Notes

Volcanic eruptions and its kinds
A volcanic eruption is an awesome display of the Earth’s power. Yet while eruptions are spectacular to watch, they can cause disastrous loss of life and property, especially in densely populated regions of the world. In general, eruptions can be categorized as either effusive or explosive. Effusive eruptions involve the outpouring of basaltic magma that is relatively low in viscosity and in gas content. Explosive eruptions generally involve magma that is more viscous and has a higher gas content. Such magma is often shattered into pyroclastic fragments by explosive gas expansion during an eruption. Based on character of eruption, volcanic activity and volcanic areas are commonly divided into six major types, shown schematically in the diagram. They are listed as follows in order of increasing degree of explosiveness:
The Icelandic type is characterized by effusions of molten basaltic lava that flow from long, parallel fissures. Such outpourings often build lava plateaus.
The Hawaiian type is similar to the Icelandic variety. In this case, however, fluid lava flows from a volcano’s summit and radial fissures to form shield volcanoes, which are quite large and have gentle slopes.
The Strombolian eruptions involve moderate bursts of expanding gases that eject clots of incandescent lava in cyclical or nearly continuous small eruptions.
The Vulcanian eruptions involves moderate explosions of gas laden with volcanic ash. This mixture forms dark, turbulent eruption clouds that rapidly ascend and expand in convoluted shapes.
The Pelean eruption is associated with explosive outbursts that generate pyroclastic flows, dense mixtures of hot volcanic fragments and gas described in the section Lava, gas, and other hazards. The fluidized slurries produced by these eruptions are heavier than air but are of low viscosity and pour down valleys and slopes at great velocities. As a result, they are extremely destructive.
The Plinian type is an intensely violent kind of volcanic eruption. In this type of eruption, gases boiling out of gas-rich magma generate enormous and nearly continuous jetting blasts that core out the magma conduit and rip it apart. The uprushing gases and volcanic fragments resemble a gigantic rocket blast directed vertically upward.
All kinds of volcanic eruptions are dangerous so we should follow those instructions from the government everytime they have warnings about in every disastrous events may happen.