This document summarizes information about volcanoes. It defines a volcano as a rupture in the Earth's crust that allows hot lava, ash, and gases to escape from below the surface. Volcanoes form over time as a result of magma rising through cracks and releasing pressure during volcanic eruptions, which cool to form new crust. Characteristics of volcanoes include their cone shape and the lava and ash produced during eruptions. Volcanic hazards pose risks and can include lava flows, explosions, toxic gases, ash falls, pyroclastic flows, and mudflows. Volcano forecasts rely on studying past eruptions to estimate potential hazards, and monitoring for earthquake activity and surface deformation to provide useful warnings of

1. Volc no
BY:
THOMAS CHINNAPPAN . A ,
M.SC.APPLIED GEOLOGY,
PERIYAR UNIVERSITY,
SALEM.

2. Contents
Volcano
Volcano Formation
Characteristics Of Volcanoes
Volcanic Hazards
Volcano Forecast

3. Volcano
A volcano is a rupture in the crust of a planetary-mass object, such
as Earth, that allows hot lava, volcanic ash, and gases to escape from
a magma chamber below the surface. On Earth, volcanoes are most
often found where tectonic plates are diverging or converging, and
most are found underwater.

5. Volcano formation
Magma rises through cracks or weaknesses in the Earth's crust.
Pressure builds up inside the Earth.
When this pressure is released, eg as a result of plate movement, magma
explodes to the surface causing a volcanic eruption.
The lava from the eruption cools to form new crust.
Over time, after several eruptions, the rock builds up and a volcano forms

7. Characteristics of volcanoes
A volcano is formed by eruptions of lava and ash.
Volcanoes are usually cone shaped mountains or hills.
When magma reaches the Earth's surface it is called lava. When the lava cools,
it forms rock.
Volcanic eruptions can happen at destructive and constructive boundaries, but
not at conservative boundaries or collision zones.
Some volcanoes happen underwater, along the seabed or ocean floor.

8. Volcanic Hazards
A volcanic hazard is the probability a volcanic eruption or related
geophysical event will occur in each geographic area and within a
specified window of time. The risk that can be associated with a
volcanic hazard depends on the proximity and vulnerability of an
asset or a population of people near to where a volcanic event might
occur

9. The list of hazards associated with
volcanic eruptions is long and
varied: lava flows, explosions, toxic
gas clouds, ash falls, pyroclastic
flows, avalanches, tsunamis, acid
rain and mudflows.

10. Volcano Forecast
The greatest hazard at potentially active volcanoes is human
complacency. The physical hazards can be reliably estimated by
studying past eruptive activity as recorded in history or in the
prehistoric deposits around a volcano. Volcano observatories can
monitor local earthquake activity and the surface deformation of a
potentially active volcano and make useful, if not yet precise,
forecasts of eruptions.

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