Theme 2 - volcanoes and earthquakes Flashcards
(21 cards)
How is the volcano formed
- magma rises through cracks in the crust
- pressure builds up
- pressure and tension are released - > plate movement
- magma explodes to the surface, causing eruption
- lava cools and forms a new crust
- over time, rock builds up, new crust form on top, forming volcano
what are the features of a volcano
lava, pyroclastic flow, ash, lahars, main vent, secondary cones, crater and magma chambers
what is lava
magma that reached the surface
what is pyroclastic flow
fast moving clouds of mixed posionous gases and ashes
what is ash
very fine grained volcanic material
what are lahars
snow and ice melt and combine with ash
what is the main vent
centrel tube through the volcano
secondary cones
eruptions from the other vents lead to the formation of secondary cones on the sides
craters
bowl shaped basin at the top of the volcano
magma chamber
large, underground pool of magma
Difference between magma and lava
lava is above the earths surface and magma is under
Impacts of volcanic eruption
- loss of life and injury
- collapse or destruction of buildings
- transport network damaged
- Loss of jobs and businesses
- loss of crops
- power and water supply damaged
opportunites of volcanoes
fertile soil, tourism, minerals n precious stones, geothermal energy, creating new land areas
stages of volcanoes
active, dormant and extinct
active stage
has errupted recently, likely to erupt again
dormant stage
has not erupted recently, but may errupt in the future
extinct stage
no evidence to errupt again
types of volcanoes
shield and composite volanoes
featutes of shield volcano
- low viscosity , balsaltic lava
- low in height, gently sloping sides with
broad base - low silica content so covers longer distances
- frequent eruptions but low in magnitude
- high temperature
- low gas content
- little build up in pressure
features of composite volcano
- high viscosity , andestic lava
- high in height, steep sides volcanic cones
- high silica content so covers shorter distances
- rare eruptions but high in magnitude
- low temperature
- high gas content
- enormous build up in pressure
causes of erruption
- At constructive margins, plates move away from each other, and magma fills the gaps
- At destructive margin, oceanic crust melts from friction and heat from the mantle, newly formed magma is lighter,so it rises to the surface
