Transcript File

Mr.McMahon
Learning Objectives
1. To understand WHY
volcanic activity
occurs.
2. To understand HOW
the distribution of
Volcanic activity
relates to plate
boundaries.
3. To EXPLAIN how
Volcanic activity can
be predicted.
4. To be able to
identify different
types of volcano and
name its parts
5. To understand the
impact that volcanic
activity has had on
the Irish landscape
6. To study how
geothermal energy
can be harnessed.
7. To understand the
effects that
Volcanoes have on
people.
Why do Volcanoes Erupt ?
• Ans – Pressure
• Molten Magma is less
dense than hard rock.
• It is capable of flow.
• Gasses held under
high pressure in a
magma chamber
force the magma to
the surface through
vents.
• Vents develop along
fault lines, hotspots,
ridges and trenches.
Mount Pinatubo eruption
as seen from space
http://www.youtube.com/watch?v=jRfEGvp6wDU
What is a Volcano ?
• A volcano is a opening in
the earths crust through
which molten material
from the interior can
make its way to the
surface.
• Volcanoes form along
plate boundaries where
rock is recycled.
• The distribution of the
worlds volcanoes can be
explained by studying the
worlds plate boundaries.
Global distribution of Volcanoes
http://www.youtube.com/watch?v=JfHBCYTzuck
Global Distribution
• The global
distribution of
volcanoes can be
explained by their
location in relation
to fault lines.
• Volcanoes are found
on convergent,
divergent and
transform
boundaries.
Destructive Boundaries
A
• When subduction occurs
as plates collide the
descending old crust is
melted in the
asthenosphere. The
melted rock rises
through the crust
through a vent.
• This creates central
vent eruptions along
chains of fold
mountain's.
• E.g. The Andes, South
America
Divergent Boundaries
• At Divergent
Boundaries new
crust is created.
• As the plates pull
apart the sea floor
spreads and magma
rises to fill the
void.
• This results in the
creation of new
crust and ocean
ridges which rise to
form islands.
• Iceland and the
Mid-Atlantic Ridge
Cycle of Volcanic Activity
• Active (Live): Erupts on
a Regular basis.
• Dormant (live):
Volcanoes that have not
erupted in recent
recorded history. Can
be asleep from 100-600
years.
• Extinct (dead) Has not
erupted since historical
times. There is no lava
supply.
Volcanoes In Europe
Eurasian Plate
African Plate
Volcanic Material
• Magma – Molten
material inside the
earth.
• Lava – over 1000 C.
Low in silica so it is
less viscous and
runny.
• Acidic Lava :
Contains gas
bubbles that cannot
escape easily and so
explodes with
force.
http://www.youtube.com/watch?v=ePr
a9ycif7M
Pyroclastic Material
• This is the material
ejected by a volcano.
It includes ash,
cinders, Pebbles and
rock –Volcanic bombs
and pumice.
• Lahars : Devastating
mudflows that result
when volcanic
material mixes with
snow melt water or
heavy rainfall
http://www.youtube.com/watch?v=yvG_N7eqMWk&feature=related
Volcanic Gasses
Steam
Carbon Monoxide
Chlorine
Hydrogen
Sulphurous Oxides.
Depending on the
type of lava
explosions can be
devastating.
• Acid Rain can result
when the gasses
react with moisture
in the atmosphere.
•
•
•
•
•
•
Volcanic Landforms
• Volcanic landforms
fall into two main
categories.
Intrusive : Formed
inside the earth.
Extrusive formed
on the surface.
Extrusive : Central Vent Eruption
• Form at
destructive
boundaries.
• As lava and other
material builds up
on the surface it
creates a volcanic
cone.
Anatomy of a Central Vent Eruption
Cloud of Pyroclastic Material
Crater
Lava Flow
Secondary Flow
Alternate Layers
Of Ash and Lava
Pipe
Vent
Magma Chamber
Types of Central Vent Eruptions
1. Composite Volcano :
Layers of alternate ash
and lava.
1
2. Lava Dome: Thick viscous
lava that solidifies to
form a dome over a vent.
3. Caldera. A large surface
crater where a cone
collapses in as it was
consumed by the Magma
chamber below it.
3
2
Fissure Eruptions
• Fissures are cracks
caused by plate
movement .
• Krafla : This is a
20KM long fissure in
Iceland that has
been erupting for
over 30 years
spewing lava.
• The Derry Antrim
Plateau formed from
fissure eruptions 65
million years ago.
Hot Spots
• Hot Spots are places
where volcanic activity
takes place far in from
plate margins.
• They from where there
is often a thin crust
overlying a hot mantle.
• A plume of magma rises
from the mantle and
melts a spot in the
crust through which
lava escapes.
• E.g. The Hawaiian
Islands.
Intrusive Landforms
• Landforms of
volcanic activity
that are created
beneath the
surface.
• Magma cools slowly
inside the crust to
create intrusive
igneous rock e.g.
Granite.
• Plutons is the
collective name for
intrusive landforms.
http://www.youtube.com/watch?v=A5LdZJiKsVk
Intrusive Landform's …
cont’d
• Batholiths: The
Largest of the
Plutons. Coarse
with large crystals.
They are exposed
after denudation
wears away the
crust above them.
• E.g. Leinster
Batholith
Dublin, Wicklow
Mountains.
Laccoliths
• Dome like
structures of hard
intrusive igneous
rock that bulged
upwards against
the overlying rock
strata.
Sills
• Horizontal sheets
of igneous rock that
run parallel to the
under and overlying
rock strata.
• They formed when
magma forced its
way into the
bedding planes of
sedimentary rock
where it cooled and
solidified.
Dykes.
• Vertical sheets of
volcanic rock that
cooled and
solidified in
vertical cracks in
the crust.
Plutonic Landforms
Predicting Volcanic Activity
Measuring Gas samples
• Increase in sulphur and
carbon levels in soils on
or close to volcanic
slopes.
• Increase in the
temperatures of
groundwater.
• Changes in the shape of
the volcano as magma
upwells within.
• Some volcanic activity
may be preceded by
plumes of smoke, ash and
steam.
• Magma heating rock in
the upper mantle may
cause small tremors.
Beneficial effects of Volcanoes
• The creation of
fertile soils. Ash and
cinders are natural
fertilisers. Cash crops
such as tea, coffee,
cotton and coco are
grown in volcanic soils.
• Tourist Attractions:
Yellowstone National
Park, USA and Mt.
Etna , Sicily.
• http://www.youtube.com/wat
ch?v=bVYD2gtq4IA
• Geothermal
Activity: A
renewable source
of energy whereby
the heat of
volcanically heated
springs are
harnessed to
provided clean
green energy. E.g.
Iceland.
Before and after
http://www.youtube.com/watch?v=UK--hvgP2uY
Mount St Helen’s Fallout.
Volcanic Activity In Ireland
• As we have
studied Ireland
moved from 60
south of the
equator to its
present position
• The Derry –
Antrim Plateau
• The Leinster
Batholith
Slemish Mountain
The Derry-Antrim Plateau
• Formed by basaltan extrusive igneous
rock that cooled
slowly on the
surface.
• Covers 4,000km2
rising to 350m in
height.
• When the lava
cooled 60 million
years ago it covered
over the original
chalk seafloor.
• The Giants
Causeway on the
Antrim coast is but
a part of the
Derry-Antrim
Plateau.
• To understand how
the structure was
formed we can look
at Iceland today.
• When the Eurasian
–American plates
pulled apart 60
million MYA the
crust thinned and
magma cooled slowly
The Leinster Batholith
• A batholith is a
Pluton- an intrusive
igneous formation
that formed slowly
inside the crust.
• Large crystals had
time then to form in
granite.
• The Leinster
batholith stretches
south west over a
distance of 120 km.
C
D
A
B
Geothermal Energy in Iceland
• Geothermal energy is a
form of renewable
energy derived from
heat deep in the earth's
crust.
• Geothermal Energy has
been around for as long
as the Earth has existed.
"Geo" means earth, and
"thermal" means heat.
So, geothermal means
earth-heat.
• Geothermal power
is generated in over
20 countries around
the world including
Iceland, the United
States, Italy,
France, Lithuania,
New Zealand,
Mexico, Nicaragua,
Costa Rica, Russia,
the Philippines,
Indonesia, the
People's Republic of
China and Japan.
Iceland
• Iceland –The land
of Ice and Fire.
• 307,000 Population.
• Lowest Population
Density in Europe.
• 85 % of all houses
and 30% of
electricity in
Iceland is produced
by geothermal
energy.
http://www.geoberg.de/en/2010/06/12/geothermal-energy-in-iceland/
How is Geothermal Energy used
• Domestic :
Homes, swimming
pools, public baths
• Industrial:
Fishfarming-de
icing holding pools,
Kiln drying timber
in saw mills,
electricity
production.
http://www.youtube.com/watch?v=kWN
5yXCYeXc
?
How Geothermal Energy Works
http://www.youtube.com/watch?v=rfUQy86ZMpQ
Key Concepts
1. Volcano
2. Pyroclastic
Material
3. Lava (Basis and
Acidic)
4. Magma
5. Active Live
6. Dormant Live
7. Extinct
8. Intrusive
9. Extrusive
10.Central Vent
11.Caldera
12.Fissure
13.Hotspot
14.Lahar
15.Geyser
16.Cascadia
17.Pacific Ring of
Fire
18.Plutons
19.Laccoliths
20.Batholiths
21.Sills
22.Dikes
23.Plateau
24.Geothermal Energy