The document is about volcanoes and includes definitions of key terms like vent and crater. It classifies volcanoes into three types - active, extinct, and dormant - based on their chances of eruption. Active volcanoes frequently erupt, extinct volcanoes will not erupt again, and dormant volcanoes have erupted in the past but could erupt again. Examples are given for each type. In conclusion, while volcanic eruptions threaten human life, the areas around volcanoes are useful as they are rich in minerals and some soils are suitable for cotton cultivation.

1. Welcome

2. NAME OF THE STUDENT : DIJITHA KRISHNAN
OPTIONAL SUBJECT : SOCIAL SCIENCE
CANDIDATE CODE: 13359005
YEAR : 2013- 2014

3. VOLCANOES

4. INTRODUCTION
Volcanoes are caused when molten rock (magma)
flows out onto the earth’s surface through fissures
that are caused due to the movement of plates.

5. Volcanoes
 The rocks and other material which come on to the
surface of the earth from the interior of the earth
accumulates to develop volcanic mountains.
 Some volcanoes erupt the lava out with a great
explosion and some others, silently.

6. VENT
The fissures, through which the magma comes out
from the aesthenosphere on to the crust of the earth
is known as the vent.
CRATER
The funnel shaped depression that can be seen on
the summit of a volcano is known as a crater.

7. Different types of volcanoes
Based on the chances of eruption the volcanoes are
classified into three.
Active volcanoes
Extinct volcanoes
Dormant volcanoes

8. Active Volcano
•Those that frequently erupt.
•E.g. Mount Etna in Italy
Extinct Volcano
•Active at a time, but will not erupt again.
•E.g. Kilimanjaro in Africa
Dormant Volcano
•Those that have erupted earlier and not active in the
recent past but can become active.
•E.g. Vesuvius in Italy

9. Conclusion
Volcanoes are helpful in many ways.
Though volcanic eruptions are threats to human life,
the areas where the eruptions have taken place are
useful too.
These areas are rich in minerals.
The black soil that formed as a result of a volcanic
eruption is very suitable for cotton cultivation.

10. REFERENCE
Text book of Std. IX
 Teachers’ handbook

11. Thank YOU