A landslide is a natural phenomenon which occurs when a mass of soil, rock, snow or mud moves suddenly and violently down a slope, dragging everything in its path. Also known as landslide or avalanchelandslides can be caused by various causes, such as heavy rain, melting snow, earthquakes, volcanic activity, erosion or human action.
Definition and meaning of “alud”
an avalanche is a sudden and violent displacement of a land mass, snow or rock down a slope. Avalanches can have devastating consequences, since they can range from destroying homes, infrastructure and crops and causing injuries and deaths to generating serious comprehensive damage to the environment.
It is important to know How do these natural disasters occur? and what measures can be taken to prevent them and minimize their effects.
How does the avalanche occur?
An avalanche occurs when a mass of earth, snow, or rock moves abruptly down a slope due to the force of gravity. The causes that can trigger an avalanche are diverse, and may be related to meteorological, geological or anthropic factors.
Below are some of the main factors that can cause an avalanche:
- Heavy rain: It is a meteorological event in which a very abundant precipitation in a short period of time. This phenomenon can cause flooding, landslides and other types of damage.
- snow melt: Occurs when the ambient temperature rises enough to cause accumulated snow to melt and turn into water. This phenomenon is common in mountainous regions and can cause landslides or river floods.
- earthquakes: They are sudden and violent movements of the ground that occur due to the release of energy accumulated in the geological faults. Earthquakes can cause landslides and other types of mass displacements.
- Volcanic activity: Refers to events related to the activity of volcanoes, such as eruptions, explosions, pyroclastic flows, lahars and others. These events can cause landslides and other types of mass displacements.
- Erosion: It is the process of wear and degradation of soil and rocks that produced by the action of water, wind, ice and other factors. Erosion can weaken the ground and cause landslides.
- human action: It refers to the activities carried out by human beings, such as the construction of buildings, the carrying out excavations, the felling of forests and others. These activities can modify the terrain and increase the risk of landslides and other types of mass displacement.
In addition to the terms that have already been defined, there are others that are related to the avalanche phenomenon and that may be relevant:
- moraine: It is an accumulation of rocks and sediments that form at the edges of glaciers. The moraines can be a factor that contributes to the formation of avalanches, since they can weaken the ground and increase the instability of the slopes.
- permafrost: It is a permanently frozen layer of soil or rock found in the polar and high mountain regions. The thawing of permafrost can cause the weakening of the ground and increase the risk of landslides.
- volcanic tuff: It is an igneous rock composed of fragments of ash and solidified lava that are formed during volcanic eruptions. Volcanic tuffs can contribute to the formation of landslides and other types of mass displacements.
- fault zone: It is an area of the earth’s crust where a fracture and displacement of the rock blocks. Fault zones can be a contributing factor to avalanche formation.
How are avalanche risks classified?
Avalanche risks can be classified in various ways, but one of the most common classifications is that based on intensity and frequency of the avalanches Below we explain the four most common risk levels:
- Low risk: Refers to areas where avalanches are infrequent and have a low or moderate intensity. In these areas the presence of snow and ice on the slopes is limited and the probability of an avalanche occurring is low.
- moderate risk: Refers to areas where avalanches are more frequent and can have a moderate to high intensity. In these areas, the presence of snow and ice on the slopes it is more common, which increases the probability of an avalanche occurring.
- High risk: Refers to areas where avalanches are very frequent and can have a high intensity. In these areas, the presence of snow and ice on the slopes is constant and the probability of an avalanche occurring is very high.
- extreme risk: Refers to areas where avalanches are extremely frequent and have a very high intensity. In these areas, the presence of snow and ice on the slopes is permanent and the probability of an avalanche occurring is practically safe.
It is important to take into account that there are other factors that can also increase the risk of avalanches, such as topography, exposure to sunlight, temperature, humidity and the presence of obstacles on the slopes. Therefore, it is necessary carefully assess each risk area before taking preventive or emergency measures.
What are the types of avalanches?
There are several types of avalanches, which they differ by the way the earth or snow moves and by the characteristics of the land. Here are the most common types of avalanches:
- dry snow avalanches: Occurs when the snow is not cohesive and slides down the slope as a block or as a loose mass. They are the most frequent avalanches in mountain areas and can be very dangerous, since the snow moves at great speed and drags everything in its path.
- wet snow avalanches: They are produced when the snow becomes wet and turns into a heavy and viscous dough, which slides down the slope dragging rocks, trees and other objects. They are less frequent than dry snow avalanches, but they can also be very dangerous.
- plate avalanches: They occur when a denser and more compact layer of snow slides over a layer of looser snow. Snow sheets are formed by the wind or by changes in temperature, and they can break and slide like a giant slab. They are the most dangerous avalanches and can affect large areas of the slope.
- cornice avalanche: They occur when an accumulation of snow forms on the edge of a ridge or a cliff, forming a kind of platform that extends beyond the edge of the terrain. The cornices can break and slip easily, causing dangerous avalanches.
- mudslides: They occur in areas of rocky terrain or bare soil, when snow and water mix with the earth and form a mass of mud that slides down the slope. They are less frequent than snow avalanches, but they can also be very dangerous.
each type of avalanche has specific characteristics and risksand it is important to know them in order to take appropriate preventive or emergency measures in each case.
Plate avalanches are a type of avalanche that occurs when a denser and more compact layer of snow glides on a looser layer of snow. Snow packs are formed by wind or changes in temperature, and can break off and slide like a giant slab.
These avalanches are the more dangerous and can affect large areas from the hillside Furthermore, they are difficult to predict and can occur without warning. Snow plates can be present on any type of terrain, but they are more frequent in mountain areas with strong winds and temperature changes.
recent snow avalanches
Recent snow avalanches are a type of avalanche that occurs when a layer of freshly fallen snow slides on an older layer of snow. These avalanches are common in mountain areas after a snowfall and can be very dangerous, since recent snow may not be cohesive with old snow and can easily slide down the slope.
Fresh snow can be very unstable and break-prone, plus it it can slide due to the weight of a person or from an object moving on the snow, or due to an external disturbance such as wind or noise. Fresh snow avalanche can be very large and can travel at high speed, making them especially dangerous.
Melt avalanches are a type of avalanche that occurs during spring or summer, when snow melts and turns into water. These avalanches are common in mountainous areas with permanent snow and ice and can be very dangerous, as snow and ice can easily slide down the slope due to increased weight and decreased cohesion.
melting avalanches can occur due to exposure to sunlight, temperature, rain and humidity, which can speed up the melting process. Water seeping into snow or ice can weaken the structure and cohesion of the snow, increasing the risk of an avalanche occurring. Meltslides are also large and travel at high speed.
How to avoid avalanches?
Avalanches can be unpredictable and dangerous, but there are measures that can be taken to avoid them or reduce the risk of being caught in one. Here are some safety measures you can follow to avoid avalanches:
- Know the weather and snow conditions: Before venturing into a mountain area, check the weather and snow conditions. find out about the Weather forecastthe layer and quality of the snow, the slope of the land, etc.
- Learn to detect the danger of avalanches: Learn to detect the danger signs of avalanches or landslides, such as cracks in the snow, the noise of thunder or the presence of areas of very heavy snow steep or unstable.
- keep your distance: Keep a safe distance between the members of your group to avoid the increased load in the snow and reduce the risk of an avalanche triggering.
- Use proper equipment: Use appropriate safety equipment, such as a snow shovel, an avalanche detector, a thermal camera, a probe and a climbing harness.
- Avoid the most dangerous areas: Avoid mountain areas with a slope greater than 30 degrees and areas exposed to the sun or areas with running or accumulated water.
- Learn security techniques: Learn proper safety techniques for traveling on snowy and icy terrain, such as the use of crampons and ice axes, and creating anchors.
- Travel in groups: Always travel in groups of at least two or three people and make sure someone knows where you are at all times.