Volcanos Flashcards
What is home to 90% of the world’s earthquakes and 75% of the world’s volcanoes.
The ‘Ring of Fire’ is an area of the Pacific Ocean that is shaped like a Horseshoe.
How are volcanos formed
Deep in the earth, it is extremely hot. It is so hot, in fact, that rocks actually melt and form magma, which makes up the mantle of the earth. The upper mantle mixes and moves, which creates pressure underneath the crust. This pressure can sometimes cause the mantle to leak out onto the surface of the earth, this is a volcano
Magma is less dense than the surrounding rock, so it rises buoyantly towards the surface.
Three stages of Volcanoes:
Active: An active volcano is one that has erupted recently, and there is the possibility that it may erupt again.
Dormant: A dormant volcano is one that has not erupted for a long time, however, it may still erupt in the future.
Extinct An extinct volcano is one which has erupted thousands of years ago, but it will probably never erupt again
Two types of eruptions:
Effusive Eruptions- lava steadily flows out of a volcano onto the ground.
Eruptive/Explosive Eruptions- Most violent eruption. Gas and broken fragments of magma are shot up
Different types of volcanos:
Composite VolcanoesThese volcanoes are steep-sided volcanoes and are made up of lots of layers of volcanic rocks. They usually erupt in an explosive way because the magma in these volcanoes is quite sticky whichclogs up the passage that it has to pass through. Pressure is built inside the volcanic chamber and this results in the volcano erupting violently.
Cinder Cones: Cinder cones are circular or oval cones. They are made up of small fragments of lava, which are blown into the air through a single vent. When they cool down, they form rock around the vent. They grow quickly, but are not usually very big. They are not usually dangerous either.
Shield Volcanoes: Shield volcanoes are bowl or shield-shaped in the middle. When they erupt, the lava is quite runny and it travels long distances down the side of the volcano before it cools down. This lava forms long, gentle slopes that look like a warrior’s shield, which is how they got their name. These volcanoes do not often explode.
