What is Ejecta?

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  • Written By: Jessica Ellis
  • Edited By: Bronwyn Harris
  • Last Modified Date: 03 November 2019
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Ejecta is a term used to describe material ejected in a sudden event. In medical terms, ejecta can be used to refer to abnormal bodily fluids such as vomit, although it is much more commonly used in scientific realms. Volcanology, geology, and astrophysics all use ejecta to determine information about present or past events.

In volcanology, the term refers to particles and matter shot out of an erupting volcano. The substance can be comprised of many different materials, including partially liquid magma and rock. Volcanic ejecta is sometimes classified by the size of samples; extremely fine samples are referred to as ash, samples with a diameter of less than 2.5 inches (63.5 mm) are called lapilli, and anything larger is referred to as either a block or a bomb, depending on the solidity of the sample. Collectively, volcanic ejecta is often called tephra.

Studying tephra can help volcanologists in a variety of ways. In addition to providing data about the makeup and state of the volcano itself, some scientists hope to improve volcano warning systems and technology by studying the trajectory and speed of volcanic tephra. By gathering data from active volcanoes, computer modeling programs may developed that could improve human understanding of how a volcano would act in an eruption.


Ejecta is also a major area of study when considering impact craters on Earth, the moon, and other celestial bodies. When the impact of a meteor or other falling body on a landmass creates a crater, a debris layer of varied materials forms around the rim of the crater. This layer, called the ejecta blanket, can be a major target of scientific study. By analyzing these blankets on Earth, scientists gain important information about the crashing body and its chemical makeup. On human missions to Mars and the moon, probes study and take samples from debris blankets at impact craters to help further understanding of the planetary makeup, as well as learn about the source of the crater.

In astrophysics, the term has yet another meaning, indicating a violent and sudden event. When a star explodes, material is flung away from the source and into space. This potent form of ejecta helps scientists to identify supernovas, as the layer of exploded material is often visible to scanning equipment. Any stellar ejecta discovered can be of great importance to scientific discovery, as the chemical components may carry important information about the elemental makeup of stars billions of light years away.


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Post 3

@Charred - We've had some bad eruptions, I'll agree. But nothing in recent memory compares to the eruption that buried the ancient city of Pompeii when Mount Vesuvius blew up.

I think that lingering plumes of ash in the atmosphere are nothing compared to a complete and violent overthrow of a city by the force of the volcano exploding.

Post 2

I think the worst part of a volcanic eruption, provided that you are not near ground zero when it happens, has to be the ejecta blanket.

In recent years we have had well publicized stories of violent volcanic eruptions that have blanketed parts of Europe for months on end, bringing airline travel and other businesses to a halt and costing billions of dollars.

Fortunately, the scientists assure us that these kinds of eruptions (and ensuing blankets of ash) don’t happen very often. I just don't want to be anywhere near it when it does.

Post 1

This article answers the question, “What do volcanoes, supernovas, and nauseated humans have in common?” I have always thought that the spewing rim of a volcano looked like the mouth of a sick man, but I did not know that they shared the term “ejecta.”

It seems that volcanic ejecta includes everything that comes out of it, regardless of how fast and violently it is ejected. Even steam and gas can be classified as ejecta.

The same holds true for vomit. Whether it be a small amount of fluid or projectile vomit full of chunks, it is still referred to as ejecta.

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