Volcanism and earthquakes are one of the oldest processes on Earth. They occurred billions of years ago and continue to exist today. Moreover, they participated in the formation of the relief of the planet and its geological structure. What are volcanism and earthquakes? We will talk about the nature and places of occurrence of these phenomena.
What is volcanism?
Once our entire planet was a huge red-hot body, where alloys from rocks and metals were boiling. After hundreds of millions of years, the upper layer of the Earth began to solidify, forming the thickness of the earth's crust. Under it, molten substances or magma remained seething.
Its temperatures reach from 500 to 1250 degrees Celsius, which is why solid sections of the mantle of the planet melt and gases are released. At certain points, the pressure here becomes so great that the hot liquid tends to literally burst out.
What is volcanism? This is the vertical movement of magma flows. Rising up, it fills the cracks of the mantle and the earth's crust, splits and lifts hard layers of rocks, punching its way to the surface.
Sometimes the liquid simply freezes in the thickness of the Earth in the form of laccoliths and igneous veins. In other cases, it forms a volcano - usually a mountainous formation with an opening through which magma spills out. This process is accompanied by the release of gases, stones, ash and lava (molten rock).
Varieties of volcanoes
Now that we have understood what volcanism is, let's look at the volcanoes themselves. All of them have a vertical channel - a vent through which magma rises. At the end of the channel there is a funnel-shaped hole - a crater, the size of several kilometers or more.
The shape of volcanoes differs depending on the nature of eruptions and the state of magma. Under the action of a viscous fluid, dome formations appear. Liquid and very hot lava forms thyroid-shaped volcanoes with gentle slopes resembling a shield.
From multiple eruptions, slag and stratovolcanoes are formed. They have a conical shape with steep slopes and grow in height with each new eruption. Complex or mixed volcanoes are also distinguished. They are asymmetrical and have several crater vertices.
Most eruptions form positive reliefs protruding above the earth's surface. But sometimes the walls of the craters collapse, in their place appear vast depressions several tens of kilometers in size. They are called calderas, and the largest of them belongs to the Toba volcano on the island of Sumatra.
Earthquake nature
Like volcanism, earthquakes are associated with internal processes in the mantle and the earth's crust. These are powerful shocks that shake the surface of the planet. They arise as a result of volcanoes, mountain collapses, as well as movements and uplifts of tectonic plates.
In the center of the earthquake - the place where it originates - the tremors are the strongest. The farther from it, the shake is less noticeable. The consequences of earthquakes often become destroyed buildings and cities. Landslides, landslides and tsunamis can occur during seismic activity.
The intensity of each earthquake is determined in points (from 1 to 12), depending on its scale, the damage done and the nature. The lightest and most inconspicuous thrusts give 1 point. A shake of 12 points leads to the elevation of individual sections of the relief, large faults, destruction of settlements.
Volcanism and earthquake zones
The complete geological structure of the Earth from the earth’s crust to the very core is still a mystery. Most of the data on the composition of the deep layers are just speculations, because no one has been able to look beyond 5 kilometers into the bowels of the planet. Because of this, it is impossible to predict the eruption of another volcano or the appearance of an earthquake in advance.
The only thing that researchers can do is identify areas where these phenomena occur most often. They are clearly visible in the photo, where a light brown color indicates a weak activity, and a dark color indicates a strong one.
Usually they occur at the junction of lithospheric plates and are associated with their movement. The two most active and extended zones of volcanism and earthquakes: Pacific and Mediterranean-Trans-Asian zones.
The Pacific belt is located along the perimeter of the ocean of the same name. Here, two-thirds of all eruptions and tremors occur on the planet. It stretches for 56 thousand kilometers in length, covering the Aleutian Islands, Kamchatka, Chukotka, the Philippines, the eastern part of Japan, New Zealand, Hawaii, the western regions of North and South America.
The Mediterranean-Trans-Asian belt stretches from the ranges of Southern Europe and North Africa to the Himalayan mountains. It includes the mountains of Kun-Lun and the Caucasus. About 15% of all earthquakes occur within it.
In addition, there are secondary zones of activity where only 5% of all eruptions and earthquakes occur. They cover the Arctic, Indian (from the Arabian Peninsula to Antarctica) and the Atlantic Ocean (from Greenland to the Tristan da Cunha archipelago).