Volcanoes and Dams, Causes of volcanoes, Types of volcanoes, Volcanic Activity, types of Dams,

1. VOLCANOES AND
EARTHQUAKES

2. VOLCANOES
VOLCANO – a vent, or orifice, in the Earth’s crust connecting the surface with a
body of molten rock below.
Masses of igneous and pyroclastic materials which accumulate around the vents
are known as volcanic cones, cinder cones, lava domes and plug domes.
CALDERAS – crater-like basins formed by subsidence of volcanic mountains.
MAGMA – molten rock below the
crust.
LAVA – molten rock when it reaches
the surface.

3. TYPES OF MAGMA
BASALTIC
characterized by lower gas content, higher temperature
of fusion, and greater mobility, even at relatively low
temperature.
RHYOLITIC
characterized by lower temperature of fusion but are
more viscous and less mobile even at relatively high
temperature.

4. WHAT CAUSES VOLCANOES?
Volcanic activity frequently occurs on the boundaries of tectonic
plates as the pressure within causes the magma below to rise up and
explode or escape to the surface.
DIVERGENT PLATE BOUNDARIES
- where new crust is generated as the plates pull away from each other

5. WHAT CAUSES VOLCANOES?
CONVERGENT PLATE BOUNDARIES
- Where crust is consumed in the earth’s
interior as one plate dives under another
TRANSFORM PLATE BOUNDARIES
- Where crust is neither produced nor
destroyed as plates slide horizontally past
each other

6. TYPES OF VOLCANOES
FISSURE VOLCANOES
Are cracks in the ground that are only
a few meters wide but can be several
meters in length.
Are not usually explosive. Instead, the
lava seeps out the gaps in the surface
of the crust.

7. TYPES OF VOLCANOES

8. TYPES OF VOLCANOES
SHIELD VOLCANOES
composed almost entirely of
relatively thin lava flows built up over
a central vent.
Vent after vent flows out through the
volcano to the center vent.
Most shield volcanoes have a roughly
circular or oval shape in map view.

9. TYPES OF VOLCANOES

10. TYPES OF VOLCANOES
COMPOSITE VOLCANOES
Are some of the grandest on the world.
They are typically large, steep, symmetrical
cones built of alternating flows of lava ash
and cinders
Most have a crater at the summit which
contains a central vent or clustered group
of vents.
Also called as Stratovolcanoes

11. TYPES OF VOLCANOES

12. TYPES OF VOLCANOES
CINDER CONE VOLCANOES
Are formed large glob of lava being launched from a
single vent.
As the gas-charged chambers explodes, lava gets
launched into the air only to fall back down around
the main vent as cinders in an oval or circular cone.
Most have a bowl-shaped crater in the center.

13. TYPES OF VOLCANOES

14. THE RING OF FIRE
The Ring of Fire is a string of volcanoes that runs around the edge of
the Pacific Ocean.
The Ring of Fire is quite a circle, more like 40,000 kilometer long
horseshoe.
A string of 452 volcanoes stretches from the southern tip of South
America, up along the coast of North America, across the Being Strait,
down through Japan, and into New Zealand

15. THE RING OF FIRE

16. TYPES OF VOLCANIC ACTIVITY

17. TYPES OF VOLCANIC ACTIVITY
PHREATIC TYPE – an eruption driven by the heat from magma
interacting with water. The water can be from groundwater, surface
runoff, a lake or the sea. Phreatic eruptions pulverize surrounding rocks
and can produce ash but do not include new magma.

18. TYPES OF VOLCANIC ACTIVITY
ICELANDIC TYPE – an eruption characterized by effusions of molten
basaltic lava that flow from long, parallel fissures. Such outpourings
often build lava plateaus.

19. TYPES OF VOLCANIC ACTIVITY
PELEAN TYPE – Peléan eruptions are characterized most prominently by
the incandescent pyroclastic flows that they drive. Peléan eruptions (or
nuée ardente) are a type of volcanic eruption, named after the volcano
Mount Pelée in Martinique, the site of a massive Peléan eruption in 1902
that is one of the worst natural disasters in history.

20. TYPES OF VOLCANIC ACTIVITY
VULCANIAN TYPE – its eruption is characterized by the solidification of
the lava between explosion, and as a result, the clouds emitted are not
incandescent. When very old and cold material is ejected, the eruption
is often termed ultra- Vulcanian.
Vulcanian eruptions are small to moderate explosive eruptions, lasting
seconds to minutes. Ash columns can be up to 20 km in height, and lava
blocks and bombs may be ejected from the vent.

21. TYPES OF VOLCANIC ACTIVITY
HAWAIIAN TYPE – the mildest form of activity, and is characterized by
quiet flows of thinly liquid lava without explosive escape of gases and
the ejection of fragmental material. Hawaiian eruptions are a type of
volcanic eruption named after the Hawaiian volcanoes with which this
eruptive type is hallmark. Hawaiian eruptions are the calmest types of
volcanic events, characterized by the effusive eruption of very fluid
basalt-type lavas with low gaseous content.

22. TYPES OF VOLCANIC ACTIVITY
STROMBOLIAN TYPE – marked by mild explosions occurring every 10 to
15 minutes. The lava does not crust over between successive eruptions
and clouds of incandescent materials are emitted. Strombolian
eruptions are the smallest type of explosive eruptions. Strombolian
eruptions consist of intermittent, generally relatively small explosions or
weak pulsating fountains of fluid (usually basaltic) lava from a single
vent or crater.

23. TYPES OF VOLCANIC ACTIVITY
PLINIAN TYPE – the most extremely violent activity of the Vesuvian type.
The gases are expelled with great violence to a height of several miles.
Plinian eruptions (or Vesuvian) are a type of volcanic eruption, named
for the historical eruption of Mount Vesuvius in 79 of Mount Vesuvius
that buried the Roman towns of Pompeii and Herculaneum.
Plinian eruptions are similar to both Vulcanian and Strombolian
eruptions, except that rather than creating discrete explosive events,
Plinian eruptions form sustained eruptive columns.

24. PREDICTION OF ERUPTIONS
The best criteria of impending activity are:
1. Increase in the frequency of local earthquakes,
2. Swelling of the volcanic edifice indicated by accumulating earth tilt;
3. Unusual changes in the behavior of hot springs;
4. Comparison of former cycles of activity;
5. Strong magnetic disturbance;

25. PREDICTION OF ERUPTIONS
6. Low buzzing sounds detectable by the use of earth-contact
microphones;
7. Sympathetic eruptions of neighboring volcanoes;
8. When the lava stands high in the conduits and the conditions of
eruption are at hand, the precise time eruption may be influenced
by lunar-solar controls and;
9. When the lava column is high, the danger of flank eruptions is at
maximum.

26. EARTHQUAKES
EARTHQUAKE – is the shaking of the earth caused by the sudden release
of energy from rocks under tectonic stress.
SEISMOLOGY, as the scientific study of earthquake is called, is one of
the youngest of the natural sciences, but despite its brief life span, great
progress has been made in explaining the origin and mechanics of
earthquakes.

27. FOCUS AND EPICENTER
FOCUS – is where it begins, this is where
the plate slips on a fault line, usually at
the plate edges.
EPICENTER – is the point directly above
the focus on the surface of the earth.
This area will suffer from the most direct
damage

28. SEISMIC WAVES
SEISMIC WAVES – are the waves of energy caused by the braking of
rock during an Earthquake.

29. INSTRUMENTAL RECORDING OF EARTHQUAKES
The vibrations earthquakes produce are detected,
recorded and measured by instruments called
SEISMOGRAPHS.
The line made by seismograph is called a SEISMOGRAM
and shows the changing intensity of the earthquake by
responding to motion of the ground below the
instrument.
From the data expressed in seismograms, scientist are
able to determine the time, the epicenter, the focal
depth, the type of faulting of an earthquake and how
much energy was released.

31. CLASS EFFECTS BRIEF DESCRIPTION
I
Recorded by a single seismograph. May be felt by
an experienced observer. Almost imperceptible
II
Recorded by seismographs of different kinds. May
be felt by a number of person at rest. Feeble
III
Felt by a number of person at rest. Strong enough
for the duration or direction to be appreciable Very slight
IV
Felt by several person in motion, movable objects
disturbed ; doors, windows creaking of floors. Slight
V
Generally felt. Disturbance of furniture and beds ,
ringing of bells. Weak.
THE ROSSI-FORREL SCALE OF EARTHQUAKE
INTENSITY

32. THE ROSSI-FORREL SCALE OF EARTHQUAKE
INTENSITY
VI
Generally awakening of those asleep. General
ringing of bells. Oscillation of chandeliers,
stopping of clocks, visible disturbance of trees and
shrubs, some persons leave their dwellings
Moderate
VII
Overthrow of movable objects, fall of plaster,
ringing of church bells, general panic, without
serious damage to buildings
Strong
VIII Fall of chimneys, cracks in the walls of buildings. Very strong
IX Partial or total destruction of some buildings. Severe
X
Great disasters, ruins, disturbance of strata,
fissures in the earth’s crust, rock falls from
mountains, landslides, etc.
Violent or destructive

33. MAGNITUDE SCALE

34. Engineering Connection
While volcanoes cannot be prevented, we can do our best
to predict them so that human populations near volcanoes can
be safely evacuated before an eruption. To predict eruptions,
engineers design and build many different devices to detect
subtle changes in a volcano that occur before it erupts. Engineers
use their science and math skills to build specialized instruments
that can detect gases, changes in the shape of the volcano, as
well as monitor earthquakes that may signal a possible eruption.