geography presentation a2

8/13/2019 Geography Presentation A2

1/24

VOLCANO

RENO

HASBUR

NAZMI

AIMAN


2/24

1. WHAT IS VOLCANO?

A volcano is a vent or 'chimney' that connects molten rock (magma) to the Earth

includes the surrounding cone of built-up material. Magma erupting from a volca

lava. Gases and pieces of rock erupt from volcanoes too.

A volcano is active if it erupts lava, releases gas or shows seismic activity. It is d

hasn't erupted for a long time but could again one day. An extinct volcano will ne

again.

The explosiveness of a volcanic eruption depends on how easily magma can flo

amount of gas trapped in it. Large amounts of water and carbon dioxide are diss

magma. They behave like gas in fizzy drinks. After opening the bottle the gas ex

forming bubbles that escape. This also happens when magma rises quickly thro

- gas bubbles form and expand up to 1000 times their original size.


3/24

2. LIST DOWN TYPES OF ERUPTION.DESCRIBE EACH TYPES USING DIAGR

The most common type of volcanic eruption occurs when magma (the term fo

when it is below the Earth's surface) is released from a volcanic vent. Eruption

effusive, where lava flows like a thick, sticky liquid, or explosive, where fragme

explodes out of a vent. In explosive eruptions, the fragmented rock may be

accompanied by ash and gases; in effusive eruptions, degassing is common b

usually not.

Volcanologists classify eruptions into several different types. Some are named

particular volcanoes where the type of eruption is common; others concern th

shape of the eruptive products or the place where the eruptions occu


4/24

Distinct bursts of fluid lava (usually basalt or basaltic andesite

the mouth of a magma-filled summit conduit. The explosions u

occur every few minutes at regular or irregular intervals. The

explosions of lava, which can reach heights of hundreds of me

are caused by the bursting of large bubbles of gas, which trav

upward in the magma-filled conduit until they reach the open a

This kind of eruption can create a variety of forms of eruptive

products: spatter, or hardened globs of glassy lava; scoria, wh

hardened chunks of bubbly lava; lava bombs, or chunks of lavcm to a few m in size; ash; and small lava flows (which form w

spatter melts together and flows downslope). Products of an e

eruption are often collectively called tephra.


5/24

A Vulcanian eruption is a short, violent, relatively small explosion of

magma (usually andesite, dacite, or rhyolite). This type of eruption

from the fragmentation and explosion of a plug of lava in a volcanic

or from the rupture of a lava dome (viscous lava that piles up over a

Vulcanian eruptions create powerful explosions in which material cafaster than 350 meters per second (800 mph) and rise several kilom

into the air. They produce tephra, ash clouds, and pyroclastic densi

currents (clouds of hot ash, gas and rock that flow almost like fluids

Vulcanian eruptions may be repetitive and go on for days, months,

or they may precede even larger explosive eruptions. They are nam

the Italian island of Vulcano, where a small volcano that experience

type of explosive eruption was thought to be the vent above the forg

Roman smith god Vulcan.


6/24


7/24

When plates push together, one plate slides beneath the other.

subduction zone. When the plunging plate gets deep enough ins

mantle, some of the rock on the overlying plate melts and formsthat can move upward and erupt at the Earth's surface. At rift zo

are moving apart and magma comes to the surface and erupts.

volcanoes occur in the middle of plates at areas called hotspots

where magma melts through the plate and erupts.


8/24


9/24

4. USING CASE STUDY OF ONE LEDC (E.GKRAKATOA, INDONESIA) & ONE EXAMPLE FMEDC (MT ST HELEN):


10/24


11/24

(A) WHERE (VOLCANO) AND WHEN OC

a volcanic island situated in the Sunda Strait between the islands of

and Sumatra in Indonesia. The name is also used for the surroundi

group comprising the remnants of a much larger island of three volc

peaks.

St Helen - It is the Juan de Fuca plate, Pacific and the North Americ

The Juan de Fuca plate went under the North American plate.


12/24

(B) NATURE OF VOLCANO (WHERE ITLIES/PLATES)

Indonesia - subduction of the Indo-Australian tectonic plate as

moves northward towards mainland Asia.

St Helen -It is the Juan de Fuca plate, Pacific and the North A

plates. The Juan de Fuca plate went under the North America

and is melted into material in the mantle. This is called a destr

plate margin.


13/24

(C) MAGNITUDE

The 1883 eruption of Krakatoa has been assigned a Volcanic

Explosivity Index or VEI of 6 which rates as "colossal.

St Helen - The Mount St. Helens explosion of 1980 had a VEI


14/24

(D) EFFECTS OF ERUPTION TO PEOPLAND ENVIRONMENT

Indonesia (ledc) - obliterated in a cataclysmic 1883 eruption, unleashing h

tsunamis (killing more than 36,000 people) and destroying over two-thirds

island. The explosion is considered to be the loudest sound ever heard in

history, with reports of it being heard up to 3,000 miles (4,800 km) from its

origin.

U.s (medc) - The eruption killed 57 people, in the lateral blast, ashfall, and

The causes to death included asphyxiation, thermal injuries, and trauma. Findirect death were caused by a cropduster hitting powerlines during the a

traffic accident during poor visibilty, and two heart attacks from shoveling a


15/24

The Cost of Volcanic Eruptions details the economic impacts of the e

The Toutle River was flooded by melting snow and ice from the moun

12 million board feet of stockpiled lumber were sweep in the river. Eig

were destroyed. 200 homes were destroyed or damaged. Debris damadded to help control sediment in the rivers.

Thirty logging trucks, 22 transport vehicles, and 39 railcars were dam

destroyed along with 4.7 billion board feet of timber.

Shipping was stopped on the Columbia River and some vessels were

In eastern Washington, falling ash stranded 5,000 motorist. Ash had t

cleared from runways and highways.


16/24


17/24

1 - Lava flows are less dangerous to human life than to property

and communication because probable path, of lava flows can be

predicted, diversion measures, cool advancing front with water,

disruption of source or advancing front of lava flow by explosive

taken in principle: however, such measures, often turn out to nosuccessful. Highly viscous lava generallly does not advance far,

commonly piles, up above an active vent as a lava dome. Such

collapse repeatedly and generate dangerous hot block and ash

hot surges and blasts. Kilauea lava flows.( V.Clavel):


18/24

2 -Poisonous, even lethal, gases can be ejected during the erup

volcano or can be released without a triggering eruption (e.g. Ny

gases are transported away from vent as acid aerosols, as com

absorbed on tephra and as microscopic salt particles. Sulfur com

chlorine and fluorine react with water to form poisonous acids dathe eyes, skin and respiratory systems of animals even in small

concentrations. Most volcanic gases are noxious and smell bad

can cause mass fatalities. The time available for early warning o

release is extremely short, and intensified investigation on such

eruption, as well as keen observation of the respective locationsabsolutely necessary. Gas Nyos effect (J.Lockwood):

3 A hf ll d i l i ti ll d t di tl


19/24

3 - Ashfalls during volcanic eruption generally do not directly en

although the collapse of roof and houses under the ash load are

uncommon. Considerable damage may be caused, however, fo

agriculture and industry even at distances up to tens of kilomete

vent. Many of the hazards of tephra falls can be mitigated with pplanning and preparation. This includes clearing tephra from roo

accumulates, designing roofs with steep slopes, strengthening r

walls, designing filters for machinery, wearing respirators or wet

over the mouth and nose. Cinder emission at Fogo (H.Gaudru):

4 Pyroclastic flows and low density surges that are frequently a


20/24

4 - Pyroclastic flows and low-density surges that are frequently a

with blast are extremely hazardous types of volcanic eruptions.

flows consist of a mixture of volcanic gases and ash and are gen

during many volcanic eruptions. Some may be as hot as 900C

move swiftly with velocities of up to several 100 m/s. Early warnvolcanic phenomenon is virtually impossible. A most dangerous

develops if pyroclastic flows are generated on snow or glacier co

volcanoes, causing the cover to melt. The only effective method

mitigation is evacuation prior to such eruption from areas likely t

affected by pyroclastic flows. Pyroclastic flows -Soufriere of Mon(H.Gaudru ):

5 L h ( l i d d d b i fl ) j


21/24

5 - Lahars ( volcanic mud and debris flows) are a common major

hazard for people and property. Lahars likewise proceed very qu

possess great destructive power. They develop either as a direct

consequence of a volcanic eruption, if , for instance, crater lake a

out, or as a secondary event as a result of heavy rainfall during oeruption. Areas farther away may be warned several hours in ad

sufficient monitoring of individual volcanoes, however, rarely is

guaranteed. Small lahars can be diverted by barriers or by artific

channels which lead them away from valuable land or property, b

cases the volume and force of the lahar is such that it beyond hupower to control. Lahars of Pinatubo - Philippines- (Y. Miller)

f


22/24

6 -Volcanic debris avalanches generated by sliding of larger por

volcanic cones are common. These avalanches are highly mobi

not only bury large tracts of land and dam stream to form lakes t

drain catastrophically and generate lahars and floods but also c

devastating tidal waves ( tsunamis) if they advance into lakes orThe only effective method of risk mitigation is evacuation prior to

debris avalanche or tsunamis ( if expecting) from areas likely to

affected by this kind of phenomena. Api Siau Island (V. Clavel)


23/24

Damage and hazard to human life, social structure, and property may

induced only by direct effects of volcanic eruptions. Some of the most

secondary phenomena are tsunamis, contaminated (e.g., fluorine-rich

long-Iasting aerosol clouds that can orbit the Earth for years after larg

eruptions. Aerosol clouds basically consist of condensed volcanic gas

sulfuric acid. The emission of large quantities of SO2 and also possib

into the stratosphere may lead to a temperature decrease on the Eart

by increasing the global albedo and also can contribute significantly to

destruction of the stratospheric ozone layer. The correlation between

hazards, destructive potential, and the erupted mass is not universal. cases, the destructive potential depends less on the mass and tempe

erupted material than it does on the specific environment of the eruptiv

especcially the degree of magma-water interaction and the energy of

blasts.

SUPERVOLCANO


24/24

SUPERVOLCANOES IS THE VOLCANOES THAT HAVE REACHED

RATED AS APOCALYPTIC WITH PLUME OF 50KM. EG: YELLOWS

geography presentation a2

Documents