Factors affecting extent of volcano Flashcards
Nature of hazards
Low silica lava
Less viscous → flows further before cooling and solidifying → larger area affected
● Less volcanic gases trapped → effusive eruption → less harmful gases ejected and less volcanic rocks ejected→ less damage to people and environment
Eg. 2018 eruption of Kilauea, Hawaii many homes destroyed
High silica content
More viscous → flows shorter distance before cooling and solidifying → smaller area affected
● More volcanic gases trapped → explosive eruption → volcanic bombs and materials travel to faraway places and more volcanic gases emitted to the atmosphere
Eg. 2010 Mount Merapi, Indonesia volcanic bomb spreads over a distance, people were killed, huge forest areas were destroyed
Vulnerability conditions
Availability of surface and groundwater
● When there are large amounts of water, lahars can develop more easily.
Eg. water from rapid melting of ice and snow from volcano summit
○ Groundwater released through cracks in the ground
○ Heavy rainfall
○ Existing rivers or lakes nearby
● More water → more lahars formed when water mixes with volcanic materials
→ more damage to local area by burying people and destroying properties
● Eg. Mt Agung, 2017 / 1985 Nevado Del Ruiz, Colombia
Prevailing Wind Conditions
The strength and duration of wind will affect how long and how far the volcanic materials (ash and tephra) will be carried
Strong wind, long duration → larger area affected over a longer period of time → more damage to the local area
● Ash can cause respiratory problems to people who inhale it. Ash can also accumulate on roofs and cause them to collapse. Ash and tephra can also destroy crops and kill animals
1991 Mt Pinatubo, Philippines ash fall and tephra spread across large distances due to fast wind speed
Exposure
Presence of human settlements increases risk to volcanic eruptions.
● Similar to earthquakes: higher population density → higher damage.
● Why people live near volcanoes
○ Rich, fertile, volcanic soil for farming
○ Geothermal energy to provide electricity
○ Valuable minerals (eg. sulfur) that can be mined for sale
● Eg. Mt. Sinabung—> despite many explosive eruptions, ppl continue to live near it due to fertile soil for farming
