Volcanoes are classified in to five groups based on the shape of the volcano, the materials they are built of and the way the volcano erupts.
1. Composite Volcanoes (Strato Volcanoes) are formed by alternating layers of lava and rock fragments. This is the reason they are called "composite". They usually erupt in an explosive way. This is usually caused by viscous magma.
2. Shield Volcanoes (Shields) are huge in size. They are built by many layers of runny lava flows. It may be produced by hot spots which lay far away from the edges of tectonic plates.The eruptions of shield volcanoes are characterized by low-explosivity lava-fountaining that forms cinder cones and spatter cones at the vent.
3. Cinder Cones is a steep conical hill formed above a vent. They are among the most common volcanic landforms found in the world.hey aren't famous as their eruptions usually don't cause any loss of life. They are chiefly formed by Strombolian eruptions.The cones usually grow up in groups and they often occur on the flanks of strato volcanoes and shield volcanoes.
4. Spatter Cones
When hot erupting lava contains just enough explosive gas to prevent the formation of a lava flow, but not enough to shatter it into small fragments the lava is torn by expanding gases into fluid hot clots, ranging in size from 1cm to 50cm across, called "spatter".
When the spatter falls back to Earth the clots weld themselves together and solidify forming steep-sided accumulations. These accumulations focused on an individual vent are called "spatter cones".
When the spatter falls back to Earth the clots weld themselves together and solidify forming steep-sided accumulations. These accumulations focused on an individual vent are called "spatter cones".
5. Complex Volcanoes
In fact all volcanoes could be complex volcanoes since all of them are made up of multiple flows, ash layers, domes, cones, etc. in varying amounts.
However, when we call a volcano a complex volcano it is because we mean the "system" of those volcanoes is not "simple". Caldera complexes for instance have often got a large caldera with many subsidiary vents and deposits, some of which could be considered "volcanoes" in their own right.
In Thailand, there are so many volcanoes all around the regions. Almost all of them are Shield volcanoes, which the eruptions of shield volcanoes are characterized by low-explosivity lava-fountaining. However, all of them are "extinct volcanoes".
Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava supply.
Volcanoes in Thailand are found :
Northern (city) : Lampang, Chiang Rai, Phrae, Nan, Uttaradit
Central (city) : Sukhothai, Kamphaeng Phet, Phetchabun, Saraburi, Lop Buri
East (city) : Chanthaburi, Prachin Buri, Nakhon Nayok, Trat
West (city) : Kanchanaburi, Tak
Northeast (city) : Nakhon Si Thammarat, Si Sa Ket, Ubon Ratchathani, Buri Ram, Loei, Surin
The oldest volcano of Thailand is in Loei (city). The volcano is around 395-435 million years.
References
- ORACLE ThinkQuest., "types of volcanoes".
http://library.thinkquest.org
ไม่มีความคิดเห็น:
แสดงความคิดเห็น