Geology for Students

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Geology: Studying the Story of Rocks  

Imagine a canyon of rock one mile deep, up to 18 miles wide, and 277 miles long. That is a big slice through the ground! Grand Canyon displays more than 20 layers of rocks, and each layer is like a page in Earth's history book. Geology, the study of Earth, helps tell the story of rocks.

 
 
 
Outlined drawing, labeling the layers of Grand Canyon

Grand Canyon's Rock Layers

What does Grand Canyon have in common with pancakes? The oldest layers, which formed first, are usually at the bottom, while the younger layers are stacked on top.

Sedimentary rocks form the middle and top layers of Grand Canyon. Layers of sediment hardened into sedimentary rocks over time.

Most of the canyon's igneous and metamorphic rocks make up the bottom layers of Grand Canyon, near the Colorado River. Igneous rocks formed when liquid magma cooled. Metamorphic rocks formed when heat and pressure changed igneous, sedimentary, and other metamorphic rocks.

One of Grand Canyon's oldest rocks, Vishnu schist, is about 1.8 billion years old, more than one-third the age of Earth!

To explore more, navigate through an interactive map of Grand Canyon's rock layers.

 
 
three fossils against a gray background. from left to right: a trilobite on green rock, fossil fern on rust-colored rock, a clam-like shell on white rock

NPS Photo

Fossils Tell Stories of Ancient Life

Many rock layers in Grand Canyon contain fossils. Fossils give scientists clues about Earth's past environments and the animals and plants that lived in them.

 
Series of graphics advertising various geology programs are in rotation and crafted in watercolor paint.
Explore more about geology through Canyon Field School @Home activities!

How Fossils Form

Fossils often form in sedimentary rocks. When layers of sediment hardened into rock, they sometimes trap the remains of animals and plants that have died. Over millions of years, these bones, shells, footprints, leaves and other remains turned into stone.

Stories in Stone

By studying fossils and comparing them to similar animals and plants that live today, scientists can find out what the environment was like before the canyon was carved.

Not all of Grand Canyon's fossils have been found in rock. Some fossils from the Ice Age have been discovered in caves, where animals and plant remains dried out and preserved over time.

Learn more about Grand Canyon geology through Canyon Field School @Home activities, partnered with the Grand Canyon Conservancy!

 
 

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    Last updated: September 16, 2021

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