Volcanic Eruptions
An eruption begins when pressure on the magma chamber forces magma up
through the conduit and out the volcano’s vents. Volcanic eruptions vary
considerably. It may be violent, mild, or quiet. The number of gases dissolved
in the magma and its composition and cosity are some of the factors that
determine whether an eruption violent or quiet.
Types of Volcanic Eruption
1. Explosive or Violent Eruptions
During explosive eruptions, the lava ejected is torn into shreds, forming
pieces of pyroclastic materials called tephra. Explosive eruptions can eject a
large number of materials into the air. Very violent explosive eruptions are
called Plinian eruptions after the Roman naturalist Pliny the Elder. These
eruptions can last for several hours to days, ejecting large amounts of
pyroclastic materials. The composition of the magma affects volcanic
activity. When magma contains silica, the magma is thicker and more
viscous. The greater the viscosity of the magma, the more difficult it is for
gases to escape from it. In this case, the eruption is a violent one, releasing
huge volumes of tephra. Lava, which has high silica content is thicker and
more viscous; examples of them include granitic and andesitic lava.
Figure 8.10. Edge of advancing lava from Kilauea crater's eruption
2. Quiet Non-explosive Eruption
Basaltic magma has relatively low silica content. It is less viscous and gases
can escape readily from it. As a result, the volcanic eruption is mild and a
gentle flow of lava follows. Mild eruptions and quiet flow of lava are typical of
Hawaiian shield cones like Mauna Kea and Mauna Loa. Even if the eruption is
quiet and non-explosive, it is still capable of inflicting massive damage on
communities. It may be slow, but this eruption is still capable of doing
damage to lives and properties. With this kind of eruption, affected people
would have more time in terms of preparing and evacuating communities
and localities.
Benefits of Volcanic Eruptions
Volcanic eruptions can obviously cause serious effects on living things, the
economy, and in the environment. However, volcanic activities can also
produce some benefits to various sectors of society because of the very rich
nature of ejected materials. Volcanic eruptions can also lead to the formation
of new landforms. These eruptions could give rise to volcanic islands which
could provide us with essential materials and elements that could be useful
for us in terms of the production of multitudes of products. As time passes,
these islands could also develop rich vegetation which would prove beneficial
to people, especially to those that live in a territory near the said volcanic
island.
1.
Agricultural Benefits - The greatest resource from a volcanic eruption is the
land formed by the erupted materials. After a volcanic eruption, the burning
lava can turn into one of the
richest or most fertile soils in the world.
2. Energy and Industrial Benefits Geothermal energy serves as an alternative
source of
electricity. It utilizes the heat beneath the earth's surface to create energy.
Materials and essential minerals ejected by the volcanoes, on the other
hand, serve as sources of materials intended for the development of the
community and the industry.
Dangers of Volcanic Eruption
1. Effects of Volcanic Gases - Volcanic ashes like sulfur dioxide, nitrous oxide,
and hydrochloric fumes can lead to acid precipitation. These gases pose the
greatest potential to people, animals, agriculture, and properties.
2. Effects of Lava and Pyroclastic Flows - Lava destroys anything in its path.
Huge volumes of lava
flow can cause massive damage to property and tremendous economic loss.
Massive debris flow or lahar forms when hot ashes, very fine rock fragments,
and hot lava are mixed with water from nearby lakes or rivers or when heavy
rains occur. Lahar can travel at high speeds.
Precautionary Measures Before, During, and After a Volcanic Eruption
Before a Volcanic Eruption
1. Learn about your community's warning system and develop an emergency
communication plan.
2. Prepare disaster supplies or a survival kit.
3. Your local government has evacuation plans. Follow evacuation plans and
the authorities' instructions, and leave the area before the disaster begins.
Go to higher grounds away from the eruption.
4. Evacuate before the volcano erupts. It is not safe to stay at home.
During a Volcanic Eruption
1. Avoid areas near the slopes of the volcano. Lava could flow near the
slopes.
2. If caught indoors, close all windows, doors, and other openings. Remain
indoors.
3. If caught outdoors, protect. your head from rocks and immediately find
safe shelter.
4. Avoid low-lying areas where lava flow could reach and poisonous gases
can collect.
5. Avoid mudflows. Mudflows occur when rain falls and mixes with ashes and
debris.
6. Immediately evacuate the area instead of doing "selfies" with the scene of
the eruption.
After a Volcanic Eruption
1. Listen to a battery-powered radio or television for the latest emergency
information.
2. Stay away from volcanic ash fall. When outside, protect your eyes, mouth,
and nose from volcanic ashfalls. Wear goggles to protect your eyes and use a
damp cloth to protect your mouth and nose. You may also use an N-95 mask
in place of a damp cloth.
3. If you have a respiratory ailment, stay indoors to avoid inhaling dust and
ash. Follow local health officials. Seek advice if it is safe to go outside.
4. Do not return immediately to your affected home since more eruptions
could occur.
