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VOLCANOES. Formation. Magma is forced upward flows out of an opening in crust. Parts of a Volcano. Parts. Vents –areas from which lava flows. Crater – bowl shaped dent where vent is located. Parts. Gas- most common steam, carbon dioxide, sulfur dioxide . Lava- molten rock on surface .

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  • Magma is forced upward flows out of an opening in crust
  • Vents –areas from which lava flows
  • Crater – bowl shaped dent where vent is located

Gas- most common steam, carbon dioxide, sulfur dioxide

Lava- molten rock on surface

Ash- VERY small rock , minerals, volcanic glass less than 2 mm

  • Conduit - a pipe that extends from magma chamber to vent
  • Magma chamber – area where magma is stored until it erupts
  • Divergent boundaries
  • Convergent boundaries
  • Hot spots
divergent boundaries
Divergent Boundaries
  • Plates move apart forming rifts
  • Lava flows forms rifts & cools quickly by seawater
  • Keeps building until it rises above sea level
convergent boundaries
Convergent Boundaries
  • Plates move together (collide)
  • Oceanic slide under continental
  • Older oceanic under younger oceanic
  • Plate melts down to form magma
  • Then forced upward
andes mountains
Andes Mountains



cascade mountains
Cascade Mountains

Mt. Rainier

Mt. St. Helens

hot spots
Hot Spots
  • Magma burns through crust
  • NOT near a boundary
factors that control type of eruption
Factors that control type of eruption
  • Trapped gases
      • water vapor, carbon dioxide, sulfur dioxide
  • Composition of Magma
factors that control type of eruption1
Factors that control type of eruption

Trapped gases (water vapor, carbon dioxide, sulfur dioxide

Composition of Magma

Low silica basaltic magma quiet eruption

  • Gases can escape easily less pressure quiet eruption
factors that control type of eruption2
Factors that control type of eruption

Trapped gases (water vapor, carbon dioxide, sulfur dioxide

Silica rich rhyolitic magma explosive eruption

Composition of Magma

  • Gases build up to high pressure explosive eruptions
eruption products
Eruption Products
  • Pyroclastics (broken pieces of volcanic rock)- tephra





eruption products1
Eruption Products


  • Lava



eruption products2
Eruption Products
  • Gases
    • Water
    • Carbon dioxide
    • Sulfur dioxide
types of volcanoes
Types of Volcanoes
  • Shield volcano
    • Quiet eruptions
    • Basaltic magma
    • Fast moving lava
    • Very large
    • Broad gentle slope
    • Can erupt hundreds of feet into air  fountains
    • Kilauea
types of volcanoes1
Types of Volcanoes
  • Composite (Stratovolcanoes)
    • Explosive eruptions
    • Andesitic or rhyolitic magma
    • Can switch from quiet to explosive forming layers of tephra and lava
    • Steep sided
    • Tall
    • Mt. St. Helens
types of volcanoes2
Types of Volcanoes
  • Cinder cone volcano
    • Explosive eruptions
    • Small in size
    • Steep sided loosely packed
    • Short lived
    • Paricutin
classification of volcanoes
Classification of volcanoes
  • Active- currently active or erupted in recorded history


classification of volcanoes1
Classification of volcanoes
  • Dormant –“resting“ not currently erupting but likely to do so

Mt. Hood, Oregon

classification of volcanoes2
Classification of volcanoes
  • Extinct –not erupted in recorded history and are not expected to erupt again

Mount Kilimanjaro

kinds of volcanic eruptions
Kinds of Volcanic Eruptions
  • Hawaiian
    • Quiet
    • Very fluid lava
    • Little explosive activity
kinds of volcanic eruptions1
Kinds of Volcanic Eruptions
    • Strombolian
    • small amounts of lava in very short bursts
    • impressive booming sounds, but the eruptions are relatively small
  • tephra
kinds of volcanic eruptions2
Kinds of Volcanic Eruptions
    • Vulcanian
    • short, violent, small explosion
  • tephra, ash clouds, and pyroclastic flows

Santiaguito volcano in Guatemala

kinds of volcanic eruptions3
Kinds of Volcanic Eruptions
    • Pelean
  • large quantity of gas, dust, ash and lava fragments
  • pyroclastic flows
  • one of the most dangerous - tremendous destruction

Mont Pelee

kinds of volcanic eruptions4
Kinds of Volcanic Eruptions
  • Plinian
    • largest and most violent
    • propels pyroclastic material as high as 30 miles
    • huge amount of tephra
    • extremely fast moving lava

Mt. St. Helens

effects of eruptions
Effects of Eruptions
  • Lava
    • Destroys whatever is in its path
    • Usually not harmful to humans
effects of eruptions1
Effects of Eruptions
  • Gas
    • Some are poisonous
    • Acid rain


carbon dioxide poisoning

Sulfur banks

effects of eruptions2
Effects of Eruptions
  • Pyroclastics
    • Collapse buildings
    • Breathing problems
    • Kills vegetation
    • Suffocates and buries animals & people
effects of eruptions3
Effects of Eruptions
  • Pyroclastic flow
  • Superheated gas and debris rush down side of volcano
  • faster than 700 km/hour, higher than 1000 degrees C
effects of eruptions4
Effects of Eruptions
  • Lahars
    • Mud flows
effects of eruptions5
Effects of Eruptions
  • Volcanic dust
    • Reflects sunlight
      • Cools earth
      • Fantastic sunsets
    • Rich soil
tambora 1815 largest recorded eruption
Tambora 1815 Largest recorded eruption

Year without a summer: places like New England and Canada, frost was recorded in every month of the year, and snow fell in June

volcanic features
Volcanic features
  • Batholiths
    • Magma bodies forced upward cools slowly inside earth
    • Some maybe exposed after years of erosion
    • Examples
      • Yosemite National Park



Devil’s Tower

Shiprock, New Mexico

volcanic features1
Volcanic features
  • Dike
    • Magma that hardens after being forced into a crack across rock layers
  • Sill
    • Magma that hardens after being forced into a crack parallel to rock layer
volcanic features2
Volcanic features
  • Caldera
    • Large depression formed when the top of a volcano collapsed into an emptied magma chamber
    • Examples
      • Crater Lake Oregon
      • Yellowstone
famous eruptions
Famous Eruptions
  • Mt. Vesuvius
  • 79 AD
  • buried Pompeii and its sister city, Herculaneum


Ruins of Pompeii

79 AD

famous eruptions1
Famous Eruptions
    • Crater Lake
  • formed when a massive eruption of Mount Mazama 7700 years ago caused the mountain to collapse, leaving a steaming caldera. Centuries of rain and snow filled the caldera creating Crater Lake.
famous eruptions2
Famous Eruptions
    • Krakatau-1884
  • two-thirds of the island collapsed beneath the sea, generating a series of devastingpyroclastic flows and immense tsunamis
famous eruptions3
Famous Eruptions
    • Yellowstone
  • 28- by 47- mile caldera
  • Last eruption 600,000 years ago
  • largest and most active caldera in the world
famous eruptions4
Famous Eruptions
  • Mt. St. Helens
    • May 18, 1980
    • 5.1 earthquake 8:32am
    • The eruption lasted 9 hours










recent eruptions
Recent Eruptions
    • Kilauea
  • Eruption began 1983 and continues
recent eruptions1
Recent Eruptions
  • Iceland near the Eyjafjallajökull volcano
  • 2010 shut down airports across Europe
recent eruptions2
Recent Eruptions
  • Mt. Redoubt
predicting eruptions
Predicting Eruptions
  • Seismograph
  • Tiltmeter
  • Levels of escaping gas
  • Gravimeter
  • Satellite