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.

How do Fossils get Inside Rocks?

Michael Anissimov
By
Updated May 23, 2024
Our promise to you
InfoBloom is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

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.

Editorial Standards

At InfoBloom, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Most of the earth's surface is covered in a type of rock called sedimentary, because it forms from layers of sediment building on top of each other. One of the characteristic features of sedimentary rocks is the high amount of fossils that they contain. All sorts of extinct plants and animals are preserved in sand, silt, or mud from ages long past.

Over time, animal corpses on sedimentary rock surfaces are covered by silt. The bones undergo mineralization, whereby minerals replace the original organics to leave a cast of the organism. Over great lengths of time, the organism becomes entirely replaced by durable minerals. In the petrification of wood, the cellulose and woody fibers are replaced by minerals such as silica.

Even delicate features are sometimes preserved in fossils. The eyes of flies and the delicate wings of butterflies have been found preserved in fossils. The majority of fossils, though, are thick shells or skeletons. Animals with lasting fossils are also some of the most widely studied and understood.

It is surprising that something as soft and subtle as sand can turn into something as rigid as a fossil. The reason is in the pressurization that sediments undergo as they are buried further and further. For every 100 feet (31 meters) of depth, average temperature increases by about 1°C. Average pressure increases about 1 ppsi (pound per square inch), or about 7 kilopascals, for each foot (31 centimeters) of depth. The increased pressure and temperature leads to a process called compaction, whereby the delicate particles in sediment are closely worked into each other and become rock.

Mud is purified of water during the process of compaction, becoming rock. Sometimes the increased heat leads the material to undergo chemical transformations, called cementation, which causes minerals such as calcite, silica, and iron oxide to build up films on the surface of the sediment. This is how fossils are made. The minerals also occupy air pockets between the sand molecules.

Fossils can also preserve things other than actual bodies. Footprints, tracks, trails, and burrows have been found. Since coal itself is compacted vegetation, many fossils can be found within it.

InfoBloom 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.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated InfoBloom contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By AnswerMan — On Feb 09, 2014

As a kid, I would go down to the bank of the Allegheny river in Pennsylvania and look for fossils. Because that river has always been part of a body of water, there are plenty of small fossils trapped in the rocks on the bank. There are also a lot of shale deposits in the western Pennsylvania area, and I could also find sea lilies and even a few trilobites in the loose layers.

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated InfoBloom contributor and brings his expertise in paleontology, physics, biology,...
Learn more
InfoBloom, in your inbox

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

InfoBloom, in your inbox

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