volvanoes Flashcards
(20 cards)
define volcanoes
Volcanoes form when
magma
, which is molten rock from beneath the Earth’s crust, reaches the surface. The magma erupts to form
lava
whhat 2 plate boundaries do volcanoes usually form on
divergent and convergent
what type of country will volcanoes affect the most
poorer countries - due to the fewer resources to predict and prepare
what are the 4 distinctive features of volcanoes
magma chamber - where molten rock is stored beneath the ground
main vent - channel through which magma travels to reach earths surface
secondary vent - some magma may escape through the sides of the volcano especially if the main vent becomes blocked
crater - found at the top of the volcanoe where the magma erupts from
what stuff do volcanoes produce
ash(affects global climate) , lava , volcanic bombs , pyroclastic flows and lahars
positive effect of volcanoes
ash ejected acts as a good fertiliser for soils
volcanoes attract tourists
geothermal energy used to generate electricity
negative impacts of volcanoes
dangerous - can kill people and damage property
economic activity can suffer as its hard for businesses to operate after an eruption
habitats and landscapes are damaged by lava flows
what are the 2 main types of volcanoes
composite and sheild
what plate boundary is composite volcanoes found
convergent - oceanic subducts beneath continential
characteristics of composite volcanoes
andesitic magma - magma lower in temperature , has more silica +disolved gases and more likely yo explode once it reaches the surface
acidic lava which is very viscous
steep sides - magma doesnt flow very far before it solidifies
Alternate layers of ash and lava. For this reason, they’re also known as
stratovolcanoes. Strato means layers.
violent eruptions
longer periods between eruptions
what plate boundaries are sheild volcanoes found at
divergent - plates moving apart from eachother
characteristics of sheild volcanoes
basaltic magma - high in temp magma ,low silica and low gas content : fluid magma with little explosive activity
basic lava - not acidic and very runny
gentle sides - magma flows for long distance before solififiying
no layers volcano consists of just lava
less violent eruptions
shorter periods between eruptions
what can me used to estimate volcano eruption
tiltmeters and GPS satillites , seisometers , looking at past history of volcanic eruptions
CS when did the La Palma eruption happen
19th of september to 13 december 2021
what does intraplate mean
This means that they are located above a ‘hot spot’ rather than along a plate boundary.
prediction
A build-up of magma swelled beneath the ground a week before the first eruption. Warnings were sent out and nearly 7,000 people evacuated the affected areas. An ‘earthquake swarm’ of more than 20,000 earthquakes took place in the days and weeks before the eruption.
primary impacts
More than 7,000 people had to leave their homes
Over 1,300 homes were destroyed by the lava flow
Many other buildings, such as churches and schools, were damaged or destroyed.
secondary impacts
Hundreds of acres of farmland, including banana plantations, were destroyed
Flights were cancelled and tourist resorts closed, which affected the local economy
The molten rock increased the size of the island as it flowed into the ocean.
responses
The Spanish prime minister, Pedro Sanchez, promised to repair any damage to the island
The government also set aside €225m euros (£192m) to help people living on the island.
