section through a Cenozoic shield volcano:Two overlapping scoria cones preserved
10
SiO2-rich lava flowsand lava domes
Importance of volcanotopographic hiati:Spacially differentiated!
PhD project Marion Geißler
Drilling Angermünde (Am) 1/68
?
* = core segments
sediments of aplaya-environment,
with anhydritic blasts
sandstones andmostly andesiticconglomerates
andesite lava flows,mostly vesicular;with interbedded
"block-lava", brecciasand few paleo-soils
vitric rhyodacitic tuff
Carbonif. sedimentsconglomerates
conglomerates and?sandstones
with rhyodacite(?andesite) fragmentsand interbedded tuff
= ?ignimbrite(no cores available)
}
Profile (this project)
rhyodacitic sequenceof massflows
(ignimbrite) and tuffs
sediments of aplaya-environment,
with anhydritic blasts
thin conglomeratehorizont and sandst.
several intermediatelava flows,
partly vesicular
Carbonif. sediments
conglomerates
ash fall deposits
andesite lava flows,mostly vesicular;with interbedded
brecciasand paleo-soils
*
* = core segments
CS
B-Tuff
B-Tuff
B-TuffLava
Lava
Lava
Lava
B-Tuff
4750
4500
4250
4000
Depth[m]
?
?
?
Profile(this project) Lithology
Time
post-variscan flat landscape, covered by tuff and ignimbrite
Mg-andesite shield volcanoes create a high topography
flat landscape, covered by playa sedimentsDrilling Oranienburg (Ob) 1/68
4500
4250
4000
3750
4750
Depth[m] CS
*
Fig.1: Schematic modell of thevolcano-sedimentary evolutionof the area NE of Berlin(from the well Ob 1/68 in theSW through Grüneberg (Gür) 3/76to Am 1/68 in the NE)
x xx
x xx
x xx
xx
xx
pre-ignimbriticporphyric
rhyodaciticlava, lava dome
or sill-intrusionA
B
C
coarse grained clasticsof the Parchim Fm. lake and fan deposits
of the Grüneberg Fm.
sandflat, mudflat and playa lake deposits
E Gür 3/76 E Am 1/68E Ob 1/68
aktive strike-slip (NW-SE) faultingunder slightly extensional (N-S) regime
aktive extrusive and intrusive volcanism,andesitic and rhyolithic (e.g. in well Tuchen 1/74)developement of paleosoils
at the top of andesite lava flows
developementof paleosoils
last rhyodaciticash fall activities
SW
SW
SW NE
NE
NE
conglomerate exclusively withclasts of Carboniferous sediments
Mg-andesite shield volcano complex in Brandenburg
L.Rotlieg.
U.R
otlieg.
PhD projectMarion Geißler
Katzung 1995
„Inundation“ of shield volcano topographyby playa sediments during Upper Rotliegend II
11
Plateau basaltsAlias trapp basalt or flood basalt
Typically hot spot-relatedTypically fissure eruptions Iguazú Cascades
Stratovolcanoes:- longlasting intermediate to SiO2-rich magmatism
Lincancabur, N Chile
Mt. Shasta, California
12
Cone facies - volcanic ring plain facies
Mt. Egmont, New Zealand
Sector collapse: oversteepening, hydrothermal alteration, incompetent substrate, active faulting, earthquakes, eruption
Mt. Egmont, debris avalanche deposit
13
Mt. St. Helens
Socompa, N ChileSector collapse
Fig. 3.4 General calderacycle (after Lipman, 1984). Stage 1 –precaldera volcanismdevelops clusters of smallintermediatestratovolcanoes, Stage 2 –eruption of zoned magmachamber develops caldera. Ash flow tuffs interfinger with caldera collapsebreccia whereas a thinoutflow sheet extendsoutward from the caldera, Stage 3 – postcalderadeposition of volcanicsand sediment and resurgent doming (FromOrton 1996).
Mik
e Br
anne
y
Main CALDERA types:- piston (SiO2-rich and –poor!)- trap door- piece meal
- resurgent- non-resurgent
14
Non-resurgent caldera
Crater Lake, Oregon
Cerro GalanNW Argentina
Valles Caldera, JemezMtns, New Mexico
Resurgent calderas
15
Fig. 3.5 Evolution of Scafell Caldera, English Lake District (after Branney & Kokelaar, 1994). The caldera developed atop basaltic to andesitic lavas (e.g. Lingcove Fm.) that formed a composite low-profile shield-like volcano. Schematic section from the Langdale area showsrelative thickness of facies from the variousstages. These are: A emplacement of Whorneyside ignimbrite and initial subsidence; Binundation of vent leads to phreatoplinianeruptions of Whorneyside bedded tuff; C onset of widespread piecemeal subsidence and eruption of Long Top Tuffs; D continued subsidence and deformation of hot ignimbrites; E eruption of high-grade ignimbrites of Crinkle Crags tuffs; Fdevelopment of a caldera lake, with subaqueousvolcaniclastic sediments and tuffs, and intrusionof rhyolite domes (From Orton 1996).
Piece meal CalderaOrdovicianLake district, W England