How do volcanoes form and what affect do they have on the Earth?

 Along convergent boundaries:  Above subduction zones  Magma forced upwards and forms volcanoes on surface  Ring of Fire in Pacific Ocean  Mediterranean belt – Mt. Vesuvius  Along divergent boundaries:  At mid-ocean ridges  Magma fills in gaps  Iceland – Mid-Atlantic Ridge

 Hot Spots are unusually hot regions of Earth’s mantle where plumes of magma rise to surface  Located away from plate boundaries  Example: Hawaii

 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  Can be very dangerous  It is very difficult to determine status 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)

 Volcanologists study deposits left from previous eruptions  Warning Signs: earthquakes activity and gas emissions  Seismometers measure EQs and correlation spectrometers measure SO 2 levels

 Structural support – walls, supportive buildings  Evacuation procedures  Communication between scientists and public

 Volcanoes may have been present in the history of other planets  Mars, Venus  Volcanoes are active on Jupiter's moon, Io