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Jai Ganesh

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Lava

Lava

Gist

In geography, lava refers to molten rock, or magma, that erupts onto the Earth's surface, typically through a volcano. It's a key component of volcanic activity and plays a significant role in shaping the Earth's surface and forming various geological features.

Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth's surface.

Lava is molten rock ejected by volcanoes in the form of a liquid. Once it emerges on the Earth's surface, it flows and gradually cools down, consuming objects along its path.

Summary

Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C (1,470 to 2,190 °F). The volcanic rock resulting from subsequent cooling is often also called lava.

A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing.

Details

Lava is magma (molten rock) emerging as a liquid onto Earth’s surface. The term lava is also used for the solidified rock formed by the cooling of a molten lava flow. The temperatures of molten lava range from about 700 to 1,200 °C (1,300 to 2,200 °F). The material can be very fluid, flowing almost like syrup, or it can be extremely stiff, scarcely flowing at all. The higher the lava’s silica content, the higher its viscosity.

Mafic (ferromagnesian, dark-coloured) lavas such as basalt characteristically form flows known by the Hawaiian names pahoehoe and aa (or a’a). Pahoehoe lava flows are characterized by smooth, gently undulating, or broadly hummocky surfaces. The liquid lava flowing beneath a thin, still-plastic crust drags and wrinkles it into tapestry-like folds and rolls resembling twisted rope. Pahoehoe lava flows are fed almost wholly internally by streams of liquid lava flowing beneath a solidified or partly solidified surface. Typically, the margin of a pahoehoe flow advances by protruding one small toe or lobe after another.

In contrast to pahoehoe, the surface of aa lava is exceedingly rough, covered with a layer of partly loose, very irregular fragments commonly called clinkers. Aa lava flows are fed principally by rivers of liquid lava flowing in open channels. Typically, such a feeding river forms a narrow band that is 8 to 15 metres (25 to 50 feet) wide along the centre line of the flow, with broad fields of less actively moving clinker on each side of it. At the front of the flow, clinkers from the top roll down and are overridden by the pasty centre layer, like a tread on an advancing bulldozer.

Pahoehoe and aa flows from the same erupting vent are usually identical in chemical composition. In fact, it is common for a flow that leaves the vent as pahoehoe to change to aa as it progresses downslope. The greater the viscosity and the greater the stirring of the liquid (as by rapid flow down a steep slope), the greater the tendency for the material to change from pahoehoe to aa. The reverse change rarely occurs.

A third type of mafic lava, pillow lava, is named for the pillow-shaped masses that form underwater as highly fluid lava is quenched by the surrounding water.

Lavas of andesitic or intermediate composition commonly form a somewhat different type of flow, known as a block lava flow. These resemble aa in having tops consisting largely of loose rubble, but the fragments are more regular in shape, most of them polygons with fairly smooth sides. Flows of more siliceous lava tend to be even more fragmental than block flows.

Thin basaltic lava flows generally contain many holes, or vesicles, left by bubbles of gas frozen into the congealing liquid. Thick flows, which remain hot for long periods, may lose most of their gas before the lava congeals, and the resulting rock may be dense with few vesicles.

Pyroclastic flows, which are low-viscosity, fluidized mixtures of hot but solid volcanic fragments and hot gas, are often described in newspaper accounts as lava flows. This causes much confusion. Molten lava flows are relatively high-viscosity liquids, and most of them advance slowly (a few metres per minute to less than a metre per day). Pyroclastic flows move more like a dense, low-viscosity gas pouring down a slope and even move upslope if they have enough momentum; their downslope velocities often exceed 100 km (60 miles) per hour.

Additional Information:

What is Lava?

Lava is a hot, molten rock that is expelled from volcanoes. It is made up of several elements, including silicon, oxygen, aluminium, magnesium, and iron. The temperature of Lava can reach up to 2,000 degrees Celsius! When Lava cools, it forms a rock called igneous rock. Lava is very dangerous because it can destroy anything in its path. When Lava meets water, it can create steam explosions that can shoot rocks and debris hundreds of metres into the air. Lava is an important part of the Earth’s cycle. It helps to create new landforms and can even be used to produce electricity!

Composition Of Lava

Lava is molten rock that has been expelled from the Earth’s surface through an opening or vent. The molten rock, called magma when it is underground, rises to the surface when the pressure on the magma becomes too much. When the upper mantle melts, magma is formed. This can actually occur when the earth’s burning core heats the mantle, and then when it comes in contact with molten rock from an immediately preceding eruption. The molten rock that makes up lava is made up of various minerals, including feldspar, quartz, and olivine. The composition of lava varies depending on the type of rocks that make up the mantle and the temperature of the magma. Basaltic lava, for example, is made up of rocks from the mantle that has a low silica content. Andesitic lava, on the other hand, is made up of rocks from the mantle that has a high silica content. The chemical composition of the lava is similar to that of magma, but it also contains small amounts of gas. The most common gases found in lava are carbon dioxide, water vapour, and sulphur dioxide. Lava also contains trace amounts of other elements, including potassium, sodium, calcium, and magnesium. The composition of lava can vary depending on the type of volcano that it comes from. For example, shield volcanoes tend to produce lava with a high silica content, while cinder cone volcanoes tend to produce lava with low silica content. The physical and chemical composition of lava makes it a very dangerous substance. Lava can destroy anything in its path, and when it comes into contact with water, it can create steam explosions that can shoot rocks and debris hundreds of metres into the air. Lava is an important part of the Earth’s cycle, but it is also a force to be reckoned with.

Properties Of Lava

Lava is very hot, with a temperature that can reach up to 2000 degrees Celsius. It is also very viscous, meaning that it flows slowly. Lava can be either effusive or explosive. Effusive lava flows slowly and calmly, while explosive lava is very violent and can shoot rocks and debris into the air. Lava is also very dangerous because it can destroy anything in its path. When lava meets water, it can create steam explosions that can shoot rocks and debris hundreds of metres into the air.

Formation Of Lava

Lava is formed when the earth’s mantle (a layer of solid rock) melts. This can happen when the mantle is heated by the earth’s hot core, or when it comes into contact with magma from a previous eruption. The molten rock that makes up lava is made up of various minerals, including feldspar, quartz, and olivine. The composition of lava varies depending on the type of rocks that make up the mantle and the temperature of the magma. Basaltic lava, for example, is made up of rocks from the mantle that has a low silica content. Andesitic lava, on the other hand, is made up of rocks from the mantle that has a high silica content.

Hazards

Lava can pose a significant hazard to people and property. When active, lava flows can destroy houses, trees, and other objects in their paths. Lava flows can also dam rivers and create lakes. These lava dams can cause flooding downstream if they suddenly break. People can be injured or killed if they get too close to an active lava flow. Lava flows can also release poisonous gases into the air, which can be harmful to people and animals.

Conclusion

Lava is molten rock that emerges from a volcano. It is the result of the earth’s hot core heating groundwater, which in turn melts solid rocks found near the surface. The molten rock (lava) flows downhill and can erupt explosively from a vent in the Earth’s surface. Lava composition varies depending on the type of eruption and what kind of rocks make up the Earth’s surface. Igneous rocks are made up of cooled lava, so by studying different types of igneous rocks, we can learn about past eruptions.

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