Download Geysers: Types: cone (has a cone of “geyserite” around a small vent

Raleigh Charter High School, Dynamic Planet
Stephen Challener, Shaun Allison
Geysers: Types: cone (has a cone of “geyserite” around a small vent) fountain (explosive bursts of water from
pools with large vents/craters) and perpetual spouter (constant water issuing forth)
Explosive Eruptions/effusive eruptions
A violent, explosive eruption Driven by hot rising magma, interacts with groundwater until the pressures increases to the point
where it erupts through the mantle rock. The secondary explosion is usually more violent, the rocks, gas and pyroclastic material is often
thrown at 100,000 tons per second. Effusive is opposite of Explosive Eruptions. Outpouring of low viscosity lava that is not very violent.
Submarine Eruptions
Most common on earth. happens when lava erupts under the ocean Occur mostly at the mid-ocean ridge
Phreatic(ultravulcanian)(steam-blast) Eruptions
Steam explosions as hot magma encounters groundwater or seawater. They only blast out pre-existing solid rock from the volcano
and no new magma is erupted. They are generally weak but they have been violent like Krakatoa. Cause flat, low-relief craters called maar.
Releases large amounts of carbon dioxide and hydrogen sulfide. Some characterized by short bursts, others build sustained eruptive columns
Strombolian eruptions
Thrust small amounts of lava 50 to a few hundred feet in the air, in very short bursts. The lava has a fairly high viscosity, so gas
pressure has to build to a high level before it will thrust the material upward. These regular explosions can produce impressive booming
sounds, but the eruptions are relatively small. Strombolian eruptions generally don't produce lava flows, but some lava flow may follow the
eruption. These eruptions produce a small amount of ashy tephra.
Vulcanian Eruptions:
many short explosions. Eruptive columns are typically larger than Stromb. columns, and they are mostly made up of ashy pyrocl.
material. The explosions are initiated by hi-viscosity, hi-gas-content magma in which small amounts of gas pressure build up and thrust
material into the air. In addition to ashy tephra, Vulcanian eruptions also launch football-sized pyroclastic bombs into the air. Generally not
associated with lava flow.
Fissure (Hawaiian [Haw. can also come from a central vent) Eruptions:
Fissure eruptions occur when magma flows up through cracks in the ground and leaks out onto the
surface. These often occur
where plate movement has caused large fractures in the earth's crust, and may also spring up around the base of a volcano with a central vent.
Fissure eruptions are characterized by a curtain of fire, a curtain of lava spewing out to a small height above the ground. Fissure eruptions
can produce very heavy flows, though the lava is generally slow moving.
Plinian Eruptions
Marked by columns of smoke and ash extending as high as the stratosphere. These are like the ones caused by
High eruption plume, fast moving destructive lava flows Most powerful type of eruption!
Mt. Vesuvius.
Peléan eruption
Like Vulcanian, but with a pyroclastic flow as well.
Surtseyan Eruptions: Caused by rising magma hitting shallow water
Terms: Siliceous sinter: Porous opaline silica, precipitated as an encrustation by a geyser or hot spring, a synonym
for "geyserite" Tephra: fallen volcanic material 4 sizes of Tephra: dust/ash(<2mm), Lapilli(2-64mm), volcanic
bombs/volcanic blocks(>64mm). Summit Crater: the mouth of the volcano, where the lava exists Magma
Chamber: where the lava wells up underground Central Vent: leads from the magma chamber to the summit crater.
Lava dome: When all the gas escapes from magma, it can leave a “plug” of magma with no explosive potential which
solidifies. Felsic: silicon rich Vesicular: Lots of vesicles (small spherical holes) porphyritic: large-grained crystals in
small-grained rock Aphanitic: igneous rocks with such fine crystals they cannot be seen unaided Lahar: a flow of
volcanic mud (pyrocl material mixed w/ water). Liquefaction: when wet soil with well-sorted particles is hit with
seismic activity it can suddenly start acting like a liquid. Wadati-Benioff Zone: Deep area of seismic activity in a
subduction zone. Fracture zone is a linear oceanic feature--often hundreds, even thousands of kilometers long-resulting from the action of offset mid-ocean ridge axis segments. Volcanic arc: a chain of volcanic islands or
mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces
magma. Batholith: Mass of solidified plutonic rock which has since been brought to the surface by erosion or uplift
Dike: igneous intrusion that cuts across rock grain/strata Sill: igneous intrusion that squeezes between grain/strata.
Tsunamis are caused by mostly subduction zone earthquakes because of the displacement of water. They have a low
amplitude (wave height) offshore and a long wavelength (hundreds of kilometers long) but grow in height in shallow
water.
3
Density (in grams/cm ) continental crust: 2.7 oceanic crust: 3.3 outer mantle: 3.4-4.3 inner mantle: 4.3-5.4
outer core: 10-12.3 inner core: 15
Scales/Indices:
VEI (volcanic explosivity index): invented by Chris Newhall in 1982. Measures explosivity of an eruption based on
volume of ejected material, column height and qualitative observations. 9 levels, increase 10x each time. From “nonexplosive” to “mega-colossal”
VEI
Classification
0 Hawaiian
1
Hawaiian/Strombolia
n
Description
Plume
non-explosive < 100 m
Ejecta volume
< 10,000 m³
gentle
> 10,000 m³
100-1000 m
1-5 km
> 1,000,000 m³
2 Strombolian/Vulcanian explosive
severe
3-15 km
> 10,000,000 m³
3 Vulcanian/Pelean
cataclysmic
10-25
km
> 0.1 km³
4 Pelean/Plinian
paroxysmal
> 25 km
> 1 km³
5 Plinian
> 25 km
> 10 km³
6 Plinian/Ultra-Plinian colossal
> 100 km³
7 Plinian/Ultra-Plinian super-colossal > 25 km
mega-colossal > 25 km
> 1,000 km³
8 Ultra-Plinian
Volcano warning schemes: Normal[Green], Advisory[Yellow](elevated unrest above normal activity) watch
[Orange] [Heightened/escalating unrest increased potential for eruptive activity (timeframe variable) OR minor
eruption underway, poses limited hazards.] Warning [Red] Highly hazardous eruption underway or imminent.
Richter Scale: Charles Richter, Beno Gutenberg, 1935. Still used because it can be calculated quickly, mostly
superseded by moment magnitude scale. Logarithmic, one number up is about 30x higher.
Moment magnitude scale: logarithmic, measures energy released
Mercalli Scale - 1902
I. Not felt except by a very few under especially favorable conditions.
II. Felt only by a few persons at rest, especially on upper floors of buildings.
III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake.
Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking
sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable
damage in poorly built or badly designed structures; some chimneys broken.
VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage
great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial
buildings, with partial collapse. Buildings shifted off foundations.
X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.
XI. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.
XII. Damage total. Lines of sight and level are distorted. Objects thrown into the air.