Structure of a volcano:
● Volcano = when magma reaches Earth’s surface and erupts to
form lava
● Magma chamber = a collection of magma below the crust
● Main vent = main outlet for magma to escape
● Flank = side of a volcano
● Crater = created when an eruption blows the top off a volcano
● Dike = branch pipe that cuts through weaker rock
● Secondary cone = formed from smaller eruptions on the flank
⇒ Types of volcanoes:
2. Lahars
○ Lahar = formed when pyroclastic flows mix with ice and snow and cause them to melt
■ Consists of ice, rain and river
■ Flows down from a volcano, typically along a river valley
■ Travels at speeds of 70 kmph
■ Can destroy large areas of crops, buildings → spreads quickly and far
3. Ash cloud
○ Ash cloud = cloud of ash containing fragments of crushed rock, minerals + volcanic glass
■ Less than 2mm in diameter
■ Can spread over large distances, affect aircraft and cause health problems
4. Lava flow
○ Lava flow = flow of lava travelling at various speeds depending on viscosity
■ Made up of:
● Molten rock from eruption
● Resulting molten rock from heat of lava
○ Most common type is basaltic lava
■ Travels very slowly → can easily be outrun or avoided using barriers or diversions
■ Up to 1000°C
■ Can destroy buildings and crops
5. Volcanic bombs
○ Volcanic bombs = mass of molten rock larger than 2.5 inches in diameter
■ Formed when a volcano ejects viscous fragments of lava
■ Cools before reaching the ground
■ Only affects areas immediately next to the volcano
CASE STUDY: