Viscosity Volcanism vs. Volcano

Definitions

• Volcanism: Activity of magma forming and moving towards the surface.
• Volcano: Landform created when magma reaches the surface through Earth's crust.

Magma vs. Lava

• Magma: Hot, molten or semi-molten rock located underground.
  • Consists of solid, liquid, and gas.
  • Liquid portion: Referred to as the melt.
  • Solid portion: Made of minerals crystallizing from the melt (crystal mush) and solid rocks picked up (xenoliths or inclusions).
  • Gaseous portion: Dissolved in magma.
• Lava: Hot, molten or semi-molten rock that has reached the surface.
  • Consists of liquid and solid; most dissolved gases have escaped.

Igneous Rock Descriptions

• Felsic: High silica content, generally lighter in color (feldspar and silica).
• Intermediate: Between felsic and mafic.
• Mafic: Low silica content, high magnesium and iron content, generally darker in color.

Silica Content and Viscosity

• Viscosity: Measures a liquid's resistance to flow.
  • High viscosity: Flows slowly, thicker consistency.
  • Low viscosity: Flows fast.
• More silica = Thicker and more viscous magma.

Types of Lava

• Aa Lava:
  • Rough, jagged surface composed of broken lava blocks (clinkers).
  • Forms when lava has cooled and its viscosity has increased.
• Pahoehoe Lava:
  • Smooth surface, often wrinkled.
  • Can appear as coil, toe, ropy, or entrail.

Key Points

• Not all lavas are the same; type depends on factors like viscosity and temperature.