Some information on geology

There are three types of lavas formed by volcanoes. Mafic, Intermediate, and Felsic.

Mafic(Basaltic) %SiO2: < 50% %FeMg: 4% Temp: up to 1500C Viscosity: Low Eruptive Behavior: gentle Distribution: divergent plate boundries, hot spots, convergent plate boundries

Intermediate(Andesitic) %SiO2: ~60% %FeMg: ~3% Temp: ~1000C Viscosity: Intermediate Eruptive Behavior: explosive Distribution: convergent plate boundries

Felsic(Rhyolitic) %SiO2: >70% %FeMg: 2% Temp: 700C Viscosity: High Eruptive Behavior: explosive Distribution: hot spots in continental crusts (Yellowstone National Park)