Ich weiß nicht wie viele Besucher hier so im Forum sind, bzw. ob es hier Leute gibt die gerne mal behilflich sind und einen Text sich durchlesen und vielleicht das ein oder andere mir helfen können. Es wäre jedenfalls sehr nett wenn mir jemand helfen würde (bin echt am verzweifeln und die Zeit rückt...)! Danke schon mal!!!
1. Definition What is volcanism:
Molten rock rises from inside the Earth's, it is less dense than the surrounding rock. It forms magma chambers in the lithosphere, the outer and cooled shell of the earth, and reaches the surface from there. This process is called volcanism.
2. Plate tectonics and construction of the earth
At Earth's birth, the planet was made of magma only. During cooling, large plates were formed.
Plate tectonics was described in 1915 by Alfred Wegener. There are 7 large and many smaller plates. They all swim on the liquid mantle, but move only a few centimeters a year.
They are divided into continental and oceanic plates, the continental plates are about 35 km thick, while the oceanic are only about 7 km thick.
There are 2 types of plate boundaries where volcanism occurs:
at divergent boundaries, 2 plates move away from each other. Lava is constantly coming out. They are found mainly on the mid-ocean ridge or in continental trenches.
Convergent plate boundaries mean that 2 plates collide. The heavier oceanic plate slides under the lighter and thicker continental plate. This is also called subduction zones.
The dipping plate is melted in the earth's mantle. The resulting magma rises through the continental plate, creating volcanoes.
Most volcanoes are found in the Pacific Ocean, the so-called "Ring of Fire".
Collide 2 oceanic plates together create island volcanoes.
90% of all volcanoes are at these areas.
And there are hotspots, these are volcanoes inside plates, the most famous is the Yellowstone.
3. Super volcanoes
Super volcanoes are volcanoes with extreme eruptions and leaving a caldera of over 20km. They emit gigantic amounts of ash. They are able to destroy the mankind. The sky is darkened for years, it cools down and it comes to the volcan winter. Plant growth decreases and mass extinction occurs.
The last outbreak of such a volcano has been over 26,000 years ago.
But should break out again, for example the Yellowstone, it could mean the end of the mankind.
4. volcano eruption
Before a volcano erupts, the viscous magma collects in a chamber several kilometers below the earth's surface. This chamber is connected to the earth's surface by a vent.
Gases build up enormous pressure in the chamber. If the pressure is too high, the upper rock breaks open and the magma finds its way to the surface.
Depending on the composition of the magma and the gases, the eruption of a volcano can be different. In some outbreaks, the surface rock is blown up miles and miles into the air.
Whole mountain tops can be blown away, such as the outbreak of Mount St. Helens in 1980. It also formed a so-called Lahar, a boiling hot avalanche of rubble and ash sludge, which flank itself with more than 100 kilometers per hour down moving.
In other volcanoes, the viscous lava flows down the slope. In turn, other volcanoes emit large quantities of ash that cover the whole area.
On the other hand, the so-called pyroclastic flows are very dangerous. Hot ash and glowing clouds race down the slope and destroy everything on their way. The inhabitants of Pompeii were surprised by such streams at the eruption of Vesuvius in the year 79.
5. Warning systems
10% of people live near active volcanoes.
To warn them of a possible outbreak, modern monitoring equipment is used.
The following changes indicate an impending eruption:
Expansion of magma chambers, it comes to uplifting
Reinforced degassing and altered gas composition
Lava flows down the volcano at a speed of up to 400km / h and can cover up to 60km.
airfalls of ashes
Lapilli, bombs and blocks
Lahars (mud streams)
Landslides or landslides
7. How volcanoes are used
Volcanic soil is very fruitful and ideal for fruit and wine growing.
But also raw materials are won. Depending on the composition of the lava different ores and minerals can be found.
In the near of volcanoes, energy can be gained with geothermal energy because the magma heats the groundwater.