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By Laura Wickenhauser
Grade 4
• Volcanoes are mountains, but they are not formed the same way
• Mountains are formed from folds and uplifts on the Earth’s surface
• Volcanoes are built on top of their own lava and ash from past eruptions.
• A volcano is an opening or vent where molten rock and gases are released.
What is an Eruption?
• An eruption occurs when magma rises and reaches the Earth’s surface.
• Magma is melted rock that flows under the Earth’s surface.
• Once the magma has pushed through the vents in the Earth’s surface, it is called Lava
Layers of the Earth’s Surface
• Some eruptions are explosive and others are not. This depends if the magma is runny or sticky
• If magma is thin and runny, gases can escape easily from it. This type just flows out of the volcano
• If magma is thick and sticky, gases can’t escape easily and it causes an explosion.
There are 2 types of Lava:
1) Pahoehoe
2) A’a
Pahoehoe
• Flows at a slow speed
• The very top of the lava is cooled by the air, while the lava underneath continues to flow
• It stops flowing after a few minutes and becomes inflated with lava and a new section starts to flow
• This lava is smooth and unbroken
Pahoehoe Lava
A’a
• Flows at a fast speed and is usually results from fountains of lava erupting
• This lava has very rough top and bottom layers with a dense interior
• Formed by pasty lava that is pulled apart by twisting and shearing during flow
A’a
How much of the Earth is Volcanic?
• About 80% of the Earth’s surface (above and below sea level) is volcanic.
• Gases from the volcanoes hundreds of millions of years ago formed the Earth’s oceans and atmosphere.
• Eruptions have also produced mountains, plateaus and plains
• There are about 500 active volcanoes on Earth today
• This does not include those that lie beneath the sea
You can simulate your own volcanic eruption
To check your knowledge on volcanoes, try to complete this crossword puzzle
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