Active volcanoes

1. VOLCANOES

2. VOLCANOES

3. ~An opening in the earth's crust through which
molten lava, ash, and gases are ejected.
~A similar opening on the surface of another
planet.
~A mountain formed by the materials ejected
from a volcano.
What is a Volcano?
http://dictionary.reference.com/search?q=volcano

4. What is a volcano?
• A volcano
connects molten
rock (magma)
from within the
Earth’s crust to
the Earth's
surface.
• The volcano
includes the
surrounding cone
of erupted
material.
vent
cone
magma
chamber
conduit

5. The types Of Volcanoes
~ Shield Volcano
~ Cinder Cone Volcano
~ Composite Volcano
~ Caldera Volcano
~ Fissure Volcano

6. TYPES OF ERUPTIONS
ERUPTIONS FALL INTO 2 CATEGORIES
Violent(explosive) eruptions
destroy the volcano
Non-Violent (calm or quiet)
eruptions build up the
volcano

7. Shield volcanoes can span across hundreds of miles. Shield
volcanoes have a gentle slope and consist of frozen lava
after it is hardened. Shield volcanoes almost always have
large craters at their summit.
Gentle slopes = non-violent eruptions
Hot spots!
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

8. Cinder cone volcanoes consist of mostly loose, grainy cinders and
have very little to no lava. Cinder cone volcanoes are normally
small about a miles span and about one thousand feet vertically.
Cinder cone volcanoes have fairly steep slopes and normally have a
small crater at the top.
Steep slopes = explosive or violent eruptions
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

9. Composite volcanoes have another name called “Strato
Volcanoes.” Composite volcanoes consist of lava that is
mixed with sand or gravel which in turn creates cinders
or volcanic ash.
Steep slopes = explosive or violent eruptions
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

10. Caldera volcanoes are circular depressions in the ground over
a magma chamber. Sometimes the depression in Caldera
volcanoes are covered in with lava and volcanic ash making it
hard to recognize. This type of volcano is easier noticed from
space due to the distance and view point. When this volcano
erupts it can spew volcanic rocks for miles and miles.
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

11. Fissure volcanoes are also hard to recognize from the ground and
sometimes from space. Fissure volcanoes have no main crater, the
ground just splits and lava pours out through the cracks. After a
fissure volcano erupts and has cooled because it’s a solid it will
look mainly like the plains.
http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

12. Types Of Magma
• Granite magma consist of light-colored
rock and is not as heavy as basalt
magma. Granite magma is very sticky
and flows rather slowly.
• Basalt magma consist of dark-colored
rocks and is much heavier then granite
magma. It flows more fluidly then
molten granite.

13. Volcano Environments
~In an island-arc environment, volcanoes lie along the
crest of an arcuate.
~In an oceanic environment, volcanoes are aligned
along the crest of a broad ridge that marks an active
fracture system in the oceanic crust.
~In the continental environment, volcanoes are located
unstable, mountainous belts that have thick roots of
granite or granite like rock.

14. Where are volcanoes likely to
occur?
Volcanoes occur in weak spots in the earth’s crust
There are many volcanoes along the Pacific Ocean.
Many islands in the Pacific Ocean are actually
volcanoes. They form a ring around the ocean
which is called the “Pacific Belt of Fire.”
Although there are some other “belts of fire”, the
“Pacific Belt of Fire” is the biggest.
There are approximately five hundred active volcanoes, that are
known, lying in these belts.

15. Volcanoes In Other Places
Volcanoes aren’t just a thing from earth they also
happen on other planets as seen in this picture. But
while on other planets there is no destruction as we
have seen from volcanoes on earth.
Mariner 9 imagery of
Olympus Mons volcano
on Mars

16. VOLCANO FORMATION:
HOT SPOTS
 A fixed source of
magma rising beneath
a plate forming
volcanic islands
 Magma can be
basaltic or granitic –
so eruptions can be
explosive or “quiet”

17. When and how do eruptions occur?
Steam and gases from magma in the earth create
bubbles that expand and burst when the pressure
above them is lessened. These bubbles usually burst
with a tremendous force that along with escaping
gas comes magma too. In some cases, it takes years
for the magma to break through the surface of the
earth.

18. Why do eruptions occur?
Eruptions occur when underground pressure is
released when blocks of the earth’s crust shift.
For example, earthquakes.

19. Direct
measurements of
pyroclastic flows
are extremely
dangerous!!!

20. Effusive Eruptions
• Effusive eruptions are
characterised by outpourings
of lava on to the ground.
Hawaii
Courtesy of www.swisseduc.ch

21. Damages
The most devastating destruction from volcanoes
is the tremendous loss of life. Following an eruption in 1815, there
were 56 000 people killed by a tidal wave from a eruption. Lava from
the volcano is hot enough to catch everything in its path on fire, even
the ash from a volcano is hot enough to start fires. Lahar can wash
away houses and uproot trees. Magma can give off poisonous gases
such as carbon monoxide. Damages from volcanoes are very
expensive to repair or replace.

22. No
Yes (Cinder
Cone)
No
Yes (Shield)
No (These are
the Catskills)
No
Yes
(Composite)
No
Which of these are volcanoes?