"Mash, or thick ointment" (in Greek), it is a liquid molten hot rock of silicate nature. This is what magma is. It occurs in the earth's crust, in the upper mantle, at great depths. And when it cools down, it forms characteristic rocks.
What is magma? Dictionary Definition
In various sources, the word "magma" is interpreted as a mass of molten rock, located under solid ground. Its silicate composition and ability to form igneous rocks are also indicated.
Origin
The fact is that inside the globe is hot. The heat melts the earth's rocks, which as a result are inside in a liquid state. What is magma? This is a liquid stone enclosed in a harder shell surrounding it. It is much lighter in weight than this shell. Therefore, it rises up under the emerging pressure. Sometimes magma does not erupt outward, gradually cooling somewhere deep underground and hardening. So for millennia mountains form. Sometimes hard and colder rocks cannot withstand high magma pressure from the inside. Faults arise, through which magma breaks out, pours out. It, while still in a liquid state, spreads on the ground.
What happens then
What is magma that has come to the surface of the earth? It is called lava. After magma erupted outside, it immediately begins to cool, interacting with the external environment and the surrounding atmosphere. This happens pretty quickly. Some of the substances that make up its composition harden faster than others, forming crystals. These crystals seem to float in liquid rock. And the largest of them form lava mountains. All these mountains are made up of numerous crystals embedded in basalt. They are called porphyry.
Chemical composition
What is magma from the point of view of the science of chemistry? This liquid rock contains many chemical elements. Among them are magnesium, sodium, iron, potassium. And also - volatile components: chlorine, fluorine, hydrogen and others. And such a component as vaporous water. As volatile elements (their amount) come to the surface, they decrease and a degassing process takes place.
Classification
- Basaltic (main). It contains silica (up to 50%), in a large amount of magnesium, iron, aluminum, calcium. To a lesser extent - titanium and phosphorus, potassium and sodium.
- Granite (acidic, rhyolitic). Contains silica (up to 65%). It is more saturated with gases, has a lower density than basalt.
- Several types of magmatism are distinguished by the nature of their progress and the method of solidification . Intrusive type - magma freezes, crystallizes deep in the bowels, without going to the surface. An effusive type - magma erupts to the surface and freezes there.
Hardening process
The melt of magma consists of liquids, gases, solid crystals in a certain equilibrium state. Under the influence of the environment, the volume of magma tends to evolve. Some crystals of minerals melt, while others reappear.
What does magma mean? This is a rather complex solution in which the precipitation of solid crystals obeys physical and chemical laws. But even in the same magma, the composition sometimes changes under the influence of temperatures and pressure.
The flow velocity of the pouring magma sometimes reaches 30 km / h, the temperature - up to 1250 degrees. In liquid form, magma is stored up to a temperature of about 600 degrees, and then begins to solidify.
At the same time, minerals crystallize and concentrate on separate sites of advancement, forming endogenous deposits of iron, non-ferrous and precious metals, and diamonds. These magmatic formations arise in stratified rock complexes.
What is magma and lava?
As already mentioned, lava is erupted magma, consisting of a viscous melt of rocks, mainly silicate. The main difference between the first and the second is that there are no gases in the lava that escape when the “liquid stone” exits. Lava tends to cool and harden over time, stopping its progress. As a result, lava rocks are formed: mountains and even a plateau. In different volcanoes, lava varies in composition, temperature, and other features. For example, carbonate lavas are brittle, soft, easy to dissolve in water.
Volcanic eruptions
It only seems to us that the Earth inside is solid and motionless. In fact, deep inside, there is a constant movement of molten substances - magma. She is looking for an exit to the surface through all kinds of cracks and tubules that arise in the crust of the Earth. So volcanoes arise - magma that has found a way out erupts outward, sweeping away everything in its path. Of the most famous eruptions (recorded by science), one can note the release of magma on the island of Krakatau in 1883. As a result, the island was completely destroyed. The eruption claimed more than 200 thousand human lives!