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