VISCOSITY The resistance of material to flow –the higher the viscosity, the less easily something (magma/lava) can flow Motor oil: Flagstaff vs. Phoenix –hotter temps = lower viscosity oil –lower temps = higher viscosity oil

Cinder cones/maars Basalt Short lived (<10 years?) Cinder/scoria, lava flows (out the bottom) Most any tectonic environment Tephra, tephra, tephra ~1 km wide, 300 m tall

Shield volcanoes Very wide, tall Centuries to a few million years Basalt Often have a caldera at the rim Very low angle slopes Highly fluid flows VERY low viscosity Subduction zones and hotspots (larger volcanoes = hotspots) Cool picture is here:

Domes Relatively small (few hundred m on a side) (usually) dacite to andesite to rhyolite Convergent/subduction margins Pyroclastic flows often due to collapse of the dome Can be several thousand years, but really variable – a few years to several thousand Toothpaste 004_east_ssh.jpghttp://a.abcnews.com/images/US/volcanoe_ _east_ssh.jpg

Stratovolcanoes (also called composite volcanoes) Erupts everything (pyroclastic, lava, mudflows (lahars)) Intermediate (basalt to dacite) Hundreds of thousands years lifespan Big! 4000’ high from base (so Cascade volcanoes often 12,000’ or more) Subduction zone/convergence High viscosity, often explode polygenetic

Calderas Largest volcanoes on earth – 15 x 30 km Largest eruptions km 3 Magma rising to earth’s surface swells the surface, erupts pyroclastic material, magma chamber collapses. Shallow magma chamber. RHYOLITE!! (also dacite) All types of tectonic settings Lifespan to several million years Tuff is the most common erupted material, both as flows and as material falling from the air: pyroclastics rule Vents along margins of caldera (lava domes), earthquakes common