GEO 110 Lecture Notes - Lecture 3: Mount Vesuvius, Volcano, Magma Chamber

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5 Aug 2016
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Lecture Class 3
4 signs of volcanic Eruptions
oActivities detected, not eminent
oActivities intensifies so eruption probable
oEruption can occur within 3 weeks
oHave 48 hours till eruption
How to detect Volcanic Eruptions
Sulphur dioxide (SO2) levels increase; use a correlation spectrum in that
Seismic activities (rise and fall of magma)
Regions around the mountain will crumble
Possible to see magma movement
Nevado Ruiz, Columbia 1986
22,000 people died
1991 June 12 “Clearing its throat”
Massive Explosion occurred
More than 50% of the farm animals were killed
About 650 thousand jobs were lost
50 thousand families were displaced
15 miles radius the volcano had to be evacuated
One to four metres of ash covered the landscape and in btw 5-8 cubic km of
ash deposit
Monochromatic Landscape
Definition of Volcano
Volcanoes are openings or vents, with
or without a conical hill or mountain
near them
- They are conduit, fiscous through ash material flow through the surface lava
- Magma and others spill on
- Plutonic or intrusive rocks igneous, they are domain for many years
- When they become restless, they show signs of activities that hiss or roar
- Characterized by violent vibrations within the mountain, followed by the
explosions and release of gases and lava (have columns of ash clouds, pyro
(fire) cumulus clouds) creates a cloud of its own, identified by its own
- There are 1300 active volcano’s in the world, some are minor eruptions but
not as severe as the Philippians
Volcano Eruption
oVolcanoes occur in the Pacific Ocean is what is called
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ois the movement of plates, where they collide, strike or streak
- Accumulation of gas within mountains are forced out, (CO2, SO2, water
vapour, NO2) and kill
- Gas build up within the conduit, the constant pressure eventually explodes
and spills onto the surface.
- Not all materials bring things onto the surface, there is Initial land force by
process of orogeny (mountain building)
- Overtime the agent denudation; describes processes by which element in
atmosphere breakdown rocks, breakdown into smaller pieces
- Denudation forms into subsequent landforms called sequential landforms
- Not all materials released come to the surface, some remain inside
- Can result in Caldara (magma chamber)
- If magma doesn’t come to the surface it gets solidified
- DIKE (solid rock, also sheet like landform) its formed within the earth as
magma oozes through fishes or cracks
- Many Dikes are vertical in shape and cut across (perpendicular to)
sedimentary layers. Dike is made of igneous rock, and is very solid and
resistant to ocean. Is like a wall of rock and can be collided over time
- Sill, is formed by magma forces its way through Strata or crosses the
horizontal layers of rocks it solidifies
- It solidifies from 1cm to kilometers, and tens of thousand of km in width
- Any type of rock formed is originally plutonic rock
- Batholith rocks are globular or large forms of rocks formed in earth crust,
part of exposed surface through years of ocean
- Batholith is often formed at base of magma column
- Whereas laccolith is smaller and formed midway from base to the surface of
sedimentary layers
- Both batholith, laccolith are igneous rocks, plutonic rocks, and intrusive
- Extrusive rocks are formed on the surface layer, intrusive are formed inside
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Features associated with volcanic eruptions
1. Strato Volcano’s
-Felsic lava & cloud of hot white gases
- Are explosive or composite volcano’s, type that is
characterised by violent explosions by large amount of gases
within magma chamber and the conduit
- Have series of layers, ash deposits that are deposited at
different times of the year during steep inclines of the mountain
- Vary in different mineral compositions and thickness, and different particle
size that are deposited
- Strato are also very viscous, materials solidify in short amount of time in
short distances
- Magma doesn’t flow far enough before it hardens so it is cone shaped
- Ex. Mount St Helens, Mount Rainer, and Pinatubo.
2. Caldera (deepest Depression Volcano)
- Crater link
- Occurred in mount “crackatoa” in 1883
- Mountain is unsafe because there is no warning, the water seeps through the
rock layers and cools down the magma,
- Its very dispersive
- It occurs in East Africa
3. Shield Volcano of Oregon
- Effusive volcano; gently sloping in angle of 6-12 degrees of horizontal plane
- They are sloped but very huge, tall
- Ex. Mauna Kea in Hawaii from the death of the ocean to a very high altitude,
higher than mount Everest
- Ex. Mauna Loa, **what was the name given to Iceland volcano **
- They erupt gently with low viscosity (fluid) and spread further away from
4. Hotspots volcano’s
- plumes of upwelling basaltic
- Come so slow that you can walk away from it
- Has gases and other materials
- Very common in oceans, any cracks that occur in plate boundary cause
magma overflowing
- Once the plate boundaries are sealed they become dormant, and harden
- Very transient
5. Hot spring & Geysers
- Ground water is heated to high temperatures
- Magma interact with subterranean water reserves
- Water gets heated and gushes out steam
- Ex. Old faithful in the greater Yellowstone national park
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