5.1

• Lava flow


  A product of the quiet effusion of molten rock or magma from beneath a volcano
• Lava flow


  • Extremely low speed
• Types of Lava Flow

  • Basaltic Lava
  • Rhyolitic Lava
  • Sheet Lava
  • Andesitic Lava
  • Pillow Lava
• Basaltic Lava


  • The fastest flowing Lava because of its relatively low viscosity
  • Typically erupts at temperatures ranging from 1,100 to 1,200 degrees Celsius
• Basaltic Lava


  • Dark in color (Gray to Black)
  • Contains 45 to 53 percent silica, and is rich in iron and magnesium
  • Have more fluid than Andesites or Decites, which contains more silica
• Andesitic Lava


  • Associated with stratovolcanoes and commonly forms lava domes
  • Usually associated with the broad land forms of shield volcanoes
• Andesitic Lava


  • Think Lava flow (it can reach several KM in length)
  • Can generate strong explosive eruptions to form pyroclasting forms
  • Erupts at temperatures between 900 and 1000c
• Rhyolitic Lava


  • Have relatively higher viscosity
  • Usually associated with violent eruptions involving pyroclastic flows
  • Very steep landforms such as lava spines
• Rhyolitic Lava


  • Viscous and tend to form thick blocky lava flows or steep-sided piles of lava called lava domes
  • Its magmas tend to erupt explosively, Producing abundant Ash and Pumice
• Sheet Lava


  • Are thicker than pahoehoe and have surface textures ranging from ropy to straited
  • Associated with violet eruptions
  • Usually collapses as a result of the emptying of lava below the hardened surface
• Sheet Lava


  • Lava flows are broad, laterally extensive blankets of lava (formed during relatively high effusion rate eruptions, very fluid, and tend to fill-in and pond in low-lying areas)
  • Has fast extrusion that allows individual lobes of lava to quicky coalesce back together into a sheet
• Pillow Lava


  • Undersea volcanoes including mid-oceanic ridges are the usual sources of Pillow Lavas
  • Volcanoes on land may also directly deposit lava into water whare it is quenched
• Pillow Lava


  • Are pillow-shaped rocks (formed by sudden cooling of lava that is deposited underwater)
  • Are bulbous, spherical, or tubular lobes of lava
• Effects of Lava Flow on Humans and Animals

  • Headaches
  • Increased susceptibility to respiratory ailments
  • Watery eyes
  • Sore throat
  • Flu-like symptoms
  • General lack of energy
• Effects of Lava Flow on the Environment

  • Deterioration water quality
  • Fewer periods of rain
  • Crop damages
  • Destruction of vegetation
• Overall the effects of Lava Flow in general is, everything in the path of an advancing lava flow will be knocked over, surrounded, buried, or ignited by the extremely hot temperature of Lava
• Mitigating Effects of Lava Flow

  1. Diversions

  2. Building of artificial barriers
• In 1983 in Italy, Lava Flows were prevented by using Explosive Barriers
• In Hawaii, people considered using engineered barriers and diversion channels
• However, because of high cost involved, unknown effectiveness, and complex legal implications, these remain in the back burner