VOLCANOES! WHAT IS A VOLCANO? Volcano An opening in Earths crust through which molten rock, rock fragments and hot gases erupt. More than 1500 active volcanoes. Products: Rock Fragments: Ash Cinders Blocks Volcanic Gases: Mixture of gases and ash Volcanic gas + rock fragments= PYROCLASTIC FLOW ( a dense cloud of super hot gases and rock fragments and is very dangerous) Volcano according to Eruption Activity: Active: A volcano that is currently erupting or is just about to erupt. Ex. Mt. Helens The most active volcano Kilauea Located in Hawaii Erupting for centuries! ICELAND Famous for active volcanoes Iceland is known as the Land of fire and ice Dormant : A volcano that is not currently erupting, but that has erupted in the recent past. Mt. Rainier Extinct: A volcano that has not erupted in recorded history, and is unlikely to erupt again. Ex. Mt. Kilimanjaro Parts of a Volcano: Vent = an opening in a volcano where magma flows out through. Crater = the steep-walled depression around a volcanos vent Volcanic cone - the pile of lava, dust, ashes, and rock around the vent. It can be found in different shapes! Magma -hot molten rock inside the earth. Lava - the flowing magma that pours from the crater. Types of Volcanoes: Shield Volcano Composite Volcano Cinder Cone Depends on: Quiet or explosive eruption Type of lava it is made of (basaltic, granitic, andesitic) Shield Volcano: Broad, Flat Dome shape Built up through many eruptions of thin layered lava with low silica. Ex. Rangitoto in New Zealand Cinder Cone: Steep, cone shaped hill. Formed on the sides of other types of volcanoes by loose pile of volcanic rock fragments. Ex. Sunset Crater in Az. Composite Volcano: Cone shaped volcano High in silica Built up of layers of hardened lava and fragments. Ex. Mt. Helens Krakatau This volcano erupted with such great force that the island disappeared. Most of the island collapsed into the emptied magma chamber Noise was so loud that it woke up people in Australia!!! More than 36,000 people killed Area around the volcano was in completely dark for about 24 hours. Effects of Volcanic Eruptions Human impacts - can cause lung disease - forces people to abandon homes Environmental Impacts - collapse buildings - block roads - acid rain (sulfurous gases mix with water vapor) - cities, towns and crops can be damaged Bringing it all home Cerro Prieto ("Dark Hill") 37.5 miles away! Baja California, Mexico The last eruption at the volcano is unknown, but may be within the past 10,000 years. Home again Pinacate Northwestern Sonora, Mexico 91 miles away Composite volcanic mountains created over long periods of time by sequential eruptions from evolving magma bodies are found in many of these fields; Pinacate has Volcan Santa Clara, the only Trachyte Shield Volcano in North America (on the horizon). Magma interacted with ground water in about a third of these fields to create steam explosion hydro-volcanoes. Pinacate's steam explosion maar-calderas (Sykes Crater above) are the most spectacular such craters outside of Africa.