What is a Volcano?What is a Volcano?
• A volcano is a weak spot in the crust where Magma, comes to the surface.
• Volcanic activity is a constructive force that adds new rock to existing land.
Where do volcanoes form?Where do volcanoes form?
• Volcanoes occur mostly along PLATE BOUNDARIES!
Ring of Fire
Belt of volcanoes that surrounds the Pacific Ocean
ConvergentConvergent
• Volcanoes are also found at convergent boundaries• Ocean/Ocean collision• Ocean/Continental collision
The island of Hawaii is made up of 5 huge volcanoes of which Mauna Loa is the worlds largest mountain by volume, Mauna Kea is the worlds highest mountain measured from base to top (half of it happens to be underwater) and Kilauea which is the worlds most active volcano.
Hot Spots
PARTS OF A VOLCANOPARTS OF A VOLCANO
Magma ChamberMagma ChamberWhere magma collects beneath a volcano.
PIPEPIPE A long tube in the ground that connects the magma chamber to the surface.
PARTS OF A VOLCANOPARTS OF A VOLCANO
VENTVENT Any opening in a volcano.
CRATERCRATER A bowl shaped area that may form at the top of a volcano.
What are the two types of eruptions?
What are the two types of eruptions?
•EXPLOSIVE – ash is released
•QUIET – mostly lava released
Describe the important factors that affect the force of a volcanic
eruption?
Describe the important factors that affect the force of a volcanic
eruption?
• Dissolved Gases in magma
• Viscosity (thickness) of magma• Temperature of magma
• Composition of magma (silica content)
Factors Affecting Eruptions
10.1 The Nature of Volcanic Eruptions 10.1 The Nature of Volcanic Eruptions
Dissolved gases • Mainly water vapor and carbon dioxide
• Gases expand near the surface
• Molten rock and gases escape through vents in the volcano
Factors Affecting Eruptions
10.1 The Nature of Volcanic Eruptions 10.1 The Nature of Volcanic Eruptions
Viscosity• Factors affecting viscosity
- Temperature (hotter magmas are less viscous)
- Composition (silica content)
1. High silica—high viscosity (rhyolitic lava)
2. Low silica—more fluid (basaltic lava)
What is a pyroclastic flow?What is a pyroclastic flow?
• Pyroclastic flow occurs during an explosive eruption.
• It is composed of ash, cinders, bombs and gases.
LANDFORMS CREATED FROM LAVA
LANDFORMS CREATED FROM LAVA
• SHIELD VOLCANO
• CINDER CONE VOLCANO
• COMPOSITE VOLCANO
Shield VolcanoesShield Volcanoes• Low and broad in shape
•Have quiet eruptions
• Produce lava flows
• Produce very little pyroclastic debris
Mauna Loa— located on the big island of Hawaii, is a shield volcanoMauna Loa— located on the big island of Hawaii, is a shield volcano
Cinder ConesCinder Cones
• Small volcano with single vent•Produces only explosive eruptions.•Has very steep slopes.
•They often look like an upside-down ice-cream cone.
•Formed by alternating layers of lava and ash
•Very steep and jagged•Produces both quiet and explosive eruptions.
(They are the type of volcanoes that most likely come to mind when one usually thinks of a volcano. )
Composite or Stratovolcano
Mount St. Helens: May 19,1982 Mount St. Helens: May 19,1982 Before: 9,677ftBefore: 9,677ft :: After: 8,364 ft.After: 8,364 ft.
March 2013
What are the stages of a Volcano?What are the stages of a Volcano?
• An active volcano is currently erupting or showing signs of erupting in the future.
• A dormant volcano is sleeping and may erupt in the future.
• An extinct volcano is dead. It is not likely to erupt again.
CalderasCalderas
• Large depressions in volcanoes formed by collapse
• Nearly circular
• Size exceeds 100 km in diameter
Wizard island is a small cinder cone that formed after the collapse of Mt.
Mazama.
Wizard island is a small cinder cone that formed after the collapse of Mt.
Mazama.