Volcanoes
Volcanoes are the vents or openings that expel molten rock or magma from the earth's interior. The earth's interior has very high temperature and pressure that can cause rocks to melt as well as dissolve other substances. Earth needs to release the excess heat underneath; thus volcanoes are important in maintaining the thermal balance of Earth's system.
There are two types of volcanoes according to their activity, or how often they erupt. ACTIVE volcanoes are those that have erupted over the last 10 000 years and still continue to erupt. The Philippines has 21 active volcanoes , including the famous Mt.Mayon , which is probably the most active .INACTIVE volcanoes,on the other hand are those that do not erupt as of today but has the potential to do so. Mt.Pinatubo in Pampanga , for example, was considered an inactive volcano until991, when it erupt. It's eruption is now recorded as the second largest eruption in 20th century.`
