Volcanoes are one way the Earth gives birth to itself - Robert Gross
Volcanoes are mountains. But unlike most mountains in the world, formed from folding continental plates, uplift and erosion, volcanoes are created when material from inside the Earth escapes to the surface. When rock from the mantle melts, moves to the surface through the crust, and releases pent-up gases, volcanoes erupt. Extremely high temperature and pressure cause the rock to melt and become liquid rock or magma. When a large body of magma has formed, it rises through the denser rock layers toward Earth's surface.
The 3 types of Volcanoes
Scientists have categorized volcanoes into three main categories: active, dormant, extinct.
Active: Is a volcano that has recently erupted and possibly may erupt again.
Dormant: is a volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future
Extinct: in a volcano that erupted thousands of years ago and there's no possibility of eruption
Why do Volcanoes erupt?
Volcanoes are a natural way that Earth, and other planets have of cooling of and releasing internal heat and pressure.
Volcanoes erupt because of density and pressure. The lower density of the magma corresponding to the surrounding rocks causes it to rise. It will rise to the surface or to a depth that is influenced by the density of the magma and weight of the rocks above. As magma rise, start to form from the gas dissolved in the magma. The gas bubbles exert prodigious amount of pressure. The pressure helps force the magma to the surface and into the air, sometimes to colossal heights.
Why are Volcanoes in different shapes?
Volcanoes come in different shapes as a result of different types of eruptions and different volcanic materials inside the volcano. Low-silica lava has low viscosity (resistance to flow). Whereas, high-silica lava is more viscous.
Different types of Lava
Basaltic Lava: Basaltic lava is made with the least amount of silica (compound that occurs as the mineral quartz and as a principal constituent of sandstone and other rocks). Typically, consists of 52% of silica or silicon dioxide (SiO2). It is the fastest and hottest flowing lava, commonly discharged from shield volcano. Can appear as pillow flows when they erupt under water or ice. This allows the flows to build up, creating submarine mountains and islands over time.
Andesitic Lava: It has a higher viscosity than basaltic lava, thus flows at a slower pace. It consists between 52-63% SiO2. Andesitic lava generally produce a small volume that advances no further than the volcanoes base, its flow is described as a block flow. It is common in the Andes Mountains.
Rhyolitic Lava: Has the highest viscosity than any type of lava, and has the greatest content of SiO2. Commonly, consists of over 68% of SiO2. Since it has such a high-silica lava it flows slower than both basaltic and andesitic lava.
Types of Volcanic Rocks
Once the lava has erupted, it cools and solidifies into rock.
Rocks are classified into three groups- ingenous, sedimentary and metamorphic. Ingenous rocks are formed from magma in the Earth's mantel.
Basalt: The Earth's crust is mostly comprised of basalt rocks. It is a heavy, dark, and grainy rock. It is formed at a very high temperature (around 1200ºC), as basaltic lava. When it erupts from a volcano, it is very hot and a liquid. Since we've learned it has a low percentage of silica, it has a high percentage of iron and magnesium, which makes the rock look dark.
Andesite: These kinds of rocks are lighter than basalt because they contain less iron and more silica. It forms from andesitic lava, generally around 800-1000ºC.
Rhyolite: These are very light-colored rocks because it contains a lot of silica and not enough of magnesium or iron. They are formed at lower temperatures between 750-850ºC, and are often thick but quite light.
An ash covered victim of Indonesia's Mount Merpai volcano eruption arrives at a Yogyakarta hospital
Death toll climbs after major volcanic eruption in Indonesia
Mount Sinabung, Jakartam Idonesia erupted with plumes of ash released more than one mile into the sky. The eruption killed at least 15 people as hot ash of 700 degrees spewed down the mountain slopes in minutes.