VOLCANIC ERUPTION LESSON, Lecture notes of Earth science

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Quarter 3 Module 2

Volcanic Eruption

MAGMA

extremely hot molten rock located under Earth's surface.

is mostly found in the layer of Earth known as the mantle. The temperature in the mantle is very high that keep magma in its fluid state.

MAGMA AND ITS COMPOSITION

Crystal Content – High temperature minerals are formed as magma slowly cools down. Magma always contains crystals of high temperature.

Viscosity – magma’s silica content affects its viscosity (the resistance of the fluid to flow), low viscosity magma has low silica content. Magma with high temperatures have low viscosity.

CLASSIFICATION OF MAGMA

Composition Viscosity Temperature Gas Content (^) contentSilica^ Explosiveness^ Location offormation Basaltic magma

Low 1000 – 1200 C

1 – 2 % Almost 50 %

Least explosive

Both oceanic and continental Andesitic magma

Intermedia te

900 – 1000 C

3 – 4 % Almost 60 %

Intermedia te

Continental margins associated with subduction zones Rhyolitic magma

High 750 – 900 C 4 – 6 % Almost 70 %

Most explosive

Continental crust

PROCESS OF VOLCANIC ERUPTION

As magma continuously heated, it goes up. As it rises, the gas bubbles are formed. These gas bubbles are trapped and expanded causing the molten material to swell also, resulting in a gradual increase in pressure within the volcano. When the pressure exceeds the strength of the overlying rock, fracturing occurs. The resulting breaks lead to further drop in confining pressure, which in turn causes even more gas bubbles to form. The rapid expansion of gas bubbles drives the magma to the surface and within minutes, the volcano erupts, explosively spewing hot lava and tephra into the air.

VOLCANIC HAZARDS

are phenomena arising from volcanic activity that pose potential threat to people or property.

Pyroclastic flow

Ash flow

Lava flow

Mud flow/Lahar

Volcanic gases

VOLCANIC HAZARDS

Pyroclastic flow – fast turbulent flow of fragmented volcanic materials (ash and rocks) mixed with hot gases that travels rapidly away from the volcano to the ground.

Ash Flow – Shower of fine-to-course-grained fragmented materials resulting from a volcanic eruption.

VOLCANIC HAZARDS

VOLCANIC

HAZARDS

IMPACTS OF VOLCANIC HAZARDS

Lava flow – Areas buried will not be usable for a long time. Burn living and non-living things that come in its way.

Mud flow / Lahar – Deposits can bury large areas under more than 1-meter-thick volcanic debris. Man made, and natural landscapes can be destroyed and will be changed forever.

Volcanic gases – are toxic and can be harmful to health or cause death.

POSITIVE EFFECTS OF VOLCANIC

ERUPTION

Volcanic eruptions also provide nutrients to the surrounding soil.

Precious gems.

Volcanic eruptions exhibit beauty. It attracts tourists.

Volcanic deposits are used for building different materials.

Precautionary Measures (BEFORE)

Know about the facts in your area like danger zones and history of eruptions.

Put together an emergency supply kit.

Know the location of designated evacuation site.

Listen to the announcement of your authorities.

Precautionary Measures (DURING)

Close all windows, doors, and fireplace or woodstove dampers.

Turn off all fans and heating and air conditioning systems.

Bring pets and livestock into closed shelters.

If your eyes, nose, and throat become irritated from volcanic gases and fumes, move away from the area immediately.

Leave the area immediately.