Pyroclastic Rocks
Volcano Rocks

Introduction
Pyroclastic rocks is a general term used for all rocks that form during volcanic eruptions. The term pyroclastic means fire broken or fire fragments. New pyroclastic material form each time a volcano erupts. The molten rock, magma, that came out of the vent of a volcano cools and hardens forming the newest rocks on our planet.

Lava bomb, Photo by Myrna Martin

Lava bombs and cinder on the slope 
of a cinder cone
, Myrna Martin

Tephra
Igneous rocks that have been airborne for a period of time before settling to the Earth are all called tephra. Tephra includes all types of airborne rocks that were produced during a volcanic eruption.

Pumice
Pumice is a volcanic glass that is associated with violent volcanic eruptions. It is usually made from rhyolite or dacite lava. Pumice is always blown out of volcanoes and it is the only rock that floats.

Cinders (scoria)
Cinders are similar to pumice but are usually made of iron-rich minerals found in basalt lava. Cinders may be semi-liquid or solid when blown from a volcano vent. Cinders that are semi-liquid become aerodynamic in shape forming lava bombs like the picture above. Scoria is the more recent term preferred by most geologists for this type of rock.

Lava
Magma, which is molten rock beneath the Earth's surface, becomes lava as it flows out of a volcano during an eruption. It is also the general term used to describe rocks that form during a lava flow.

Pillow basalt
Pillow basalt form at spreading ridges on the ocean floor when two oceanic plates are separating. Pillow basalt covers the ocean floors of all the ocean on planet Earth.

More Rock Cycle Links

Aa Lava Learn more about aa lava flows that occur on the Hawaiian Islands and the lava balls that often form on their surface.

Welded Tuff Find out how welded tuff is produced during violent eruptions and by supervolcanoes.

Intrusive Rocks Learn more about intrusive rocks that cool underground forming batholiths like the Sierra Nevada Mountains in California.

Clastic Rocks Find out how bits and pieces of older rocks form shale, sandstone and conglomerate rocks.


Pyroclastic Material This page gives all kinds of information about volcanic material that forms during volcanic eruptions.

Pyroclastic Rocks Find out how pyroclastic rocks form during volcanic eruptions.

Rock Cycle Learn more about igneous, sedimentary and metamorphic rocks and how they form.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.