Volcanoes

• A volcano is an opening in the earth when magma or molten rock from the mantle is forcing its way to the surface.
• There are over 600 active volcanoes on Earth with at least 50 eruptions occurring each year
• Many volcanoes are extinct or dormant
• 75% of the world's active volcanoes are along the margin of the Pacific plate, known as the Ring of Fire
• Hot spot volcanoes form away from tectonic plate boundaries when rising magma melts through the plate above, an example being the Hawaiian Islands
• Volcanoes occur at special types of convergent plate boundaires.These boundaries occur where continental and oceanic crusts meet.
• Subdcution zone is the zone where the denser oceanic plates sinks/is pushed under by the lighter/less dense continental plate.
• Volcanoes have three stages
• Active:This is where the volcano is erupting at regular intervals.
• Dormant:This is where the volcano has not erupted for a very long time.Its is said to be sleeping or inactive.
• Extinct:This is where the volcano has not been erupted in recorded history or living memory.
• Scientists believe that there are no extinct volcano and that there are only dormant volcanoes.
• Basic lava:very runny or fluid lava.It creates gently slopping volcanoes and has very gentle europtions.
• Acidic lava:very thick or viscous it creates very steep sided cones and the eruption are very voilent and can include toxic gases,steam,ash and particles of rock which are very dangerous to humans.
• Shield volcanoes:they are formed from basic lava,they are non-voilent as volcanic gases escape quickly from the vent and the sides of the volcano is gentle and consist of ash and cinder.
• Compostie cone volcanoes:these are steep sided cones consisting of alternating thick layers of ash and cinder and biscous lava.
• Strombolian-these volcanoes produce ash,cinder and volcanic bombs which are hurled into the air.The acidic lava forms steep sided cone shaped volcancoes
• lahar-a mixture of mud and water flowing down the slope of volcanoes at high speeds.
• Magma-Molten rocks below the Earths surface.
• Lava- Molten rock on the Earths surface
• Pyroclast-pieces of fragmented material such as lava,cinder,ash and dust
• Tephra- Ash and dust ejected from a volcano.