What is pyroclastic flow for kids

The lava is ejected and shot through the air during an eruption. As the lava hurtles through the air it cools and the gases escape leaving the rock full of holes.

Pumice is so light that it actually floats on water. Huge pumice blocks have been seen floating on the ocean after large eruptions. Some lava blocks are large enough to carry small animals. Pumice is ground up and used today in soaps, abrasive cleansers, and also in polishes.

Bombs and blocks are the largest of the pyroclasts. Blocks are angular chunks of rock that has been ejected from a volcano during an eruption. The photo above is of a geologist studying pumice blocks from the May 18, eruption of Mt.

A bomb is formed as lava hurtles through the air, cooling and forming a hardened lava rock. A bomb's shape is usually more rounded or streamlined. Notice the teardrop shape of the bombs. Obsidian is a very shiny natural volcanic glass. When obsidian breaks it fractures with a distinct conchoidal fracture.

Notice in the photo to the left how it fractures. Obsidian is produced when lava cools very quickly. The lava cools so quickly tht no crystals can form. When people make glass they melt silica rocks like sand and quartz then cool it rapidly by placing it in water. Obsidian is produced in nature in a similar way.

Obsidian is usually black or a very dark green, but it can also be found in an almost clear form. Ancient people throughout the world have used obsidian for arrowheads, knives, spearheads, and cutting tools of all kinds. Today, obsidian is used as a scapel by doctors in very sensitive eye operations. Write the answers to the following questions in complete sentences on a piece of paper.

Use the page titles located directly under the questions to move your way through the lesson to locate the answers. When you have finished the questions click on the Earth icon to return to the start of the lesson. Describe pahoehoe and aa lava flows. What is a pyroclast and how do they form?

Write a definiton for the following;. Skip to main content. Toggle menu Go to search page. Search Field. Pyroclastic flows often occur in two parts.

Along the ground, lava and pieces of rock flow downhill. Above this, a thick cloud of ash forms over the fast-moving flow. Such a flow can transform the landscape drastically in a short period of time.

Not only does it destroy living material in its path, it often leaves behind a deep layer of solidified lava and thick ash. Pyroclastic flows may result in flooding as streams are blocked or rerouted by the flow. Floods may also occur when the flow of hot material melts snow and ice, swelling rivers and streams beyond their banks. A mudflow containing volcanic material, called a lahar , may also form when the rock of the pyroclastic flow mixes with water to become a quickly moving slurry.

Also called a cinder cone. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. National Geographic Society. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.

They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource. If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media. Flows usually consist of two parts - the basal flow hugs the ground and contains larger, coarse boulders and rock fragments, while an ash cloud rises above it because of the turbulence between the flow and the overlying air.

While moving, the kinetic energy of the boulders will flatten trees and buildings in their path. The hot gases and high speed make them particularly lethal.

For example, the towns of Pompeii and Herculaneum in Italy were famously engulfed by them in 79 with heavy loss of life, and in June flows killed 20 people on the Caribbean island of Montserrat. A pyroclastic flow has a red glow in the dark. Flows containing a high proportion of gas to rock are known as pyroclastic surges.