prefi reviewer

• Lava flow


  A product of the quiet effusion of molten rock or magma from beneath a volcano
• The reason why lava flow is not worrisome to many is its extremely low speed
• Types of Lava Flow

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


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


  • 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


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


  • 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 Characteristics


  • Are 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 Characteristics


  • 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
• 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
• Mitigating effects of Lava Flow

  • 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
• Volcanic gases


  Composed mainly of water, carbon dioxide, and sulfur dioxide
• During violent eruptions, these gases are injected into the stratosphere where the sulfur dioxide reacts with water to form microscopic droplets, or aerosols, of sulfuric acid which block sunlight from reaching the Earth's surface, causing cooling
• Sulfurous aerosols, along with chlorine, contribute to the destruction of stratospheric ozone, though most of this depletion comes from man-made chemicals
• Magma


  The molten rock stored beneath volcanoes, which contains dissolved gases that are released during eruptions or emitted when the volcano is quiet
• Fumaroles


  Openings in the earth's surface that emit steam and volcanic gases, such as sulfur dioxide and carbon dioxide
• Pyroclastic Flow


  • A hot mixture of fresh lava, gas, rock, pumice, and ash that moves down the side of a volcanic crater at high speeds during an eruption
• How Pyroclastic Flows Occur


  A common cause is when the column of lava, ash, and gases expelled from a volcano during an eruption loses its upward momentum and falls back to the ground
• Types of Pyroclastic Flows

  • Merapi-type
  • Pelean-type
  • Soufriere-type
• Merapi-type Pyroclastic Flows


  • Often characterized by a high velocity and a mix of hot gases, ash, and volcanic rocks
  • Can travel long distances from the volcano's summit, following valleys and ravines, and are known for their devastating impact on nearby communities
• Pelean-type Pyroclastic Flows


  • Associated with the eruption style of stratovolcanoes like Mount Pelée in Martinique
  • Characterized by the collapse of a volcanic dome or the eruption column, resulting in the formation of dense, fast-moving flows
• Soufriere-type Pyroclastic Flows


  • Associated with the eruption style of stratovolcanoes like Soufrière Hills on the island of Montserrat
  • Often involve the collapse of volcanic domes and the formation of pyroclastic flows traveling down valleys
• Effects of Pyroclastic Flows

  • Burn
  • Impact and Burial
  • Inhalation of hot ash and gases
  • Lahars and flooding
• Burn


  • The extreme temperatures of rocks and gas can burn people, houses, and vegetation
• Impact and Burial


  • By its speed, mass, and volume, a pyroclastic can knock down, shatter, bury, or carry away nearly all objects in its path
• Inhalation of hot ash and gases

  • Volcanoes emit toxic gases that can cause immediate asphyxiation of people and animal upon inhalation
• Lahars and flooding


  • Have the potential to destroy critical infrastructure such as roads, bridges, buildings, and utilities
• Mitigating the Effects of Pyroclastic Flows

  1. Implementing robust monitoring systems to detect volcanic activity and issue timely warnings

  2. Developing and practicing evacuation plans for communities located near active volcanoes

  3. Establishing well-coordinated emergency response plans involving local authorities, emergency services, and other stakeholders
• Tephra


  Volcanic rock and lava materials that are ejected into the air by explosions or carried upward by the eruption column's hot gases or lava fountains
• Ballistic Projectiles


  A special kind of tephra that follow a projectile path as they are forced out of the vent at steep angles like a cannon ball
• Types of Tephra Falls

  • Ash
  • Lapilli
  • Pele's Tears
  • Pele's Hair
  • Pumice
  • Scoria
  • Blocks & Bombs
• Ash


  • 3mm diameter fragment, mix of broken glass and pulverized rock
• Lapilli


  • Size from 2 to 64mm, bigger pumice fragments are lapilli mixed with finer ash