Today we will consider such an interesting topic as volcanoes. The structure of volcanoes and their classification are described in detail in this article.
Volcanoes got their name by name Volcano,god of fire. They are geological formations that arise over cracks and channels in the earth's crust. Large volcanoes that erupt before your eyes, with nothing comparable spectacle. Lava rocks, fragments of rocks and hot gases from magmatic sources are ejected to the earth's surface through cracks and channels. Volcanoes are usually isolated mountains of eruption products. They can be tall in size. For example, Africa’s largest volcanoes are Kilimanjaro (5,895 meters), Cameroon (4,100 meters) and Teide (3,718 meters).
К действующим относятся те, которые в настоящее time is erupted periodically or permanently. For example, active volcanoes in Africa are Nyiragongo, Meru, Karisimbi, Fako, Teide. Those who have fallen asleep are such volcanoes, about the eruptions of which there is no information, but they have retained their form and local earthquakes occur under them. The extinct are called eroded and badly destroyed, non-active volcanoes. Photo of the active volcano Arenal, located in Costa Rica, is presented below.
Volcanoes are divided by the form of supply channels onfissure and central. Considering the structure of the volcano (the diagram is presented below), it should be noted that in the upper mantle there may be magmatic foci at a depth of about 50-70 kilometers (for example, Kamchatka Klyuchevskaya Sopka volcano). They can also be in the earth's crust, at a depth of about 5-6 meters (Italian volcano Vesuvius) or deeper.
Volcanic eruptions can be lengthy (fromseveral years to several centuries) and short-term, which are measured in hours. Acoustic phenomena, volcanic earthquakes, changes in the composition and magnetic properties of fumarole gases, as well as some other phenomena that occur before volcanoes erupt, can be attributed to their precursors. A photo of an erupting volcano is shown below.
It usually begins with what happens.increased gas emissions. They are ejected first, along with cold, dark fragments of lavas, and then with red-hot. In some cases, these emissions are accompanied by the outpouring of lava. From 1 to 5 km, depending on the strength of the explosions, the height of the rise of water vapor and gases saturated with debris of lava and heat fluctuates. And the largest volcanoes can eject products of the eruption and to an even greater height. For example, in 1956 in Kamchatka, during the eruption of the Nameless volcano, it was 45 kilometers. At distances from several thousand to tens of thousands of kilometers, discarded material is transferred. Its volume sometimes reaches several cubic kilometers. The concentration in the atmosphere of volcanic ash during some eruptions is so great that there is darkness, comparable to the darkness in a closed room. It was observed, in particular, the village of Klyuchi, located 40 km from the Bezymyanny volcano, in 1956.
The layout of the volcano below will help you understand its structure.
Eruption is the alternation of strong and weakexplosions, as well as the outpouring of lavas. Maximum force explosions are called culminating paroxysis. A decrease in the force of explosions and then a gradual cessation of eruptions is observed after them. Tens of km³ of lava streams emit the largest volcanoes. The photo below shows the structure of the volcano. This scheme gives a visual representation of how it erupts.
Volcanic eruptions are not always the same.Four types of them are distinguished depending on the viscosity of lavas and the amount of products (solid, gaseous and liquid): explosive (Vulcan), extrusive (dome), mixed (Strombolian) and effusive (Hawaiian).
Hawaiian type, most often creating thyroidvolcanoes, characterized by a fairly calm outpouring of basaltic (liquid) lava, which forms lava flows in craters and fiery liquid lakes. Small amounts of gases form fountains that emit droplets and clumps of liquid lava, stretching into thin glass filaments during flight.
In the Strombolian type, which is usually createdstrato-volcanoes, together with rather abundant outpourings of lavas of andesitic-basalt and basalt composition, are dominated by small explosions, during which pieces of slag are ejected, as well as various fusiform and twisted bombs.
In the dome type it is gaseous substances.play a big role. They produce explosions, as well as emissions of large black clouds, crowded with many fragments of lavas. Small streams form viscous lava andesite composition.
Solid, gaseous and liquid products areeruptions of various volcanoes. Volcanic gases, which are released both during the eruption (they are called eruptive) and during the quiet activity of the volcano (furamal) from cracks located on the slopes of the volcano, as well as from its crater, pyroclastic rocks and lava flows, form hot springs, passing through groundwater.
Лава - раскаленная очень вязкая или жидкая, в mainly silicate mass, which during volcanic eruptions poured on the surface of the Earth (see the photo below in the section of the volcano). When it hardens, effusive rocks are formed.
Volcanic rocks (volcanic rocks) - rocks,which are formed as a result of volcanic eruptions. There are, depending on the nature of the eruption, effusive, or effuse (diabase, liparite, trachyte, andesite, basalt, etc.), pyroclastic, or volcanic-detrital (volcanic breccia, tuff), volcanic rocks.
A tectonic fault (tectonic rupture) is a violation of the integrity of rocks due to the movements of the earth's crust (thrusts, thrusts, shifts, faults, etc.).
The photo below shows the layout of the volcano.
Depending on the composition of the magma and natureEruptions appear on the surface structures of various heights and shapes. Each time the structure of the volcano is unique. The picture above is just an example. Volcanic apparatuses consist of a fissure or tubular channel, a vent (the upper part of the channel), volcanic detritus products and accumulations of lavas surrounding the channel from different sides, and a crater (a funnel-shaped or cup-shaped depression on the slope or summit of a volcano whose diameter ranges from a few meters to several kilometers ). The most common forms are cone-shaped, with a predominance of emissions of various detrital material, and dome-shaped (when viscous lava is squeezed out).
Not only through the tops of the main cratereruptions occur, but also through side craters (also called parasitic) craters that have volcanoes. The structure of volcanoes is characterized by the fact that the side craters are located on the slopes, as well as at some distance from the peaks of the main one. Often, with single eruptions of gases that pierce the channel to the earth's surface, funnel-shaped depressions are formed. They are bordered by an annular shaft, consisting of blocks of different breeds. Often these funnels are filled with water. They are called maarami. Sometimes strong eruptions are accompanied by the fact that parts of volcanic structures collapse. Often this applies to the area near which there are volcanoes. The structure of volcanoes sometimes leads to its collapse. The depressions, which are formed at the same time, in diameter reach from several to several tens of kilometers. They are called calderas.
The structure of volcanoes, we have dismantled.It should be noted that one of their varieties is underwater, located at the bottom of the reservoir. Today, the geographical coordinates of volcanoes of this type are concentrated mainly within the three volcanic zones: the Atlantic, Mediterranean-Indonesian and Pacific. According to the results of the study of the past of our planet from the point of view of geology, in terms of their scale, as well as in terms of the volume of emission products coming from the bowels of the Earth, they significantly exceed those on land. If annually on land from 20-30 eruptions on average up to 1.5 km³ of molten magma per year, then underwater volcanoes erupt 12-15 times more material during the same time. The activity of underwater volcanoes supports life in the ocean waters near its surface. And in turn, the volume of greenhouse gases absorbed by the ocean depends on it.
If the reservoir is located above a volcanic hearth,during the eruption, the pyroclastic material is saturated with water and then spread around the source. For the first time such deposits have been described in the Philippines. They formed during the eruption of the Taal volcano in 1968, which is located at the bottom of the lake. Sediments of this type are often represented by thin wavy layers of pumice. Islands may form as a result of volcanic eruptions. This is, for example, the volcanic island of Reunion in the Indian Ocean.
The close relationship between moving parts of the earthcrust and belts of volcanic activity indicates the geographical location of volcanoes. The faults formed in such zones are the channels along which magma moves towards the earth's surface. It occurs, apparently, under the influence of various tectonic processes. When the pressure of the gases dissolved in the magma becomes at a depth greater than the pressure of the overlying ones, they begin to move toward the surface of the earth, dragging the magma along. It is possible that during the crystallization of magma a gas pressure is created when the liquid and its part is enriched with steam and residual gases. Magma as if boils. In the center, as a result of the release of a large volume of gaseous substances, a high pressure is created. It may also be one of the reasons for the eruption that has begun.
The formation and structure of the volcano - the topic is veryinteresting. In this article, we only briefly reviewed them. The internal structure of the volcano is still interested in many researchers. They are still studying it.
For the first time in our school years, we are introduced towhat is a volcano. Geography gives us the opportunity to get closer to understanding how our planet works. The earth is fraught with many mysteries, to unravel the next generations to come. Of course, the school tells us only the main points when studying the structure of a volcano. Grade 5 is not the age to go into this topic. However, sometimes it can and should be done. We hope you learned something new for yourself from this article.
