Many, having heard the expression mud volcano, consider it a hyperbole or just a joke, because according to tradition, a volcano is always represented as a huge cone-shaped mountain, from which lava or black ash erupts.
In fact, mud volcanoes are actually present on our planet, and it is them that oil producers are trying to find.
Where there is a lot of dirt, there can be a lot of oil
A mud volcano is a specific geological formation in the form of a depression or hole on the earth's surface or a cone-shaped crater that erupts mud with gases, oil and water.
Mud volcanoes, depending on the location, are divided into two types. The first are formed in places where there is oil. Second, they accompany zones of volcanic activity.
If such a volcano accompanies an ordinary one, then it is called a fumarole. This is a crack in the ground that throws out a mass of groundwater and dirt. The mass is squeezed out of the ground by molten lava and gases of volcanic origin. Most often, the place of a fumarole is the slopes of an ordinary volcano.
Mud volcanoes formed in oil-bearing formations look much more interesting. They can be both underwater and terrestrial.
The occurrence of this type of volcano provokes the presence of an underground or underwater oil or gas field. 
These deposits emit combustible gas, rushing to the surface of the earth through cracks. In places of combinations of cracks with groundwater, a mud volcano arises: gases squeeze out water, mix it with soil, creating a mud mass. Such volcanoes can act constantly or periodically. The latter happens much more often.
Very often, along with water, oil in a small amount rushes to the surface of the earth. This circumstance indicates the presence of oil deposits in the depths of the earth. Almost a third of all such mud volcanoes are located in the Republic of Azerbaijan.
The danger of a mud volcano
Compared to an ordinary volcano, many consider a mud volcano to be harmless, but this is far from the case. The natural gas emitted by it can ignite, causing damage to people and buildings. And the dirt itself can be dangerous, as the Indonesian island of Java showed in 2006.
On this island, one of the local oil companies, near the city of Surabai, a test well was drilled. As a result of the activities of the drillers, a mud volcano arose: a well opened a gas field, which provoked an instant release of groundwater to the surface, and flows of liquid mud flooded the territory. 
The drillers tried to explain this by an earlier earthquake, but all attempts to block the water-mud flow ended in vain, the mud has been continuously erupted since then to the present. Experts believe that this will continue for another thirty years.
The eruption process is uneven: sometimes its activity is very low, and on other days the mud gushes out in a powerful jet. The size of the mud patch has grown to several kilometers, forcing tens of thousands of citizens to move to other places to live.
They tried to stop the activity of this volcano by filling it with concrete balls in the amount of several hundred pieces. However, this did not lead to a positive result. The eruption stopped briefly in March 2007, but soon resumed again.
Curious facts
There are a number of interesting facts about the activity of mud volcanoes:
Different countries give this phenomenon different names. The Italians call it salsa (which means "dirty"), salinella ("salt") or bollitori ("boiling"). It all depends on what type of geological formation triggered the mud volcano.
The height of the largest mud volcanoes in the world is about seven hundred meters. The diameter of the largest is ten kilometers.
According to one of the theories of 1955, the activation of the eruption of this kind of volcano is affected by solar or lunar activity, and above all eclipses. This theory has both supporters and opponents, because in some cases neither a solar nor a lunar eclipse had any effect on the nature of the accumulation of mud volcanoes. 
Some regions are distinguished by a pronounced seasonal nature of mud volcanoes: they are most active in autumn. Scientists attribute this circumstance to a change in the level of atmospheric pressure.
Russian mud volcanoes Taman
Mud volcanoes of the Taman Peninsula in the Kuban are very popular among Russian tourists, who often see underwear presentations on TV or in shopping centers. Some of the mud in these three dozen volcanoes has medicinal properties and is used in local sanatoriums.
The famous Tizdar mud volcano attracts entire tourist flows. Many people come to see this miracle of nature, as well as swim in it. The diameter of this crater-lake is about twenty meters. The composition of the mud in it is rich in iodine, bromine and selenium. Tizdar is located on the shores of the Sea of Azov near the village "For the Motherland".
Unique natural phenomena are actively used for healing. Some resort cities, for example, Anapa, include a mud volcano in the mandatory program for visiting vacationers.
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mud volcanism
Mud volcanism occupies a modest place among dangerous, and even more catastrophic phenomena. Its action is local and is not associated with any serious damage to the environment. Nevertheless, the study of this phenomenon in the context of natural hazards is of great interest, since the spatial distribution of mud volcanoes has a clear confinement to tectonically active areas, where they occupy a certain position (Fig. 2.5). The same areas are characterized by increased seismic hazard (Fig. 2.6). In addition, mud volcanoes are indicators of the potential oil and gas content of the territory, which serves as an incentive for a detailed study of the composition of gases and water, the indispensable components of hill breccia, as well as the conditions and mechanism for the formation of the eruption process itself. Mud volcanoes, being, in comparison with "real" igneous volcanoes, more superficial formations, make it possible to study the features of true volcanic eruptions.
Rice. 2.5. Areas of development of mud volcanoes associated with hydrocarbon
accumulations in deep layers:
1 - Northern Italy; 2 - the island of Sicily; 3 – Albania; 4 – Romania; 5 – Kerch and Taman Peninsulas;
6 – Eastern Georgia; 7 – southeastern subsidence of the Greater Caucasus; 8 – South Caspian;
9 – Southwestern Turkmenistan; 10 – Gorgan Plain (Iran); 11 – Makran coast
(Iran and Pakistan); 12 – Balochistan; 13 - Punjab province; 14 – Dzungaria (PRC);
15 – Assam region (India); 16 – Burma; 17 – Andaman and Nicobar Islands;
18 – South Sakhalin; 19 - about. Hokkaido; 20 - about. Taiwan; 21 - about. Sumatra; 22 - about. Java;
23 - about. Kalimantan; 24 - about. Sulawesi; 25 - about. Timor; 26 - about. New Guinea; 27 - New Zealand;
28 – Mexico; 29 – Ecuador; 30 – Colombia; 31 – Venezuela; 32 - about. Trinidad
In the global distribution of areas of development of mud volcanoes, their clear tectonic confinement is revealed. In all cases, the phenomena of mud volcanism occur in the frontal and intermountain troughs, near young orogens, in areas of relatively weakly dissected piedmont relief, where thick (hundreds and thousands of meters) strata of predominantly clayey rocks have accumulated. This is usually a formation that is commonly referred to as the lower molasse.
The areas and areas of development of mud volcanism are confined to modern mobile belts - the Alpine-Himalayan and Pacific, although they appear here as separate discrete spots. Mud hills of the Kerch-Taman region have been known for a long time, where they are confined to the southern edge of the Indolo-Kuban trough and complicate the northwestern subsidence of the megaanticlinorium of the Greater Caucasus. Mud volcanoes on the southeastern subsidence are widely developed, occupying the Apsheron Peninsula, as well as the edge of the Kusaro-Divichinsky trough adjacent to the orogenic uplift; from the south of the orogenic uplift, they are located in the north of the Nizhne-Kura depression, in the Shemakhino-Gobustan region, and also to the west within the Sredne-Kura depression, in the interfluve of the Kura and Yori. Phenomena of mud volcanism continue in the Caspian waters, along the Apsheron-Krasnovodsk threshold, moving further east to Turkmenistan, and on the meridional elongated Baku archipelago, along the western border of the South Caspian depression.
The phenomena of mud volcanism have a wide, although uneven distribution over the space of modern mobile belts of the Earth. The vast majority of known mud volcanoes (more than 50%) are concentrated in the Caucasus region - in Azerbaijan and the Kerch-Taman region - in the South Caspian region.
Rice. 2.6. Distribution scheme of mud volcanism
and seismicity in the Caspian region:
1 – earthquake epicenters; 2 – boundaries of the seismically active zone;
3 – mud volcanoes; 4 – zone of manifestation of mud volcanism
Mud volcanoes are usually relatively small gently sloping hills, rising above the terrain by several meters - 2–3, but sometimes their height reaches 50–60 m. At the top there is a crater (one or several) from half a meter to 2–3 m in diameter. In some cases, a mud volcano does not form an elevation in the relief, but is a field of dried mud, which becomes unsteady and liquid as it approaches the vent - the griffin. In their superficial expression, mud hills exhibit a wide variety of species and are models of "real" igneous volcanoes.
According to the nature of the eruptions and the consistency of the ejected mud, “thick” and “liquid” hills are distinguished. The “dense” ones form a cone of one or another height, and their eruptions are characterized by a more or less regular periodicity, which can range from 2–3 to 6–8 years. During periods of dormancy, the hill breccia dries up and can plug the vent, but slight outgassing through the cracks may continue. During the next eruption, the resulting plug breaks explosively, and the gas jet that escapes along with the liquefied mud sometimes ignites spontaneously. The turbulent stage of the eruption lasts several minutes, although a calmer outpouring of mud can last several days. In "liquid" hills, eruptions occur more calmly, like outpourings from an overflowing vessel. During periods of rest of such hills, a pulsating release of gas bubbles occurs in the crater. On the flat fields of the hill breccia one can also observe continuously pulsing gryphons. Such hills are always in an active state.
According to the composition of the eruption products, mud volcanoes show connections with oil and gas-oil deposits and can serve as indicators of the potential oil and gas content of the territory. In the composition of gases, methane plays a predominant role, at the same time, a small amount of carbon dioxide and sulfur dioxide is observed. Sopochnye waters are mainly chloride-hydrocarbonate-sodium and are close to typical oil waters. The fact that mud hills are common in oil and gas regions allows us to conclude that the similarity of oil and hill waters indicates their genetic relationship. Mud volcanoes have one important advantage compared to other oil and gas occurrences - this is their natural connection with diapiric folds, which are a favorable object for the formation of oil and gas deposits. Therefore, mud hills can serve not only as indicators of the region's oil content, but also as a criterion for assessing its structural features that affect the distribution of oil content.
The solid component of the emissions of mud volcanoes is crushed particles of surrounding and underlying rocks, which, together with water and gases, form hilly mud, which subsequently turns into hilly breccia. Liquid mud contains a few percent of solid particles (4-6%), and solid - up to 40-50%. In addition to clay finely dispersed matter, knoll mud often contains a certain amount of larger fragments of crushed stone, usually corresponding in composition to harder and more brittle rocks of the most productive stratum, but sometimes also from the rocks covering this stratum.
The specific features of mud volcanoes are the frequency of action, a relatively calm state after a violent eruption, and the process of accumulating new energy. The evolution of a mud volcano after it has already formed and there is a weakened zone of its channel for the ejection of volcanic products can be determined both by tectonic causes - uneven pressure, and by hydrodynamics that governs fluid regimes. The conditions for the periodic operation of mud volcanoes are quite similar to the conditions for the operation of geysers. All areas of development of mud volcanism are located in seismically active zones of various potential hazards.
Various physical properties of the environment where the foci of mud volcanoes and earthquakes are located make it possible to assume the following picture of their interaction. In the case when both sources are in a dynamically unstable state, near the critical discharge point, and the energy of the earthquake source exceeds the energy of the mud volcano source, an earthquake can occur, accompanied by a mud volcano eruption. Seismic energy in this case will be partially spent on the mud volcanic effect.
In the case when both sources are in a near-critical state, but the source of the mud volcano is closer to its limit, the eruption can precede a seismic shock, and the stress field in the area decreases somewhat, which can reduce the effect of the earthquake. In some cases, an earthquake may not occur. Then the mud volcanic eruption serves as a way to relieve stress. But, at the same time, if the source of a mud volcano, or the source of an earthquake, is far from its critical state of eruption, then seismic tremors can occur independently of each other.
Eruptions of mud volcanoes are associated with the stress state of the interior and reflect its dynamics, and the activity of mud volcanoes can be used as an indicator of this stress state.
Preventive measures for volcanic eruptions
Protective measures against lava
1. Bombardment of a lava flow from an airplane. Cooling, the lava flow creates barrages and flows in the flume. When it is possible to break through these shafts, the lava spills, the speed of its flow slows down and stops.
2. Removal of lava flows with the help of artificial gutters.
3. Bombardment of the crater. Lava flows are mostly caused by lava overflowing over the edge of a crater, but if the crater wall can be destroyed before the lava lake has formed, a little less lava will accumulate and its outpouring down the slope will not cause harm. The flow of lava, in addition, can be directed in the right direction.
4. Construction of safety dams.
5. Cooling the surface of the lava with water. A crust forms on the cooled surface and the flow stops.
Protection against tephra fallout
Creation and use in case of an eruption of special shelters. It is possible to carry out the evacuation of the population.
Protection from volcanic mud flows
Weak mud flows can be protected by dams or the construction of gutters. In some Indonesian villages at the foot of volcanoes, artificial hills are poured. In case of serious dangers, people run into them and thus can avoid the danger. There is another way - the artificial lowering of the crater lake. The best way is to prohibit the settlement of a dangerous area or evacuate at the first sign of a volcanic eruption.
Lava flow. At the beginning of the eruption, do not stay near the lava tongues.
Tephra eruption. Against dams and lapilli, it is preferable to use passive protection, while you need to be careful and deviate from them. However, when too many of them fall, you need to hide in a shelter. Ash does much more damage. Masks must be worn in the immediate vicinity of the volcano. It is necessary to constantly remove the ashes from the roofs (to prevent collapse), in the gardens to shake the ashes from the trees, to close the reservoirs with drinking water. It is recommended to protect sensitive devices. Until the right moment comes, it is better to stay in hiding. During the eruption itself, evacuation is impossible, as there is no visibility. After the eruption, it is necessary to remove large rough stony debris from the territory. The ashes are gradually washed away by the rains. Nature itself will take care of the cleansing of pastures, even when the vegetation is completely destroyed, its restoration occurs relatively quickly.
Volcanic mud flows.
Volcanic floods. The actions of the population should be the same as in a normal flood.
Scorching volcanic cloud. Immediate evacuation of the population at the slightest sign of an eruption.
Volcanic gases. The population of nearby areas should be provided with gas masks. It is necessary to evacuate livestock from dangerous areas. Plantations are successfully protected from the action of volcanic gases by moderate lime dressing (to neutralize acids).
2.2. Geological emergencies
(exogenous geological phenomena)
2.2.1. slope processes
Most of the Earth's surface is slopes. Slopes include surface areas with slopes greater than 1°. They occupy at least 3/4 of the land area. The steeper the slope, the greater the component of gravity, which tends to overcome the force of cohesion of rock particles and move them down. Gravity is helped or hindered by the structural features of slopes: the strength of rocks, the alternation of layers of different composition and their slope, groundwater, which weakens the cohesive forces between rock particles. Slope collapse can be caused dropping- separation from the slope of a large block of rock. Settling is typical for steep slopes composed of dense fractured rocks (eg limestones). Depending on the combination of these factors, slope processes take on a different form.
Slope processes include a large group of processes of movement of masses of soil and snow, which occurs due to gravity: collapses, rockfalls, landslides, solifluction flows, displacements of kurums and stone glaciers, snow avalanches, glaciers, etc. The general condition for the beginning of downward displacement of material along the slope - reaching a state in which the shear force (the component of gravity parallel to the slope) is greater than the holding forces (adhesion of the sheared layer with the bed, internal adhesion in a layer that does not have a sharp lower boundary).
The reasons for the start of movement are divided into three groups: an increase in shear force, a decrease in holding forces, and an additional external impulse. An increase in shear force can be caused by an increase in the mass of the shifting layer (an increase in the height of the snow cover during snowfall or a snowstorm - for avalanches; soil weighting due to wetting by rains - for the corresponding types of landslides; anthropogenic load of slopes - also for landslides, etc.). An increase in shear force can also be caused by a change in the angle of the slope - river erosion, abrasion, etc. A decrease in the holding forces on the base of the moving layer can occur due to its "lubrication" with water - during rains, snowmelt, during leaks from irrigation canals and water pipes, during flooding and flooding of the foot of the slope, etc. Additional external impulses that provide the beginning of movement (usually collapses) are all kinds of tremors - seismic tremors, mine explosions, etc.
Rockfalls, landslides, glacier collapses occur in the form of free fall for a significant part of the path, but have significant differences depending on the scale of the phenomenon. On steep (30° and more) slopes, rockfalls are common - cases of movement of single stones or small groups. The movement of stones occurs in the form of repeated "jumps" at a speed of 40–60 m/s (150–200 km/h). The reasons for the fall of stones are blowing or washing out of fine earth from under them, pushing them with tongues of creeping soil, as well as the processes of freezing and melting of ice under them. The largest rockfalls are excited by heavy showers. Rockfalls are most dangerous on highways, industrial and steep gorges of the Pamirs, Altai, Tien Shan, and the Caucasus.
Collapses differ from rockfalls not only in their large volume, but in the cohesion of the cloud of collapsing material, which changes the nature of its movement. Air is involved in the movement, the body of the collapse acquires a streamlined (teardrop-shaped) shape, is enveloped by a passing air flow (air wave) and travels a long distance. The speed of landslides in some sections of the path can reach (90 m / s) 300 km / h, the length of the path is many kilometers. Large landslides are caused by earthquakes. The mountain slope, as it were, boils and begins to move. A mass of stone and earth rushes down, splitting into streams. They merge with streams from the opposite slope and rush down the valley, enriched with water and fine earth.
Large glacial collapses are also excited by earthquakes. The Huascaran collapse in Peru during the May 1970 earthquake is the most famous.
speed up to 320 km/h. The height of the front reached 80 m. It easily overcame hills up to 140 m high and destroyed the city of Ranrairka and part of the city of Yungai, resulting in the death of 67 thousand people.
Snow falls, which are possible for slopes of 25° or more, with a relative height of 20–40 m or more, with a snow cover thickness of more than 30–40 cm above the microrelief surface, are called snow avalanches. The speed of steppe avalanches reaches several tens of m / s, the volume is million m 3, the pressure on the obstacle is 100 t / m 2 (pressure of 3 t / m 2 destroys wooden buildings, 100 t / m 2 - stone buildings), the thickness of avalanche blockages on bottom of valleys 30–50 m.
Streams up to tens of meters wide and up to hundreds of meters long are landslides. They are distributed along all slopes of different valleys and abrasion terraces. For example, in the European part of Russia, dozens of cities located on the high banks of rivers suffer from them. Landslides that are common outside the permafrost zone belong to the category of sliding landslides and occur, most often, due to undercutting of slopes by erosion or abrasion, water lubrication of the sole, shaking, or additional load on the slope. A landslide can be almost or completely immobile for many years and experience several periods of short-term activation, when the speed of its movement can reach tens of meters per hour. A special type of landslides, characteristic of the permafrost region, are stone glaciers, which are common in the mountain glacial belt in 20–40% of the valleys. Natural stone glaciers with their large mass (width - tens of meters, length - hundreds of meters, thickness - up to 20–30 m) and constant, albeit slow, movement, could pose a threat to any structures that appeared on their way.
The mass displacement of the loose cover of slopes occurs everywhere where there are no landslides and other stronger slope processes, and remains the only type of these processes on those slopes that are lower than the angle of repose. It usually affects the upper layer with a thickness of decimeters - a few meters, goes at a speed of up to decimeters per year. The reasons for the shift can be strong moisture, a change in the volume of the soil during freezing - thawing or during heating - cooling. In accordance with these reasons, the types of such processes are distinguished - solifluction, desertion, congelifluction, etc. The minimum angles of inclination at which such displacements are noticeable are in the range of 5–10°. In the range of slope angles of 10–30°, the displacement rates are approximately proportional to the square of the slope. Except for "fast solifluction" (thin landslides - slumps of wet soil), the massive displacement of the loose cover is dangerous where it occurs differentially, in stripes. The highest rates of such flows are usually in the range of 0.1-0.5 m/year, but this is enough to bend and break pipelines.
2.2.2. sat down
Mudflows
sat down- these are channel flows, including a large amount of detrital material (at least 10–15% by volume), having a density 1.5–2 times higher than the density of water, moving in the form of a wave with a front height of up to 20–40 m and at a speed of up to 20-30 m / s (10-100 km / h) and exerting pressure on an obstacle with a force of up to tens of tons per square meter. The height of the front and the velocity of the mudflow, depending on the conditions of its flow, may take on other values. The mudflows got their name from the Arabic "sail" - a stormy stream. Mudflows are typical for mountain valleys with a channel slope of 6–200; they usually last tens of minutes, less often 4–5 hours, can erode the channel to a depth of tens of meters, travel a distance of kilometers, less often - several tens of kilometers, form cones tens of meters wide, hundreds of meters long with a single sediment thickness usually up to 5 , rarely up to 10 m. Mudflows are formed in all mountainous regions of the world, except for Antarctica.
Mudflows called rapid channel flows, consisting of a mixture of water and rock fragments, suddenly arising in the basins of small mountain rivers. They are characterized by a sharp rise in the level, wave motion, short duration of action (from 1 to 3 hours), and a significant erosive-accumulative destructive effect. Mudflow is a natural (especially dangerous) hydrological phenomenon if a mudflow threatens settlements, sports and sanatorium complexes, railways and roads, irrigation systems and other important economic facilities.
Potential mudflow source- a section of a mudflow channel or mudflow basin, which has a significant amount of loose clastic soil or conditions for its accumulation, where mudflows arise under certain flooding conditions. Mudflow foci are divided into mudflow cuts, potholes and foci of dispersed mudflow formation.
Mudflow pothole called a linear morphological formation that cuts through rocky, soddy or forested slopes, composed of a weathering crust of insignificant thickness. Mudflow ruts are notable for their small length (rarely exceeding 500–600 m) and depth (rarely more than 10 m). The bottom angle of the potholes is usually more than 15°.
debris flow is a powerful morphological formation developed in the thickness of ancient moraine deposits and, most often, confined to sharp bends of the slope. In addition, mudflow incisions can be formed on accumulative, volcanogenic, landslide, landslide relief. Mudflow ruts are much larger in size, and their longitudinal profiles are smoother than those of mudflow ruts. The maximum depth of mudflow incisions reaches 100 m or more, the catchment areas of mudflow incisions can reach more than 60 km2. The volume of soil removed from a mudflow incision in one mudflow can reach 6 million m 3 .
Under the focus of dispersed mudflow formation understand the area of steep (35–55°) outcrops, heavily destroyed rocks with a dense and branched network of furrows, in which the weathering products of rocks are intensively accumulated and micro-mudflows are formed, which then unite in a single mudflow channel. They are confined, as a rule, to active tectonic faults, and their appearance is due to large earthquakes. The areas of mudflow centers reach 0.7 km 2 and rarely more.
The type of mudflow is determined by the composition of mudflow-forming rocks. Mudflows are: water-stone, water-sand and water-silty; mud, mud-stone or stone-mud; water-snow-stone.
Water-stone mudflow– flow, which is dominated by coarse-grained material with predominantly large stones, including boulders and rock fragments (volumetric weight of the flow is 1.1–1.5 t/m3). It is formed mainly in the zone of dense rocks.
Water-sand and water-dust mudflow- a stream dominated by sandy and silty material. It occurs mainly in the zone of loess-like and sandy soils during intense downpours, washing away a huge amount of fine earth.
Mud mudflow close in appearance to water-silty, is formed in the areas of distribution of rocks of predominantly clay composition and is a mixture of water and fine earth with a small concentration of stone (volumetric weight of the flow is 1.5–2.0 t/m3).
Mudstone mudflow characterized by a significant content in the solid phase (pebbles, gravel, small stones) of clay and silt particles with their clear predominance over the stone component of the flow (volumetric weight of the flow is 2.1–2.5 t/m3).
Stone-mud mudflow contains predominantly coarse-grained material, compared with the mud component.
Water-snow-stone mudflow– transitional material between the mudflow itself, in which the transport medium is water, and an avalanche.
The formation of mudflows is due to a combination of geological, climatic and geomorphological conditions: the presence of mudflow-forming soils, sources of intensive watering of these soils, as well as geological forms that contribute to the formation of rather steep slopes and channels.
Sources of solid food for mudflows can be: glacial moraines with loose filling or without it; channel blockages and blockages formed by previous mudflows; woody material. Sources of water supply for mudflows are: rains and downpours; glaciers and seasonal snow cover (during the melting period); mountain lake waters.
Mudflows of rain feeding (rain) are most often formed. They are typical for mid-mountain and low-mountain mudflow basins that do not have glacial nutrition. The main condition for the formation of such mudflows is the amount of precipitation that can cause a washout of the products of destruction of rocks and involve them in motion.
For high-mountain basins with developed modern glaciers and glacial deposits (moraines), glacial mudflows are characteristic. The main source of their solid nutrition is moraines, which are involved in the process of mudflow formation during intensive melting of glaciers, as well as when glacial or moraine lakes break through. The formation of glacial mudflows depends on the ambient temperature.
The immediate causes of mudflows are showers, intense melting of snow and ice, breakthrough of reservoirs, less often earthquakes, volcanic eruptions. Despite the variety of causes, the mechanisms of mudflow initiation can be reduced to three main types: erosional, breakthrough and landslide-landslide (Table 2.16). Thus, during the formation and development of mudflows, three stages of formation can be traced:
more or less long-term preparation on the slopes and in the channels of mountain basins of the material that serves as a source for the formation of mudflows (as a result of rock weathering and rock erosion);
rapid movement of rocky, unbalanced material from elevated sections of mountain watersheds to lower ones along mountain channels in the form of mudflows;
accumulation of mudflows in the lower parts of mountain valleys in the form of channel cones or other forms of mudflow deposits.
Mudflows are formed in mudflow catchments, the most common form of which in plan is pear-shaped with a catchment funnel and a fan of hollow and valley channels, passing into the main channel. The mudflow catchment area consists of three zones in which mudflow processes are formed and occur: debris flow zone where water and solid material are fed; transit zone(debris flow); unloading area(mass deposition of debris flows).
Usually in the understanding of man, the word "volcano" is associated with hot lava flows. However, in nature there is a less "aggressive" type of geological formations - these are mud volcanoes. They are located mainly in the basins of the Black, Azov and Caspian Seas, as well as in Italy, America and New Zealand.
fire-breathing mountains
A mud volcano is either a cone-shaped elevation with a crater (makaluba, or mud hill), or a recess in the earth's surface (salsa), from which mud and gases constantly or periodically erupt, often in combination with oil or water. During a mud eruption, gases can ignite, and spectacular, sometimes huge fire torches are formed.
For example, the eruption of the Colombian volcano Zambe in 1870 was compared by eyewitnesses to a fire-breathing mountain. A column of fire erupted from the Zambe crater illuminated the area within a radius of 30 km. Before the explosion, a powerful underground rumble was heard (a characteristic harbinger of a mud eruption), and then a column of fire shot up into the sky. The flames blazed for 11 days. In 1933, during the eruption of one of the Romanian volcanoes, a burning gas "candle" 300 meters high shot up.
With each eruption, the volcano increases in size due to the ejected portions of dirt. The highest height of mud volcanoes is 700m, but the diameter of such formations can be about 10km. This type of volcanoes has a characteristic feature: during the eruption, they emit into the atmosphere small molten particles of dirt, "lapilli", which are sometimes carried away by air currents to distances of up to 20 km. These particles are hollow, structureless bodies, and if a person falls under the precipitation from the lapilli, then he will have the feeling that hot rain is falling.
Mud volcanoes are rather restless formations. Some of them, such as Ayrantekyan, Lokbatan (Azerbaijan) erupt once every few years. Others (Cheildag, Touragay) can “doze off” for 60-100 years. Volcanic mud in some cases has healing properties due to its rich mineral composition. The most famous "healing" volcanoes on the territory of the Russian Federation include Hephaestus and Tizdar, located in the Krasnodar Territory.
Compared to igneous volcanoes, mud volcanoes are relatively harmless and do not cause much damage to humans. The exception is when people accidentally find themselves in the epicenter of the explosion. A similar thing happened in 1902 during the eruption of the Bozdag-Kobi volcano. Shepherds drove herds of sheep to its top to the crater lake.
A column of flame suddenly escaping from the bowels of the earth killed both people and animals. Sometimes powerful explosions push out a very large amount of dirt. For example, the Voskhodovsky mud volcano is located in the eastern part of the Kerch Peninsula. In 1930, its eruption was accompanied not only by fire, but also by the release of mud mixed with oil. The height of the mud flow reached 3 m, and on about. Dzharzhava covered several houses with mud up to the roofs.
Why do mud volcanoes wake up?
The causes of mud eruption are not fully understood. Some researchers associate them with the tides of the sea, others see a relationship with the lunar cycle, others believe that the cause is in the tides caused by the Moon or the Sun. It is known for certain that the eruption of mud volcanoes is often preceded by an earthquake. But it happens that anthropogenic activity causes mud volcanoes to erupt.
This happened in May 2006, when employees of the gas producing company PT Lapindo Brantas provoked the mud eruption of the Lucy volcano in Sidoarjo (Indonesia) by drilling operations. Already by September, mud flows flooded villages and rice crops, 11,000 people were forced to relocate. Shrimp farms were destroyed, factories closed. By 2008, about 36,000 peasants from the villages closest to the disaster site had already left their homes, as the mud spread another 6.5 km².
In addition, the volcano began to collapse under its own weight, which threatens to form a basin with a depth of about 150m. According to preliminary forecasts, the flow of mud from Lucy will pour out for about 30 more years. So, although for the most part mud volcanoes do not pose a danger, it is still not worth taking them lightly.
Mud volcanoes of the Azov-Black Sea basin and adjacent territory and assessment of their danger to buildings and structures
Mironyuk S. G., [email protected] Introduction This review is based on the results of surveys carried out by Piter Gaz LLC in the Black Sea in 2002-2009, as well as an analysis of the literature describing mud volcanoes in the Azov-Black Sea basin and the adjacent territory as of 2009. In addition, the review includes individual materials on mud volcanoes of the South Caspian basin (Azerbaijan). The history of studying mud volcanoes is about 180 years old. However, despite the good geological knowledge of the complex phenomenon under consideration, many aspects of mud volcanism, and its very nature, require further study. In particular, in connection with the extraction of minerals on the shelf, the construction of engineering structures in areas with a wide development of mud volcanic activity, the task of assessing the real degree of danger of this formidable natural phenomenon is relevant. Based on the definition of the basic term "natural hazard", "mud volcanic hazard" refers to a threatening phenomenon that develops in the lithosphere, in tectonically active areas, which is estimated by the probability of manifestation, indicating the spatio-temporal coordinates and intensity of the eruption.
Characteristicmud volcanic manifestations and theirplacein the general classification of hazardous natural processesand phenomena
According to , mud volcanism is "a phenomenon accompanied by ejections of rocks as a result of anomalously high in-situ pressures in gas-fluid rocks." Mud volcanoes in the world are a fairly widespread geological phenomenon. In Russia, they are described on the Taman Peninsula and about. Sakhalin, in the Black and Barents Seas, lake. Baikal. It has now been established that mud volcanoes are common in the most active seismotectonic zones of marginal troughs filled with a thick layer molasse formations in the presence of large gas accumulations and abnormally high reservoir pressures (AHRP). A number of researchers attribute the origin of mud volcanoes and diapiric structures to the presence of not only AHFP but also anomalously high pore pressures (AHPOP) in the sedimentary sequence. In this regard, it is proposed to subdivide all mud volcanoes into two genetic types - gas-mud volcanoes and proper mud volcanoes. At the same time, gas-mud volcanoes owe their origin to AHFP, caused by a significant accumulation of hydrocarbon gases, and proper mud volcanoes are associated with AHMF in areas of thick strata of plastic clay rocks. The following classes of mud volcanic manifestations are distinguished: mud volcanoes, mud lumps, salses, griffins. There are volcanoes: land (continental) and sea. Marine mud volcanoes, in turn, are divided into insular and underwater. When the mud volcanic islands are washed away, the so-called. banks. Underwater mud volcanoes can also be divided into shallow and deep water. According to a number of features (structure, morphology, nature of activity, etc.), marine mud volcanoes are complete analogues of terrestrial volcanoes. According to the degree of activity and position in the geological section, volcanoes are distinguished, respectively, active and extinct; open and buried (not expressed in the topography of the sea bottom). So far, there are no clear criteria for dividing mud volcanoes (as well as magmatic ones) into active (actually or potentially active) and extinct ("dead"). Both terrestrial and marine mud volcanoes are very rarely solitary; as a rule, they are grouped into mud volcanic provinces of various sizes. Analysis of data characterizing several hundred mud volcanoes Crimean-Caucasian and South Caspian regions, made it possible to distinguish several morphogenetic types among them: [ 45, 46] 1. Diapiric formations; 2. Cone-shaped buildings with salses and griffins; 3. In the form of swampy areas with puddles of liquid mud - a mud swamp; 4. Depressed synclines (second order mud volcanic structure). Similar types of volcanoes in the Black Sea basin (Sorokin trough) were identified by M. K. Ivanov:
- -- Conical in cross plan and round in plan mud volcanoes; -- Mud volcanoes with distinct collapse calderas along a system of concentric faults; -- "Barbados type" (Dvurechensky volcano). The structure is rounded, more than 1 km in diameter with a flat roof and highly liquefied eruption products; -- Mud volcanoes of fissure type.
- -- An eruption with the release of a large volume of mud volcanic breccia with numerous fragments of rocks, accompanied by explosions (explosions) of various power, emissions of strong gas jets (with or without ignition) and the formation of cracks (this type of eruption is often called "explosive"); -- Emission of gas and formation of large fractures, without ejection of hill breccia; -- Relatively small breccia outflows without intense gas emission; -- Squeezing out breccias with low gas emissions.
Normative and methodological support of the assessment proceduremud volcanicdangerousti
According to SNiP 11-02-96, in the course of surveys, it is necessary to assess the danger and risk of a particular geological (geological engineering) process. The risk assessment procedure from geological processes is carried out on the basis of complex engineering-geological and socio-economic studies, and includes 4 consecutive operations:
- -- Assessing the danger of geological processes; -- Assessing the vulnerability of structures to hazardous processes; -- Assessment of the exposure of a group of people and structures to hazardous processes in a certain area; -- Assessment of probable economic and social damage (risk).
- -- Selection and substantiation of a methodology for assessing the hazard of a geological process or a complex of interrelated processes; -- Parametrization of the geological process; -- Selection of criteria for assessing the danger of the geological process; -- Substantiation of the hazard category of the geological process.
Hazard and risk assessment experiencefor structures
There are few works devoted to the assessment of the danger and risk of mud volcanoes, and they mainly consider the dangerous effects associated with the activity of volcanoes located on land. There are examples of a quantitative assessment of the danger of eruptions in the territory of Azerbaijan based on a statistical analysis of the frequency, volumes of breccia and gas eruptions, linear parameters of mud flows. Data on 220 volcanic eruptions over the past two centuries were used by these authors to estimate the likelihood of eruptions, the height of the resulting flame column, and the prediction of the spatial characteristics of mud flows, which together determine the level of risk created by these natural phenomena. The most important results of the work performed on the assessment of hazard and risk in the areas of development of mud volcanoes are: classification of their emissions by volume and composition, zoning of the territory around an active mud volcano according to the degree of danger of gas manifestations, and characterization of hazard and risk factors. Among the hazardous effects in the zone of mud volcanic activity are: flows of mud volcanic breccia, subsidence, displacement and rupture of soil, ground shaking, gas shows, gas ignition, emissions of solid products, formation of zones of abnormally high reservoir pressure (Fig. 1). The work of Azerbaijani specialists concerning the assessment of the risk of mud volcanic eruptions for pipeline systems deserves special attention. The report, prepared as part of the environmental impact assessment of the Baku-Tbilisi-Ceyhan gas pipeline project, describes in detail the morphology of mud volcanoes near the gas pipeline route, the hazardous effects associated with them, and a qualitative assessment of the risk from mud volcanic activity. The paper notes that the route of the Baku-Tbilisi-Ceyhan pipeline system and the South Caspian gas pipeline will pass in close proximity to two active mud volcanoes. In this regard, there is a threat of damage to pipelines by local earthquakes that occur during paroxysms of volcanic eruptions. Mud volcanic breccia flows, faults and soil subsidence also pose a threat to the integrity of pipelines. Unexpected loading due to the accumulation of a large mass of breccia in a certain section of the route can put significant pressure on the pipeline. A certain threat to the integrity of the pipeline system is also posed by some geochemical features of the hilly breccia. Within the hill covers, the likelihood of metal corrosion increases due to the increased salinity of the mud volcanic breccia. An expert assessment of the danger of underwater mud volcanoes was carried out in the course of surveys for the construction of the Russia-Turkey gas pipeline. So, for example, at the base of the Turkish continental slope, 600 m from the route, an isometric isolated hill with a diameter of up to 2500 m and a height of 60 m was found with traces of landslides on the slopes and with vertical faults - a presumably inactive mud volcano. In addition, a structure resembling a mud volcano was discovered in the Russian sector of the Black Sea on the abyssal plain at the 100th km of the gas pipeline route. The proposed mud volcano is not dangerous, because it is buried under a thickness of Quaternary sediments with a thickness of 400 m and is not active.
Brief description of mud volcanic activity inAzov-Black Sea basin
In the Azov-Black Sea basin, manifestations of mud volcanism have been found within all the main morphological elements of the sea bottom: the shelf, the continental slope, and the deep-sea basin. Mud volcanoes are concentrated within several mud volcanic provinces: the Tuapse trough, the Shatsky swell, the Sorokin trough, the East Black Sea and West Black Sea depressions, etc. A total of 139 mud volcanoes have been recorded in the Black Sea basin, including 105 active ones. Their age is Pliocene-Quaternary, mainly Oligocene-Lower Miocene. Almost all mud volcanoes form positive forms in the form of underwater cones 10-120 m high, the diameters of the cones are 250-4000 m. Volcanoes are rarely observed in the form of a negative relief structure (Tredmar volcano - the central part of the Black Sea) and fissure type (mud volcano of the Temryuk Bank in the Sea of Azov) (Fig. 2). As a rule, mud volcanoes are structurally located to the axes of anticlinal uplifts, complicated by faults, located on domes or slightly shifting to the periclines and wings of the fold. Mud volcanoes in the deep parts of the Black Sea have become objects of study as geological hazards only very recently in connection with the construction of gas pipelines. In particular, when choosing the route of the South Stream gas pipeline, almost all currently known mud volcanoes in the Black Sea were taken into account. During the survey, a new volcano was also discovered (Fig. 3). Volcanoes in the Tuapse trough are associated with anticlines. In particular, two volcanoes are confined to the largest anticline of the Tuapse trough, Manganari: Manganari-1 and Manganari-2, respectively, 1000 by 600 m and 300 by 250 m in size and 60 and 10 m high. Judging by the age of the sediments overlying the Manganari volcano -1, its last eruption took place in the pre-Holocene epoch. He is probably going through a dormant stage at the moment. From the west, the buried Geoeko anticline adjoins the Manganari anticline with the Ekolog and Neftyanoy volcanoes, which pierced the 200-meter thick sediments of the Late Pleistocene alluvial fan of the Kuban. Volcano Neftyanoy is a modern, active one, there are no Holocene sediments on its top. The last eruption of the Ekolog volcano probably occurred at the end of the Late Pleistocene - at its peaks there are New Euxinian-Black Sea oozes with a thickness of more than 2 m. Sixteen mud volcanoes have been discovered and studied in detail within the Sorokin Trough, on the southeastern slope of the Crimean Peninsula. Volcanism here is confined to the slopes or vaults of diapiric ridges, relatively "young and dynamic". Many volcanoes are accompanied by seeps fixed in the water column. Near a number of volcanoes, geophysical methods have revealed undulating forms in the bottom topography and the structure of bottom sediments. The Shatsky swell separates the Sorokin and Tuapse troughs from the East Black Sea depression. It has a sharply asymmetric shape with a very steep (up to 20°) southwestern and gentle northeastern slopes. There are at least 6 brachyanticlines 3 to 10 km long and up to 100 m high on the arch. Three brachyform uplifts with a diameter of 7 to 10 km and a height of up to 300 m complicate the northern flank. An extensive area of fluidogenic deformations is confined to the arch of the shaft. Up to 7 mud volcanoes have been found within the described province. The dimensions of the mud volcanic structures here are quite significant and reach 1000 by 1000 m in plan. The largest of them (Dolgovskoy) rises 45 m above the bottom. Giant domed forms of diapirism of gas-saturated bottom sediments were found in the East Black Sea depression. One of their so-called. "gas swelling domes" has a diameter of 8 km and a height of several meters. A small mud volcano Gnom is confined to the center of the dome (its height is about 10 m, dimensions in plan are 250 by 250 m). Ten volcanoes have now been recorded within the West Black Sea depression, to the west of the Andrusov swell (central region). Summarizing materials for this area were published by M.K. Ivanov, L.B. Meisner, D. A. Tugolesov., E. M. Khakhalev. . The sedimentary cover of the most sag part of the basin is characterized by the presence of numerous rootless very gently sloping anticlines and dome-shaped uplifts of Maikop and overlying deposits. Low-amplitude discontinuities, normal faults, small grabens, and subsidence funnels are often recorded in the arches of anticlines. Some of the anticlines are associated with mud volcanoes. In total, 10 mud volcanoes with a diameter at the base from 0.5 to 4.0 km and a height of 20 to 120 m have been discovered so far in the central region. Almost all volcanoes and their eruptions are overlain by a half-meter layer of Holocene silts and sapropelites. Radiocarbon analysis of these sediments showed that the last eruptions of volcanoes in this group took place more than 2000 years ago. Currently, they are going through a stage of passive gryphon-salsa activity. Modern mud volcanic activity is shown only by Treadmar and MSU volcanoes. In addition to the discovered ones, seven buried mud volcanoes were discovered in the province under consideration. Mud volcanic morphostructures in the central part of the Black Sea can probably also include a basin with a diameter of 11-12 km, discovered at a depth of about 2100 m during seismoacoustic studies of the R/V "Kyiv" . It is a negative ("concave") form of the bottom mesorelief, limited by ring or semi-ring faults and multi-stage (from 2 to 5) ledges up to 30 m high. "gas swamp" In its central part, presumably, mud volcanic hills were recorded. The basin is probably one of the varieties of fluidogenic deformations of the seabed surface. The geography of mud volcanism in the western sub-basin of the Black Sea is expanding every year. In particular, the paper describes a previously unknown plateau-like mud volcanic structure located on a gentle slope of one of the tributaries of the Paleo-Dniester, approximately 440 by 240 m in size and 30 m high. Three gas fountains are observed above the mud volcanic plateau. The volcano (named Vladimir Parshin) has been functioning since the Neo-Euxine time. In the same area, another mud volcanic chamber was recorded, consisting of 4 volcanoes confined to the arches of anticlines. Analyzing the system of cracks in the arches of the anticlines, the authors of the work come to the conclusion that seeps can occur at a distance of up to 4 km from the vent of the volcano. In addition to the mud volcanoes described above, in the western sub-basin, mud volcanic chambers have also been reliably recorded in its southwestern part in the zone of transition from the foot of the continental slope to the abyssal plain. This area is characterized by the concentration of a significant number of mud volcanoes in the zone of near-surface diapirism. The largest number of mud volcanoes, mostly terrestrial, is concentrated in the Taman mud volcanic province. Mud volcanic activity in this province is associated mainly with Maikop deposits. There are 43 mud volcanoes here, 19 of them are active. . The mud volcanoes of the province under consideration have been studied earlier than others and in the most detail. As in other provinces, mud volcanoes, with rare exceptions, are confined to the axial parts of anticlinal ridges, predominantly NE-trending. For the purposes of our research, active marine underwater volcanoes in the shallow Temryuk Bay are of the greatest interest: Temryuksky and Golubitsky (Fig. 4). Over the past decades, repeated explosive eruptions of these volcanoes have been recorded in the bay with the formation in the sea of small islands consisting of silty clay with blocks of dolomites, sandstones, siltstones and mudstones. In total, over the past hundred years, about 30 large explosive eruptions have occurred in the Kerch-Taman region. The total number of explosive eruptions in the Sea of Azov is 12.
Evaluation criteria and hazard factorsmud volcanic activity
The most important questions hazard assessmentmud volcanic activity- find out periodicity(frequency) eruption enii active volcanoes anddetermination of the probability of occurrence of new mud volcanoes. Specified questionsconsidered in works [ 5,44, 45,57,63 ] and have not yet received a clear solution. Observations on said that eruptionsmud volcanoes occur extremely unevenly. So, for example, p periodicity of eruptionsboth ground and underwater mud volcanoes in Azerbaijan varies widelyelakh - from several monthseggs up to 100 years old or more. The presence of 1-2 year old, 11 year old, 22 year old, 50 year old, 60 year old and 80 year old cycles is noted. About 60% mud volcano eruptions originated in Azerbaijan dilo at intervals of up to 15 years. In the Black Sea, the periods of activation of mud volcanoes are: 130-1200; 45-120; 2.5-25 years, and in Azov over the past 200 years, the eruption of the Golubitsky volcano of varying intensity occurs on average after 14-15 years. According to the calculation m [52] in within the Taman mud volcanoprovince There are three major cycles of activity with a period of 75 years. Within the established cycles, the presence of 11-12 summer cycles is noted. Khainim V.E. and Khalilov E.N., based on the generalization of a large empirical material, an important conclusion was made from the point of view of predicting the intensity of volcanic activity: "the longer the time between the maxima of the activation of volcanoes, the higher the degree of subsequent activation." A similar conclusion ("In general, the longer the rest interval between eruptions, the more powerful the eruption" was previously made by D. Rothery. The probability of new mud volcanoes occurring within areas where they have not been observed before is very low. For example, only 4 new mud volcanoes have emerged in Azerbaijan on an area of 17,600 km 2 over the past 100 years. The duration of volcanic eruptions ranges from 10-15 minutes. up to several days. Explosive eruptions are usually of short duration. During explosive (explosive) eruptions of mud volcanoes, the following main damaging factors arise: dynamic, thermal (thermal) and chemical. The cumulative impact of damaging factors on the environment leads to its pollution, ground shaking and deformation of the earth's surface, cracking, activation of landslide processes, the release of mud volcanic breccia, tsunamis. The radius of the impact zone of damaging factors during an explosive eruption can reach several kilometers. The most dangerous are the following phenomena, directly or indirectly associated with mud volcanic eruption: Mud volcanic earthquakes. Catastrophic eruptions are always accompanied by earthquakes, which often leads to the destruction of buildings and structures, bending or breaking of the production strings of oil and gas wells. The intensity of earthquakes varies from 3-3.5 to 6-7 points and sometimes can reach 8 points on the MSK scale. Explosive volcanic eruptions can serve as a potential source of tsunamis. However, the question of the efficiency of tsunami generation during mud volcano eruptions has not been practically studied at present. Flows of mud volcanic brecciaandmud flooding. Hill (mud volcanic) breccia during explosive eruptions erupts in the form of powerful (thickness from 5-6 m to 10-20 m depending on the consistency of the hill breccia) fan-shaped or tongue-shaped streams with a width of several hundred meters to 1.5 km and a length of 1-4 km. As a rule, hill breccia contains fragments of semi-rocky rocks (argillites, dolomites, marls, etc.). Inclusions of fragments of hard rocks in breccias usually make up no more than 10% of the total volume of the mass, the sizes of blocks in breccias reach 2-10 m 3 . The area of mud volcanic covers varies from 0.8 to 38 km2. Mud volcanic breccia flows, considered as a type of hazard, can be divided into three groups depending on their location: flows located inside the crater; streams that form tongues on the slope of a volcanic cone and streams that go beyond the mud volcanic structure. The latter are the most dangerous, as they pose a threat to the population living in the vicinity of the volcano, as well as to nearby buildings. In the past, mud flooding of ancient cities (Fanagoria, Taman Peninsula, 63 BC) and villages ("Old Gyady", Azerbaijan, XV century) took place. In 1930, a breccia flow (up to 3 m high) flooded several one-story houses on the outskirts of Kerch, and in 1982, as a result of the pressure of the hilly breccia, a number of buildings collapsed in the same place. On the Taman Peninsula, in our days, there was a case of overturning of high-voltage poles as a result of the mechanical pressure of the knoll mass. There were also cases of flooding of trenches and pits by the plastic mass of rocks, passed near mud volcanoes in the stage of their passive gryphon-salsa activity. In addition, cases of narrowing of wellbores, blowouts of pipes and bulging of clay mass to the surface during drilling of oil wells within the Baku archipelago are described. At the bottom of the sea, the outpouring of breccia leads to the formation of banks, streams dangerous for navigation and underwater structures. There are known cases of ships landing on the ground on banks that arise in the Kerch Strait as a result of mud volcanic activity. crack formation. Among the dangers that arise during the eruption of mud volcanoes, one should include cracking in the center and along the periphery of the eruption. The greatest danger for buildings and structures in the areas of development of mud volcanoes is associated with large linear ruptures (up to 3 km or more) with displacements up to 1.5 - 8 m. Their depth reaches 15 m, their width is 5 m or more (Fig. 5). Ddeformationssurfacessushiand seabed. Very often, with the explosive nature of the volcanic eruption along the faults, a part of the volcanic structure and adjacent bottom sections subside. Mud volcanoes with clearly defined collapse calderas along a system of concentric faults have been studied in the central part of the Black Sea (Tredmar volcano), and on land - within the Kerch Peninsula (here, dips along the periphery of volcanoes are called "depressed synclines"), the West Kuban trough and in a number of other provinces. For example, the eruption of the Golubitsky volcano in 1994 and 2002 was accompanied by the subsidence of the seabed in the coastal strip within a radius of 500 m southeast of the volcanic island, which caused damage to a number of structures. The consequences of deformations of sections of the seabed with commercial facilities erected within them may be a violation of their stability, contributing to the emergence of emergency situations. gas shows. When assessing the possible dangers in the development of mud volcanoes, it is necessary to pay special attention to the degree of danger of gas manifestations. The gases of mud volcanoes, along with mud waters and breccias, are the main component of eruption products. The gases of mud volcanoes contain methane, carbon dioxide, heavy hydrocarbons, nitrogen, argon, helium, sometimes hydrogen, hydrogen sulfide, carbon monoxide, radon, helium are found. There are six types of knoll gases: methane (predominant), methane-carbon dioxide, carbon dioxide, nitrogen, heavy hydrocarbon and carbon dioxide-nitrogen-methane. In a number of cases, gas torches (seeps) are observed above the craters of active underwater volcanoes (Dvurechensky, Admiral Mitin, and others). It is possible that gas emissions occur pulsatingly. It has been established that natural flares (seeps), as well as near-surface gas emissions during drilling from the so-called. "gas pockets" with AHFP can form at a distance of up to 4-5 km from the volcanic vent. . The depressurization of horizons with AHFP, the release and spread of gas create an explosive situation on the deck of a drilling ship, platforms, threaten people's health, and lead to a catastrophic loss of buoyancy of drilling units. In the waters of the Caspian Sea, in the areas of mud volcanism, there were accidents with human casualties during the drilling of prospecting and exploratory wells for oil and gas. Explosion and burninggases. Explosive eruptions in mud volcanic provinces are among the most dangerous phenomena. Described phenomenonoccurs during explosive reactions of gas with air ("explosive mixture"), i.e. at the content of gas (mainly methane) in the airin the amount of 5-15%. Ignition of gases sometimes also occurs during eruptions of underwater mud volcanoes. On land, during fiery eruptions, the region of the volcano and the territory within a radius of up to 1-2 km from it represent an area of increased temperature. flame height during the most powerful eruptions of mud volcanoes reached 500 m , combustion temperature(according to V. A. Nesterovsky) -1400 o C. A model for the formation of a mud eruption flame has been created, which takes into account the influence of strong winds and makes it possible to calculate the height of its column. The temperature distribution in the vicinity of the flame column was also estimated. In a number of cases, gas explosions during volcanic eruptions (Big Bozdag in the Shamakhi region, Svinoye in the Caspian Sea) were accompanied by the death (as a result of thermal exposure) of people and domestic animals. Often, due to the occurrence of a shock wave, destruction and damage to nearby buildings and structures occurs. explosive eruptions often accompanied scattering of fragmentsbreccias and blocks of hard rocks weighing up to 100 kg or more at a distance of up to 100-200 m. Environmental pollution. Ecological and geological aspects of mud volcanic activity are still poorly understood. At the same time, mud volcanoes are natural sources of increased environmental hazard in water areas. They spew, as shown above, huge masses of gases, mainly methane, carbon dioxide, nitrogen and hydrogen sulfide, which pose a potential threat to aquatic ecosystems. The gas released during a volcanic eruption can be both flammable and toxic. A case of the death of a large number of cormorants was recorded during the eruption of an island mud volcano in the Caspian Sea, which was accompanied, presumably, by the emanation of carbon dioxide. Mass mortality of aquatic organisms was observed in the Turkish sector of the Black Sea two days before the Izmit earthquake (August 17, 1999), which is explained by the release of methane from bottom sediments. Of particular danger may be the release of hydrogen sulfide from underwater volcanoes located on the shelf. At great depths and in stagnant conditions, it is able to accumulate, which leads to a deterioration in water quality and the conditions for the existence of bottom biocenoses. Among the dangerous effects of mud volcanic activity, one should also include the release of environmentally hazardous chemicals. Mud volcanic deposits are enriched to the greatest extent in mercury, arsenic, lithium, boron, lithium, manganese and nickel, the concentrations of which are higher than clarke ones. The ecological situation in the areas where mud volcanoes are located is usually assessed as "satisfactory" and "crisis". Material and social losses from the eruption of mud volcanoes can be quite large. Given the nature of this process (the uncertainty of the moment of occurrence and intensity of manifestation), as well as the severity of the consequences, there is reason to classify explosive eruptions as catastrophic processes that can cause an emergency of one class or another.Identification of underwatermud volcanoesandevaluation of themactivity
Identifying mud volcanoes on land is not a difficult task, with the possible exception of buried structures. On the day surface, in some cases, there are practically no morphological and geological signs of the previous existence of a mud volcano, since their mud volcanic structures are destroyed by denudation, and the hill deposits are buried under younger formations. The greatest difficulties are associated with the identification of underwater volcanoes, especially in the deep parts of the sea. To date, there are the following main signs of underwater mud volcanism (but with additions): - morphological (the presence of a cone-shaped structure on the bottom surface or, in rare cases, a negative relief shape surrounded by an annular swell along the periphery); -- lithological (the presence of breccia of a certain chemical and mineralogical composition , pseudoturbidites and turbidites);-- gas-hydrogeochemical (anomalous gas saturation of sediments, anomalously high concentrations of hydrocarbon gases, the presence of radon and helium in them, excess of background values of arsenic and mercury in bottom waters); -- structural-geological (dipirism, depressed synclines, anticlinal folds, discontinuities, fluidogenic deformations, etc.); -- seismoacoustic (diffracted waves within the upper part of the volcano's vent, lack of regular seismic recording, characteristic "bright spots" above the volcano's vent, change in amplitude and polarity of reflections); -- thermal ( positive water temperature anomalyover the crater of the volcano). Signs of the activity of mud volcanoes are considered to be the presence of: liquefied, supersaturated with gas breccia directly on the surface of the seabed, gas torches above the vent of the volcano, griffins, etc.
Conclusion
Summing up the results of the analysis of materials on mud volcanoes of the Azov-Black Sea basin and Primorye and associated hazardous phenomena, we can state the following:
- -- Territories (water areas) around active mud sites are periodically exposed to dangerous impacts, characterized by difficult natural conditions, therefore, during their economic development, additional engineering surveys are needed, including an assessment of the danger and risk from mud volcanic eruptions. -- During explosive eruptions, such impacts extend to 4-5 km from the vent of the volcano and can lead to the death of people, animals, the destruction of buildings and structures, environmental pollution, and the occurrence of emergencies on ships and offshore platforms. The main hazard and risk factors are earthquakes, mud flows, spontaneous combustion of methane, subsidence of the land surface and the sea bottom, cracking in the center and along the periphery of the eruption. -- In a potentially dangerous zone, when performing surveys, it is necessary to establish: the type of volcano, the structure of the upper part of the sedimentary cover, lithological, chemical composition, properties and age of bottom sediments, morphometric characteristics of the mud volcanic structure and breccia flows, fluidogenic deformations, gas manifestations and composition of gases, AHFP zones , area of manifestation, periodicity and intensity of eruptions. -- The main method of preventing possible emergencies during mud volcanic eruptions is to limit construction in the hazardous zone. An analysis of the consequences of the most dangerous type of eruptions - explosive ones, makes it possible to recommend removing construction sites outside the zone of possible thermal impact, shock wave and the border of possible mud flooding of the territory. The construction sites of especially dangerous and technically complex facilities should be at least 4-5 km away from the crater of the volcano. -- It is recommended to carry out strength analysis of structures, taking into account possible explosive, shock and seismic effects caused by the eruption of a mud volcano, and, if necessary, to increase their resistance to external critical pressure. -- In order to ensure the safety of the population and the safety of buildings and structures in the mud volcanic provinces, it is necessary to organize monitoring of the activity of mud volcanoes.
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