What Happens When a Volcano Erupts?

Hidden deep within the core of the earth, one of the world’s most extraordinary wonders is taking shape and positioning itself for a spectacular emission. That wonder is a volcano. Situated all over the earth, volcanoes are amazing sites that can be found in the form of hills, mountains, craters or even under ice caps on the ocean floor. For centuries, volcanoes have drawn great attention from eager scientists, geologists, archaeologists, and of course, enthusiasts.

Before a volcano erupts, the center of the earth stirs up an extraordinary commotion of melted rocks, creating a substance that spills over onto the earth during the eruption. These rocks contribute to creating magma.

Composed of a mixture of gases, liquid rock, silica, and crystals, magma is the molten lava that flows down the side of a volcano. The rock element of the magma is categorized as either Rhyolite, Andesite, or Basalt, and each has different characteristics.

• Rhyolitic magma is composed with a high content of gas. The flow speed is high and the temperature ranges between 800 – 1000 degrees Centigrade.
• Andesitic magma has an intermediate gas content. It flows at an intermediate speed and ranges between 800 – 1000 degrees Centigrade.
• Basaltic magma, the hottest of the three, is between 1000 – 1200 degrees Centigrade. It has a low content of gas, and flows slower than the others. (In fact, the general rule is the hotter the magma, the slower it flows.)

Before the magma can be expelled, a high and low pressure disturbance must cause it to rise to the surface and spill over the top.

The Eruption

Eruptions are at the core of all the volcanic dynamics. They are not always aggressive as you might imagine, as this depends on the location and magma composition. There are seven types of volcanic eruptions, ranging from subtle venting to a spectacular display of ‘lava-works.’ 

Mild Eruptions

Mild eruptions are also called phreatic or ‘steam blast’ eruptions. These eruptions occur when magma flows into shallow groundwater, causing vapory steam as it is forced to cool - like a hot frying pan placed under running water.

Phreatomagmatic blasts causes a steamy display of ejected rock fragments. This activity is caused by the rapid rate of expanding groundwater it comes in contact with.

Composed of basaltic magma, Hawaiian eruptions can shoot luminescent lava as high as one kilometer above the vent top of the volcano during an eruption. Strombolian eruptions also produce luminous little bombs that fall near the opening of the volcano, eventually creating a small cone. 

Strong Eruptions

Strong blasts, or pelean blasts, are produced when a previous lava dome has collapsed. They are characterized by bright, luminous avalanches that create a block-and-ash flow.

Plinian eruptions are blasts that characterized by large ash clouds that circle the earth. Vulcanian explosions or eruptions contain solidified rhyolite or andesite magma that produce pyroclastic or liquified lava flows that can cause great damage.

Generally, most eruptions occur when gas expands inside the earth, reducing pressure and causing aggressive volcanic behavior. It is much like what happens when you pop the cap of a bottle of carbonated soda. 

Expelled magma on the surface of the earth can take up to several hundred years to cool depending on its composition and location. Once it cools, it forms into a remarkable variety of granite and other attractive rocks that can be rich soures of scientific data.