Why do earthquakes occur 2

Earthquake areas

The earthquake risk is very unevenly distributed on earth. While it is usually very quiet in the middle of the old continental plates, extensive earthquake areas extend along the plate boundaries. About 90 percent of all earthquakes (and especially the most severe events) are concentrated along the "Pacific Ring of Fire".

Pacific ring of fire

The ring of fire bears its name after the numerous volcanoes that run along a round 40,000 kilometers long line line up around the pacific ocean. This is essentially the boundary of the Pacific tectonic plate and some adjacent tectonic plates (Nasca plate, Cocos plate, Philippine plate).

The said plates move towards the surrounding continental masses of Asia, America, Australia and the Antarctic. And not only that: the ocean floors are slowly pushing themselves under the continents. Where the ocean floors submerge, “deep sea gullies” form, which are among the deepest oceans on our planet. Beyond these "subduction zones", the continental mountains are pushed up higher and higher. For example, the American coastal mountains such as the Andes were created by this tectonic activity. In other regions of the Pacific Ring of Fire, volcanic island chains formed.

The submergence of the oceanic crust below the mainland crust is associated with tremendous subterranean tensions, which can open magma channels for volcanoes and trigger powerful earthquakes. Affected countries are among others Indonesia, Philippines, Japan, USA, Mexico, Peru and Chile.

Central and South Asia

Another very important danger zone lies north of the Arabian and Indian continental plates. Both tectonic plates move northward, pressing against the huge Eurasian plate. In contrast to the Pacific Ring of Fire, the tectonic plates collide directly with one another and push up high mountains.

The northern movement of the Indian plate is particularly explosive. When it collided with the Eurasian continental plate, the highest mountain range in the world, the Himalayas, piled up. Not only North India and Nepal must therefore expect earthquakes at any time, but also the central and eastern one China is intensely affected: The enormous pressure of the Indian plate leads to a build-up of tension in far-away Chinese regions.

Mediterranean Sea

The European Mediterranean is also a tectonically active region. The main trigger is the African continental plate, which is pushing northwards against the Eurasian plate. In the complex interplay of forces, other, small earth plates such as the Aegean or Anatolian plates also play a role. The geological conditions have not yet been fully clarified.

The pressure of the African plate is essentially responsible for the fact that it is particularly common in Italy, Greece and Turkey the earth is shaking. The western Mediterranean can look forward to lower seismic activity.

Other earthquake areas worldwide

The Caribbean plate is also responsible for some major earthquakes. The great quake of Haiti in 2010 is still dreadfully remembered. The Caribbean plate moves eastwards, sinks under the floor of the Atlantic Ocean and has led to the formation of the Antilles island chain.

In addition to the earthquake areas listed, small quakes occur time and again in many parts of the world. The cause is mostly the tectonic stress reduction in the countless smaller weak zones of the earth's crust. Severe earthquakes that threaten human life are very rare here.