Volcanoes Notes

Volcanoes

• Volcano: A mountain or hill with an opening (crater) that erupts lava, rock, ash, and gases.

Where Volcanoes Occur

• Active volcanoes: Approximately 50-70 worldwide.
• Locations:
  • West coast of the Americas.
  • East coast of Siberia, Japan, Philippines, and Indonesia.
  • Island chains from New Guinea to New Zealand (Ring of Fire).
  • Iceland, Kenya Rift Valley, Italy, and Hawaii.

Hot Spots and the Ring of Fire

• Hot spots can be located on, near, or far from tectonic plate boundaries.
• Examples:
  • Hawaiian Hot Spot: Volcanic chain extending 6,000km across the northwest Pacific Ocean.
  • Yellowstone Hot Spot: 650km long, located in the United States.

The Ring of Fire

• Area with many earthquakes and volcanic eruptions in the Pacific Ocean basin.
• Contains 452 volcanoes (over 50% of world's active and dormant volcanoes).
• 90% of world’s earthquakes and 81% of largest earthquakes occur here.
• High volcanic and seismic activity due to continuous movement and collision of tectonic plates.

Why Volcanoes Occur

• Tectonic plate collision: One plate slides under another, melting the mantle to form magma.
• Magma rises through cracks and weak points in the crust, collecting in magma chambers.
• Eruption: High pressure or crustal cracks force magma up the vent and out through the crater.
• Eruptions cause lava flows, ash flows, mudslides, avalanches, ashfall, and floods.
• Three basic types of volcanoes: shield, cinder cone, and composite.