Lava boiling point. Lava movement

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 turned into characteristic rocks, the eyes of specialists are aimed at them with special 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? Not quite 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 planet

The 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.

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 hardens. 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:

Lava flow flows straight into the ocean, Hawaii:

Volcanoes have always attracted both scientists and ordinary people. They are called tunnels or passages to the center of the Earth, because when they erupt, lava comes to the surface, filling the deep bowels of our planet. It was the study of volcanoes that allowed scientists to put forward many hypotheses about complex physical and chemical processes occurring at depths of thousands of kilometers.

Volcanic eruption

Volcanic eruptions can begin in different ways. Sometimes a sleeping giant warns in advance of his imminent awakening. In this case, small-scale earthquakes occur in its vicinity, and from the vent before the lava flows out smoke mixed with ash, which rises high into the atmosphere and prevents the rays of the Sun from penetrating to the earth's surface. It even happens that the phenomena preceding the volcanic eruption itself begin several weeks and even months before the lava leaves the volcano. But this doesn't always happen. Sometimes a volcano erupts almost instantly, without prior warning signs.

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Earthquakes and volcanoes

Volcanic eruption rate

Scientists have found that the speed of this process directly depends on the substance that forms the basis of the lava. These substances have different melting points and different effects on the fluidity of lava, which is dominated by andesite and dacite in slow-erupting volcanoes, and rhyolite in rapidly erupting volcanoes. In addition to the chemical composition of lava, the rate of volcanic eruptions is greatly influenced by the amount of gases dissolved in the lava. The more of them, the higher the flow rate. Sometimes, with a very large amount of gases, an explosion can occur, leading to the rapid release of an avalanche from a volcanic vent.

Lava Outfall Experiment

Some data about volcanoes have been confirmed in laboratory conditions: rhyolite was heated to 800 degrees Celsius, which approximately corresponds to the temperature of the volcanic interior at the start of the eruption. It has been proven that under these conditions this substance becomes very fluid due to its low viscosity. Therefore, in real conditions, it allows it to exit the volcano’s mouth at high speed. Unfortunately, the impetus for this experiment was a natural disaster that took place in Chile in the town of Chaiten, which is located 10 kilometers from the volcano of the same name.

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Why do volcanic eruptions occur?

The tragedy occurred on May 1, 2008. Less than a day before the eruption, intense tremors began, and soon smoke and ash began to rise into the atmosphere. Everything happened so quickly that it was almost impossible to carry out rescue measures. The eruption was long and intense, so much so that it could be observed even from Earth orbit. It was a global event, followed by scientists from many countries. The analysis of pumice samples was carried out by two scientists - Donald Dingwell and Jonathan Castro.

) or a very viscous (extrusion) mass from a rock melt, predominantly of silicate composition (SiO 2 from about 40 to 95%), pouring onto the surface of the Earth during volcanic eruptions.

Term

Word lava borrowed from Italian (lava, Latin labor) and French (lave) in the 18th century. It means “falling, crawling, sliding, descending (down)”, or “that which descends” as a result of a volcanic eruption.

Lava formation

Lava is formed when a volcano releases magma onto the Earth's surface. Due to cooling and interaction with gases that make up the atmosphere, magma changes its properties, forming lava. Many volcanic island arcs are associated with deep fault systems. The centers of earthquakes are located approximately at a depth of up to 700 km from the earth's surface, that is, the volcanic material comes from the upper mantle. On island arcs it often has an andesitic composition, and since andesites are similar in composition to the continental crust, many geologists believe that the continental crust in these areas builds up due to the influx of mantle material.

Volcanoes that operate along oceanic ridges (such as the Hawaiian ridge) erupt predominantly basaltic material, such as aa lava. These volcanoes are probably associated with shallow earthquakes, the depth of which does not exceed 70 km. Because basaltic lavas are found both on continents and along ocean ridges, geologists hypothesize that there is a layer just below the Earth's crust from which basaltic lavas come.

However, it is unclear why in some areas both andesites and basalts are formed from mantle material, while in others only basalts are formed. If, as is now believed, the mantle is indeed ultramafic (enriched in iron and magnesium), then lavas derived from the mantle should have a basaltic rather than andesitic composition, since andesites are absent in ultramafic rocks. This contradiction is resolved by the theory of plate tectonics, according to which the oceanic crust moves under island arcs and melts at a certain depth. These molten rocks erupt in the form of andesite lavas.

Types of lava

Lava varies from volcano to volcano. It differs in composition, color, temperature, impurities, etc.

By composition

Basalt lava

The main type of lava erupted from the mantle is characteristic of oceanic shield volcanoes. It is half silicon dioxide and half oxides of aluminum, iron, magnesium and other metals. This lava is very mobile and can flow at a speed of 2 m/s. Has a high temperature (1200-1300 °C). Basaltic lava flows are characterized by a small thickness (meters) and a large extent (tens of kilometers). The color of hot lava is yellow or yellow-red.

Carbonate lava

Half is composed of sodium and potassium carbonates. This is the coldest and most liquid lava, it spreads like water. The temperature of carbonate lava is only 510-600 °C. The color of hot lava is black or dark brown, but as it cools it becomes lighter, and after a few months it becomes almost white. Solidified carbonate lavas are soft and brittle and easily dissolve in water. Carbonate lava flows only from the Oldoinyo Lengai volcano in Tanzania.

Silicon lava

Most characteristic of the volcanoes of the Pacific Ring of Fire. It is usually very viscous and sometimes freezes in the crater of a volcano even before the end of the eruption, thereby stopping it. A plugged volcano may swell somewhat, and then the eruption resumes, usually with a powerful explosion. The average flow rate of such lava is several meters per day, and the temperature is 800-900 °C. It contains 53-62% silicon dioxide (silica). If its content reaches 65%, then the lava becomes very viscous and slow. The color of hot lava is dark or black-red. Solidified silicon lavas can form black volcanic glass. Such glass is obtained when the melt cools quickly, without having time to

Ecology

Volcanoes on our planet are geological formations on the earth's crust.

From here magma comes to the surface of the earth , which forms lava, as well as volcanic gases, rocks and mixtures of gas, volcanic ash and rocks. Such mixtures are called pyroclastic flows.

It is worth noting that the word “volcano” itself came to us from Ancient Rome, where the god of fire was called Vulcan.

There is a lot of interesting information about volcanoes, and below you can find some facts about them.

25. Strongest volcanic eruption (Indonesia)

Of all the documented volcanic eruptions, the largest was recorded at the Tambora stratovolcano on the island of Sumbawa, Indonesia, in 1815.

According to the indicator of volcanic explosiveness, the force of the eruption reached 7 points (out of 8).

This eruption lowered the average temperature on Earth by 2.5 °C over the next year, which was called the "year without summer."

It is worth noting that the volume of emissions into the atmosphere was approximately 150-180 cubic meters. km.

24. Long-lasting effects of a volcanic eruption

Gas and other particles released into the atmosphere during the 1991 eruption of Mount Pinatubo on the island of Luzon, Philippines, lowered global temperatures by about 0.5 degrees Celsius over the next year.

23. Lots of volcanic ash

The 1991 eruption of Mount Pinatubo sent 5 cubic kilometers of volcanic material into the air, creating an ash column 35 km high.

22. Big volcano explosion

The largest explosion of the 20th century occurred in 1912 during the eruption of Novarupt, one of the chain of Alaska volcanoes - part of the Pacific volcanic Ring of Fire. The force of the eruption reached 6 points.

21. Kilauea's long eruption

One of the most active volcanoes on Earth, Hawaii's Kilauea has been erupting continuously since January 1983.

20. Deadly volcanic eruption

The colossal magma chamber that was located inside the Taupo volcano continued to fill for a very long time, and finally the volcano exploded.

After the eruption in April 1815, the strength of which reached 7 points, from 150 to 180 cubic meters were thrown into the air. km of volcanic material.

Volcanic ash also filled the remote islands, leading to a huge number of deaths. Their number was approximately 71,000. About 12,000 people died directly from the eruption, while the rest died as a result of starvation and disease that resulted from the eruptive fallout.

19. Big mountains

18. Active volcanoes today

Hawaii's Mauna Loa volcano is the largest active volcano in the world, rising 4,1769 meters above sea level. Its relative height ( from the ocean floor) - 10,168 meters. Its volume is about 75,000 cubic kilometers.

17. The surface of the earth covered with volcanoes

More than 80 percent of the Earth's surface above and below sea level is of volcanic origin.

16. Ashes Everywhere (Volcano St. Helens)

During the eruption of Mount St. Helens in 1980, approximately 540 million tons of ash covered an area exceeding 57,000 square meters. km.

15. Volcano disaster - landslides

The St. Helens eruptions resulted in the largest landslides on Earth. As a result of this eruption, the height of the volcano was reduced by 400 meters.

14. Underwater volcano eruptions

The deepest recorded volcanic eruption occurred in 2008 at a depth of 1,200 meters.

The cause was the West Mata volcano, located in the Lau Basin near the Fiji Islands.

13. Lava lakes of a volcano in Antarctica

The southernmost active volcano is Erebus, located in Antarctica. It is worth noting that the lava lake of this volcano is the rarest phenomenon on our planet.

Only 3 volcanoes on Earth can boast of “non-healing” lava lakes - Erebus, Kilauea in Hawaii and Nyiragongo in Africa. And yet, a lake of fire in the middle of eternal snow is a truly impressive phenomenon.

12. High temperature (what comes out during a volcanic eruption)

Temperatures inside a pyroclastic flow - a mixture of high-temperature volcanic gases, ash and rocks that form during a volcanic eruption - can exceed 500 degrees Celsius. This is enough to burn and carbonize the wood.

11. First in history (Nabro volcano)

On June 12, 2011, the active Nabro volcano, which is located in the southern Red Sea, near the borders of Eritrea and Ethiopia, awoke for the first time. According to NASA, this was its first recorded eruption.

10. Volcanoes of the Earth

There are about 1,500 volcanoes on Earth, not counting the long volcanic belt on the ocean floor.

9. Pele's tears and hair (volcano parts)

Kilauea is where Pele, the Hawaiian volcano goddess, is said to live.

Pele's Tears

Several lava formations were named after her, including Pele's tears (small drops of lava cooled by air) and Pele's hair (splashes of lava cooled by wind).

Pele's hair

8. Supervolcano

Modern man could not witness the eruption of a supervolcano (8 points), which could change the climate on Earth.

The last eruption occurred approximately 74,000 years ago in Indonesia. In total, there are approximately 20 supervolcanoes known to scientists on our planet. It is worth noting that on average, such a volcano erupts once every 100,000 years.