VOLCANIC HAZARD

• 24 - Number of Active Volcanoes
• 42 - Number of Recorded Significant Eruptions for the Past 400 Years
• 30 Taal Volcano - Highest Number of Recorded Eruptions
• June 15, 1991 - Date of Mount Pinatubo Eruption
• Lava - a molten rock or magma that has reached the surface of the Earth.
• Lava flow - occurs when magma contacts the surface of a volcano and

  erupts or overflows.
• fluid lava flow - less silica and gas content, high temperature.
• Viscous lava flow - high silica and gas content, low temperature.
• Pahoehoe & aa - Types of Lava Flows
• Water vapor, sulfur dioxide, carbon dioxide, hydrogen chloride and hydrogen fluoride - types of Volcanic Gases
• sulfur dioxide - negative impacts can form into sulfuric

  acid, a component of acid rain
• carbon dioxide - negative impacts: causes asphyxiation without warning.
• monitoring, bulletin or advisories, recommendation, evacuation, public awareness - Mitigating the Negative Effects of Volcanic Gas
• turbulent ash cloud - riding over the basal flow
• basal flow - coarse pyroclastic materials
• fresh or solidified lava, hot volcanic gases, volcanic ash - pyroclastic materials
• turbulent ash clouds and basal flow - 2 parts of pyroclastic flows
• pyroclastic materials - also known as tephra
• pyroclastic materials or tephra - a collective term for volcanic fragments that have been ejected out of a volcano.
• Soufriere, Pelee, Merapi - types of pyroclastic flow
• Soufriere type - forms from the collapse of a high vertical column from a highly explosive eruption.
• Pelee type - occurs when a highly viscous lava dome blocks the opening of a volcano, building pressure until it can no longer be contained and explodes to one side of the volcano.
• Merapi type - occurs when a lava dome grows too steep over a volcanic crater and falls due to gravitational force.
• high heat content, high velocity, high volume - Negative Impacts of Pyroclastic Flows
• HazardHunterPH - an initiative of DOST-PHIVOLCS through

  GeoRisk Philippines.
• ash - (< 2mm)
• lapilli - 2-64 mm
• blocks and bombs - (> 64 mm)
• ballistic missiles and tephra falls - tephra
• ballistic missiles - negative impacts: have effects that are in relative proximity to the volcanic source.
• tephra falls - negative impacts: have widest range of effects amongst all other volcano hazards.
• mudflow - meaning of indonesian term lahar
• lahar - It is created when tephras mix with water and form a slurry that flows along the slopes of a topography.
• Primary lahar - forms when pyroclastic flows occur along areas with bodies of water such as s t reams and rivers .
• glacier bursts - A particular type of primary lahar that occurs in Iceland and the Andes region.
• Secondary lahar - forms after an eruption event. Its flows are generated when rain wets unconsolidated tephra and mobilizes them downward.
• hazard avoidance, hazard modification, hazard warning, hazard response and recovery - mitigation of lahar