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A volcano is an opening in the planet's crust, which allows hot molten rocks, ash and gases to escape from below the surface.  A volcano is a mountain that opens downward to a pool of molten rock called magma. Magma is liquid rock inside a volcano.


The name "volcano" comes from the word Vulcan who was the god of fire in Roman mythology. The Earth's crust is made up of huge slabs called tectonic plates. These plates fit together like a complicated jigsaw puzzle that sometimes move, shift and crack.


As the plates crash together, pressure within the volcano builds up. It is like shaking a fizzy drink but much worse.  The pressure like a safety valve needs to escape somewhere so it travels upwards causing cracks up the main vent/throat until it finally erupts through the top.  Once the magma erupts through the earth’s surface it is called lava. Lava is the liquid that flows out of a volcano. 



It blasts out along with ash, rocks, and a cloud of dust that is very thick. The lava burns down everything in its way as it reaches temperatures ranging from 700° to 1,200° C. The ash and rock crumble to the ground while the lava moves its way down the volcano side. A volcanoes structure can be damaged during the explosion as it literally blows its top off.


                                                             Structure of a Volcano



Parasitic Cone - A small cone-shaped volcano formed by an accumulation of volcanic debris.


Sill - A flat piece of rock formed when magma hardens in a crack in a volcano.


Vent - An opening in Earth's surface through which volcanic materials escape.


Flank - The side of a volcano.


Lava - Molten rock that erupts from a volcano that solidifies as it cools.


Crater - Mouth of a volcano - surrounds a volcanic vent.


Conduit - An underground passage magma travels through.


Summit - Highest point;


Throat - Entrance of a volcano. The part of the conduit that ejects lava and volcanic ash.


Ash - Fragments of lava or rock smaller than 2 millimeters in size that are blasted into the air by volcanic explosions.


Ash Cloud - A cloud of ash formed by volcanic explosions




The process by which solid, liquid, and gas materials are ejected into the earth's atmosphere and onto the earth's surface by volcanic activity.


Hot Spot

A volcanic center. This is the hottest spot within the volcano.



Magma which has reached the surface through a volcanic eruption. Streams of liquid rock that flow from the top of the crater.



Molten rock beneath the surface of the earth.


Ring of Fire

The regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean.



The opening at the earth's surface through which volcanic materials  erupt.


Volcanic eruption

When hot rocks and lava burst from a volcano.