monioring volcanoes

• risk mapping is studying the history of a volcano to predic frequency and hazards
• magma chambres can be located by placing seismometers around volcanoes. a wave will slow if it meets magma
• earthquakes, short and long period earthquakes and harmonic tremors. increase in frequency may mean imminent eruption
• ground movement is the swelling of a volcano that indicates magma moving up a vent
• increased gas emissions suggests magma near the surface
• a change/increase in ground water levels from increased gas pressure can indicate volcanic activity