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.

What Is a Sheet Intrusion?

Andrew Kirmayer
Updated Jun 04, 2024
Our promise to you
All Things Nature 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 All Things Nature, 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.

A sheet intrusion is a rock formation generally created by the rising of molten rock, or magma, in between the top layers of the Earth’s crust. The top layers can expand as a result, and the underlying material is sometimes exposed because of surface erosion. Rock sheets are usually somewhat flat in shape, but can take on an undulating or dome-like structure; geological processes can alter a relatively flat sheet intrusion into a more vertical position. The intrusion also usually appears different from material that originated as flowing lava, by incorporating components of the surrounding rock into the top and bottom layers.

Rising magma typically causes heated material to crystallize as it cools, forming igneous rock. It can form dikes, or sheet-like formations that cut across layers; a sheet intrusion, however, is generally oriented across, over, or under the landscape. Both variations are often seen in volcanically active areas, as well as places known to have been so in the past.

One type of sheet intrusion is called a laccolith. The molten material is typically pushed up between layers of overlying sedimentary rock, which in turn rises because of the force. A laccolith’s base is usually horizontal and the rock normally cools slowly. By the time these are discovered, the overlying layers have usually eroded away and it can be difficult to determine the original shape of the intrusion. Some of these structures or dome-shaped or they can be vertical in nature; wind and water often remove many layers of rock over time.

A sill is generally a kind of sheet intrusion that sits flat in between two other layers of rock, or even solidified lava. The material that is part of this structure usually forms deep underground, so pressure typically prevents gases from escaping while it hardens. Bubble-like formations that are common in lava are generally not seen in sills, which are protected for much of their life by the layers of rock surrounding them.

Computerized seismic mapping is often used to see where a sheet intrusion is. Sills and laccoliths can be mapped fully and the flow pattern of an underground sheet intrusion can be determined as well. The pressure during formation of the structure in the host rock, and how much space there was in the sediment when it formed, can be determined as well. Molten rock movement and erosion have led to the formation of many different features of landscapes throughout the world.

All Things Nature 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.
Link to Sources
Andrew Kirmayer
By Andrew Kirmayer
Andrew Kirmayer, a freelance writer with his own online writing business, creates engaging content across various industries and disciplines. With a degree in Creative Writing, he is skilled at writing compelling articles, blogs, press releases, website content, web copy, and more, all with the goal of making the web a more informative and engaging place for all audiences.
Discussion Comments
Andrew Kirmayer
Andrew Kirmayer
Andrew Kirmayer, a freelance writer with his own online writing business, creates engaging content across various...
Learn more
All Things Nature, in your inbox

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

All Things Nature, in your inbox

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