PART 1. Types of Volcanic Eruption

Which of the following is NOT one of the factors that affects the viscosity of magma?

• Silica content of lava

• Temperature of the lava relative to the cooler temperature at which it solidifies

• Pyroclastic flow

• Gas dissolved in magma

Which of the two types of eruption is characterized by gas-driven explosion that propels magma?

• explosive eruptions

• effusive eruption

• phreatic eruption

• magmatic eruption

Vulcanian eruption is also called nuee ardente eruption that occurs when large quantity of gas, ash and lava fragments.

• True

• False

Refer to the figure below. Determine the type of magmatic eruption shown.

• Vulcanian

• Strombolian

• Plinian

• Pelean

Why Plinian eruption is considered to be the most explosive and strongest type of eruption?

(Image shows Mount St. Helens in Washington State that experienced a Plinian eruption following a major flank collapse in 1980. Photo by Austin Post, USGS, May 18, 1980.)

It is classified as one of the types of phreatomagmatic eruptions and takes place beneath the surface water. It is generated at subduction zones and within tectonic plates where hotspots can be located.

• Plinian

• Subglacial

• Surtseyan

• Submarine

Phreatic eruption, is also called steam-blast eruptions, are those driven by explosive expanding steam resulting from cold ground or surface water coming into contact with hot rock or magma. But, why does pheratic eruption not always result to usual explosive or effusive eruption?

• Rock face is strong enough to withstand the explosive force.

• Magmastatic pressure is lower thatn lithostatic pressure

• There is an equilibrium in magmastatic and lithostatic pressure

• Rocks turned into soft clays due to hydrothermal alteration

Topic: Volcano alert levels in the Philippines.

Volcano eruption cannot be predicted bu t how do geologists monitor and record possible volcanic activities?

• Use devices |(like thermal imaging, tilt-meter)

• Interviewing locals

• Check the volcano type

• Observe changes in volcanic shape

This is a tilt-meter. How does it work?

• measures the amount of volcanic gas

• records motion of the ground

• measures the expansion of volcano

• checks the the temperature

A service institute of the Department of Science and Technology that is principally mandated to mitigate disasters brought about by geotectonic phenomena such as volcanic eruption, earthquakes, and tsunami within the Philippine territory.

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