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Volcanic ActivityWhat caused Mt. St. Helen’s to erupt?
Where do Volcanoes Occur?
Where do volcanoes occur?
• Along convergent boundaries above subduction zones– Ring of Fire
• Along divergent boundaries at mid-ocean ridges
Hot Spots
• Hot Spots are unusually hot regions of Earth’s mantle where plumes of magma rise to surface
• Located away from plate boundaries
• Example: Hawaii
Volcano Status• Active – Erupts Regularly– Lifetime can span months to millions of years– Can be currently erupting or showing signs of
unrest (earthquakes, emitting gas)– Ex: Mt. St. Helens
• Extinct– Unlikely to erupt again– No magma/lava supply– Ex: Hawaiian Islands not over hot spot
• Dormant– Erupted in past but is now quiet
*Difficult to determine status of volcanoes*
Effects of Volcanoes • Volcanoes emit water vapor, carbon dioxide,
and sulfur dioxide into the air• Gases are suspended in atmosphere and block
radiation from sun• Global temperatures can be affected• Health issues for humans (Respiratory) • Pyroclastic flows, tephra, lahars (hot mud
flow)
Volcano Predictions?• Volcanologists study
deposits left from previous eruptions
• Warning Signs: earthquakes activity and gas emissions
• Seismometers measure EQs and correlation spectrometers measure SO2 levels
Volcano Safety
• Structural support – walls, supportive buildings
• Evacuation procedures
• Communication between scientists and public
Volcanoes in our Solar System• Volcanoes may have been present in the
history of other planets– Mars, Venus
• Volcanoes are active on Jupiter's moon, Io