The Changing World

Volcanoes are conic mounds that comprise a crater, a conduit, and a magma chamber.

Volcanoes can be differentiated according to types of eruption, which are explosive (accompanied by pyroclastic flow), effusive (accompanied by lava flow) and mixed (accompanied by lava and pyroclastic flow). The steps of the mixed-type eruption of stratovolcanoes are as follows: eruption of steam and gases, eruption of ash and debris, lava flow.

Volcanoes can be active, dormant or extinct.

Conduit

Magma, steam and gases
are ejected to the surface through this channel.

Volcanic cone

A hill created by volcanic eruptions around the volcano’s conduit.

An active volcano can erupt any time.

Typical example: Krakatoa

Krakatoa is located in the Sunda Strait in Indonesia. Its most famous eruption was in August 1883. The explosion could be heard even
in Mauritius. This was one
of the biggest volcanic eruptions
in history.

An extinct volcano erupted several thousand years or million years ago, but is not expected to erupt ever again.

Typical example: Kilimanjaro

The Kibo is the highest volcanic cone on Kilimanjaro and its crater is the best-preserved. Kilimanjaro has no recorded volcanic eruption since the history of mankind.

A dormant volcano has not been ac­tive for a long time, but its eruption is expected in the future.

Typical example: Paektu Mountain

This volcano is located on the border between China and North Korea.
Its biggest eruption, which is also
one of the biggest volcanic eruptions in the history of mankind, took place more than a thousand years ago. There was a minor eruption in 1903. Currently it is inactive, and there are no signs of an eruption in the near future.

Magma chamber

A pool where magma accumulates beneath the Earth’s surface.

The explosive eruptions of cinder cone volcanoes are accompanied
by steam and gases that escape through the crater with massive explosions, resulting in a tall erup­tion column and pyroclastic flow. Wind can spread the ash cloud over a large area. The pyroclastic flow rolls down the volcanic cone at a high speed. Krakatoa, Mt Pelée and Mt St Helens are the best-known examples of such volcanoes.

Effusive eruptions are characte­ris­tic of shield volcanoes. This type of eruption is not accompanied by explosions or a pyroclastic flow; the only substance that rises to the surface is liquid lava. Once the lava solidifies, it creates a volcanic cone. Examples of volcanoes where effu­sive eruptions occur are Mauna Kea and Mauna Loa, both on the Hawaiian Islands.

Mixed eruptions are characteristic of stratovolcanoes. This type
of erup­tion is accompanied by explosions and lava flows as well. The volcanic cone consists of alternating layers of tephra,
or fragments, and solidi­fied lava. The best-known examples of
stra­to­volcanoes are Stromboli, Mt Etna and Cotopaxi.