What comes out of a volcano? | Volcano World | Oregon State University What comes out of a volcano? lava flow can develop. If the amount of lava feeding the flow is high, then the flow will move rapidly downhill away from the vent. Rapid-moving flows continually disrupt their surfaces and are constantly exposing more red-hot lava to the atmosphere. This means that the flow is losing a lot of heat and consequently its a'a flow develops. In some eruptions there is almost no fountaining and the lava just flows slowly away from the vent. In these cases the surface of the lava is not disrupted and can solidify even while the inside is still molten. This is how pahoehoe flow move. If these pahoehoe flows go on long enough then lava tubes can develop within the flow. These lava tubes allow lava to reach the flow front from the vent without losing much heat so it is still pretty fluid even 10's of kilometers from the vent. At more explosive volcanoes eruptions are very different. The main difference is that the viscosity of the plug on the vent and allows gas pressures to build to very high. Eventually the gas pressure is higher than even the viscous lava can stand, and an explosive eruption occurs.

These explosions remove the cap of viscous lava that was plugging the vent so that the pressure is now lower. With the new low pressure, more gas bubbles can expand and push more lava out of the vent, and on and on and on. Once one of these explosive eruptions starts it pretty much continues until the available magma is used up. These big explosions reach 10's of km into the atmosphere sometimes, and spread fine ash over huge areas. Sometimes instead of going up, the hot mixture of gas and ash flows out of the vent and hugs the ground. These fast-moving hot mixtures are called pyroclastic flows and they are very dangerous. Because they are mostly gas, they can move quickly, up to 200 km/hour. They are sometimes up to 600 degrees centigrade. With this combination of speed and heat they are the most dangerous phenomenon that a volcano can produce. They may leave only a thin layer of ash after they pass through, but for those few moments while the VOLCANOES Volcanoes Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay First - time Visitors: Please visit Site Map and Disclaimer . Use "Back" to return here.

The property of a magma that determines whether or not it has high viscosity: Created 30 Dec 1996, Last Update 24 February 2011 Not an official UW-Green Bay site Definitions | Volcano World | Oregon State University OREGON STATE UNIVERSITY Definitions Volcano Term Definitions Click one of the letters above to advance the page to terms beginning with that letter. a whose surface is broken into rough angular fragments. Accessory A mineral whose presence in a rock is not essential to the proper classification of the rock. Accidental . Accretionary Lava Ball A rounded mass, ranging in diameter from a few centimeters to several meters, [carried] on the surface of a around a core of already solidified lava. Acid that is erupting. Also, a volcano that is not presently erupting, but that has erupted within historical time and is considered likely to do so in the future. Agglutinate and formed by the coherence of the fragments upon solidification. Alkalic Rocks which contain above average amounts of sodium and/or potassium for the group of rocks for which it belongs. For example, the basalts of the .

They contain more sodium and/or potassium than the shield-building basalts that make the bulk of the volcano. Andesite and moderate amounts of iron and magnesium. Aquifer A body of rock that contains significant quantities of water that can be tapped by wells or springs. Ash or fissure. The mass of pyroclastics is normally of very high temperature and moves rapidly down the slopes or even along a level surface. Ashfall . A deposit so formed is usually well sorted and layered. Asthenosphere The shell within the earth, some tens of kilometers below the surface and of undefined thickness, which is a shell of weakness where movements take place to permit pressure adjustments. Avalanche A large mass of material or mixtures of material falling or sliding rapidly under the force of gravity. Avalanches often are classified by their content, such as snow, ice, soil, or rock avalanches. A mixture of these materials is a , and generally is rich in iron and magnesium. Basement The undifferentiated rocks that underlie the rocks of interest in an area. Basic (SiO2) between 44% and 52%. Bench formed by the puffing-up of gas or vapor beneath the flow.

Blisters are about 1 meter in diameter and hollow. Block . Bomb Fragment of molten or semi-molten rock, 2 1/2 inches to many feet in diameter, which is blown out during an condition, bombs are often modified in shape during their flight or upon impact. c Caldera The Spanish word for cauldron, a basin-shaped volcanic depression; by definition, at least a mile in diameter. Such large depressions are typically formed by the subsidence of volcanoes. , and related rocks build a steeply, sloping cap on the main shield of the volcano. Central Vent constructed by the ejection of debris and lava flows from a central point, forming a more or less symmetrical volcano. Cinder Cone A volcanic cone built entirely of loose fragmented material (pyroclastics.) Cirque A steep-walled horseshoe-shaped recess high on a mountain that is formed by glacial erosion. Cleavage The breaking of a mineral along crystallographic planes, that reflects a crystal structure. Composite Volcano Solid, outer layers of the earth, including the rocks of the continents.

Continental Drift The theory that horizontal movement of the earth's surface causes slow, relative movements of the continents toward or away from one another. Country Rock . Craton A part of the earth's crust that has attained stability and has been little deformed for a prolonged period. Curtain of Fire and moderate a mounts of sodium and potassium. Debris Avalanche A rapid and unusually sudden sliding or flowage of unsorted masses of rock and other material. As applied to the major . Debris Flow The surface along which a landslide disconnects from its original position. Devonian A period of time in the Paleozoic Era that covered the time span between 400 and 345 million years. Diatreme that was formed by a gaseous explosion. Dike A sheetlike body of igneous rock that cuts across layering or contacts in the rock into which it intrudes. Dome The area of land drained by a river system. e Echelon Set of geologic features that are in an overlapping or a staggered arrangement (e.g., faults). Each is relatively short, but collectively they form a linear zone in which the strike of the individual features is oblique to that of the zone as a whole.

Ejecta bombs. Eruption The process by which solid, liquid, and gaseous materials are ejected into the earth's atmosphere and onto the earth's surface by volcanic activity. Eruptions range from the quiet overflow of liquid rock to the tremendously violent expulsion of pyroclastics. Eruption Cloud . If it is of sufficient volume and velocity, this gaseous column may reach many miles into the stratosphere, where high winds will carry it long distances. Eruptive Vent The opening through which volcanic material is emitted. Evacuate Temporarily move people away from possible danger. Extinct that is not presently erupting and is not likely to do so for a very long time in the future. Extrusion and permit it to rise to the surface. Fault Scarp and representing the exposed surface of the fault before modification by erosion and weathering. Felsic An igneous rock having abundant light-colored minerals. Fire fountain . Fissure eruptions typically produce liquid flows, but pyroclastics may also be ejected. Flank Eruption (in contrast to a summit eruption.) Fluvial Produced by the action of of flowing water. Formation position and is mappable at the earth's surface or traceable in the subsurface.

Fracture The manner of breaking due to intense folding or faulting. Fumarole Energy derived from the internal heat of the earth. Geothermal Power Power generated by using the heat energy of the earth. Graben that has a platform top. Named for a nineteenth-century Swiss-American geologist. h The resistance of a mineral to scratching. Harmonic Tremor Movement of heat from one place to another. Heterolithologic Material is made up of a heterogeneous mix of different rock types. Instead of being composed on one rock type, it is composed of fragments of many different rocks. Holocene The time period from 10,000 years ago to the present. Also, the rocks and deposits of that age. Horizontal Blast and other material moves laterally rather than upward. Horst of the earth's crust, generally long compared to its width, that has been uplifted along faults relative to the rocks on either side. Hot Spot A volcanic center, 60 to 120 miles (100 to 200 km) across and persistent for at least a few tens of million of years, that is thought to be the surface expression of a persistent rising plume of hot material.

Hot spots are not linked to arcs and may not be associated with ocean ridges. Hot-spot Volcanoes into water, ice, or water-saturated sediment and its consequent granulation or shattering into small angular fragments. Hydrothermal Reservoir An underground zone of porous rock containing hot water. Hypabyssal or the resulting solidified rock. Hypocenter . The term was originally applied only to densely welded deposits but now includes non-welded deposits. Intensity of the earthquake, but also on the distance from the epicenter and the local geology. Intermediate (SiO2) between 54% and 65%. Intrusion in pre-existing rock. Also, the term refers to igneous rock mass so formed within the surrounding rock. j l Laccolith A body of igneous rocks with a flat bottom and domed top. It is parallel to the layers above and below it. Lahar . Landsat A series of unmanned satellites orbiting at about 706 km (438 miles) above the surface of the earth.

The satellites carry cameras similar to video cameras and take images or pictures showing features as small as 30 m or 80 m wide, depending on which camera is used. Lapilli Literally "little stones." Round to angular rock fragments, measuring 1/10 inch to 2 1/2 inches in diameter, which may be ejected in either a solid or molten state. Lava or fissure. It also refers to cooled and solidified rock. Lava Dome or fissure. Also, a solidified tongue like or sheet-like body formed by outpouring lava. Lava Fountain cools and solidifies while the still-molten interior flows through and drains away. Limu O Pele Delicate, translucent sheets of spatter filled with tiny glass bubbles. Lithic Of or pertaining to stone. Lithosphere The reflection of light from the surface of a mineral. m An igneous composed chiefly of one or more dark-colored minerals. Magma Molten rock beneath the surface of the earth. Magma Chamber .

Magnitude A numerical expression of the amount of energy released by an earthquake, determined by measuring earthquake waves on standardized recording instruments (seismographs.) The number scale for magnitudes is logarithmic rather than arithmetic. Therefore, deflections on a seismograph for a magnitude 5 earthquake, for example, are 10 times greater than those for a magnitude 4 earthquake, 100 times greater than for a magnitude 3 earthquake, and so on. Mantle The zone of the earth below the crust and above the core. Matrix The solid matter in which a fossil or crystal is embedded. Also, a binding substance (e.g., cement in concrete). Miocene An epoch in Earth's history from about 24 to 5 million years ago. Also refers to the rocks that formed in that epoch. Moho High School Earth Science/Volcanic Eruptions - Wikibooks, open books for an open world High School Earth Science/Volcanic Eruptions From Wikibooks, open books for an open world This is the latest reviewed version , checked on 1 May 2016. (+) Quality: minimal 9 Points to Consider Figure 8.8: Mount St.

Helens, Washington, two years after its eruption. In 1980, Mount St. Helens erupted in one of the most deadly and costly volcanic eruptions in the United States ever. The eruption was particularly deadly since Mount St. Helens, one of the Cascade Range, is in a populated area between Portland, Oregon and Seattle, Washington. The eruption killed 57 people, destroyed 250 homes, and swept away 47 bridges. The elevation of the volcano dropped by over 400 meters (1,300 feet) because of the immense explosion created by the eruption. Today, Mt. St. Helens is still active (Figure 8.8). The volcano now has a horseshoe-shaped crater that is 1.5 km (nearly one mile) across. Within the crater, a new lava dome has formed. How did this eruption occur? Why aren't all volcanoes explosive like Mt. St. Helens? Why did so many people perish if we knew that it was going to erupt? The study of volcanoes has many questions still unanswered. However, scientists have studied volcanoes for many years and are piecing together evidence that explains these powerful geologic phenomena.

Describe and compare the types of volcanic eruptions. Distinguish between different types of lava and understand the difference between magma and lava. Describe a method for predicting volcanic eruptions. How Volcanoes Erupt[ edit ] All volcanoes share the same basic features. The magma collects in magma chambers that can be 160 kilometers (100 miles) beneath the surface. As the rock heats, it expands, which creates even more pressure. As a result, the magma seeks a way out pushing toward the surface, and seeps through cracks in the Earth's crust called vents. Eventually, it reaches the surface; when it comes out, we call it an eruption. The word eruption is used in other contexts, as well. An eruption can be an outburst or explosion, a violent and sudden occurrence, like when a crowd erupts in anger. But an eruption can also be a spreading of something like a rash on your skin, gradual and relatively calm. These two definitions are similar to the two kinds of eruptions that we see in volcanoes. Types of Eruptions[ edit ] Every geological formation is unique. Their composition and construction depend on so many factors, that it would be impossible for two formations to be exactly alike.

In the same way, each volcano and its eruptions are unique. However, we tend to see two major kinds of eruptions. We talked about eruption to mean both a violent explosion or a sort of silent spreading. These are the two types of volcanic eruptions that we see–explosive and non-explosive eruptions. When we think of volcanic eruptions, we often think of huge clouds of volcanic ash ejected high into the atmosphere and then thick rivers of red lava snaking down the mountainside. In reality, these two phenomena rarely occur in the same volcano. Volcanic eruptions tend to be one or the other. Explosive Eruptions[ edit ] Imagine the devastation and force caused by the atom bomb dropped on Nagasaki at the end of World War II in which over 40,000 people died. Now imagine an explosion 10,000 times as powerful. Explosive volcanic eruptions can be that powerful (Figure 8.9). As hot magma beneath the surface interacts with water, gases accumulate and the magma pressure builds up. This pressure grows and grows until these dissolved gases cause it to burst in an enormous explosion.

Figure 8.9: An explosive eruption from the Mayon Volcano in the Philippines in 1984. This great explosion takes with it the magma and volcanic gases, which can shoot many kilometers into the sky and forms a mushroom cloud, similar to that formed by a nuclear explosion (Figure 8.10). The debris travels up into the air at very high speeds and cools in the atmosphere to form solid particles called pyroclasts. Some of these particles can stay in the atmosphere for years, which can disrupt weather patterns and affect the temperature of the Earth. The rest of the debris comes falling back to Earth where it rains down for kilometers and kilometers around. Figure 8.10: Explosive eruption of Mt. Redoubt in Alaska, 1989. This huge mushroom cloud reached 45,000 feet and caught a Boeing 747 in its plume. Sometimes secondary explosions occur that are even greater than the first. Additionally, volcanic gases like water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide, and hydrogen chloride can form poisonous and invisible clouds that roam about the atmosphere.

These gases contribute to environmental problems like acid rain and ozone destruction, and can actually cool the Earth's atmosphere. In the Cascade Range, the explosive eruption of Mount St. Helens was preceded by the eruption of Lassen Peak, one of the three Cascade Volcanoes in northern California. On May 22, 1915, an explosive eruption sent a column of ash and gas 30,000 feet into the air and triggered a high-speed pyroclastic flow, which melted snow and created a lahar. Lassen continues to have geothermal activity and could erupt explosively again. Mt. Shasta erupts every 600 to 800 years. An eruption would most likely to create a large pyroclastic flow, and perhaps a lahar. However, the volcano could explode like Mt. Mazama, which blew itself in an eruption about 42 times more powerful than Mount St. Helens in 1980, to create Crater Lake. Non-explosive Eruptions[ edit ] A second type of volcanic eruption is a non-explosive or effusive eruption (Figure 8.11).

Because the composition of magma is different in different volcanoes, the properties of the lava are different. In effusive eruptions, lava flows are relatively calm and do not explode out of the volcano. As a result, people generally have a great deal of warning before lava reaches them, so non-explosive eruptions are much less deadly. That does not keep them from being destructive, however. Even when we know that a lava flow is approaching, there are few ways of stopping it, given the huge quantity and temperature of lava. Magma and Lava[ edit ] Volcanoes wouldn't be nearly as interesting without the great explosions they create and the glowing red rivers of lava. All igneous rock comes from magma or lava. The next time you go hiking near a volcanic zone, you might try to identify the types of lava that the volcano erupted, based on the types of igneous rocks you find. Figure 8.12: When lava flows readily, pressure does not build up so great explosions do not occur. Magma[ edit ] Deep beneath the Earth, magma forms as the first stage in creating a volcano. This occurs because rock below the surface is subjected to great amounts of pressure from gravity. The decay of radioactive materials generates additional heat.

The substantial heat and pressure melt the rock below the surface to form a taffy-like substance. You may have seen a candle that has been left out in the hot sun too long. It becomes softer and more like a liquid. As the molecules absorb heat, they begin to slide past one another becoming more fluid. A similar process occurs with magma. However, different substances melt at different temperatures. For that reason, the temperature at which rocks melt depends on the specific types of rocks. The Earth's crust and mantle are made of many substances so the temperature required to create magma varies. Most magmas are formed between 600°C and 1300°C (Figure 8.13). Figure 8.13: Cutaway of the Earth. The melting of rock in the crust and upper mantle create magma. Melted rock or magma can be found in magma chambers beneath the Earth. Since the magma chambers are so far beneath the Earth's surface, it is difficult for scientists to study them. Scientists know that magma chambers are created where the heat and pressure are greatest. When tectonic plates collide and rub against each other, magma is formed there. That is how the Pacific Ring of Fire was created.

We also know there are volcanoes far away from plate boundaries, so we know there are magma chambers in these areas as well. Magma chambers can be found where there are mantle plumes or hot spots. Just how or why these hot spots are created isn't exactly known. However, because different substances melt at different temperatures, the creation of magma depends on what substances make it up—its composition. Just like the flavor of a cake depends on the ingredients that you put in it, the behavior of magma and lava depends on its composition. Certain melted rocks act in certain ways. So when the magma becomes lava, not all lava acts the same. Lava[ edit ] Figure 8.14: Honey flows slowly; it is more viscous than water. Once magma reaches the surface, it becomes lava. Consider different liquids that you might see in your house—honey and a bottle of cola, for example. You might agree that the two liquids are different in many regards. They taste different, have different colors, have different gases in them, and they flow differently. In fact, honey is a liquid that resists flowing, whereas cola flows easily.

Honey has a higher viscosity than the cola; it resists flowing (Figure 8.14). Cola has a low viscosity because it flows easily. One of the major differences in different types of lava is their viscosity. A highly viscous lava is one that doesn't tend to flow easily. It tends to stay in place. Lavas with high silica contents tend to be more viscous. Since it is so resistant to moving, it clogs the vents in a volcano. The pressure becomes greater and greater until the volcano finally explodes. This type of lava is found in explosive eruptions. It also tends to trap a lot of gas. When the gas is released, it makes the eruption more explosive. Most of this lava is shot up into the air where it hardens and becomes solid rock. This molten rock that solidifies in the air is known as pyroclastic material. In an igneous rock like pumice, small holes in the solid rock show where gas bubbles were when the rock was still liquid lava. Low-viscosity lava slides or flows down mountainsides. There is more than one type of low-viscosity lava.

The differences between them come from the lavas' different composition and different spots where they come to the surface. The type of igneous formations formed depends on which type of lava it is. The three major categories are a'a, pahoehoe, and pillow lava. A'a Lava[ edit ] A'a lava is the more viscous of the non-explosive lavas (Figure 8.15). This lava forms a thick and brittle crust which is torn into rough and jagged pieces. The solidified surface is jagged and sharp. It can spread over large areas as the lava continues to flow underneath. Figure 8.15: A'a lava flow. Pāhoehoe Lava[ edit ] Pāhoehoe lava is less viscous than a'a lava, and flows more readily. Its surface looks more wrinkly and smooth than the jagged a'a lava. Pāhoehoe lava flows in a series of lobes or rounded areas that form strange twisted shapes and natural rock sculptures (Figure 8.16). Pāhoehoe lava can also form lava tubes beneath the ground (Figure 8.17). Figure 8.16: Pāhoehoe lava.

Pillow Lava[ edit ] Pillow lava is lava that comes out from volcanic vents underwater (Figure 8.18). When it comes out underwater, it cools down very quickly and forms roughly spherical rocks that resemble pillows, from which more lava leaks and creates more pillows. Pillow lava is particularly common along underwater spreading centers. Figure 8.18: Pillow lava. Predicting Volcanic Eruptions[ edit ] Volcanic eruptions can be devastating, particularly to the people who are closer to volcanoes. As meteorologists attempt to predict, or forecast, hurricanes and tornadoes, so too do vulcanologist attempt to forecast volcanic eruptions. Although predicting volcanic eruptions is far from perfect, many pieces of evidence can indicate that a volcano is about to erupt. Some of those factors are hard to measure, contributing to the difficulty in predicting eruptions. History of Volcanic Activities[ edit ] One important factor in predicting eruptions is a volcano's history. That is, we consider how long since it has erupted and the time span between its previous eruptions. Volcanoes are categorized into three subdivisions—active, dormant, and extinct.

An active volcano is one that is currently erupting or shows signs of erupting in the near future. A dormant volcano no longer shows signs of activity, but has erupted in recent history (Figure 8.19). Finally, an extinct volcano is one that has not erupted in recent history and will probably not erupt again in the future. Both active and dormant volcanoes are heavily monitored because even dormant volcanoes could suddenly show signs of activity. Figure 8.19: Vesuvius is a dormant volcano near the city of Naples. Although it shows no current signs of eruption, it could one day become active. Earthquakes[ edit ] As magma beneath a volcano pushes upward, it shakes the ground and causes earthquakes. Although earthquakes probably occur every day near a volcano, the quantity and size of the earthquakes increases before an eruption. In fact, a volcano that is about to erupt may produce a continuous string of earthquakes, as magma moving underground creates stress on the neighboring rocks. In order to measure these earthquakes, scientists use seismographs that record the length and strength of each earthquake. Slope Deformation[ edit ] All that magma and gas pushing upwards can make the ground or the volcano's slope begin to swell.

Sometimes, ground swelling reveals huge changes in the shape of a volcano. Most cases of ground deformation are subtle, though, and can only be detected by tiltmeters, which are instruments that measure the angle of the slope of a volcano. Additionally, ground swelling may cause increased rock falls and landslides. Gas Emissions[ edit ] Oftentimes, gases are able to escape a volcano before magma reaches the surface in an eruption. So, scientists can measure gas output, or gas emissions, in vents on or around the volcano. Gases, like sulfur dioxide (SO2), carbon dioxide (CO2), hydrochloric acid (HCl) and even water vapor can be measured at the site or, in some cases, at a distance with satellites. The amounts of gases and their ratios are calculated to help predict eruptions. Remote Monitoring[ edit ] As mentioned, some gases can be monitored using satellite technology (Figure 8.20). Satellites are able to measure other factors, too, like temperature readings of particularly warm spots at a volcano site or areas where the volcano surface is changing. As our technology continues to improve, scientists are better able to detect changes accurately and safely.

Figure 8.20: An Earth-observation satellite before launch. Although monitoring methods are getting better and better, it is still difficult to predict a volcanic eruption with certainty. No scientist or government agency wants to be considered alarmist by announcing that an eruption is going to occur and then it really doesn't. The cost and disruption to society of a large-scale evacuation would leave many people displeased and the scientists embarrassed. However, the possibility of saving lives and property most certainly makes the pursuit of eruption prediction a worthy cause. Lesson Summary[ edit ] Volcanoes are produced when magma rises towards the Earth's surface because it is less dense than the surrounding rock. Volcanic eruptions can be non-explosive or explosive depending on the viscosity of the magma. Explosive type eruptions happen along the edges of continents and produce tremendous amounts of material ejected into the air. Non-explosive type eruptions mostly produce various types of lava, such as a'a, pāhoehoe and pillow lavas. Some signs that a volcano may soon erupt include earthquakes, surface bulging, gases emitted as well as other changes that can be monitored by scientists. Review Questions[ edit ] What are the two basic types of volcanic eruptions?

Several hundred years ago, a volcano erupted near the city of Pompeii. Archaeologists have found the remains of people embracing each other, suffocated by ash and rock that covered everything. What type of eruption must have this been? What is pyroclastic material? Name three liquids that have low viscosity and three that have high viscosity. What is the difference between a magma chamber and a mantle plume? The boiling point of water is 100°C. Why might water make an eruption more explosive? What are three names for non-explosive lava? What factors are considered in predicting volcanic eruptions? Why is predicting volcanoes so important? Given that astronomers are far away from the subjects they study, what evidence might they look for to determine the composition of a planet on which a volcano is found? A rock made up of fragments of volcanic rock thrown into the air by volcanic eruptions. viscosity The "thickness" or "stickiness" of a liquid. The more viscous a liquid is, the harder it will be for the liquid to flow. Points to Consider[ edit ] What types of evidence do you think would tell scientists whether an ancient volcanic eruption was explosive or non-explosive?

Are all volcanoes shaped like tall mountains with a crater on the peak? What do you think is the origin of the names A'a and Pāhoehoe? Earthquakes do not always indicate that a volcano is going to erupt. What factors about an earthquake might indicate a relationship to a volcanic eruption? Weather Wiz Kids weather information for kids (Volcanoes are not associated with weather, but instead are natural disasters.) What is a volcano? 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. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash and floods. Volcano eruptions have been known to knock down entire forests. An erupting volcano can trigger tsunamis, flash floods, earthquakes, mudflows and rockfalls. Click Here to learn more about volcanoes from USGS. 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. Continental Drift: To see this animation again, just refresh this page! This animation shows you what our planet looked like millions of years ago and what it looks like now! (Graphic Credit: Geology Department at University of California, Berkeley) Click Here to learn more about plate tectonics and the drifting of our continents. 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? Volcanoes are grouped into four types: cinder cones, composite volcanoes, shield volcanoes and lava 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. Why does lava take a long time to cool down? 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. What is pumice?

Pumice is a light, porous volcanic rock that forms during explosive eruptions. It resembles a sponge because it consists of a network of gas bubbles frozen amidst fragile volcanic glass and minerals. All types of magma (basalt, andesite, dacite, and rhyolite) will form pumice. What is the largest active volcano? The world's largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils. Mauna Loa is 13,677 feet above sea level. From its base below sea level to its summit, Mauna Loa is taller than Mount Everest. What is the Ring of Fire? The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. The Ring of Fire has 452 volcanoes and is home to over 50% of the world's active and dormant volcanoes. Ninety percent of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire. When did Mount St. Helens erupt? On May 18, 1980, Mount St. Helens erupted.

It's located in southwestern Washington State in the Cascade Range. The blast was heard as far away as Montana, Idaho, Canada and California. Fifty-seven people died and the eruption caused $1.2 billion in damage. Click Here for more info on Mount St. Helens. What are some other notable volcano eruptions? Krakatoa was a dormant volcano in Indonesia, which awakened and produced one of the biggest volcanic eruptions in 1883. So massive was the eruption that the sound of it was heard as far away as Australia. Its widely reported as the loudest sound heard in recorded history. The Krakatoa eruption created a huge amount of ash cloud which covered the Earth and reduced global temperatures for 5 years! A total of 40,000 people died in that explosion and an entire chain of the volcanic island was destroyed. For more info: Click Here! Mount Pelee was a dormant volcano situated in the Caribbean island of Martinique. In 1902, it erupted in a massive horizontal explosion sending huge clouds of ash released towards the nearby town of Saint-Pierre.

The side of the volcano exploded and lava flowed straight into the town, killing 30,000 people in a matter of minutes. It is regarded as one of the biggest and most devastating volcanic eruptions of the 20th century, a benchmark for future eruptions. Mount Fujiyama, also popularly known as Mount Fuji, is an active volcano which last erupted in 1708. It is incidentally the tallest mountain in Japan. If you are visiting Tokyo, the capital of Japan, look in the west on a clear day and you will be able to see Mount Fuji. It is an iconic volcano. Mount Fuji is 3,776 meters high and it is snow clad throughout the year, with five lakes surrounding it. Currently in a state of dormancy, there has not been any eruption reported for more than 300 years. The last known eruption lasted for about 3 weeks during which it covered the surrounding villages with ash and cinders. Mount Fuji is now a popular tourist location with a large number of climbers actively scaling the mountain top. What is a tsunami? A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves.

Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage! Click Here to see an animation of an earthquake and the resulting tsunami. It's great for kids, because they get to see how it actually happens! Click Here to get the latest tsunami warning information from the NWS. Know the Lingo MAGMA - Magma is the liquid rock inside a volcano. LAVA - Lava is the liquid rock (magma) that flows out of a volcano. Lava glows red hot to white hot as it flows. ACTIVE VOLCANO - An active volcano is one that erupts regularly. DORMANT VOLCANO - A dormant volcano is one that has not erupted for many years, although there is still some activity deep inside. EXTINCT VOLCANO - An extinct volcano is a volcano that is no longer active. GEYSERS - Geysers are springs that throw boiling water high in the air. They are caused by volcanic heat warming trapped ground water.

ASH - Ash are very small fragments of lava or rock blasted into the air by volcanic explosions. PUMICE - It is a light-colored volcanic rock containing lots of bubbles from trapped gases. Click Here to see if there has been any recent volcanic activity across the U.S. Volcano Safety Tips PLAN FOR A VOLCANO: First of all, have a disaster plan and know whether or not you are at risk for danger. Be prepared for mudslides, flash floods, earthquakes, ash falling, acid rain and tsunamis. Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing, dust mask, goggles and sturdy shoes. Don't forget, know all of your evacuation routes. DURING A VOLCANO: Follow the evacuation order issued by authorities. Avoid areas downwind and river valleys downstream of the volcano. If your caught indoors, close all windows and doors, put machinery inside a barn, and bring animals inside. If youre trapped outdoors, seek shelter indoors. If youre caught in falling rocks, roll into a ball and protect your head.

If youre caught near a stream, be aware of mudflows and move to higher ground. Protect yourself when ash falls by wearing long-sleeved shirts and long pants. Use goggles to protect your eyes. Wear a dust mask and keep car engines off. AFTER A VOLCANO: Cover you mouth and nose. Volcanic ash can irritate your respiratory system. Wear goggles and protect your eyes. Keep your skin covered. Clear roofs of ash, because the ash is very heavy and can cause the building to collapse. Volcano Activities Lesson Plan: Here are great lesson plans on learning more about volcanoes. These are great lesson plans for elementary school students. Volcano Experiment: Here is an experiment on how to make a soda bottle volcano with Mentos. Volcano Experiment: Here is another experiment on how to make a baking soda volcano. Science Fair Project Ideas: Here is a complete list of science fair project ideas. Discover the science behind the weather that impacts us every day. USGS: Volcano Hazards Program Volcano Hazards Program Lava flows destroy everything in their path. La va flows typically move slowly enough to outrun them, but they will destroy everything in their path. Lava type dictates flow shape and travel distance.

Lava flows are streams of molten rock that pour or ooze from an erupting vent . Lava is erupted during either nonexplosive activity or explosive lava fountains . The speed at which lava moves across the ground depends on several factors, including (1) type of lava erupted and its viscosity; (2) steepness of the ground over which it travels; (3) whether the lava flows as a broad sheet, through a confined channel, or down a lava tube ; and (4) rate of lava production at the vent. Fluid basalt flows can extend tens of kilometers from an erupting vent . The leading edges of basalt flows can travel as fast as 10 km/h (6 mph) on steep slopes but they typically advance less than 1 km/h (0.27 m/s or about 1 ft/s) on gentle slopes. But when basalt lava flows are confined within a channel or lava tube on a steep slope, the main body of the flow can reach velocities >30 km/h (19 mph). Viscous andesite flows move only a few kilometers per hour (couple feet per second) and rarely extend more than 8 km (5 mi) from their vents .

Viscous dacite and rhyolite flows often form steep-sided mounds called lava domes over an erupting vent . Lava domes often grow by the extrusion of many individual flows >30 m (100 ft) thick over a period of several months or years. Such flows will overlap one another and typically move less than a few meters per hour. Lava flows may instigate other types of hazards. Everything in the path of an advancing lava flow will be knocked over, surrounded, buried, or ignited by the extremely hot temperature of lava . When lava erupts beneath a glacier or flows over snow and ice, meltwater from the ice and snow can result in far-reaching lahars . If it enters a body of water or water enters a lava tube , the water may boil violently and cause an explosive shower of molten spatter over a wide area. Methane gas, produced as lava buries vegetation, can migrate in subsurface voids and explode when heated. Thick viscous lava flows, especially those that build a dome , can collapse to form fast-moving pyroclastic flows . Deaths caused directly by lava flows are uncommon because most move slowly enough that people can move out the way easily.

Death and injury can result when onlookers approach an advancing lava flow too closely or their retreat is cut off by other flows. Deaths attributed to lava flows are often due to related causes, such as explosions when lava interacts with water, the collapse of an active lava delta that forms where lava enters a body of water, asphyxiation due to accompanying toxic gases, pyroclastic flows from a collapsing dome , and lahars from meltwater. Other natural phenomena such as hurricanes, tornadoes, tsunami , fires, and earthquakes often destroy buildings, agricultural crops, and homes, but the owner(s) can usually rebuild or repair structures and their businesses in the same location. Lava flows, however, can bury homes and agricultural land under tens of meters of hardened black rock; landmarks and property lines become obscured by a vast, new hummocky landscape. People are rarely able to use land buried by lava flows or sell it for more than a small fraction of its previous worth. Explainer: The volcano basics | Science News for Students Explainer: The volcano basics Oct 1, 2014 — 1:57 pm EST An ash burst coming from Washington’s Mount St. Helens in May 1982.

Lyn Topinka/ USGS A volcano is a spot in Earth’s crust where molten rock, volcanic ash and certain types of gases escape from an underground chamber. Magma is the name for that molten rock when it’s below ground. Scientists call it lava once that liquid rock erupts from the ground — and may start flowing across Earth’s surface. (It’s still “lava” even after it’s cooled and solidified.) Roughly 1,500 potentially active volcanoes exist across our planet, according to scientists at the U.S. Geological Survey, or USGS. About 500 volcanoes have erupted since humans have been keeping records. Of all volcanoes that have erupted in the past 10,000 years, roughly 10 percent reside in the United States. Most of them exist in Alaska (particularly in the Aleutian Island chain), in Hawaii and in the Cascade Range of the Pacific Northwest. But volcanoes are not just an Earthly phenomenon. Several large volcanoes rise above the surface of Mars. Mercury and Venus both show signs of past volcanism. And the most volcanically active orb in the solar system is not Earth, but Io.

It’s the innermost of the four largest moons of Jupiter. Indeed, Io has more than 400 volcanoes, some of which spew plumes of sulfur-rich material 500 kilometers (about 300 miles) into space. (Fun fact: The surface of Io is small, only about 4.5 times the area of the United States. So its volcano density would be about comparable to 90 continuously active volcanoes erupting across the United States.) Where do volcanoes form? Volcanoes can form on land or below the sea. Indeed, Earth’s biggest volcano lies submerged a mile below the ocean’s surface. Certain spots on our planet’s surface are especially susceptible to volcano formation. Most volcanoes, for instance, form at or near the edges — or boundaries — of Earth’s tectonic plates. These plates are large slabs of crust that jostle and scrape past each other. Their movement is driven largely by the circulation of the scalding, liquid rock in Earth’s mantle. That mantle is thousands of kilometers (miles) thick. It lies between our planet’s outer crust and its molten outer core. The edge of one tectonic plate may begin sliding beneath a neighboring one.

This process is known as subduction. The downward-moving plate carries rock back toward the mantle, where temperatures and pressures are very high. This disappearing, water-filled rock melts easily. Because the liquid rock is lighter than the surrounding material, it will try to float back up toward Earth’s surface. When it finds a weak spot, it breaks through. This creates a new volcano. Many of the world’s active volcanoes reside along an arc. Known as the “Ring of Fire,” this arc surrounds the Pacific Ocean. (In fact, it was the fiery lava erupting from volcanoes all along this boundary that inspired the arc’s nickname.) Along almost all sections of the Ring of Fire, a tectonic plate is shoving beneath its neighbor. Many more of the world’s volcanoes, especially those located far from the edge of any plate, develop over or near broad plumes of molten material that rise up from Earth’s outer core. These are called “mantle plumes.” They behave very much like the blobs of hot material in a “lava lamp.” (Those blobs rise from the heat source at the bottom of the lamp. When they cool, they fall back towards the bottom.) Many oceanic islands are volcanoes.

The Hawaiian Islands formed over one well-known mantle plume. As the Pacific plate gradually moved northwest over that plume, a series of new volcanoes punched their way through to the surface. This created the island chain. Today, that mantle plume fuels volcanic activity on the island of Hawaii. It’s the youngest island in the chain. A small fraction of the world’s volcanoes form where Earth’s crust is being stretched apart, as it is in East Africa. Tanzania’s Mount Kilimanjaro is a prime example. In these thin spots, molten rock can break through to the surface and erupt. The lava they exude can build, layer upon layer, to create tall peaks. How deadly are volcanoes? Throughout recorded history, volcanoes have probably killed about 275,000 people, according to a 2001 study led by researchers at the Smithsonian Institution in Washington, D.C. Scientists estimate that almost 80,000 of the deaths — not quite one in every three — were caused by pyroclastic flows. These hot clouds of ash and rock sweep down a volcano’s slopes at hurricane speeds.

Volcano-triggered tsunamis likely triggered another 55,000 deaths. These big waves can pose a threat to people living along coasts even hundreds of kilometers (miles) from the volcanic activity. Many volcano-related deaths happen in the first 24 hours of an eruption. But a surprisingly high fraction — about two in every three — occurs more than a month after an eruption begins. These victims may succumb to indirect effects. Such effects might include famines when crops fail. Or people may return to a danger zone and then die in landslides or during follow-up eruptions. Each of the past three centuries has seen a doubling of fatal volcanic eruptions. But volcanic activity has remained roughly constant during recent centuries. This suggests, the scientists say, that much of the increase in fatalities is due to population growth or to the decision of people to live (and play) near (or on) volcanoes. For instance, nearly 50 hikers died on September 27, 2014, while climbing Japan’s Mount Ontake. The volcano unexpectedly erupted . Some 200 other hikers escaped to safety. How big can a volcanic eruption be?

Some volcanic eruptions amount to small, relatively harmless puffs of steam and ash. At the other extreme are cataclysmic events. These can last for days to months, changing climate across the globe. Early in the 1980s, researchers invented a scale to describe the strength of a volcanic eruption. This scale, which runs from 0 to 8, is called the Volcanic Explosivity Index (VEI). Each eruption gets a number based on the amount of ash spewed, the height of the ash plume and the power of the eruption. For each number between 2 and 8, an increase of 1 corresponds to an eruption that’s ten times more powerful. For example, a VEI-2 eruption releases at least 1 million cubic meters (35 million cubic feet) of ash and lava. So a VEI-3 eruption releases at least 10 million cubic meters of material. Small eruptions pose a threat only to nearby regions. Small clouds of ash might wipe out a few farms and buildings on the slopes of a volcano or on the surrounding plains. They also might smother crops or grazing areas. That could trigger a local famine. Larger eruptions pose different types of hazards.

Their ash can spew dozens of kilometers from the peak. If the volcano is topped with snow or ice, lava flows can melt it. That can create a thick mix of mud, ash, soil and rocks. Called a lahar, this material has a consistency like wet, newly mixed concrete. It can flow far from the peak — and destroy anything in its path. Nevado del Ruiz is a volcano in the South American nation of Colombia. Its eruption in 1985 created lahars that destroyed 5,000 homes and killed more than 23,000 people. The lahars’ effects were felt in towns up to 50 kilometers (31 miles) from the volcano. A volcano’s threats can even extend into the sky. Ash plumes can reach altitudes at which jets fly. If ash (which actually is tiny bits of broken rock) gets sucked into an aircraft’s engine, high temperatures there can re-melt the ash. Those droplets can then solidify when they hit the engine’s turbine blades. This will disrupt the flow of air around those blades, causing the engines to fail.

(That’s not something anyone would like to experience when they are several kilometers in the air!) What’s more, flying into a cloud of ash at cruising speed can effectively sandblast a plane’s front windows to the point that pilots can no longer see through them. Finally, a really big eruption can affect global climate. In a very explosive eruption, particles of ash can reach altitudes above where rains are available to quickly wash them from the air. Now, these ash bits can spread around the world, diminishing how much sunlight reaches Earth’s surface. This will cool temperatures globally, sometimes for many months. Besides spewing ash, volcanoes also emit a witches’ brew of noxious gases, including carbon dioxide and sulfur dioxide. When sulfur dioxide reacts with the water vapor spewed by eruptions, it creates droplets of sulfuric acid. And if those droplets make it to high altitude, they too can scatter sunlight back into space, cooling climate even more. It’s happened. In 1600, for instance, a little-known volcano in the South American nation of Peru erupted. Its ash plumes cooled global climate so much that many parts of Europe had record-setting snowfalls the next winter.

Large portions of Europe also suffered unprecedented floods the next spring (when the snow melted). Heavy rains and cool temperatures during the summer of 1601 ensured massive crop failures in Russia. The famines that followed lasted through 1603. In the end, this one eruption’s impacts resulted in the deaths of an estimated 2 million people — many of them half a world away. (Scientists didn’t make the connection between the Peruvian eruption and the Russian famines until several years after the 2001 study that estimated the death tolls from all volcanoes in recorded history.) Power Words BBC Earth - Lava - See close-up video of molten lava flows Liz Bonnin gets a close look at hot, molten lava flowing from Mount Kilauea. Liz Bonnin gets a close look at hot, molten lava flowing from Mount Kilauea in Hawaii. Lava Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is also called lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites. The source of the heat that melts the rock within the earth is geothermal energy.

When first erupted from a volcanic vent, lava is a liquid usually at temperatures from 700 to 1,200 °C (1,292 to 2,192 °F). A lava flow is a moving outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. The term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic and shear thinning properties. Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is probably derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma (molten rock below the Earth's surface) was apparently in a short account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4, 1737.

Serao described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain. 1000+ images about Liquid Land on Pinterest | Active volcano, Islands of hawaii and Nature Forward Hawaii is known for its enchanting waterfalls, but the Big Island just took cascades to a whole new level. Behold: lavafalls. The fiery falls, as seen in the video above, are from a lava flow that began erupting from Kilauea Volcano on June T... See More

Question: What is the fiery liquid that flows from a volcano?
Answer: Lava