Conversational volcano (less challenging) Lava Magma Pyroclastic Flow Lava bomb Acid rain Convection Volcanic ash Volcanic gases The hot molten fluid rock that erupts from a volcano or volcanic fissure. Lava is what magma is called once it is on the surface! Most lavas move at 3-6mph so can usually be avoided by people, in fact nobody is recovered as ever having been killed by a lava flow it is usually volcanic gases, pyroclastic flows, tsunamis and lahars that are the most deadly. The hot molten rock stored within the Earth s crust. It is stored within magma chambers of volcanoes, and it develops within Earth s mantle or crust and then rises to the surface. Magma is between 600-1300 C, and so is lava when it is first erupted but then starts to cool. The type of magma to be erupted depends on the minerals dissolved within it, which depends on location. Literally pyro meaning fire, clastic meaning rock fragments, this is an extremely hot, dense flow of gases and rock pieces that travels down the slope of a volcano and is capable of travelling up to 400mph and at temperatures of 200-1000 C. These are near impossible to avoid, and deadly. This is what destroyed places such as Pompeii & Herculaneum. When molten lava splatters are ejected from the volcano and as they travel through the air the outer surface cools and solidifies. Lava bombs can range from a few centimetres to the size of cars, and may explode out liquid lava from inside when they land. Volcanic gases such as SO2 and CO2 are emitted from volcanoes and mix with atmospheric water to form acidic rain. Earth s mantle of liquid rock is fluid and constantly moving. Convection is this movement of hot liquid mantle rock cycling around under the Earth s crust. It happens because the core is hottest, and this gives heat energy to the mantle so that it rises and moves towards the crust. Here it is cooler so the mantle becomes more dense and sinks, only to be heated again near the core and the cycle continues. As the mantle convects it causes the tectonic plates of the Earth s crust to move. Small (less than 2mm) solid particles that are ejected from an erupting volcano. Think of it like the leftover ash you get from a bonfire. Volcanic ash is released during explosive s when the gases in the erupting lava expand rapidly as they escape. Ash creates very fertile soil. Eruptions release many gases that are trapped within the magma, for example H20 water vapour (strange to think of water inside hot magma!), CO2 carbon dioxide, SO2 sulfur dioxide, hydrogen sulphide, nitrogen, argon, methane, carbon monoxide, hydrogen chloride, etc. These gases are toxic, and can travel many miles inside ash clouds or columns as they disperse in the air. Extra info: They can also dissolve into water, to create acidic rain or acidic water sources. Gases can be deadly, for example carbon dioxide is dense and so sinks to the ground when Mount Nyiragongo erupted this led to many children dying in a playground from suffocation.
Mudflows / mudslides Explosive Effusive Fissure Caldera Stratovolcano / composite Shield volcano Subduction Divergent plate boundary Convergent plate boundary Tectonic plates When volcanoes erupt in areas that are covered in ice these will melt, mix with mud and cause mudslides/flows that power down the slopes. Mudflows are a mix of ash, mud and rock and can travel up to 40mph. This is when the volcano erupts in a more dramatic way, because the magma is more thick (viscous) and gassy. When the magma is erupting, it cannot get out quickly enough to keep up with the pressure and so often explodes out vertically (creating big columns and ash clouds) or horizontally (creating pyroclastic flows). This magma builds up steep-sided volcanoes over time, like Vesuvius. This is a more gentle, where magma is hotter and thinner/more fluid and less gassy so lava can escape the volcanic vent more easily and gently, mostly as lava flows and fountains. This usually happens at fissure s or at shield volcanoes, building shallow slopes over time, like Kilauea. A fissure is a split or rift in the Earth s crust that allows magma to escape. These fissures can be close to the volcano or far away, and they are fed magma from underground through lava tunnels/pipes. The lava can escape as fire fountains or as slow moving heavy flows (like Kilauea in Hawaii or Laki in Iceland). They are often found along shield volcanoes. A large volcanic crater, shaped like a bowl or cauldron, that is formed when a massive leads to the top of the volcano (the cone) collapsing and becoming wider and wider. E.g. Askja in Iceland. A type of volcano that is very steep sided with a cone shape and is formed through different layers of ash and lava building up over the years. 60% of Earth s volcanoes are stratovolcanoes. They often have explosive s, e.g. Eyjafjallajökull in Iceland, Etna in Sicily. A gently sloping, broad dome-shaped (or shield shaped) volcano that has gentle sides and is usually formed by gentle effusive s of thin fluid lava, e.g. Kilauea in Hawaii. The shield volcano is the largest type of volcano on Earth, like Mauna Loa in Hawaii which is the largest volcano. When tectonic plates meet at a convergent (destructive) plate boundary, and the heavier / more dense plate sinks beneath a lighter plate. At this point, the sinking plate melts due to friction and heat, creating volcanoes. This usually happens when oceanic plates meet continental plates, such as in Japan. Also known as constructive boundaries, this is when two tectonic plates are moving away from each other and as they separate this allows magma from the mantle to rise to the surface and create volcanoes or volcanic fissures. For example, the Mid-Atlantic Ridge runs through Iceland, with Iceland being part North American and part Eurasian plate. Also known as destructive this is when two tectonic plates are colliding together. As they move together the plates collide and force one plate to subduct (sink) beneath another. The pieces of Earth s crust which float on the hot magma and move around. Plates under the ocean are known as oceanic plate and are more dense and thicker (because they are newer, with new land being created constantly through underwater divergent s) whereas continental plates are under the land and are lighter, less dense.
Professional volcano (more challenging) Laze Literally Lava haze. When lava flows interact with sea water, to heat the water and create toxic chloride gas (also known as mustard gas). Vog Volcano fog. The foggy air pollution is caused by volcanic gases such as CO2, H20, SO2 which interact with atmospheric oxygen, sunlight and other gases to create a haze that stings your eyes. Reticulite pumice A volcanic rock characterised by having a really high volume of gas bubbles. The reticulitis forms when ejected lava is forced to cool abruptly and solidify so rapidly that the gas bubbles cannot escape. This leaves a very fragile glass or form of basaltic pumice. However, unlike true pumice the reticulite cannot float even though it is the least dense rock on Earth! A a lava A Hawaiian word pronounced as ah-ah that literally means lava that is difficult to walk on. This type of lava forms when lava flows rapidly, and then cools rapidly to leave chunky angular pieces of jagged cooled lava rock. A a lava is more viscous and can be explosive because the gases are trapped and cannot escape so easily. Pahoehoe lava A Hawaiian word pronounced paw-hoey-hoey that literally means lava that is easy to walk on. This type of lava forms when lava flows more slowly, so the lava develops a sort of skin and looks like fluid rock or smooth rope when it cools. Pahoehoe is less viscous, so more fluid than aa because it is less gassy. Pillow lava A type of lava that forms during submarine s. As the lava is erupted under water, it cools more quickly to form a rounded pillow-like shape which can float to the surface. Pyroclastic surge Often we only talk about pyroclastic flows, but there are also pyroclastic surges that are similar but instead there is a higher proportion of gas to rock. This means the surge is lighter so can move even faster, and it contains even more hot toxic gases so the movement is very turbulent. If it helps, think like this: a pyroclastic flow is like a rocky soup flowing downhill (still very fast), whereas the surge is like a chaotic cloud of grey ash and gases billowing down the slope. Both forms are deadly. Tephra The more accurate term for volcanic ash (it comes from the Greek for ash ) it is a more general term for all rock fragments and particles that are ejected during an. The largest fragments can include lava bombs over 6cm, whereas the smallest material is volcanic ash which has particles less than 2mm. Volcanic plume Extra info: Different materials can travel different distances due to their size and weight, so volcanic ash can travel the furthest at it floats and is blown by the wind (which is why it can travel the globe), whereas lava bombs and large rocks fall out nearer the site of the. When volcanoes erupt there is a mixture of gases and particles like tephra that are ejected. Due to the energy of the volcano and how rapidly the gases expand as they reach the surface this can create large plumes that can reach up to 80km high before the material falls back to earth. More importantly, because these plumes can travel so far and so high they can interact with Earth s atmosphere which changes the chemistry and can alter the amount of solar radiation we receive. Extra info: For example, when Mount Pinatubo erupted in 1991 it caused Earth s temperature to drop by 0.6 C for two years, and when Mount Tambora erupted in 1813 it caused the year without a summer for the whole of Europe with cold temperatures, darkness, and storms.
This is also known as an column. It can create hazards for aircraft, etc. Lahars A more technical name for a mudflow. In this case, the lahar is a hot or cold flow of concrete-like mixtures of mud and rock and water that flow downhill up to 40mph and can travel for many miles. They have enough energy to blast through buildings, carry boulders, and bury places. Sometimes lahars can happen weeks or months after an to create secondary mudflows. Extra info: When Nevado del Ruiz erupted in 1985 lahars buried an entire town and killed more than 20000 people. Lahars can happen weeks or months after an, such as in locations like Guatemala that have heavy rains which loosen the volcanic ash and mud left behind after an to create secondary mudflows. Phreatomagmatic This is when magma interacts with water, when a volcano erupts under water or ice. This causes magma to cool quickly and the gases to expand outwards, leading to explosive s. This happened at Eyjafjallajökull in Iceland in 2010 when the volcano erupted under ice. Basaltic Andesitic Rhyolitic Felsic vs mafic Jökulhlaup Hawaiian Surtseyan Plinian This is also known as mafic, and it is low in silica and high in iron and magnesium. The rock is less gassy, and dissolved gases can escape more easily from the thinner lava when it erupts. The is less viscous (less sticky) and so more fluid, and has non-explosive s often with fire fountains. The is usually hotter, at 1000-1200 C. Basaltic magma is usually found in submarine or shield volcanoes. This is an intermediate viscosity type, being slightly higher in silica than basaltic and less than rhyolitic. It is also of medium temperature, around 800-1000 C and of medium gas content. So it can be less explosive than rhyolitic but less runny lava than basaltic. This type has high silica content, and so is more viscous and less runny. It is lower temperature, between 650-800 C. It has a high gas content and so can explode violently (often creating lots of pumice. Because the magma is thick and sticky, it tends to ooze out and pile up to create lava domes. This is usually found at stratovolcanoes. It sometimes cools to form glassy obsidian. Felsic magma is rich in silica minerals such feldspar and quartz and produces granite when it cools, while mafic magma is rich in magnesium and iron and forms basalt when it cools. An Icelandic term for an ice flood, this can be caused when volcanic activity under a glacier melts the ice to create a sudden flood. A type of volcanic where lava flows out relatively gently in an effusive, as is most characteristic of Hawaiian volcanoes and other shield volcanoes. These are usually basaltic magmas and usually happens at hotspots like Hawaii, and subduction zones like Iceland (which is also a hotspot too). These s take place in shallow seas or under lakes. The lava heats the water, creating hot steam flashes and gas expansion to create lots of ash clouds. It is named after the island of Surtsey off the coast of Iceland. Also known as Vesuvian s, these have massive columns of tephra and gases that can reach high into the stratosphere and then deposit vast amounts of ash and pumice for miles. The lava is usually rhyolitic and full of silica and so s are explosive.
Strombolian Vulcanian Cinder cone Named after the Italian volcano Stromboli off the coast of Sicily. These are more gentle s similar to Hawaiian, although more viscous than Hawaiian, and they consist of fire fountains and rock fragments and gas bubbles that burst out through the lava. The can be very long lasting since it is low level, for example you can climb Stromboli and watch it erupt (from a little distance). Named after the Italian Vulcano, these s are very short and violent. The is usually caused by magma exploding out through some sort of blockage like a lava plug or dome that covers the main volcanic vent. The magma is viscous and gasses so builds up a high pressure, almost like popping a cork off a bottle. These s cause lava bombs and large blocks to be ejected, with tall columns. This type of volcano builds up from particles of lava and rock that have erupted from the main volcano, from its cinders. They are usually found on the slopes of other volcanoes, and have very small activity. If you like this activity, make sure you check out our video Living in the Shadow of Italy s Volcanoes >