Ch. 6 Volcanoes. Volcanoes RA volcano is a weak spot in the crust where magma comes to the surface...
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Transcript of Ch. 6 Volcanoes. Volcanoes RA volcano is a weak spot in the crust where magma comes to the surface...
Ch. 6 VolcanoesCh. 6 Volcanoes
VolcanoesVolcanoes
A volcano is a weak spot in the crust where magma comes to the surface
Magma is molten rock, gases, and water from the mantle
Magma becomes lava when it comes to the surface
Lava cools to become igneous rock
A volcano is a weak spot in the crust where magma comes to the surface
Magma is molten rock, gases, and water from the mantle
Magma becomes lava when it comes to the surface
Lava cools to become igneous rock
Types of RockTypes of Rock
Igneous- molten material, such as lava or magma, cools and hardensSlow cooling- large crystals (granite)Fast cooling- small crystals (basalt)
Metamorphic- great heat and pressure changes minerals or other rockHeat and pressure increases inside
the Earth
Igneous- molten material, such as lava or magma, cools and hardensSlow cooling- large crystals (granite)Fast cooling- small crystals (basalt)
Metamorphic- great heat and pressure changes minerals or other rockHeat and pressure increases inside
the Earth
Types of RockTypes of Rock
Sedimentary- sediment squeezed and glued togetherSediment- small pieces of rock or
fossils that have been broken down by erosion or weathering
Sedimentary- sediment squeezed and glued togetherSediment- small pieces of rock or
fossils that have been broken down by erosion or weathering
The Rock CycleThe Rock Cycle
The rock cycle slowly builds, destroys, and changes rock
Continuous and many pathways
The rock cycle slowly builds, destroys, and changes rock
Continuous and many pathways
The Rock CycleThe Rock Cycle
Volcanoes and Plate Tectonics
Volcanoes and Plate Tectonics
Volcanic belts are found at plate boundaries, such as the Ring of Fire around the Pacific Plate
Volcanic belts are found at plate boundaries, such as the Ring of Fire around the Pacific Plate
Volcanoes and Plate Tectonics
Volcanoes and Plate Tectonics
Divergent boundaries- magma comes out of rift valleys to build mountains
Convergent boundaries Oceanic plate sinksRock on top melts and becomes magmaMagma erupts and becomes lava
Divergent boundaries- magma comes out of rift valleys to build mountains
Convergent boundaries Oceanic plate sinksRock on top melts and becomes magmaMagma erupts and becomes lava
Volcanoes at Plate Boundaries
Volcanoes at Plate Boundaries
Hot SpotsHot Spots
Hot spots- volcanoes that form when magma erupts through crust to get to the surfaceHawaiiYellowstone National Park
Hot spots- volcanoes that form when magma erupts through crust to get to the surfaceHawaiiYellowstone National Park
Parts of a VolcanoParts of a Volcano
Magma chamber-collects magma
Pipe- tube that connects magma chamber to surface
Vent- opening on the Earth’s crust
Magma chamber-collects magma
Pipe- tube that connects magma chamber to surface
Vent- opening on the Earth’s crust
Parts of a VolcanoParts of a Volcano
Lava flow- area covered by lava
Crater- bowl-shaped area around a volcano’s central vent
Caldera- large circular depression formed when magma chamber empties and the roof collapses
Lava flow- area covered by lava
Crater- bowl-shaped area around a volcano’s central vent
Caldera- large circular depression formed when magma chamber empties and the roof collapses
EruptionsEruptions
Pressure and gases force magma out of a volcano
Silica makes magma thick and stickyTypes of eruptions
Quiet eruptions- lava oozes to surfaceThin, runny lava that is low in silicaHawaiian IslandsExamples are pahoehoe and aa
Pressure and gases force magma out of a volcano
Silica makes magma thick and stickyTypes of eruptions
Quiet eruptions- lava oozes to surfaceThin, runny lava that is low in silicaHawaiian IslandsExamples are pahoehoe and aa
EruptionsEruptions
Types of eruptionsExplosive eruptions- thick and sticky
lava which traps waterWater makes eruptions more explosive
Produces pyroclastic materialMagma that erupts as fragments of molten
material and solidifies in the airPieces of volcano that breaks off
Mt. St. Helens in 1980
Types of eruptionsExplosive eruptions- thick and sticky
lava which traps waterWater makes eruptions more explosive
Produces pyroclastic materialMagma that erupts as fragments of molten
material and solidifies in the airPieces of volcano that breaks off
Mt. St. Helens in 1980
Life CycleLife CycleGeologists determine how likely a
volcano will erupt againStages
Active- erupting or will erupt in the near futureMt. Shasta and Lassen Peak
Dormant- “sleeping,” but can become active againLong Valley in eastern Sierras
Extinct- unlikely to erupt againDiamond Head in Honolulu
Geologists determine how likely a volcano will erupt again
StagesActive- erupting or will erupt in the near
futureMt. Shasta and Lassen Peak
Dormant- “sleeping,” but can become active againLong Valley in eastern Sierras
Extinct- unlikely to erupt againDiamond Head in Honolulu
Volcanic LandformsVolcanic Landforms
Made of lava, ash, and other materials
Types of VolcanoesShield Volcano- made from
nonexplosive eruptionsLow in silicaWide with gentle slopes
Cinder Cone- made from explosive eruptionsHigh in silicaSteep, cone-shaped, found in clusters
Made of lava, ash, and other materials
Types of VolcanoesShield Volcano- made from
nonexplosive eruptionsLow in silicaWide with gentle slopes
Cinder Cone- made from explosive eruptionsHigh in silicaSteep, cone-shaped, found in clusters
Volcanic LandformsVolcanic Landforms
Types of VolcanoesComposite- alternating layers of
pyroclastic material and lava flowAlso known as stratovolcanoMost common
Types of VolcanoesComposite- alternating layers of
pyroclastic material and lava flowAlso known as stratovolcanoMost common
Volcanic LandformsVolcanic Landforms
Lava Plateaus- lava flows out of long cracks called fissuresThin, runny lava flows far before cooling
Lava Plateaus- lava flows out of long cracks called fissuresThin, runny lava flows far before cooling
Shield Volcano- Medicine Lake, CAShield Volcano-
Medicine Lake, CA
Cinder Cone Volcano- Mt. Bromo, IndonesiaCinder Cone Volcano- Mt. Bromo, Indonesia
Composite Volcano- Mt. Shasta, CA
Composite Volcano- Mt. Shasta, CA
Lava Plateau- Modoc Plateau, CA
Lava Plateau- Modoc Plateau, CA
Magma LandformsMagma Landforms
Formed when magma goes into cracks, but does not come to surface
Magma cools undergroundErosion exposes harden magma
Formed when magma goes into cracks, but does not come to surface
Magma cools undergroundErosion exposes harden magma
Magma LandformsMagma Landforms
TypesVolcanic Necks- magma hardens in pipeDikes and sills- magma cools between
rock layersIgneous intrusionsSill are horizontalDikes cross rock layers
Batholiths- massive rock forms when large body of magma cools
TypesVolcanic Necks- magma hardens in pipeDikes and sills- magma cools between
rock layersIgneous intrusionsSill are horizontalDikes cross rock layers
Batholiths- massive rock forms when large body of magma cools
Magma LandformsMagma Landforms