volcanoes

Volcanoes

They happen when pressure builds up inside the earth causing hot molten rock from earth’s mantle to push through the surface. Volcanoes are so powerful that large eruptions can oven effect the climate on a global scale.
When Mount Pinatubo erupted in 1991, so much ash was thrown up into the atmosphere that the clouds blocked out the sun rays and lowered the global temperature by one degree Celsius for several months.
The simplest is a cinder cone formed when ash is in cinders; when ashes and cinders are blown out of a single vent quickly form a small cone-shaped mountain.
Similar to the cinder cone is the composite or strato volcano. Strato’s form at convergent plate boundaries, where one plate is pushed under or sub ducted under the other, the sub ducted plate melts into the magma, which is up forced up to the surface through multiple cracks, or vents in the crust the lava from a strato volcano, is very thick and slow moving. The viscous lava hardens inside the vent, and pockets of gas get trapped inside causing mudslides and mounds of molten ash called pyrocalastic flows.
Lava and ash pour out of the crater and solidify to form a steep sided cone that gets bigger and steeper after each eruption.
This is what when learnt on volcanoes in science class.