Padilla: Some volcanic vocabulary

THE year 2019 ended with earthquakes shaking a good portion of Mindanao and just right at the beginning of 2020, Luzon’s scenic Taal Volcano is erupting.

Once more, the layperson is introduced to new terms or words that one hears or reads about but do not really understand.

When the ground shook we had liquefaction, the difference between intensity and magnitude, tectonic, earthquake waves, earthquake swarm, etc.

So now we have phreatic eruption, pyroclastic flow, volcanic gases, ejecta, fumarole, magma, seismic swarms, harmonic tremor, Alert Level 4, etc.

With the help of data from Geonet and Oregon State University websites, I am hoping my readers (if I have any) would get to understand these terms and learn to use it better:

* Phreatic: An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. Magma is not involved.

* Pyroclastic flow: Lateral flowage of a turbulent mixture of hot gases and unsorted pyroclastic material (volcanic fragments, crystals, ash, pumice, and glass shards) that can move at high speed (50 to 100 miles an hour.) The term also can refer to the deposit so formed.

* Fumarole: A vent or opening through which issue steam, hydrogen sulfide, or other gases. The craters of many dormant volcanoes contain active fumaroles.

* Volcanic gases: Magma deep in the earth contains dissolved gases. As the magma rises closer to the ground surface, these gases are released and, because they are so mobile when compared to the sluggish liquid magma, they rise to the surface and are discharged through vents, fumaroles, and the soil. The gas temperatures, absolute amounts, and relative proportions of different gases give information on the state of the magmatic system. Many of these are poisonous or cause asphyxiation.

* Ejecta: Material that is thrown out by a volcano, including pyroclastic material (tephra) and lava bombs.

* Magma: Molten or partly molten rock beneath the surface of the earth. Magma that reaches the surface erupts from a volcano as lava or explosively as ash and rocks.

* Seismic swarms: A series of minor earthquakes occurring in the same area and time, none of which may be identified as the main shock or with the same fault.

* Harmonic Tremor: A continuous release of seismic energy typically associated with the underground movement of magma. It contrasts distinctly with the sudden release and rapid decrease of seismic energy associated with the more common type of earthquake caused by slippage along a fault. Most important of all the terms is Alert Level 4.

As I write this, Taal has not erupted (and I hope it will not) and Alert Level 4 means Alert Level 4: Hazardous eruption imminent, Intense unrest with continuing seismic swarms, including harmonic tremor and/or low frequency earthquakes which are usually felt.

Knowledge is power. But what can also make this a better world is if we plant trees and generally respect the environment because at the heart of these natural disasters is the havoc humanity has wreaked on nature.


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