Volcanoes

• Viscosity is the ability of a substance to resist flow and is a measure of its consistency
• Tephra consists of pieces of all fragments of rock ejected into the air by an erupting volcano
• Pyroclastic flow is a dense, fast-moving flow of solidified lava pieces, volcanic ash, and hot gases, which is extremely dangerous to any living thing in its path
• Incandescent cinders are piles of lava
• Lapilli are rock fragments of gravel size
• Igneous rocks are formed from the cooling and solidification of molten (melted) rock
• The word igneous comes from "ignis," the Latin word for "fire"
• Molten rock material is known as magma until it is erupted onto the surface, when it is then termed lava
• Silica, or silicon dioxide, has the chemical formula SiO2 and is most commonly found in nature as quartz
• Silica is the major constituent of sand in many parts of the world
• Silica is used to make products such as glass, pottery, ceramics, bricks, and artificial stone
• Mafic magma:

  • Liquid rock containing a high level of magnesium and iron
• Felsic magma:

  • A violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water
• Lava bombs:

  • Mass of partially molten rocks larger than 64 mm (2.5 inches)
• Lahar:

  • A violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water
  • Produced when thick deposits of volcanic ash become saturated from rainfall or snowmelt
• Ashfalls:

  • Can bury nearby land and buildings with several feet of ash and choke animals
  • Consist of dust-size particles
• Lava flows:

  • May destroy property and reshape the landscape
  • Normally advance too slowly to endanger human lives
  • Typically, there is plenty of warning before a volcano emits lava flows
• Nuée Ardentes:

  • Avalanches aredDense clouds of ash and superheated gas that may flow down volcanic slopes at 60 miles per hour
  • Cook every living thing in their way
• Tsunamis:or so-called "tidal waves" may result if the flanks of island volcanoes collapse into the sea during major eruptions