by laura wickenhauser grade 4. volcanoes are mountains, but they are not formed the same way...

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