Lava temperature. What is volcanic lava and what does it consist of? What happens to the human body in a lava flow
The question of what lava is has been of interest to many scientists for a long time. The composition of this substance, as well as its shape, speed of movement, temperature and other aspects have become the subject of a number of studies and scientific works. This can be explained by the fact that it is its frozen flows that represent almost the only source of information regarding the state of the Earth’s interior.
General concept
First, you need to figure out what lava is in the modern sense? Scientists call it the material in a molten state located in the upper part of the mantle. While in the bowels of the earth, the composition of the substance is homogeneous, but as soon as it approaches the surface, the process of boiling begins with the release of gas bubbles. They are the ones who move the hot material towards the cracks in the bark. However, not all of the liquid erupts to the surface. Speaking about the meaning of the word “lava”, it should be noted that this concept applies only to the spilled part of the matter.
Basalt lava
The most common type on our planet is basaltic lava. Most of all the geological processes that occurred on Earth many thousands of years ago were accompanied by numerous eruptions of this particular type of hot substance. After it solidified, a black rock of the same name was formed. Half the composition of basaltic lavas is magnesium, iron and some other metals. Due to them, the melt temperature reaches about 1200 degrees. At the same time, the lava flow moves at a speed of about 2 meters per second, which is comparable to a running person. As studies show, in the future they move much faster in the so-called “hot pursuit”. Basaltic lava from the volcano is thin. It flows quite far (up to several tens of kilometers from the crater). It should be noted that this variety is typical for both land and ocean.
Acidic lava
In the case when the substance contains 63% or more silica, it is called acidic lava. The heated material is very viscous and practically incapable of flow. The speed of the flow often does not even reach several meters per day. The temperature of the substance is in the range from 800 to 900 degrees. Melts of this kind are associated with the formation of unusual rocks (ignimbrites, for example). If acidic lava becomes highly saturated with gas, it boils and becomes mobile. After being ejected from the crater, it quickly flows back into the resulting depression (caldera). The consequence of this is the appearance of pumice - an ultra-light material whose density is less than that of water.
Carbonate lava
Speaking about what lava is, many scientists still cannot determine the principle of formation of its carbonate variety. This substance also contains sodium. It erupts from only one volcano on the planet - Oldoinyo Lengai, which is located in Northern Tanzania. Carbonate lava is the most liquid and cold of all existing types. Its temperature is approximately 510 degrees, and it moves along the slopes at the same speed as water. Initially, the substance has a dark brown or black color, but after just a few hours of being on the outside it becomes lighter, and after a few months it turns completely white.
Conclusions
To summarize, we should focus on the fact that one of the most pressing geological problems is associated with lava. It lies in the fact that this substance heats up the bowels of the earth. Foci of hot material rise to the earth's surface, after which they melt it and form volcanoes. Even the world's leading scientists cannot give a clear answer to the question of what lava is. At the same time, we can say for sure that it is only a tiny part of a global process, the driving force of which is hidden very deep underground.
Lava is molten rock ejected from the depths of a volcano during an eruption and turns into hardened rock after cooling. During an eruption directly from the volcano's nozzle, the temperature of the lava reaches 1200 degrees Celsius. Molten lava flowing down a slope can be 100,000 times faster than water before it cools and solidifies. In this collection you will find bright and beautiful photographs of erupting lava from various parts of our planet.
Lava flows occur during a non-explosive expansive eruption. When the hot rock cools, it hardens to form igneous rock. It is composition rather than eruption temperature that determines the behavior of lava flows. Below you will find many amazing photos for which brave photographers braved extreme temperatures. Many of the images were taken in seismically active locations such as Iceland, Italy and Mount Etna and of course Hawaii. Here, for example, is the volcano with the longest name: Eyjafjallajökull in Iceland:
Lava Lake, Mount Nyiragongo, Democratic Republic of Congo:
One of the many volcanoes in the National Park called Hawaiian Volcanoes:
Hawaii again:
Mount Etna, Sicily, Italy:
Iceland:
Volcano Pacaya, Guatemala:
Kiluea Volcano, Hawaii:
Inside a hot cave, Hawaii:
Another hot lava lake in Hawaii:
Lava fountain of Eyjafjallajökull volcano:
Mount Etna:
A stream burning everything in its path, Mount Etna:
Photos from Iceland again:
Etna, Sicily:
Etna, Sicily:
Erupting volcano in Hawaii:
Eyjafjallajökull:
Puu Kahaualea, Hawaii:
Big Island of Hawaii:
A lava flow flows straight into the ocean, Hawaii.
In today's article we will look at the types of lava based on temperature and viscosity.
As you probably know, lava is molten rock that erupts from an active volcano onto the surface of the earth.
The outer shell of the globe is the earth's crust; underneath it lies a hot, liquid layer called the mantle. Hot magma makes its way to the top through cracks in the earth's crust.
The entry points of hot magma into the earth's surface are called "hot spots", which means hot spots
(pictured left). This usually occurs within the boundaries between tectonic plates and gives rise to entire volcanic chains.What is the temperature of the lava?
Lava has a temperature of 700 to 1200C. Depending on the temperature and composition, lava is divided into three types of fluidity.
Liquid lava has the highest temperature, more than 950C, and its main component is basalt. With such a high temperature and fluidity, lava can flow for several tens of kilometers before it stops and hardens. Volcanoes that erupt this type of lava are often very gentle, since it does not linger at the vent, but spreads around.
Lava with a temperature of 750-950C is andesitic. It can be recognized by its frozen round blocks with a broken crust.
Lava with the lowest temperature of 650-750C is acidic and very rich in silica. A characteristic feature of this lava is its slow speed and high viscosity. Very often, during an eruption, this type of lava forms a crust over the crater (pictured on the right). Volcanoes with this temperature and type of lava often have steep slopes.
Below we will show you some photos of hot lava.
Scientists have been interested in lava for a long time. Its composition, temperature, flow speed, shape of hot and cooled surfaces are all subjects for serious research. After all, both erupting and frozen streams are the only sources of information about the state of the interior of our planet, and they constantly remind us of how hot and restless these interiors are. As for the ancient lavas, which have turned into characteristic rocks, specialists are looking at them with particular interest: perhaps, behind the bizarre relief, the secrets of catastrophes on a planetary scale are hidden.
What is lava? According to modern ideas, it comes from a center of molten material, which is located in the upper part of the mantle (the geosphere surrounding the Earth's core) at a depth of 50-150 km. While the melt remains in the depths under high pressure, its composition is homogeneous. Approaching the surface, it begins to “boil”, releasing gas bubbles that tend upward and, accordingly, move the substance along cracks in the earth’s crust. Not every melt, otherwise known as magma, is destined to see the light. The same one that finds its way to the surface, pouring out into the most incredible forms, is called lava. Why? It's not entirely clear. In essence, magma and lava are the same thing. In the “lava” itself one hears both “avalanche” and “collapse”, which, in general, corresponds to the observed facts: the leading edge of flowing lava often really resembles a mountain collapse. Only it’s not cold cobblestones that roll down from the volcano, but hot fragments that fly off the crust of the lava tongue.Over the course of a year, 4 km 3 of lava pours out of the depths, which is quite a bit, considering the size of our planet. If this number were significantly larger, the processes of global climate change would begin, which has happened more than once in the past. In recent years, scientists have been actively discussing the following disaster scenario at the end of the Cretaceous period, approximately 65 million years ago. Then, due to the final collapse of Gondwana, in some places the hot magma came too close to the surface and erupted in huge masses. Its outcrops were especially abundant on the Indian platform, which was covered with numerous faults up to 100 kilometers long. Almost a million cubic meters of lava spread over an area of 1.5 million km 2. In some places the covers reached a thickness of two kilometers, which is clearly visible from the geological sections of the Deccan Plateau. Experts estimate that the lava filled the area for 30,000 years - fast enough for large portions of carbon dioxide and sulfur-containing gases to separate from the cooling melt, reach the stratosphere and cause a decrease in the ozone layer. The subsequent dramatic climate change led to mass extinction of animals at the border of the Mesozoic and Cenozoic eras. More than 45% of the genera of various organisms have disappeared from the Earth.
Not everyone accepts the hypothesis about the influence of lava flow on climate, but the facts are clear: global extinctions of fauna coincide in time with the formation of extensive lava fields. So, 250 million years ago, when a mass extinction of all living things occurred, powerful eruptions occurred in Eastern Siberia. The area of lava covers was 2.5 million km 2, and their total thickness in the Norilsk region reached three kilometers.
Black blood of the planetThe lavas that caused such large-scale events in the past are represented by the most common type on Earth - basalt. Their name indicates that they subsequently turned into a black and heavy rock - basalt. Basaltic lavas are half made of silicon dioxide (quartz), half of aluminum oxide, iron, magnesium and other metals. It is the metals that provide the high temperature of the melt - more than 1,200 ° C and mobility - the basalt flow usually flows at a speed of about 2 m/s, which, however, should not be surprising: this is the average speed of a running person. In 1950, during the eruption of the Mauna Loa volcano in Hawaii, the fastest lava flow was measured: its leading edge moved through sparse forest at a speed of 2.8 m/s. When the path is paved, the following streams flow, so to speak, in hot pursuit much faster. Merging, lava tongues form rivers, in the middle reaches of which the melt moves at high speed - 10–18 m/s.
Basaltic lava flows are characterized by a small thickness (a few meters) and a large extent (tens of kilometers). The surface of flowing basalt most often resembles a bunch of ropes stretched along the movement of lava. It is called the Hawaiian word "pahoehoe", which, according to local geologists, does not mean anything other than a specific type of lava. More viscous basaltic flows form fields of sharp-angled, spike-like lava fragments, also called "aa lavas" in Hawaiian fashion.
Basaltic lavas are not only common on land; they are even more common in the oceans. The ocean floors are large slabs of basalt 5–10 kilometers thick. According to American geologist Joy Crisp, three-quarters of all lavas erupting on Earth each year come from underwater eruptions. Basalts constantly flow from the cyclopean ridges that cut through the ocean floors and mark the boundaries of lithospheric plates. No matter how slow the plate movement, it is accompanied by strong seismic and volcanic activity on the ocean floor. Large masses of melt coming from ocean faults do not allow the plates to become thinner, they are constantly growing.
Underwater basalt eruptions show us another type of lava surface. As soon as the next portion of lava splashes out to the bottom and comes into contact with water, its surface cools down and takes the form of a drop - a “pillow”. Hence the name - pillow lava, or pillow lava. Pillow lava forms whenever molten material enters a cold environment. Often during a subglacial eruption, when the flow rolls into a river or other body of water, the lava solidifies in the form of glass, which immediately bursts and crumbles into plate-like fragments.
Vast basalt fields (traps) hundreds of millions of years old hide even more unusual forms. Where ancient traps come to the surface, as, for example, in the cliffs of Siberian rivers, you can find rows of vertical 5- and 6-sided prisms. This is a columnar separation that is formed during the slow cooling of a large mass of homogeneous melt. Basalt gradually decreases in volume and cracks along strictly defined planes. If the trap field, on the contrary, is exposed from above, then instead of pillars, surfaces appear as if paved with giant paving stones - “pavements of giants”. They are found on many lava plateaus, but the most famous are in the UK.
Neither the high temperature nor the hardness of solidified lava serves as an obstacle to the penetration of life into it. In the early 90s of the last century, scientists found microorganisms that settle in basalt lava that erupted at the bottom of the ocean. As soon as the melt cools down a little, the microbes “gnaw” passages in it and establish colonies. They were discovered by the presence in basalts of certain isotopes of carbon, nitrogen and phosphorus - typical products released by living beings.
The more silica in lava, the more viscous it is. The so-called medium lavas, with a silicon dioxide content of 53–62%, no longer flow as fast and are not as hot as basaltic lavas. Their temperature ranges from 800 to 900°C and their flow speed is several meters per day. The increased viscosity of lava, or rather magma, since the melt acquires all its basic properties at depth, radically changes the behavior of the volcano. From viscous magma, it is more difficult to release the gas bubbles accumulated in it. On approaching the surface, the pressure inside the bubbles in the melt exceeds the pressure on them outside and the gases are released with an explosion.
Typically, a crust forms at the leading edge of the more viscous lava tongue, which cracks and crumbles. The fragments are immediately crushed by the hot mass pressing behind them, but do not have time to dissolve in it, but harden like bricks in concrete, forming a rock with a characteristic structure - lava breccia. Even after tens of millions of years, lava breccia retains its structure and indicates that a volcanic eruption once occurred in this place.In the center of Oregon, USA, there is the Newberry volcano, which is interesting because of its lavas of intermediate composition. The last time it was active was more than a thousand years ago, and at the final stage of the eruption, before falling asleep, a lava tongue 1,800 meters long and about two meters thick flowed out of the volcano, frozen in the form of pure obsidian - black volcanic glass. Such glass is obtained when the melt cools quickly without having time to crystallize. Additionally, obsidian is often found on the periphery of a lava flow, which cools faster. Over time, crystals begin to grow in the glass and it turns into one of the acidic or intermediate rocks. That is why obsidian is found only among relatively young eruption products; it is no longer found in ancient volcanics.
From damn fingers to fiamme
If the amount of silica occupies more than 63% of the composition, the melt becomes completely viscous and clumsy. Most often, such lava, called acidic, is not able to flow at all and solidifies in the supply channel or is squeezed out of the vent in the form of obelisks, “devil’s fingers,” towers and columns. If the acidic magma still manages to reach the surface and pour out, its flows move extremely slowly, several centimeters, sometimes meters per hour.
Unusual rocks are associated with acidic melts. For example, ignimbrites. When the acidic melt in the near-surface chamber is saturated with gases, it becomes extremely mobile and is quickly ejected from the vent, and then, together with tuffs and ash, flows back into the depression formed after the ejection - the caldera. Over time, this mixture hardens and crystallizes, and large lenses of dark glass clearly stand out against the gray background of the rock in the form of irregular shreds, sparks or flames, which is why they are called “fiamme”. These are traces of the stratification of the acidic melt when it was still underground.
Sometimes acidic lava becomes so saturated with gases that it literally boils and becomes pumice. Pumice is a very light material, with a density lower than that of water, so it happens that after underwater eruptions, sailors observe entire fields of floating pumice in the ocean.
Many questions related to lavas remain unanswered. For example, why lavas of different compositions can flow from the same volcano, as, for example, in Kamchatka. But if in this case there are at least convincing assumptions, then the appearance of carbonate lava remains a complete mystery. It, half consisting of sodium and potassium carbonates, is currently erupted by the only volcano on Earth - Oldoinyo Lengai in Northern Tanzania. The melt temperature is 510°C. This is the coldest and most liquid lava in the world, it flows along the ground like water. The color of hot lava is black or dark brown, but after just a few hours of exposure to air, the carbonate melt becomes lighter, and after a few months it becomes almost white. Frozen carbonate lavas are soft and brittle and easily dissolve in water, which is probably why geologists do not find traces of similar eruptions in ancient times.Lava plays a key role in one of the most pressing problems of geology - what heats up the Earth's interior. Why do pockets of molten material appear in the mantle, which rise upward, melt through the earth's crust and give rise to volcanoes? Lava is only a small part of a powerful planetary process, the springs of which are hidden deep underground.
» » Cooling of lava
The time required for lava to cool cannot be determined precisely: depending on the power of the flow, the structure of the lava and the degree of initial heat, it varies greatly. In some cases, lava hardens extremely quickly; for example, one of the flows of Vesuvius froze in 1832 in two months. In other cases, lavas are in motion for up to two years; often, after several years, the temperature of the lava remains extremely high: a piece of wood stuck into it instantly catches fire. This was, for example, the lava of Vesuvius in 1876, four years after the eruption; in 1878 it had already cooled down.
Some streams form fumaroles over many years. At Jorullo, in Mexico, in the springs passing through the lava that poured out 46 years ago, Humboldt observed a temperature of 54°. Flows of significant power freeze even longer. Skaptar-jokul in Iceland in 1783 identified two lava flows, the volume of which exceeded that of Motzblanc; It is not surprising that such a powerful mass solidified gradually over the course of about a century.
We have seen that lava flows quickly harden from the surface and are covered with a hard crust, in which the liquid mass moves, as if in a pipe. If after this the amount of lava released decreases, then such a pipe will not be completely filled with it: the upper cover will gradually sink, stronger in the middle and less at the edges; Instead of the usual convex surface, which is represented by any thick fluid mass, you get a concave surface in the form of a trench. However, the hard crust covering the stream does not always sink: if it is powerful and strong enough, it will withstand its own weight; in such cases, voids form inside the frozen flow; no doubt this is how the famous grottoes of Iceland arose. The most famous among them is Surtshellir (“Black Cave”) near Kalmanstung, located among a huge lava field; its length is 1600 m, width 16-18 m and height 11 - 12 m. It consists of a main hall with a number of side chambers. The walls of the grotto are covered with glassy shiny formations, magnificent lava stalactites descend from the ceiling; Long stripes are visible on the sides - traces of a moving fiery liquid mass. Many lava flows on the island of Hawaii are cut through by long grottoes, like tunnels: in some places these grottoes are very narrow, sometimes they widen up to 20 m and form vast high halls decorated with stalactites; they sometimes stretch for many kilometers and twist, following all directions of the lava flow. Similar tunnels have also been described on the volcanic islands of Bourbon (Reunion) and Amsterdam.