28-08-2012, 04:20 PM
VOLCANOES
VOLCANOES-.pptx (Size: 1.64 MB / Downloads: 53)
What is a Volcano?
A volcano is a vent or 'chimney' that connects molten rock (magma) from within the Earth’s crust to the Earth's surface.
The volcano includes the surrounding cone of erupted material.
What are the parts of a Volcano?
1. VENT- The vent is the opening from which lava flows. Dust, ash, and rock particles can also be thrown out of the vent.
2. CONE- It is the pile of lava, dust, ashes, and rock around the vent. It can be found in different shapes.
3.CRATER - It is the top of the volcano. It is a funnel shaped pit. It is formed when the material explodes out of the vent.
Popular classification of volcanoes :
1. Active :
A popular way of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active.
Presently there are about 500 active volcanoes in the world – the majority following along the Pacific 'Ring of Fire' – and around 50 of these erupt each year.
2. Extinct :
are those that scientists consider unlikely to erupt again.
Examples of extinct volcanoes are many volcanoes on the Hawaiian – Emperor seamount chain’ in the Pacific Ocean.
3.Dormant :
It is difficult to distinguish an extinct volcano from a dormant (inactive) one.
Examples are ‘Fourpeaked mountain in Alaska (USA)’. Shown in fig.
IN SUMMARY
Volcanoes are extremely hazardous.
However, the volcano can be studied, monitored and understood.
Each volcano is different, and offers a unique set of dangers.
Plans may be emplaced to help control potential damage.