Different Types of Volcanoes

• The term “volcano” refers to mountain or hill, typically conical, having a crater or vent in which lava, rock fragments, hot vapor, and gas are contained or have been erupted into the earth's surface. 
• The lava and other volcanic materials originated from molten materials called magma found beneath the surface of the Earth.
• Magma and other volcanic materials are finding its way to the surface where they are expelled through openings like cracks and holes.
• Any activity that includes the movement of magma towards or onto the surface is called volcanism.
• STRUCTURE OF A VOLCANO

  
• Summit is the highest point or the apex of the volcano. At the summit, you have an opening called vent. 
• Slopes are the sides or flanks of a volcano that radiate from the main or central vent. 
• Base is lower outer part of the volcano.
• Magma Chamber is a region beneath the vent of a volcano where molten rock or magma is deposited or stored before eruption. 
• Main Vent is the main opening or outlet on the surface of a volcano that emits lava, gases, ash or other volcanic materials.  
• Conduit is an underground central tube-like or pipe-like structure of a volcano that connects the magma chamber to the crater through which the magma travels. 
• Side Vent is a smaller outlet through which magma escapes.  
• Crater is the mouth of the volcano which is a funnel-shaped or bowl shaped hollow at the top of the vent from where magma, ash and gas comes out. 
• Lava is a molten rock which is given off onto the surface of the Earth when a volcano erupts.  
• Ash and Gas Cloud is a of mixtures of rock, minerals, glass particles and gases expelled or pushed out of the volcano during volcanic eruption.
• There are several ways by which volcanoes can be classified. They can be classified based on structure and activity.
• Cinder Cone Volcano - simplest type of volcano. They are built from particles and blobs of solidified lava ejected from a single vent. Lava is thrown into the air, which breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a steep slope, wide crater and are the most abundant of the three major volcano types.
• Cinder Cone Volcano -  An example of this type in the Philippines are Taal Volcano in Batangas, Smith Volcano found in Babuyan Group of Islands, Mount Mayabobo found in Quezon Province, and Mount Musuan in Bukidnon. An example of this outside of the Philippines is the Paricutin volcano in Mexico. 
• Composite volcanoes or Stratovolcanoes - are large, typically steep sided, symmetrical cones of large dimension formed from alternating layers of lava flows, volcanic ash, cinders, blocks, and pyroclastic materials. 
• Composite volcanoes or Stratovolcanoes - One important feature of a composite volcanoes is the conduit system from which magma rises to the surface of the Earth. They are formed from viscous, or sticky, lava that does not flow easily. The lava builds up around the vent forming a volcano with steep sides.
• Composite volcanoes or Stratovolcanoes - Some famous composite volcanoes in the Philippines are Mount Mayon in Albay, Mount Arayat in Pampanga, Mount Kanlaon in Negros Island, and Mount Apo in Davao Region. An example of these outside the Philippines are Mount Rainier in Washington, USA, and Mount Fuji in Japan.
• Shield Volcanoes: are large, broad volcanoes that look similar to shields from above – hence the name. These volcanoes are built almost entirely of fluid lava flow thus these volcanoes are not steep. They can be easily identified because they are tall and broad, with flat, rounded shapes. 
• Shield Volcanoes - The lava is not accompanied by pyroclastic materials, which makes shield volcanoes relatively safe. Eruptions at shield volcanoes are only explosive if water somehow gets into the vent. Mauna Loa is one of the largest shield volcanoes. 
• Another way of classifying volcanoes according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS) is based on their activity as indicated by their behavior and historical records. 
• Active volcanoes are those volcanoes that have had at least one eruption during the past 10,000 years. They are those that erupted recently and still showing regular activity like emission of gases, lava and ash flows.
• Inactive volcanoes, on the other hand, are those that have not erupted for the last 10,000 years and is not expected to erupt again in a comparable time scale of the future. There are no signs of volcanic activity for a long period of time because magma supply is cut off. Also the physical form of the volcano has signs of intensive weathering and erosion.
• Potentially active volcanoes are those that have no records of volcanic activity but are morphologically young-looking.
• Our country has more than a hundred volcanoes. Twenty four (24) are active while the rest are either potentially active or inactive volcanoes.
• Different types of volcanoes erupt differently. They are generally classified as wet or dry depending on the magma’s water content. Volcanoes are described according to the style of eruption.
• Phreatic or hydrothermal is a steam-driven eruption as the hot rocks come in contact with water. It is short lived, characterized by ash columns but may be a beginning of a larger eruption. 
• Phreatomagmatic is a violent eruption due to the contact between water and magma. As a result, a large column of very fine ash and high-speed and sideway emission of pyroclastic materials called base surges are observed.
• Strombolian is a periodic weak to violent eruption characterized by a fountain of lava, just like the Irazu volcano in Costa Rica.
• Vulcanian is characterized by tall eruption columns that reach up to 20 km high with pyroclastic flow and ash fall tephra like that of Paricutin Volcano in Mexico. 
• Plinian is an xcessively explosive type of eruption of gas and pyroclastic materials, like in Pinatubo Volcano in Zambales. 
• SIGNS OF AN IMPENDING VOLCANIC ERUPTION