Multiple trilobite fragments fossilized in the same rock
USNM_35225 and USNM_35227: Pictured are multiple trilobite fragments fossilized in the same rock. These are commonly known as hash beds. "Hash" is an indicator of a near-shore environment, where waves could hav... More
Multiple trilobite fragments fossilized in the same rock
USNM_35227 (pictured) and USNM_35225: Multiple trilobite fragments are fossilized in the same rock, these are commonly known as hash beds. "Hash" is an indicator of a near-shore environment, where waves could h... More
The fossil featured here is a leaf of a Macginitiea wyominensis, which...
YELL_92942: The fossil featured here is a leaf of a Macginitiea wyominensis, which is a member of the sycamore family. This particular plant existed during the Eocene, between 50 and 34 million years ago.
Yellowstone National Park, Articulate brachiopods
YELL-92017 and YELL-92024 (pictured here): Both the inarticulate (YELL-92017) and articulate brachiopods (YELL-92024) existed about 520 million years ago. The inarticulate was collected from the Park Shale, whi... More
Yellowstone National Park, Agnostid trilobite
YELL-165705: A small, Agnostid trilobite (YELL-165705) head is shown here. How did these little arthropods survive 500 million years ago? From their lack of eyes and poorly suited swimming body, scientists infe... More
Yellowstone National Park, Inarticulate brachiopods
YELL-92017 (pictured here) and YELL-92024: Both the inarticulate (YELL-92017) and articulate brachiopods (YELL-92024) existed about 520 million years ago. The inarticulate was collected from the Park Shale, wh... More
Multiple trilobite fragments fossilized in the same rock
USNM_35236: Charles D. Walcott, renowned invertebrate paleontologists, identified trilobite specimen Solenopleura? weedi (USNM 35236) from the Upper Cambrian (~500 million years ago) Pilgrim limestone in northw... More
Multiple trilobite fragments fossilized in the same rock
USNM_61523: Dated about 500 million years old and collected from the Pilgrim Limestone in Yellowstone National Park, is type trilobite Tricrepicephalus yellowstonensis (USNM 61523). This particular species is j... More
trilobite Blountia polita, Yellowstone National Park
USNM_96488: The trilobite Blountia polita (USNM 96488) (pictured) was discovered in the Middle Cambrian (~520 million years ago), Pilgrim Formation of Yellowstone National Park. As trilobites continued to evolv... More
Passive Continental Margin (Ancient)—Grand Canyon National Park, Arizo...
The layering in the upper part of the canyon formed over 200 million years ago, when the Colorado Plateau region was part of an ancient passive continental margin.
Cathedral Valley, Capitol Reef National Park, 2012.
Glass Mountain (foreground) is made of large gypsum (selenite) crystals deposited when seawater evaporated around 165 million years ago. After deposition and burial under rock layers, the gypsum began to move s... More
West Elk Breccia, Curecanti National Recreation Area, 2013.
The West Elk Breccia is formed from a huge volcanic lahar (i.e., volcanic flow) of ash and debris that spewed from violent, pyroclastic eruptions (i.e., spitting/fountaining lava is thrown into the air along wi... More
Twisted and folded rock near the Quarry Visitor Center
When the Rocky Mountains rose approximately 50-60 million years ago, it both folded and twisted these rock layers. With weathering, they became what you see today. This is an end of summer picture, taken late... More
Hoodoos, Bryce Canyon National Park, 2015.
Hoodoos are tall, skinny spires of rock that protrude from the bottom of arid basins and 'broken' lands. Formed in sedimentary rock, the shape of a particular hoodoo is affected by the erosional patterns of alt... More
Growth of the Pacific Northwest
200 million years ago the coastline of the Pacific Northwest was near Idaho’s western border. There was no Oregon and Washington!
Tectonic Evolution of the Southern Appalachian Mountains—300 Million Y...
300 Million Years Ago—Iapetus Ocean Completely Closes. The Southern Appalachians develop as the African portion of Gondwanaland crashes in, forming the supercontinent of Pangea.
West Coast Tectonic Evolution—20 Million Years Ago
As the mid-ocean ridge separating the Farallon and Pacific Plates entered the subduction zone, the Farallon Plate separated into the Juan de Fuca and Cocos Plates. A transform plate boundary developed where the... More
Tectonic Development of the Appalachian—Ouachita—Marathon Mountain Ran...
500 Million Years Ago—Iapetus Ocean Opens. Land that will later become Florida is part of Africa. The Yucatan Peninsula and Cuba may have been on the north side of South America.
Tectonic Development of the Appalachian—Ouachita—Marathon Mountain Ran...
250 Million Years Ago—Iapetus Ocean Closes. Pangea forms as the continents collide. The Appalachians are part of a larger zone of continental collision that includes the Marathon and Ouachita mountains in the s... More
![West Coast Tectonic Evolution—40 Million Years Ago [1 of 3]](https://cache.getarchive.net/Prod/thumb/cdn2/L3Bob3RvLzIwMTkvMDEvMDEvd2VzdC1jb2FzdC10ZWN0b25pYy1ldm9sdXRpb240MC1taWxsaW9uLXllYXJzLWFnby0xLW9mLTMtOTZhMzRmLTEwMjQuanBn/40/41/webp "West Coast Tectonic Evolution—40 Million Years Ago [1 of 3]")
West Coast Tectonic Evolution—40 Million Years Ago [1 of 3]
Forty million years ago, a large tectonic plate, known as the Farallon Plate, was between the Pacific and North American plates. Subduction of the Farallon Plate beneath the entire West Coast created a line of ... More
Emperor Hotspot Track—Ocean Floor
The topography and bathymetry (underwater topography) of the northern Pacific Ocean reflect the movement of the Pacific Plate over the Hawaiian Hotspot. Prior to 42 million years ago, the Pacific Plate was movi... More
Growth of the Pacific Northwest—Cross-section Illustration
Sometimes a terrane crashes in and clogs the subduction zone. A new subduction zone develops farther west. The Cascadia Subduction Zone is just the latest of several subduction zones that developed in the weste... More
![West Coast Tectonic Evolution—20 Million Years Ago [2 of 3]](https://cache.getarchive.net/Prod/thumb/cdn2/L3Bob3RvLzIwMTkvMDEvMDEvd2VzdC1jb2FzdC10ZWN0b25pYy1ldm9sdXRpb24yMC1taWxsaW9uLXllYXJzLWFnby0yLW9mLTMtMDdlMjc3LTEwMjQuanBn/40/41/webp "West Coast Tectonic Evolution—20 Million Years Ago [2 of 3]")
West Coast Tectonic Evolution—20 Million Years Ago [2 of 3]
As the mid-ocean ridge separating the Farallon and Pacific Plates entered the subduction zone, the Farallon Plate separated into the Juan de Fuca and Cocos Plates. A transform plate boundary developed where the... More
West Coast Tectonic Evolution—40 Million Years Ago
Forty million years ago, a large tectonic plate, known as the Farallon Plate, was between the Pacific and North American plates. Subduction of the Farallon Plate beneath the entire West Coast created a line of ... More
Western U. S. Terrane Accretion
The yellow and green shows material added (accreted) to the western edge of North America during the past 200 million years. The North American Craton refers to the continent that existed prior to that time. Ro... More
Yellowstone Hotspot Track—Columbia Plateau, Oregon
Columns of basalt represent vast outpourings of fluid lava that covered large portions of Oregon, Washington, and Idaho as the hotspot surfaced 17 million years ago.
Paleogeographic Globe of the Late Triassic—217 Million Years Ago
The paleogeographic map shows that, during the Late Triassic Epoch, North America straddled the equator and Petrified Forest National Park (white dot on red map of Arizona) was at about 4° north latitude.
Tectonic Evolution of the Southern Appalachian Mountains—500 Million Y...
500 Million Years Ago—Iapetus Ocean Opens. Continental blocks destined to become North America and Gondwanaland drift apart. The eastern edge of ancient North America developed into a passive continental margin... More
Emperor Hotspot Track - National Parks Gallery
The topography and bathymetry (underwater topography) of the northern Pacific Ocean reflect the movement of the Pacific Plate over the Hawaiian Hotspot. Prior to 42 million years ago, the Pacific Plate was movi... More
Collisional Mountains—Shenandoah National Park, Virginia.
Shenandoah National Park, Virginia. The rugged Appalachian Mountains are the eroded remnants of much higher mountains that formed as continents collided 300 million years ago.
Petrified Forest Badlands - National Parks Gallery
Badlands area in Petrified Forest National Park. The Amazon-like landscape has evolved over more that 200 million years from a green tropical forest to red Painted Desert. Layers of the Late Triassic Chinle For... More
Hotspot Sites in the National Park System
The landscapes of National Park System sites along hotspot tracks differ depending on if the plate riding over the hotspot is capped by thin oceanic or thick continental crust. Oceanic Hotspots: Sites in Hawaii... More
Tourist Attraction - Ouachita Mountains, Arkansas
The sandstone, shale and chert layers are part of a thick pile of sediments that were deformed and uplifted as Gondwanaland collided with the southern edge of ancient North America 280 million years ago.
Tectonic Evolution of the Southern Appalachian Mountains—750 Million Y...
750 Million Years Ago—Old Continent Rips Apart. The long mountain ranges and rift valleys were similar to those forming today in East Africa and the Basin and Range Province.
Southern Alaska Subduction Zone
Plate convergence that built Alaska outward as a series of accreted terranes during the past 200 million years continues today. Kenai Fjords has oceanic sedimentary layers that have been metamorphosed, uplifted... More
Tectonic Evolution of the Brooks Range—200 Million Years Ago
200 Million Years Ago—Ocean separating northern Alaska and a continental fragment begins to close.
Tectonic Development of the Appalachian—Ouachita—Marathon Mountain Ran...
"Today"—Atlantic Ocean and Gulf of Mexico Open. The modern oceans originated about 200 million years ago when Europe, Africa and South America ripped away from North America. Fragments of the collision zone mou... More
The Landscapes of Denali National Park Reveal Different Accreted Terra...
Pillow Basalt—The blobs of lava formed as fluid lava poured out on an ancient seafloor about 200 million years ago. They have since been accreted to North America and uplifted as part of the McKinley Terrane. T... More
Tectonic Development of the Atlantic Ocean and Gulf of Mexico (1 of 2)
The supercontinent of Pangea formed 300 million years ago as an ancient ocean closed. A chain of mountains formed as the continents collided, including the Marathon, Ouachita and Appalachian mountians in the Un... More
Tectonic Evolution of the Southern Appalachian Mountains—400 Million Y...
400 Million Years Ago—Iapetus Ocean Narrows during Subduction. Oceanic sediments and volcanic islands were at times added to the edge of North America.
NPS Sites in Alaska - Public Domain image, National Parks Gallery
The terrane accretion that built Alaska onto the rest of North America over the past 200 million years includes the continental collision that formed the Brooks Range in the northern part of the state. The Nort... More
Tectonic Evolution of the Brooks Range—
120 Million Years Ago—Mountains Rise. The northern continent extends laterally for more than 60 miles (100 kilometers) beneath northern Alaska, thickening the crust.
Ancient Passive Margin—Colorado Plateau Region during the Paleozoic
Near the beginning of the Paleozoic Era, 500 million years ago, western North America was smaller than it is today, and near the equator. The Colorado Plateau region was along a passive continental margin. The ... More
Continental Rift Diagram - National Parks Gallery
Passive continental margins abutting the Atlantic Ocean and Gulf of Mexico developed as a large continent, Pangea, ripped apart about 200 million years ago.
Tectonic Evolution of the Brooks Range—100 Million Years Ago
100 Million Years Ago—High Mountains. The mountains reach heights similar to those of the modern-day Alps, as the hard crust of northern Alaska breaks and uplifts.
Tectonic Evolution of the Brooks Range—150 Million Years Ago
150 Million Years Ago—Thick Sedimentary Layers. Continents collide but continue to converge.
Changing Coastline as Sea Level Rises and Falls
The position of the coastline is sensitive to changes in sea level. During the peak of the last ice age, about 18,000 years ago, the coastline was near the edge of the continental shelf. It would have been poss... More
Tectonic Evolution of the Ouachita Mountains—400 Million Years Ago
400 Million Years Ago—Iapetus Ocean Closes. A passive continental margin of ancient North America approaches a subduction zone on the edge of Gondwanaland.