Earth Rocks!

National parks are magnificent places to witness geology in action, and to learn how to coexist with our dynamic planet. This year, we are celebrating Earth Day and National Park Week by sharing the types of rocks found on public lands as well as national parks that showcase our nation’s geodiversity.

Be sure to join us on social media as we explore the earth sciences and stewardship this week and every week. And, remember that natural objects, such as rocks and minerals, contribute to the beauty and wonderment of our national parks and you should leave these natural objects as you found them.

Igneous Rocks


Granite boulders at Joshua Tree National Park. Photo by Hannah Schwalbe, National Park Service.

Igneous rocks (from the Greek word for "fire") form when hot, molten rock (magma) crystallizes and solidifies. Magma comes from deep within the Earth, near active plate boundaries or hot spots. Magma that rises to the surface is called lava. Hawai'i Volcanoes National Park and Acadia National Park both feature igneous rocks.

Hawai'i Volcanoes National Park

Shoreline at sunset at Hawai‘i Volcanoes National Park.
Photo by Jacob W. Frank, National Park Service.

Hawai‘i Volcanoes National Park protects some of the most unique geological, biological, and cultural landscapes in the world. Extending from sea level to 13,677 feet, the park encompasses the summits of two of the world's most active volcanoes: Kīlauea and Mauna Loa.


Halapē Tidepools. Photo by Jacob W. Frank, National Park Service.

Kīlauea is the youngest and most active volcano on the island of Hawaiʻi, and one of the busiest in the world. In recorded history, Kīlauea has only had short periods of rest. It has covered almost 90% of its surface in lava flows within the last 1,000 years.

Mauna Loa volcano at sunrise.
Mauna Loa rising from behind Kīlauea Caldera. Photo by J. Wei, National Park Service.

Mauna Loa is the largest active volcano on the planet. Meaning "long mountain" in Hawaiian. With its broad, rounded slopes, it is the quintessential shield volcano. The volcano makes up roughly 51% of Hawaiʻi Island and stands 13,678 feet (4,170 meters) above sea level. It rises an astonishing 30,000 feet (9,144 m) from the bottom of the sea, a greater height than Mount Everest.


Photo by J. Wei, National Park Service.

Molten lava that reaches the surface during volcanic eruptions is still adding mass to the island of Hawaiʻi. In fact, the island itself is made up of flows that have built upon one another over many thousands of years. Molten lava is only visible during an eruption, but its solidified form makes up the island of Hawaiʻi.

A person stands next to solidified lava flows.
Whether it is solidified or molten, lava is everywhere on the island of Hawaiʻi. Photo by J. Wei, National Park Service.

Lava and magma are the same substance, but in different places. The term magma refers to molten rock that is still within the Earth. Once it breaks through the Earth's surface, it is called lava.


Kīlauea Iki crater may look tranquil these days. But in 1959, this now 400-foot (120 m) crater held a seething lava lake that spewed fountains of molten lava thousands of feet into the air. Photo by U.S. Geological Survey.

According to Native Hawaiian tradition, molten lava is the manifestation of Pele, the volcanic deity and creator of new lands. According to tradition, she is embodied by the lava and natural forces associated with volcanic eruptions.

Acadia National Park

Pastel colors highlight the sky with the landscape in the foreground at sunrise.
Photo by Emma Forthofer, Friends of Acadia.

The landscape at Acadia National Park tells the tale of a time when fire and ice covered these lands. The geologic history of Acadia National Park stretches back in time through millions of years to the formation of the oldest rocks on Mount Desert Island and continues through today by the persistent forces of erosion (the process of rocks gradually wearing away).


Waves crash along cobblestone beach at Monument Cove. Photo by Kylie Caesar, National Park Service.

The landscape that we know as Acadia had its beginnings more than 500 million years ago, when mud, sand, and volcanic ash were deposited in an early ocean. With time these sediments were buried, and pressure turned them to rock. You can find evidence of this rich geologic past across the park.

Waves crashing over a rocky coastline at sunset.
Black igneous intrusive rocks at Schoodic Point illustrate the interplay between fire and ice true of Acadia's geologic history. Photo by Kent Miller, National Park Service.

The varied landscape of Acadia National Park is the result of continuing geologic processes. The weathering of granite ridges is one such activity. Large joints, or fractures, in the rock form square blocks. The joints enlarge and expand when water fills them and freezes. Eventually the rock breaks away from the cliff, leaving behind granitic rubble and bright pink scars on precipitous rock faces.


A panorama of the summit of Cadillac Mountain. Photo by Alex Demas, U.S. Geological Survey.

At 1,528 feet in elevation, Cadillac Mountain is the highest point in Acadia National Park. The Cadillac Mountain Granite is among the largest bodies of granite on the island, and it is also one of the oldest in the region (~420 million years old).

Sedimentary Rocks

Red rocks at Canyon Lands National Park.
Canyonlands National Park shows millions of years of erosion on a landscape of sedimentary rock. Pictured above, the Green River has carved a channel out of rock layers deposited nearly 300 million years ago. Photo by Neal Herbert, National Park Service.

Sedimentary rocks form from deposits of pre-existing rocks or pieces of once-living organisms that accumulate on the Earth's surface. If sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock.


Arches National Park offers a landscape of contrasting colors, land forms, and textures unlike any other in the world. Photo by National Park Service.

These rocks often have distinctive layering or bedding and create many of the picturesque views of the desert southwest. Badlands National Park and White Sands National Park have examples of sedimentary rocks.

Badlands National Park

Layered badlands buttes reach into a clear blue sky above.
Badlands National Park. Photo by Andreas Eckert (

Badlands National Park is known for its geology and paleontology. You may have heard the term “badlands” before, but not in reference to this park. That’s because in addition to being a geographic term, describing Badlands National Park in South Dakota, this word is also a geologic term.


Badlands formations with vibrant colors and grasses at sunset. Photo by Donna Schneider (

The lowercase version of badlands is used to describe most terrains that look like the formations in our park. They are typically characterized by soft sedimentary rocks that erode easily. The formations in the park are the result of two simple processes: deposition (process of rocks gradually building up) and erosion.

The Badlands formations have a lifespan of approximately one million years. They erode at about one inch per year. Scientists estimate that in the next 500,000 years, the Badlands will have eroded completely.

Sand colored mountains at sunset.
Photo by William Green (

Badlands buttes contain millions of years of history -- much of which can be unpacked with the sciences of geology and paleontology. There are several types of rocks that can be found in the Badlands, including sandstones, siltstones, mudstones, claystones, limestones, volcanic ash, and shale.

There are badlands formations all over country in places like Wyoming, Utah, North Dakota, Colorado, and Nebraska. You can even check out badlands formations in the National Park Service like Theodore Roosevelt National Park in North Dakota and Petrified Forest National Park in Arizona, or visit one on National Grasslands like Toadstool Geologic Park in Nebraska. There are also badlands formations throughout the world in Canada, New Zealand, Italy, Spain, and Argentina.

White Sands National Park


Stormy skies provide a dramatic backdrop for this Skunkbush Sumac and its plant pedestal. Photo by National Park Service.

White Sands National Park is one of the world's great natural wonders. Great wave-like dunes of gypsum sand engulf 275 square miles of desert, creating the world's largest gypsum dunefield.

Two people walk along great wave-like dunes of gypsum sand.
Photo by National Park Service.

The story of the world’s largest gypsum dunefield began 280 million years ago when the Permian Sea covered this area and gypsum settled on the sea floor. The formation of the dunefield continues today in an endless cycle of erosion and renewal.


Photo by National Park Service.

White Sands National Park preserves a major portion of this unique dunefield, along with the plants and animals that live here.

Metamorphic Rocks

Rugged rock formations under a glowing sunset.
The rugged topography at Death Valley National Park, as well as sand dunes, craters, and flood-carved canyons, indicate that Death Valley has experienced a lengthy and complex geologic history. Photo by National Park Service.

Metamorphic rocks form when high temperatures and pressure act on a rock to alter its physical and chemical properties. These conditions often stretch, twist, and fold the rock as it cools. 


Powell Point on the South Rim of Grand Canyon National Park. Photo by M. Quinn, National Park Service.

In metamorphic rocks some or all of the minerals in the original rock are replaced, atom by atom, to form new minerals. Grand Teton National Park and Shenandoah National Park both feature many examples of metamorphic rocks.

Grand Teton National Park

Clouds over the major peaks of the Teton Range over Jackson Lake and Willow Flats.
The Teton Range rises steeply due to uplift on the Teton fault. Photo by National Park Service.

Grand Teton National Park has a fascinating natural and cultural history. The Tetons are one of the youngest mountain ranges in North America. They have been uplifting for less than 10 million years, making them "adolescent" mountains, as compared to the "middle-aged" Rockies (50-80 million years old) or the "elderly" Appalachians (more than 300 million years old). Over billions of years and natural forces including earthquakes, glaciers, and erosion have shaped this magnificent landscape.

The Teton Range contains some of the oldest rocks in North America, similar to those exposed in other major mountain ranges of the western U.S., including the Bighorns, the Gros Ventre and Wind River ranges.


Left: 2.7 billion year old metamorphic gneiss. Photo by P. Sasnett, National Park Service. Right: Mount Moran captures all geologic elements: ancient basement rock, black diabase dike, overlain by sedimentary sandstone, flanked by five glacier. Photo by National Park Service.

A 2.7 billion-year old metamorphic rock called gneiss makes up much of the Teton Range. These rocks were formed when sea floor sediments and volcanic debris were buried up to 18 miles deep as two tectonic plates collided – similar to the collision of India and Asia today forming the Himalayas.

The sunrise morning light hits the mountain peaks.
The sunrise morning light hits the mountain peaks in Grand Teton National Park. Photo by National Park Service.

The intense heat and pressure at these great depths changed or metamorphosed the sediments into today's rocks, separating different minerals into lighter and darker layers. Watch for the zebra-striped layers as you step over rocks on your hike!


Left: The southern Teton Range showing layers of sedimentary limestone, shale and dolomite tilting westward. Photo by S. Zenner, National Park Service. Right: Limestone containing crinoid marine fossils. Photo by E. Helton, National Park Service.

The Teton fault is still active and capable of generating a magnitude 7.0-7.5 earthquake. Geoscientists have dated the three most recent earthquakes at about 5,900, 8,000, and 10,000 years ago.

Shenandoah National Park

Rocks and tree at Hazel Mountain Overlook at sunset.
The many textures of Hazel Mountain Overlook. Photo by N. Lewis, National Park Service.

Shenandoah National Park rises above the Virginia Piedmont to its east and the Shenandoah Valley to its west. The story of Shenandoah’s mountains is the story of two mountain ranges, spanning over one billion years of Earth’s history.


View from Bearfence. Photo by Katy Cain, National Park Service.

Current geological activity in Shenandoah National Park is a result of natural and man-made forces acting on the surrounding mountains and valleys. Freezing and thawing can result in rockfalls and spalling from cliff faces. Severe thunderstorms and rain events can cause flooding and associated erosion. In extreme cases, large amounts of rain can cause landslides. Some forces act together to produce geological change.

Morning sunlight illuminates a wintery scene of ancient, snow-covered rocks and barren trees.
From ancient tectonic collisions to the rolling Appalachians of today, the geological story of Shenandoah is old and unfinished. Photo by National Park Service.

A wind storm may bring down trees that were killed in a wildland fire on land where, in turn, severe rain could cause significant erosion. Most often these events are relatively small, but over millions of years, these small events produce sizable changes in the land. The result is a landscape undergoing constant change.

Learn More About America’s Geologic Legacy

You can enhance your appreciation of geoheritage sites and scenic vistas by understanding the fundamentals of geology.

Learn how plate tetonics shape our landscapes, why geologists use relative age dating to determine the depth of geologic time, discover geoscience concepts, and more by visiting the America’s Geologic Legacy section of To explore geology concepts, visit the U.S. Geological Survey’s Geology directory.