If magma is sticky and thick gasses can't escape easily, pressure builds up until it finally explodes. Magma will blast into the air and breaks into pieces called tephra. Tephra ranges in sizes from small particles to boulders the size of houses. Explosive volcanoes are deadly. They blast out tephra from the sides or tops of volcanoes. The lava runs down the side destroying almost everything in its path. The ash will cover the ground like snow. It might be thick enough to suffocate all forms of life.

In a Hawaiian volcanic eruption, large amounts of runny lava erupt and produce large, low volcanoes

In a peleean volcanic eruption, a burning cloud of ash and gas follows blocks of thick, sticky lava.

In a strombolian volcanic eruption, small sticky lava bombs and blocks, ash, gas and, glowing cinders erupt.

In a vulcaian eruption, violent explosions shoot out very thick lava and large lava bombs.

In a plinian volcanic eruption, burning cinders, and ash from put out cinders erupt great distances into the air.

What is Needed for an Eruption: Rocks and a planet with a hot mantel are what is needed for a volcanic eruption. Rocks and a planet mantel are needed because rocks will melt in the mantels and produce a substance called magma. Magma is what a volcano erupts, but when it passes through the earth's surface the name changes to lava.

Why Volcanoes Erupt: When rocks deep in the earth's surface melt, and make a substance called magma. The rocks around the magma are heavier than the magma itself the magma rises. The magma collects in magma chambers, and when the magma chambers become full it blows through the surface and turns into lava.