Making Connections with New Stuff 1. 3 types of volcanoes 2. Volcanoes and the formation of Early Earth 3. Minerals, Rocks, and the Rock Cycle 4. Divergent and Convergent Boundary Volcanoes 5. Erupted Materials 6. Creative and Destructive Forces

What is Viscosity? A substances ability to RESIST flowing Mafic Lava = low viscosity = flows easily Felsic Lava = high viscosity = very sticky

1. Shield Volcano (low viscosity mafic lava) TALL, FLAT, mostly grow from the ocean floor Made from layers of lava (very little ash, dust, or cinders) Examples: Hawaii, Iceland

2. Cinder Cone Made mostly from cinders and ash, normally do not have lava flow from them Erupt only once, commonly found in lava fields or on the sides of larger volcanoes – SMALL, STEEP Layers of ash, dust, cinder

3. Composite Cones (gas and felsic lava) TALL, STEEP, very common along the ring of fire, explosive eruptions Very viscous lava that only travels a short distance creating the steep slopes AND layers of Cinder Alternating layers of ash, dust, cinder and lava Sometimes called strato-volcanoes

Composite VolcanoCinder Cone VolcanoShield Volcano

Types of Eruptions Quiet Eruptions – 1) Low viscosity magma (flows easily) - high temperature, low silica content, mafic 2) Low gas pressure - Carbon dioxide and water vapor escape easily Violent Eruptions – 1) High viscosity magma (does not flow easily) - low temperature, high silica content, felsic 2) High gas pressure - Carbon dioxide and water vapor can’t escape

Volcanic Material (Tephra) 1)Lava Flows (liquid) 2) Gases - Carbon dioxide, water vapor, nitrogen, sulfur, chlorine, hydrogen, argon 3) Pyroclastic Material (solid) -Ash and dust (small) -Lapilli or cinder (medium) -Blocks and Bombs (large)

Anatomy of a Volcano Crater Vent, Pipe, Neck (through which magma reaches the surface) Caldera (collapsed magma chamber)

Dangers of Eruptions Pyroclastic Flows - hot gases, glowing ash, large rock fragments that travel at 120+ mph

Dangers of Eruptions Lahars – destructive mudflows resulting from water saturated volcanic debris (usually from melted snow on tall volcanoes)

Creative and Destructive Forces Creative Forces – make new crust or other landforms (islands, sea-floor) Destructive Forces – destroy crust or other landforms (volcanoes that blow up, subduction)

Convergent vs. Divergent Boundary Volcanoes Divergent Boundary (mid-ocean ridges) – lava oozes out, low viscosity mafic lava Convergent Boundary - Subduction (ring of fire) – explosive eruptions, high viscosity lava,

Volcano Classifications Active – erupted in the last 100 years Dormant – erupted in the last 1,000 years Extinct – has not erupted in over 1,000 years