We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Science

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What are Clastic Rocks?

Mary McMahon
By
Updated: May 21, 2024

Clastic rocks are rocks which are composed of small fragments of other rocks. These fragments, known as clasts, determine the composition and texture of the clastic rock. One well-known example of clastic rock is sandstone, a type of rock made from sand-sized fragments of other rocks. Despite the name, sandstone is not necessarily made from sand, although it often contains at least some sand, depending on where and how it formed.

The classic example of clastic rocks is sedimentary rocks. Sedimentary rocks are distinguished by being composed of sediments of varying sizes and composition, and they can be found all over the world. They form when the deposition of sediments over time creates an area of high pressure. The high pressure of successive layers of sediment causes the bottom layers to compact, eventually resulting in the formation of a deposit of sedimentary rock.

Other types of rock can be clastic as well. Igneous rocks, which form as a result of volcanic activity, may take the form of clastic rocks. Tuff, for example, is an igneous rock which is actually comprised of a number of fragments, making it both igneous and clastic in nature. Numerous other types of igneous rocks can include a mixture of rock fragments.

Metamorphic rocks may also be clastic in nature, if they contain fragments of other rocks. The heat and pressure associated with metamorphic processes can fold fragments into rock formations, force rock fragments together, and create clastic rocks. The composition of metamorphic clastic rocks can provide key information about the age of the Earth's crust in a particular area, and about the history of processes which have taken place in that area.

The formation of clastic rocks starts with weathering, in which existing rock is broken down into fragments. These weathered fragments are brought back together again by a variety of processes, such as deposition of mineral salts, pressure, volcanic activity, and so forth. The character of a clastic rock can be determined by looking both at the texture, and at the composition. Sometimes the clasts are uniform in nature, as in sandstone, for example, and sometimes they vary in size, as in a breccia, a deposit of clasts of many different sizes.

Clastic rocks can sometimes contain interesting geological clues. They can provide information about the geologic history of a particular region which may be interesting, for example, and the information in their clasts can be used to gather data about how rock formations develop and what kind of factors can influence rock formation.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a All The Science researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By OeKc05 — On Jan 09, 2013
Clastic sedimentary rocks are sometimes formed from the clay and sand in a river bed. I have found several pieces of breccia in the stream that runs through my backyard, and they are all made of the kinds of rocks that I've seen scattered at various spots along the stream.

A piece of this breccia looks just like fruitcake to me! The matrix is the color of rusty clay, and the rock pieces look like nuts and fruit.

I learned in geology class that breccia always has angular shards of rock in it. The kind with rounded rock pieces is called conglomerate.

By feasting — On Jan 09, 2013

@StarJo – I think that kind of concrete would fall under the clastic rock classification. True, it is manmade, but it was through a sedimentary process, even though it was very rapid.

The wet concrete was probably poured in with some rock fragments or pebbles. It solidified, creating a matrix in a short amount of time.

By StarJo — On Jan 08, 2013

I have a collection of clastic and non-clastic sedimentary rocks in a geology kit that I got as a gift when I was ten. I've always been fascinated with rocks and minerals, and this kit came with an instruction manual that told me how to tell which kind was which.

I still remember the term “clastic” and how to distinguish clastic rocks from the other kind. I remember a piece of clastic rock that had pretty big chunks of different kinds of rock in it, and it made me think of the concrete sidewalk by the school.

By Oceana — On Jan 07, 2013
Has anybody here ever seen a rock with bits of shiny minerals embedded in it? Would this be considered a clastic rock, or is it called something else?
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

Learn more
Share
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.