Volcanism and earthquakes are among the oldest processes on Earth. They happened billions of years ago and continue to exist today. Moreover, they participated in the formation of the planet's topography and its geological structure. What is 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 of rocks and metals boiled. After hundreds of millions of years, the top layer of the Earth began to solidify, forming the thickness of the earth's crust. Under it, molten substances or magma remained to seethe.
Its temperatures reach from 500 to 1250 degrees Celsius, causing the solid parts of the planet's mantle to melt and gases to be released. At certain points, the pressure here becomes so great that the hot liquid tends to literally break out.
What is volcanism? This is the vertical movement of magma flows. Rising up she fills the cracksthe mantle and the earth's crust, splitting and lifting solid rock layers, punching its way to the surface.
Sometimes the liquid just freezes in the thickness of the Earth in the form of laccoliths and magmatic 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 (liquid rock melt).
Variety of volcanoes
Now that we have figured out 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, ranging in size from several kilometers and above.
The shape of volcanoes differs depending on the nature of the eruptions and the state of the magma. Under the action of a viscous fluid, dome formations appear. Liquid and very hot lava forms thyroid-shaped volcanoes with gentle shield-like slopes.
Slag and stratovolcanoes are formed from repeated eruption. They have a conical shape with steep slopes and grow in height with each new eruption. There are also complex or mixed volcanoes. They are not symmetrical and have several crater peaks.
Most eruptions form positive landforms that protrude above the earth's surface. But sometimes the walls of the craters collapse, in their place appear vast basins several tens of kilometers in size. They are called calderas, and the largest of them belongs tovolcano Toba on the island of Sumatra.
Nature of earthquakes
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 result from volcanoes, rock falls, and movements and uplifts of tectonic plates.
In the focus of an earthquake - the place where it originates - the tremors are the strongest. The farther away from it, the less shaking is felt. The consequences of earthquakes are often destroyed buildings and cities. During seismic activity, landslides, rock falls and tsunamis can occur.
The intensity of each earthquake is determined in points (from 1 to 12), depending on its scale, damage and nature. The lightest and most imperceptible shocks are given 1 point. Shaking of 12 points leads to uplifts of individual sections of the relief, large faults, destruction of settlements.
Zones of volcanism and earthquakes
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 assumptions, because no one has yet been able to look further than 5 kilometers into the bowels of the planet. Because of this, it is impossible to predict in advance the eruption of the next volcano or the appearance of an earthquake.
The only thing researchers can do is to identify areas where these phenomena occur most often. They are clearly visible in the photo, where light brown indicates weak activity, and dark indicates strong activity.
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: the Pacific and Mediterranean-Trans-Asian belts.
The Pacific belt is located along the perimeter of the ocean of the same name. Two-thirds of all eruptions and tremors on the planet occur here. It stretches for 56 thousand kilometers in length, covering the Aleutian Islands, Kamchatka, Chukotka, the Philippines, the eastern part of Japan, New Zealand, the Hawaiian Islands, the western edges 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).
