Thomas chinnappan geologist keeranur, pudukkottai, tamilnadu, india.

1. VOLCANIC HAZARDS &
BY:
THOMAS CHINNAPPAN . A ,
M.SC.APPLIEDGEOLOGY,
PERIYAR UNIVERSITY,
SALEM.
VOLCANIC ACTIVITY

2. VOLCANIC ACTIVITY ;
Volcanic activity ranges from
emission of gases, non-explosive lava
emissions to extremely violent
explosive bursts that may last many
hours.
 The types of eruptions determine the
relative volumes and types of
volcaniclastic material and lava flows,
consequently the shapes and sizes of
volcanoes.

3. CAUSES OF VOLCANIC ERUPTION ;
Although there are several factors triggering a volcanic
eruption, three predominate ways:
The buoyancy of the magma.
The pressure from the exsolved gases in the magma.
The injection of a new batch of magma into an already filled
magma chamber.

4. VOLCANIC HAZARD:
A volcanic hazard refers to any
potentially dangerous volcanic process
(e.g. lava flows, pyroclastic flows, ash).
A volcanic risk is any potential loss or
damage as a result of the volcanic
hazard that might be incurred by
persons, property, etc. or which
negatively impacts the productive
capacity/sustainability of a population.

5. PRIMARY EFFECTS OF A VOLCANIC ERUPTION:
Volcanic gases: All magma contains dissolved
gases. These gases are mainly steam, carbon
dioxide and compounds of sulphur and chlorine.

6. Lava flows:
These are streams of molten
rock.
Pyroclastic flows:
These are high speed
avalanches of hot ash, rock
fragments and gas which
move down the sides of a
volcano.

7. Flooding: Explosive eruptions can change the surface areas
around a volcano and disrupt drainage patterns, leading to
long-term flooding.

8. VOLCANIC COLLAPSE :

9. Volcanic eruptions produce
earthquakes. Earthquakes may
proceed and accompany and
frequently followed by volcanic
eruptions.
They are caused by sudden
displacement of lava within or
beneath the earth crust.

10. There are two general categories of earthquake that can occur at a
volcano ;
 Volcano-Tectonic Earthquake
Long Period Earthquake.

11. VOLCANO-TECTONIC EARTHQUAKE
A volcano tectonic earthquake is
caused by the movement of magma
beneath the surface of the earth.
The movement results in pressure
changes where the rock around the
magma has experienced stress.
At some point, this stress can
cause the rock to break or move.

12. LONG PERIOD EARTHQUAKES ;
These earthquakes are a result of pressure changes during the
unsteady transport of the magma.
When magma injection is sustained a lot of earthquakes are
produced. This type of activity indicates that a volcano is about
to erupt.
Scientists use seismographs to record the signal from these
earthquakes. This signal is known as volcanic tremor.

13. VOLCANOES ALONG SUBDUCTION PLATE
BOUNDARY ;
So, volcanic activity tends to occur along subduction plate
boundaries, where one plate slides underneath another.
The edges of the Pacific Plate make up a long subduction
boundary. There are a huge number of earthquakes along these
boundaries, because these are regions where the plates are
colliding.
For the same reason, the majority of the volcanic activity on the
Earth also occurs along these convergent boundaries. This is
called the Pacific Ring of Fire where over 75% of the world’s
volcanoes are found.

14. PACIFIC RING OF FIRE :

15. CONCLUSION
Though volcanic eruptions are threats to human life, the areas
where the eruptions have taken place are useful too. They have
helped to create beautiful Hawaiian Islands.
These areas are rich in minerals.
(Most of the metallic minerals mined in the world--such as
copper, gold, silver, lead, and zinc--are associated with magmas
found deep within the roots of extinct volcanoes.)
 Volcanic materials ultimately break down and weather to
form some of the most fertile soils on Earth.

16. THANK YOU