What is a volcano?
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A volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments.
How are volcanoes formed?
Volcanoes are formed when magma from within the Earth's upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger.
What are the different stages of volcanoes?
Scientists have categorized volcanoes into three main categories: active, dormant, and extinct. An active volcano is one which has recently erupted and there is a possibility that it may erupt soon. A dormant volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future. An extinct volcano is one which has erupted thousands of years ago and there’s no possibility of eruption.
Why do volcanoes erupt?
The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. The friction causes earthquakes and volcanic eruptions near the edges of the plates. The theory that explains this process is called plate tectonics.
What are plate tectonics?
The theory of plate tectonics is a interesting story of continents drifting from place to place breaking apart, colliding, and grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. The plates are all moving in different directions and at different speeds. Sometimes the plates crash together, pull apart or sideswipe each other. When this happens, it commonly results in earthquakes.
How many volcanoes are there?
There are more than 1500 active volcanoes on the Earth. We currently know of 80 or more which are under the oceans. Active volcanoes in the U.S. are found mainly in Hawaii, Alaska, California, Oregon and Washington.
What are the different types of volcanoes?
- Cinder Cones
Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent. - Composite Volcanoes
Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris. Mt. Rainier and Mount St. Helens are examples of this type of volcano. - Shield Volcanoes
Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Basalt lava flows from these volcanoes are called flood basalts. The volcanoes that formed the basalt of the Columbia Plateau were shield volcanoes. - Lava Volcanoes
Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent. The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.
What is the difference between lava and magma?
Magma is liquid rock inside a volcano. Lava is liquid rock (magma) that flows out of a volcano. Fresh lava glows red hot to white hot as it flows. Lava cools slowly because lava is a poor conductor of heat. Lava flows slow down and thicken as they harden.
What is a pyroclastic flow?
A pyroclastic flow is a fluidized mixture of solid to semi-solid fragments and hot, expanding gases that flows down the sides of a volcano. These awesome features are heavier-than-air emulsions that move much like a snow avalanche, except that they are fiercely hot, contain toxic gases, and move at phenomenal, hurricane-force speeds. They are the most deadly of all volcanic phenomena.
What is lahar?
A lahar is a type of mudflow or debris flow composed of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. It is very dangerous because it's consistency and the way it acts is very much like cement. It is liquid when it's moving, but when it stops, it solidifies. This can cause just as much devastation as lava itself.
Kinds of Volcanoes
- ACTIVE VOLCANO - An active volcano is one that erupts regularly.
Some active volcanoes in the Philippines
*Banahaw (Laguna, Quezon)
*Didicas (Cagayan)
*Hibok-Hibok (Camiguin)
*Kanlaon (Negros Oriental)
*Mayon (Albay)
*Matutum (Cotabato)
*Musuan (Bukidnon)
*Parker (Cotabato)
*Pinatubo (Zambales)
*Taal (Batangas) - DORMANT VOLCANO - A dormant volcano is one that has not erupted for many years, although there is still some activity deep inside.
*Apo (Davao City)
*Cuernos de Negros (Dumaguete City)
*Gorra (Jolo)
*Maripipi (Tacloban City)
*Mariveles
*Negron - EXTINCT VOLCANO - An extinct volcano is a volcano that is no longer active.
*Alligator (Laguna)
*Alu (Sulu)
*Anilao Hill (Batangas)
*Arayat (Pampanga)
*Batelian (Zamboanga del Sur)
*Boctong (Palawan)
How can we tell when a volcano will erupt?
Most volcanoes provide various types of warnings before eruptions begin. Although an explosive eruption could occur without warning, some premonitory events more likely will precede the next eruption. Steam-blast eruptions could occur with little or no warning as superheated water flashes to steam; magmatic eruptions, however, involve rise of magma toward the surface. Such an upward movement of magma normally will generate detectable earthquakes, may deform the ground surface, and may cause anomalous heat flow or changes in the temperature and chemistry of the groundwater and spring waters.
People living near volcanoes may detect premonitory events before an eruption. Both the frequency of occurrence and intensity of felt earthquakes commonly increase before eruptions begin. Eruptions may also be preceded by noticeable steaming or fumarolic activity and perhaps by new or enlarged areas of hot ground. However, most precursory changes are subtle and the most effective means of monitoring are instrumental and include a variety of geophysical, geodetic, and geochemical techniques. Seismometers are used to detect and locate earthquakes associated with the rise of magma. Swelling of the ground surface can be detected by using precision instruments and techniques that measure minute changes in slope, distance, or elevation at the ground surface. Other techniques involve measurement of changes in heat flow at a volcano by repeated infrared surveys or by direct measurements of hot spring or fumarole temperatures. Changes in the composition or relative abundances of fumarolic gases may also precede eruptions and can be detected by frequent or continuous analysis of gases.
These and other types of monitoring may be useful in detecting warning signs of impending eruption.
However, the overall success of a monitoring system depends on detection and interpretation of precursory events in time to warn and evacuate people from threatened areas and to initiate other measures to mitigate the effects of the eruption. Although monitoring systems may be useful in indicating an increase in the probability of volcanic activity and its possible location, they typically do not indicate the kind or scale of an expected eruption, particularly the first magmatic event, or the surrounding areas that might be affected. Precursors to volcanic activity may continue for weeks, months, or even years before eruptive activity begins, or they can subside at any time and not be followed by an eruption. Thus, monitoring of volcanic precursors may provide a general warning that volcanic activity in a specific area is becoming more likely, but it often does not pinpoint the nature or timing of an eruption or even its certainty.
People living near volcanoes may detect premonitory events before an eruption. Both the frequency of occurrence and intensity of felt earthquakes commonly increase before eruptions begin. Eruptions may also be preceded by noticeable steaming or fumarolic activity and perhaps by new or enlarged areas of hot ground. However, most precursory changes are subtle and the most effective means of monitoring are instrumental and include a variety of geophysical, geodetic, and geochemical techniques. Seismometers are used to detect and locate earthquakes associated with the rise of magma. Swelling of the ground surface can be detected by using precision instruments and techniques that measure minute changes in slope, distance, or elevation at the ground surface. Other techniques involve measurement of changes in heat flow at a volcano by repeated infrared surveys or by direct measurements of hot spring or fumarole temperatures. Changes in the composition or relative abundances of fumarolic gases may also precede eruptions and can be detected by frequent or continuous analysis of gases.
These and other types of monitoring may be useful in detecting warning signs of impending eruption.
However, the overall success of a monitoring system depends on detection and interpretation of precursory events in time to warn and evacuate people from threatened areas and to initiate other measures to mitigate the effects of the eruption. Although monitoring systems may be useful in indicating an increase in the probability of volcanic activity and its possible location, they typically do not indicate the kind or scale of an expected eruption, particularly the first magmatic event, or the surrounding areas that might be affected. Precursors to volcanic activity may continue for weeks, months, or even years before eruptive activity begins, or they can subside at any time and not be followed by an eruption. Thus, monitoring of volcanic precursors may provide a general warning that volcanic activity in a specific area is becoming more likely, but it often does not pinpoint the nature or timing of an eruption or even its certainty.
Volcanic Alert Levels
An eruption may occur at any level, and levels may not move in sequence as activity can change rapidly.
Eruption hazards depend on the volcano and eruption style, and may include explosions, ballistics (flying rocks), pyroclastic density currents (fast moving hot ash clouds), lava flows, lava domes, landslides, ash, volcanic gases, lightning, lahars (mudflows), tsunami, and/or earthquakes.
Volcanic unrest hazards occur on and near the volcano, and may include steam eruptions, volcanic gases, earthquakes, landslides, uplift, subsidence, changes to hot springs, and/or lahars (mudflows).
Volcanic environment hazards may include hydrothermal activity, earthquakes, landslides, volcanic gases, and/or lahars (mudflows).
*Ash, lava flow, and lahar (mudflow) hazards may impact areas distant from the volcano.
Eruption hazards depend on the volcano and eruption style, and may include explosions, ballistics (flying rocks), pyroclastic density currents (fast moving hot ash clouds), lava flows, lava domes, landslides, ash, volcanic gases, lightning, lahars (mudflows), tsunami, and/or earthquakes.
Volcanic unrest hazards occur on and near the volcano, and may include steam eruptions, volcanic gases, earthquakes, landslides, uplift, subsidence, changes to hot springs, and/or lahars (mudflows).
Volcanic environment hazards may include hydrothermal activity, earthquakes, landslides, volcanic gases, and/or lahars (mudflows).
*Ash, lava flow, and lahar (mudflow) hazards may impact areas distant from the volcano.
Precautionary Measures Before, During, and After Volcanic Eruptions
Before volcanic eruptions:
1. Each one should be aware of the dangers that volcanic eruptions pose to lives and be prepared to face whatever circumstances the eruption may bring.
2. Prepare all necessary things to bring once evacuation is needed. Those in danger zones are warned when to evacuate. Once given the signal refrain from saying you will be all right. Refusing to evacuate will pose more serious problems.
3. Store as much food, water, light sources and batteries that are very useful in case of emergency.
4. Volcanic eruptions have ash falls so be prepared for masks or anything to cover nose and mouth.
5. Prioritize the safety of kids before other things. If you have relatives or friends who are far from the volcano, take your children there until such time that your place is safe.
During volcanic eruptions:
1. Avoid all low-lying places because lava flows and mudflows are more likely to pass here.
2. Seek cover in case of ash falls rock falls.
3. Use masks and cover your mouth and nose to avoid breathing in ashes.
4. If you are inside a house; close all doors and windows to avoid ashes from getting inside.
5. Always stay indoors.
6. Stay in the evacuation center until further instructions. Do not attempt to leave the place unless told to do.
7. Keep a watchful eye on the kids because they might be tempted to go out and see what’s going on outside.
After volcanic eruptions:
1. Go back to your house but leave the kids behind someone who can take care of them while you check your house.
2. Clean everything around and check all damages incurred.
3. Use masks while cleaning ash and other debris.
4. Wait for further announcements related to the volcano activities.
5. Make sure that your house is still safe for all of you.
1. Each one should be aware of the dangers that volcanic eruptions pose to lives and be prepared to face whatever circumstances the eruption may bring.
2. Prepare all necessary things to bring once evacuation is needed. Those in danger zones are warned when to evacuate. Once given the signal refrain from saying you will be all right. Refusing to evacuate will pose more serious problems.
3. Store as much food, water, light sources and batteries that are very useful in case of emergency.
4. Volcanic eruptions have ash falls so be prepared for masks or anything to cover nose and mouth.
5. Prioritize the safety of kids before other things. If you have relatives or friends who are far from the volcano, take your children there until such time that your place is safe.
During volcanic eruptions:
1. Avoid all low-lying places because lava flows and mudflows are more likely to pass here.
2. Seek cover in case of ash falls rock falls.
3. Use masks and cover your mouth and nose to avoid breathing in ashes.
4. If you are inside a house; close all doors and windows to avoid ashes from getting inside.
5. Always stay indoors.
6. Stay in the evacuation center until further instructions. Do not attempt to leave the place unless told to do.
7. Keep a watchful eye on the kids because they might be tempted to go out and see what’s going on outside.
After volcanic eruptions:
1. Go back to your house but leave the kids behind someone who can take care of them while you check your house.
2. Clean everything around and check all damages incurred.
3. Use masks while cleaning ash and other debris.
4. Wait for further announcements related to the volcano activities.
5. Make sure that your house is still safe for all of you.