Mudflow classification and types mudflows... The type of mudflow is determined by the composition of mudflow rocks. The main types of mudflows: water-stone; mud; mudstone. Mudflows are characterized by linear dimensions (length and width), movement speed, duration and power (volume). By power (volume) mudflows are subdivided into catastrophic, powerful, medium and low power. Catastrophic mudflows are characterized by the removal of more than 1 million cubic meters of material. m, most often formed as a result of earthquakes and volcanic eruptions. Powerful mudflows are characterized by the removal of material from 100 thousand to 1 million cubic meters. m and are rare. With mudflows of medium thickness, material removal is observed from 10 to 100 thousand cubic meters. m and occur once every 2-3 years. With mudflows of low power, the removal of material does not exceed 10 thousand cubic meters. m and arise annually, sometimes several times a year. Mudflow classification. Classification of mudflows according to the height of their sources. Classification of mudflows by composition.
Slide 9 from the presentation "Sat down" to OBZh lessons on the topic "Mountains"Dimensions: 960 x 720 pixels, format: jpg. To download a free slide for use in the OBZH lesson, right-click on the image and click "Save Image As ...". You can download the entire presentation "Seli.ppt" in a zip-archive of 1212 KB.
Download presentationThe mountains
"Earthquake Lesson" - Earthquakes. Secondary lesions. 5. 3. What services are the first to arrive at the disaster site? Man is not able to prevent an earthquake! Lesson in the 7th grade of the N-Rotayevskaya school. 2. Primary lesions. Prepare for evacuation. Turn on the means of receiving information available in the house - TV, radio point.
"Natural disasters" - Volcanic eruption. Flood. Drought. Avalanche. Natural disasters. Natural disasters have threatened the inhabitants of our planet since the beginning of civilization. Tornado. Somewhere more, somewhere less. The presentation was carried out by a student of 3 А CLASS Kristina Papyan. Earthquake. Tsunami. Fire in the steppe. Fire in the forest.
"Landslides mudslides landslides" - Collapse of glaciers. Mud (say - "stormy stream") - a mountain stream, consisting of a mixture of water, mud, stones (there are mud, stone, mud-stone). Mudflows are formed in the mountains. The descent of an avalanche is accompanied by the formation of an air pre-shock wave, which produces the greatest destruction. An avalanche is a fast, sudden movement of snow and / or ice down steep mountain slopes, posing a threat to human life and activities.
"Natural situations" - What are the causes and possible consequences of an earthquake? Important to remember! How to render the first medical assistance? What exist general rules transportation of the victim? 1st group "Rescuers" Earthquake. Earthquakes Floods Forest and peat bog fires. I. Goethe. V. Hugo. Is it possible to save life for yourself and those around you in dangerous situations?
"Tsunami in the Ocean" - Tsunami. Events at the arrival of the tsunami. Emergencies natural character. Check yourself. Wave height is the vertical distance between the crest and the base of the wave. Unusual drift of ice and other floating objects, formation of cracks in the fast ice. Organization of evacuation of the population. Volcanic eruptions(around 5%).
In general terms, the process of formation of a torrential mudflow proceeds as follows. Initially, the water fills the pores and cracks, while simultaneously rushing down the slope. In this case, the adhesion forces between the particles sharply weaken, and the loose rock comes into a state of unstable equilibrium. Then the water begins to flow over the surface. The first to move are small soil particles, then pebbles and rubble, and finally stones and boulders. The process is growing like an avalanche. All this mass enters the ravine or channel and draws new masses of loose rock into motion. If the water consumption is insufficient, then the mudflow seems to fizzle out. Small particles and small stones are carried down by the water, large stones create a chimney in the channel. The mudflow can also stop as a result of the attenuation of the current speed with a decrease in the slope of the river. No definite frequency of mudflows is observed. It is noted that the formation of mud and mud-stone flows is facilitated by the preceding dry long weather. At the same time, masses of fine clay and sand particles accumulate on the mountain slopes. They are washed away by the downpour. On the contrary, the previous rainy weather favors the formation of water-stone flows. After all, the solid material for these streams is mainly found at the foot of steep slopes and in riverbeds and streams. In the case of good previous moisture, the connection of stones with each other and with the bedrock weakens.
V last years anthropogenic factors have been added to the natural causes of the formation of mudflows, that is, those types of human activity that cause the formation of mudflows or their activation. These factors include:
Deforestation on mountain slopes;
Degradation of the soil cover by unregulated grazing;
Incorrect placement of waste rock dumps by mining enterprises;
Explosions during the construction of railways and highways and various structures;
Insufficient land reclamation after stripping works and unregulated water discharge from irrigation facilities on the slopes;
Deterioration of soil and vegetation cover by industrial waste.
So, the destruction of vegetation, quarrying, cutting of slopes by roads, massive construction on the slopes led to the development of mudflows in almost everything Black sea coast Caucasus (from Novorossiysk to Sochi).
Mudflow classification.
According to the particle size distribution of the solid component:
Vodokamenny - a mixture of water with mainly large stones, including boulders and rock debris. Bulk density 1.1 -1.5 t / m3. It is formed mainly in the zone of dense rocks. - Mud - A mixture of water with a solid phase of clay and dusty particles with a low concentration of stones. Volumetric weight 1.5-2.0 t / m3. - Mudstone - a mixture of water, fine earth, pebbles, gravel, small stones; there are also large stones, but there are few of them, they either fall out of the stream, then again begin to move with it. Volumetric weight 2.1-2.5 t / m3. - Water-snow-stone - a transitional stage between the mudflow itself, in which the transporting medium is water, and an avalanche. This classification shows that the mudflow is very heavy, as a result of which the impact of the mudflow reaches 5-12 t / m2.
By genesis:
- Alpine type - characterized by rapid seasonal snowmelt (USA, Canada, Andes, Alps, Himalayas)
- Desert type - occurs in arid or semi-arid areas during sudden heavy rainfall (Arizona, Nevada, California)
- Lahars - volcanic mud flows that appear after heavy rain on the slopes of volcanoes recently covered with powerful, still unstable deposits of dust and ash.
According to the frequency of mudflows, there are 3 groups:
High mudflow activity (with a repeatability of once every 3-5 years and more often);
Average mudflow activity (with a repeatability of once every 6 - 15 years);
Low mudflow activity (with a repeatability of once every 16 years or less).
By their effect on structures:
Low-power - small erosion, partial plugging of culvert openings.
· Medium - heavy erosion, full hole plugging, damage and demolition without foundations.
Powerful - great destructive force, demolition of bridge trusses, destruction of bridge supports, stone structures, roads.
Catastrophic - complete destruction of buildings, road sections along with the road bed and structures, burial of structures under sediments. By water source:
By water source:
Rainwater -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 washout of the products of destruction of rocks and involve them in movement.
Glacial - typical for alpine basins with developed modern glaciers and glacial deposits (moraines). The main source of their solid food is moraines, which are involved in the process of mudflow during the intensive melting of glaciers, as well as during the breakthrough of glacial or moraine lakes. The formation of glacial mudflows significantly depends on the ambient temperature.
Volcanic - can form during earthquakes. In some cases (during volcanic eruptions), when there is a joint formation of liquid and solid components of mudflows.
By the state of the water:
Associated (structural) flows - consist of a mixture of water, clay and sand particles. The solution has the properties of a plastic substance. All water is contained in micelle shells. The stream moves as a whole. Unlike a water stream, it does not follow the bends of the channel, but destroys and straightens them or passes over obstacles.
Unconnected streams - they move with great speed; there is a constant impact of stones, their rolling and abrasion. There is a large amount of water, which acts as vehicle... The stream mainly follows the bends of the channel, destroying it in places.
Mudflows are subdivided, based on the main factors of occurrence, into three classes (Table 2.18) and, based on the root causes of occurrence, into eight types (Table 2.19).
According to the composition of the transferred solid material, mudflows are usually distinguished as follows:
mud flows, which are a mixture of water and fine earth with a low concentration of stones (volumetric weight of the flow is 1.5–2.0 t / m 3);
mud-stone streams, which are a mixture of water, fine earth, pebbles, gravel, small stones; there are also large stones, but there are not many of them, they either fall out of the stream, then again begin to move with it (the volumetric weight of the stream is 2.1–2.5 t / m 3);
water-stone streams, which are a mixture of water with mainly large stones, including boulders and rock debris (volumetric weight of the stream 1.1–1.5 t / m 3).
Mudflows are subdivided by the nature of their movement in the channel into connected and incoherent.
Table 2.18
Classification of mudflows based on factors of occurrence
|
Classes mudflows |
Formation factors |
Peculiarities distribution and regime |
|
Zonal manifestations |
Climatic (variability of hydrometeorological elements) |
Distribution is ubiquitous and zonal. Mudflows are systematic; exit paths are relatively constant |
|
Regional manifestation |
Geological - active endogenous processes |
Limited distribution (in areas of greatest tectonic activity). Mudflows are occasional; exit paths are inconsistent |
|
Anthropogenic |
Economic activity - disturbances in the stability of mountain landscapes |
They develop in areas of greatest economic pressure on the mountain landscape. Characterized by the emergence of new mudflow basins with episodic, less often - systematic descent of mudflows |
Connected streams consist of a mixture of water, clay and sand particles. The solution has the properties of a plastic substance. The flow, as it were, represents a single whole. Unlike a water stream, it does not follow the bends of the channel, but destroys and straightens them or rolls over an obstacle.
Table 2.19
Classification based on the root causes of mudflows
|
Types |
Root cause formation |
Areas of distribution and the mechanism of origin |
|
Rain |
Showers, heavy rains |
The most widespread type of mudflows on Earth, prevailing in the mountains of the equatorial, tropical and temperate climatic zones. The origin of mudflows is associated with erosion of slopes and channels, as well as landslides. |
|
Snow |
Intense snow melting in spring |
The dominant type of mudflows in the Subarctic mountains; the solid component of mudflows is represented by snow. The origin of mudflows is associated with the breakdown of waterlogged snow masses and with the breakthrough of snow dams |
|
Glacial |
Intense melting of snow and ice |
Formed in the zone of modern mountain glaciation; the most powerful - mudflows of the Alpine highlands. The origin of mudflows is associated with the breakthrough of accumulations of melted glacial waters, as well as the collapse of moraines and ice |
|
Volcanic |
Explosive volcanic eruptions |
Formed in areas active volcanoes; reach the largest sizes among all types of mudflows in terms of the length of the track and the volume of outflows. The origin of mudflows is associated with the transformation of pyro-classical flows into mudflows due to rapid snow melting, with the descent of crater lakes, etc. |
|
Seismogenic |
High-grade earthquakes |
Formed in areas of high seismicity (8 points or more). The origin of mudflows is associated with the breakdown of soil masses from the slopes into the channel |
|
Limnogenic |
Development dynamics natural lake dams |
Formed in areas of the alpine highlands, which are characterized by dam lakes. The origin of mudflows is associated with the destruction of dams and erosion of channels by a breakthrough wave |
|
Anthropogenic impact |
Creation of accumulations of technogenic rocks in potentially mudflow-hazardous basins; construction of low-quality earth dams, etc. |
Formed in dump storage areas mining enterprises, below reservoirs and elsewhere. The origin of mudflows is associated with the erosion and sliding of man-made rocks, with the destruction of dams and erosion of channels, etc. |
The end of the table. 2.19
Disconnected(current)streams moving at great speed. There is a constant impact of stones, their rolling and abrasion. The stream follows the bends of the channel, subjecting it to destruction in different places.
Mudflows are classified and by volume of transferred solid mass or, in other words, by power, and are divided into three groups:
powerful (strong) - with the removal of more than 100 thousand m 3 of materials to the foot of the mountains, there are once every 5-10 years;
medium capacity - with the removal from 10 to 100 thousand m 3 of materials, there are once every 2-3 years;
low power (low power) - with the removal of less than 100 thousand m 3 of materials, they happen annually, sometimes several times a year.
Quite often, there are very powerful (extremely strong) mudflows, with the removal of more than 1 million m 3 of debris; there are times in 30-50 years.
The classification according to the volume of one-time drifts characterizes both the thickness of the mudflow and the potential of the given mudflow basin. According to the volume of one-time removals, mudflows are divided into 6 groups (Table 2.20).
A stream consisting of a mixture of water and rock debris that suddenly appears in the basins of small mountain rivers.
The body of the stream is formed by a mudflow mixture; the content of solid material in it is from 10 to 75% by volume, the density is from 1 100 to 2 500 kg / m3. Mudflows are characterized by pulsating (wave) movement, a sharp rise in level, short duration of action (in most cases - 1–4 hours). The average depth of the moving stream is 2–10 m, increasing in narrowings and at bends of the channel up to 15–20 m. The speed of mudflows ranges from 2 to 10 m / s; the maximum discharge in small catchments is 20–40 m3 / s, reaching 210 thousand m3 / s in large ones. The volume of detrital material carried out by mudflows is measured in thousands of cubic meters in small slope mudflows and tens to hundreds of thousands in valley mudflow basins. The maximum values of the volume of removals in the middle mountains are 500–600 thousand m3, in the high mountains - 5–6 million m3.
The direct reasons for the origin of mudflows are heavy rains, intense melting of snow and ice, breakthroughs of water bodies, less often - volcanic eruptions and high-magnitude earthquakes.
Eight main types of mudflows are distinguished by their genesis. The degree of mudflow activity is assessed using an integral indicator that includes the characteristics of the relative density of mudflow channels and the average maximum volume of debris carried out by mudflows. Thus, the integral indicator takes into account both the prevalence of mudflows and their capacity.
The zoning of the country's territory according to the degree of mudflow hazard made it possible to identify patterns of spatio-temporal variability of the mudflow process and to distinguish two zones, six regions and fourteen mudflow regions. The zones - warm and cold - differ in the prevailing genetic types of mudflows: in the warm zone, mainly rain mudflows are formed, in the cold zone - snow (water-snow flows). The border between them corresponds to the border between the temperate and subarctic climate types. The division of zones into regions is determined by differences in the mudflow regime: the duration and calendar dates of the mudflow hazardous period, as well as the frequency of mudflows. These differences depend on the shift climatic conditions... When identifying mudflow areas, differences in the degree of mudflow activity associated with the absolute and relative heights of mountains, types of altitudinal zonation, the level of development and in the set of genetic types of mudflows were taken into account.
The period of the greatest mudflow hazard in the South Siberian region falls on July-August, in the Pacific - in August-September. This is due to the change continental climate in Siberia to monsoon in the south Of the Far East(causing the descent of most mudflows are characteristic of late summer - early autumn). In the Eastern region of the cold zone, snow flows descend twice as often as in the Western one (every 5 and 10 years, respectively). The main reasons for the higher frequency of mudflows in the Eastern region are the simultaneous melting of snow over a vast area and a homogeneous structure in a sharply continental climate.
The highest mudflow activity is typical for the North Caucasian and Baikal mudflow regions. In the high-mountainous part of the Greater Caucasus, it is due to the high values of the absolute and relative heights of the mountains and the presence of significant glaciation, which is in the stage of degradation. The maximum volume of detrital material carried out here reaches 3 million m3, with a high density of mudflow channels. In the Baikal mudflow region, the ridges lying in the axial part of the Baikal rift zone (Eastern Sayan, Khamar-Daban, ridges) are characterized by high mudflow activity. This area is characterized by "live", the contrast of the relief is high. The specificity of the mudflow hazard in the Kamchatka region is made up of volcanic mudflows, among which there are also giant ultra-mudflow flows (for example, descended from the Bezymyanny volcano on March 30, 1956).
Activation of mudflow processes caused by economic activities, is most pronounced on and.
The descent of mudflows is often accompanied by destruction and casualties. The reasons for such a dangerous nature are the high speed and shock impact of the leading front of the stream, the drift of the territory by mud-stone, mud-ice or mud-snow masses, strong deep and lateral erosion of the channel, and temporary damming of rivers. The main objects of the negative impact of mudflows are most often settlements, railways and highways, communication lines and power transmission lines, canals, agricultural land, recreational facilities.
