Volcanic Eruptions

Describe pyroclastic material and lava flows

What is pyroclastic material?

Pyroclastic material fragments of rocks that form during a volcanic eruption.felsic magma has high viscosity and silica and feldspar and has more trapped gasses and is light colored.

Volcanic blocks & bombs

A volcanic block is a fragment of rock that measures more than in diameter and is erupted in a solid condition and a volcanic bomb is a as they spin thorough the air they cool and develop a round or spindle shape.


Rock fragments ejected from a volcano.

Volcanic ash & volcanic dust

Is less than 0.25 mm in diameter is called volcanic dust. & pyroclastic particles that are less than 2 mm in diameter volcanic ash.

Mafic magma

Mafic magma has low viscosity and has magnesium and iron ans trapped less gas and is dark colored.


Pahoehoe is the least viscous type of mafic lava. It forms wrinkly volcanic rock when it cools.

Aa lava

Aa lava is more viscous than pahoehoe lava and forms sharp volcanic rock when it cools.

Blocky lava

Blocky lava is the most viscous type of mafic lava and forms chunky volcanic rock when it cools.

Types of volcanoes

Volcanic activity produces a variety of characteristic features that for during both quiet and explosive eruptions.

Shield volcanoes

Volcanic cones that are broad at the base and have gently sloping sides are called shield volcanos.

Cinder cones

A type of volcano that has very steep slopes in a cinder Cone. The slope angles of the cinder cones can be close to 40*degrees and the slopes are rarely more than a few hundred meters high. Costa Rica volcano

Composite volcanoes

Composite volcanoes are made of alternating layers of hardened lava flows and pyroclastic material. During a quiet eruption, lava flows Cover the sides of the cone. Then, why an explosive erruption occurs, large amounts of pyroclastic material are deposited around the vent.