-some volcanoes are only 30 meters high and fromed during a single eruptive phase that may last only a few days.
-Alaska's vallry of ten thousand smokes is a flat top depoist consisting of 15 cubic kilometers of ash that erupted in less than 60 hours and blanketed a section of river vallry to a depth of 200 meters.
-As the gas rich magma moves toward the surface fissure its path is usually localized into a circular condit or pipe that terminates at a surface opening called a vent.
-Volcano:is build by successive eruptions of lava, pyroclastic materal or frequently a combination of both.
-Crater =a bowl is located at the summit of most volcanoes.
-Parasitic cone: made contined activity from flank eruption.
-fumaroles:gasses that vents emit.
-Shield volcanoes:are made by accumuation of fluid basaltic lavas and exhibit theshape of a broad.
-Extenise study of Hawaiian islands comfirms that each shield was built from a myriad of basaltic lava flows averaging a few meters thick.
-ilauea the most active and intensely studied shield volcano in the world is located on the island of Hawwaii in the shadow of Mauna Loa.
-Cinder cones also called scoria are built from ejected lava fragments that take on the apperance of cinders or clinkers ad they begin to hardenwhile in flight.
-One of the very few volcanoes studied by geologists from the beginning to end is the cinder cone called Paricutin.
-Earth's most picturesque yet potentially dangerous volcanoes are composite cones or stratovolcanoes.
Notes 12-8
- Volcanic activity is commonly perceived as a process that produces a picturesque, cone shaped structure that periodically erupts in violent manner like mount st helens.
- The thing that determines if a volcano erupts violently or gently is composition and its temperture and tha amount of dissolved gases it contains.
- To varying degrees these factors affect the magma's mobilty or viscosity.
- The mobility of the lava is strongly influenced by the temperature.
- A more significant factor influencing volcanic behavior is the chemical composition of the magma.
- A magma's viscosity is directly related to its silica content.
- Volatiles: the gaseous component of magma mainly in water.
-The amount of volatiles contained in magma also affects its mobility.
- Most magma is generated by partial melting in the upper asthenosphere at depths of about 100 kilometers.
-Once melt is formed it will rise to the top because it is less dense than rock.
- One of the simpleat ways to trigger a volcano is the arrival of a new batch of melt into a near surface magma reservoir.
- The injection of a fresh supply of melt causes the perssure in the magma chamber to rise until cracks develop in the rock above.
- All magmas cintain a small percentage of water and other volatilies that are held in solution by immense perssure of the overlying rock.
- Very fluid basaltic magmas allow the expanding gases to migrate upward and escape from the vent with relative ease.
- Eruption columns: Gaes that evolve into buoyant plumes.
-Most explosive eruption are followed by the quiet emission of degassed lavas.
-some volcanoes are only 30 meters high and fromed during a single eruptive phase that may last only a few days.
-Alaska's vallry of ten thousand smokes is a flat top depoist consisting of 15 cubic kilometers of ash that erupted in less than 60 hours and blanketed a section of river vallry to a depth of 200 meters.
-As the gas rich magma moves toward the surface fissure its path is usually localized into a circular condit or pipe that terminates at a surface opening called a vent.
-Volcano:is build by successive eruptions of lava, pyroclastic materal or frequently a combination of both.
-Crater =a bowl is located at the summit of most volcanoes.
-Parasitic cone: made contined activity from flank eruption.
-fumaroles:gasses that vents emit.
-Shield volcanoes:are made by accumuation of fluid basaltic lavas and exhibit theshape of a broad.
-Extenise study of Hawaiian islands comfirms that each shield was built from a myriad of basaltic lava flows averaging a few meters thick.
-ilauea the most active and intensely studied shield volcano in the world is located on the island of Hawwaii in the shadow of Mauna Loa.
-Cinder cones also called scoria are built from ejected lava fragments that take on the apperance of cinders or clinkers ad they begin to hardenwhile in flight.
-One of the very few volcanoes studied by geologists from the beginning to end is the cinder cone called Paricutin.
-Earth's most picturesque yet potentially dangerous volcanoes are composite cones or stratovolcanoes.
Notes 12-8
- Volcanic activity is commonly perceived as a process that produces a picturesque, cone shaped structure that periodically erupts in violent manner like mount st helens.
- The thing that determines if a volcano erupts violently or gently is composition and its temperture and tha amount of dissolved gases it contains.
- To varying degrees these factors affect the magma's mobilty or viscosity.
- The mobility of the lava is strongly influenced by the temperature.
- A more significant factor influencing volcanic behavior is the chemical composition of the magma.
- A magma's viscosity is directly related to its silica content.
- Volatiles: the gaseous component of magma mainly in water.
-The amount of volatiles contained in magma also affects its mobility.
- Most magma is generated by partial melting in the upper asthenosphere at depths of about 100 kilometers.
-Once melt is formed it will rise to the top because it is less dense than rock.
- One of the simpleat ways to trigger a volcano is the arrival of a new batch of melt into a near surface magma reservoir.
- The injection of a fresh supply of melt causes the perssure in the magma chamber to rise until cracks develop in the rock above.
- All magmas cintain a small percentage of water and other volatilies that are held in solution by immense perssure of the overlying rock.
- Very fluid basaltic magmas allow the expanding gases to migrate upward and escape from the vent with relative ease.
- Eruption columns: Gaes that evolve into buoyant plumes.
-Most explosive eruption are followed by the quiet emission of degassed lavas.