September 9, 2010
My travels from Redmond to La Grande took me through the volcanic lands of central and eastern Oregon. I saw many remnants of ancient volcanic activity in the Ochoco National Forest and the John Day Fossil Beds National Monument. And of course, there were many pieces of information left by the Forest Service and the National Park Service to tell us about these geological landmarks. Before the day was done, I read many a sign interpreting the landscape around me. And when the day was done, I was a little bit smarter on the subject of geology.
Here are the interpretive signs that taught me some geology in Oregon ...
Steins Pillar
Ochoco National Forest
Clues to a Volcanic Past
Around 44 million years ago, avalanches of hot ash, pumice and volcanic dust flowing from local volcanic centers filled this ancient valley. A long period of erosion followed.
These flows are still visible in the layers of Stein's Pillar. Finally, Mother Nature patiently sculpted the landscape you see today. Rain, wind, and frost slowly chiseled along cracks in the rocks forming the valley and leaving Stein's Pillar as a beacon to travelers.
Major Enoch Steen explored the area in the 1860's. His name was misspelled so often that the incorrect version being official. The pillar has aided travelers and enticed geologists for many years.
Entrance
Painted Hills Unit
John Day Fossil Beds National Monument
Painted Hills Unit
John Day Fossil Beds National Monument
Look Below the Surface
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| Entrance to the Painted Hills |
Now only hilly remnants to the west, the ancestral Cascade Range of volcanoes once erupted cloud after cloud of ash that landed here. These beds of ash-fall make up the John Day formations - The Big Basin, Turtle Cove, and Haystack Valley strata, each revealing ancient changes in regional geology and life forms.
Further clues reveal that the John Day formations were later subjected to massive forces that tilted the layers downward to the east. Then, floods of lava poured out across the surface, forming flat molten lakes. This series of basalt floods hardened and protected much of the softer layers underneath from the forces of erosion.
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| Graphic on interpretive sign showing geologic formations of area |
Fossils on the Frontier
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| Carroll Rim |
The Dalles-Canyon City Military Road was built in 1864, linking the Canyon City gold camps with settlements along the Columbia River. Thomas Condon, Congregational minister in The Dalles and an avid naturalist, recognized the value of Captain Drake's fossil discovery. Condon joined a military patrol to this region in 1865 and came face-to-face with the fossil treasures that were to be his life work. Dr. Condon became the first State Geologist in 1872 and Professor of Geology at the University of Oregon in 1876.
Leaf Hill Trail
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| Map on interpretive sign showing location of military road in the area |
Painted Hills Unit
John Day Fossil Beds National Monument
Once thought extinct, the fossil leaves of genus Metasequoia, the Dawn Redwood, are commonly found all over the Northern Hemisphere in deposits dating from the Ice Ages back over 130 million years. The Bridge Creek Flora fossil discoveries here have uncovered thousands of Metasequoia leaves. Why were so many leaves of just this conifer fossilized here? Other conifers existed then? A big reason is that the Dawn Redwood is deciduous, similar to the modern Larch, or Tamarack. They would drop their leaves each fall season, transport, and fossilize at the bottom of lakebeds along with many other deciduous hardwood leaves.
In the early 1900s, Dawn Redwoods were discovered still living in one small valley in Chine. Metasequoia is now Oregon's state fossil.
Remember, all fossils, rocks, artifacts, plants, animals, and other natural and cultural features in the park are protected by Federal law. Do not collect, dig, or disturb them.
The quarter-mile-long Leaf Hill Trail starts to your right and leads to an important research location.
Much different than the near-desert landscape you see today, a hardwood forest dominated the scene here about 33 million years ago. A vast assemblage of plant fossils discovered here, called the Bridge Creek Flora, reveal evidence of one of Earth's cooling trends. From a previously rainy, hot, and jungle-like environment, about 45 million years ago, the region became drier and more seasonal. The new hardwood forests, with scattered lakes and swamps, resembled the balmy parts of the southeastern United States. Many trees in this ancient forest are related to modern alders, elms, beech, birch, maples, and oaks.
The Bridge Creek Flora also contain fossils of fish, amphibians, birds, and insects. They were preserved like pressed flowers in a book within ashy, lakebed sediments, turned to shale.
At first glance, Leaf Hill seems like an ordinary knoll among the scenic Painted Hills, yet it has captured the attention of many people over the last hundred years. The reason? The hill is rich with fossilized remnants of plants over 30 million years age.
Of the many scientists who have studied this site, one of the most active was Ralph W. Chaney. He was a University of California paleobotanist who, in 1923, wrote about Leaf Hill: "I quarried 98 cubic feet of leaf-bearing shale from three pits in the low hill to the right of the road; I split the slabs of ashy shale into thin layers which yielded a total of 20,611 specimens."
Chaney found many delicate leaf impressions, such as Mesasequoia (Dawn Redwood), alder, oak, sycamore, beech, elm, and maple. He studied the abundant and diverse plant fossils from the hill and compared them to modern species and environments. From his finds, Chaney envisioned a prehistoric scene at this site made up of a lake surrounded by a hardwood forest, existing in a moist, temperate climate.
A 1993 study at this hill revealed more. The hill contains evidence of a series of prehistoric ecosystems. From the bottom of the hill up, one finds deposits from an oak-sycamore forest, then a series of savannah-like woodlands, two swamps, then a succession of three lakes. One finally enters another hardwood forest, which was incinerated and inundated by hot ash fall during a volcanic eruption.
The latest research inspires a vision of changing environments within the layers of Leaf Hill, many more than Chaney ever imagined.
Painted Cove Trail
Painted Hills Unit
John Day Fossil Beds National Monument
About 33 million years ago volcanic ash-fall from the ancestral Cascade Mountains settled in deep deposits forming the colorful layers in these hills. Natural processes changed they layers into bentonite, a type of clay which expands greatly as it absorbs water. When drying, the clay contracts, cracks, and breaks up, giving the hills a "popcorn-like" appearance.
Bentonite clay is used in products in many ways, the particles being very sticky and absorbent. Bentonite can be used as an emulsifier in toothpaste and chocolate, and as kitty later.
The lavender-gray (purple-like) layer in front of you is the highly weathered remains of a rhyolite lava flow. It is about 40 million years old and part of the Clarno formations.
We think its source must have been nearby, since rhyolite lava is slow-moving and viscous, surging relatively short distances. It contains significant amounts of feldspart and quartz, which the basalt lava layers on the distant ridgeline (to the left of this hill) do not. Basalt lava flows much faster than rhyolitic lava, more like a fluid.
The colors of the Painted Hills constantly change. After light rains, the hills darken greatly from their normal color. During very wet periods, the clay absorbs so much water they saturate. They clay then expands and seals the surface of the hills. This causes more light to be reflected, changing the red and yellows to a sheen of pastel pink and gold.
When the hills dry the clay contracts, producing surface cracks that diffuse the light and deepen the color. Ad
d sunlight, time of day, cloud shadows, and the colors of the hills constantly change.
Painted Hills Overlook
Painted Hills Unit
John Day Fossil Beds National Monument
Through this dry land in 1865 rode a pioneer minister and amateur scientist named Thomas Condon. It was the first of his many visits. Imagine his reaction when he discovered the imprints of countless fossilized leaves near these Painted Hills, leaves of plants that could not possibly survive this modern, near-desert environment. These fossils opened a window onto vast changes in climate, plants and animals.
The colorful Painted Hills are part of the lower John Day formations, with layers of the Clarno formations and Picture Gorge Basalts visible nearby. At Sheep Rock and Clarno units, explore other aspects of the John Day Fossil Beds.
The ground before you is like a puzzle. A long streak of color breaks off, then seems to continue in the next hill, but at a different level. To connect the pieces, look for similar color, thickness, and sequence in a series of layers.
Ash and pumice from the ancestral Cascades and local volcanoes buried this area layer by layer. The colorful layers before you were deposited 33 million years ago. Soil formation processes affected each layer differently. Clays were formed and deeply buried, turning to stone. Underground forces lifted and faulted the strata, interrupting the symmetry.
The red in the Painted Hills is from rusty iron minerals, oxidized by long exposure. The golden layers reveal a mix of oxidized magnesium and iron, metamorphic claystone minerals. Black hash marks are rich with manganese. Each of the colors represent a different geologic process.
This valley is a gently contoured theater of geologic change, with erosion from rain the latest sculptor.
Volcanic ash can be gentle and fine enough to preserve a leaf's structure in great detail. Nearby 34 million-year-old "Bridge Creek Flora" fossils reveal many species of an ancient, hardwood forest. This forest had a blend of trees found today only in parts of the Appalachians, China, and spots along the Pacific Coast.
Fossils indicate that some types of trees changed little during the Age of Mammals. From that evidence and comparisons to modern trees and their settings, we have learned a great deal about past ecosystems and climates.
About thirty million years ago there was a period of significant global change. As the air cooled and the seasons became more pronounced, the earlier near-tropical plants of the area retreated southward. Many hardwoods and conifers replaced them, as did a whole new set of forest creatures.
Straining to scent a water source, searching for a tender leaf, sensing immediate danger -- to live in this near-desert today, mule deer, coyotes, quail, and humans must possess special skills and abilities. Without them they cross the threshold from survival to extinction. This holds true in any environment on the plant - now, and in the past.
Here, about 30 million years ago, major shifts in temperature and humidity occurred. Great changes in the plant life inevitably resulted. The animals that survived this transition were those that evolved new behaviors, different bodies, new abilities to survive. Still, long-term survival was not assured, as the fossil record reveals.
Fossils from the John Day country imply more than an odd-shaped mammal or exotic plant. Here they portray a healthy forest ecosystem long gone, and suggest reasons for its disappearance. Gathering such information may help us predict the future of modern species.
Picture Gorge
Sheep Rock Unit
John Day Fossil Beds National Monument
The dark layers of Picture Gorge were formed from seventeen distinct floods of lava flowing from nearby cracks in the earth. These basalt flows joined with others covering much of eastern Washington and Oregon, and northern Idaho, beginning about 16 million years ago. Powerful forces have since broken and tilted the land. Erosion has shaped it, the river cutting this gorge.
The bottom two layers of the gorge are the same two that cap Sheep Rock peak, behind you. In recent centuries, American Indian pictographs were drawn upon the rock, giving the gorge its name.
As the surface of each new lava flow rapidly cooled to a crust, the interior remained hot and somewhat fluid for many years. Heat released above the hot flow into the atmosphere was much faster than heat released from the bottom into the earth. A jumbled, shattered appearance in the hardened, upper layer resulted from the quicker cooling, and subsequent cracking, of the lava flow downward from the top.
Vertical columns formed when the molten lava slowly cooled, contracted and cracked uniformly, upward from the bottom of a layer, forming six-sided pillars. In this region, basalt layers commonly feature both jumbled and columnar patterns, making each layer look like two layers.
Over 70 miles to the south, a violent volcanic explosion sent a fiery torrent of superheated gases, ash, and large particles sweeping across the surface of the land. This surge slowed and settled, welding into hard rock called ignimbrite. The high, flat-topped mesa, capped with this ignimbrite layer, is part of the Rattlesnake Group.
Blue Basin
Sheep Rock Unit
John Day Fossil Beds National Monument
About 6,000,000 years ago land-building processes, such as volcanic activity, diminished in this area. Water and wind carved deep into the land. Some soil and rock eroded faster than others.
The nearby butte is capped by "Blue Basin tuff," a harder rock than the claystone below. The cap still protects the butte, though eventually both will erode away. A layer of "Blue Basin tuff" is also in the high cliff-side to the left of the trail.
John Day Fossil Beds National Monument
To the Edge of Extinction
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| Entrance to Leaf Hill Fossil Trail |
In the early 1900s, Dawn Redwoods were discovered still living in one small valley in Chine. Metasequoia is now Oregon's state fossil.
Remember, all fossils, rocks, artifacts, plants, animals, and other natural and cultural features in the park are protected by Federal law. Do not collect, dig, or disturb them.
The quarter-mile-long Leaf Hill Trail starts to your right and leads to an important research location.
A Forest Long Gone
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| Leaf Hill |
The Bridge Creek Flora also contain fossils of fish, amphibians, birds, and insects. They were preserved like pressed flowers in a book within ashy, lakebed sediments, turned to shale.
Treasure Amidst The Beauty
At first glance, Leaf Hill seems like an ordinary knoll among the scenic Painted Hills, yet it has captured the attention of many people over the last hundred years. The reason? The hill is rich with fossilized remnants of plants over 30 million years age.
Of the many scientists who have studied this site, one of the most active was Ralph W. Chaney. He was a University of California paleobotanist who, in 1923, wrote about Leaf Hill: "I quarried 98 cubic feet of leaf-bearing shale from three pits in the low hill to the right of the road; I split the slabs of ashy shale into thin layers which yielded a total of 20,611 specimens."
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| Leaf Hill |
A 1993 study at this hill revealed more. The hill contains evidence of a series of prehistoric ecosystems. From the bottom of the hill up, one finds deposits from an oak-sycamore forest, then a series of savannah-like woodlands, two swamps, then a succession of three lakes. One finally enters another hardwood forest, which was incinerated and inundated by hot ash fall during a volcanic eruption.
The latest research inspires a vision of changing environments within the layers of Leaf Hill, many more than Chaney ever imagined.
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| Samples, included with the interpretive sign, of fossils found at Leaf Hill |
Painted Cove Trail
Painted Hills Unit
John Day Fossil Beds National Monument
Rust Colored Hills
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| Painted Cove |
Bentonite clay is used in products in many ways, the particles being very sticky and absorbent. Bentonite can be used as an emulsifier in toothpaste and chocolate, and as kitty later.
Rhyolite Flow
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| Rhyolite Flow on bottom |
We think its source must have been nearby, since rhyolite lava is slow-moving and viscous, surging relatively short distances. It contains significant amounts of feldspart and quartz, which the basalt lava layers on the distant ridgeline (to the left of this hill) do not. Basalt lava flows much faster than rhyolitic lava, more like a fluid.
Changing Colors
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| The colors of Painted Cove |
When the hills dry the clay contracts, producing surface cracks that diffuse the light and deepen the color. Ad
d sunlight, time of day, cloud shadows, and the colors of the hills constantly change.
Painted Hills Overlook
Painted Hills Unit
John Day Fossil Beds National Monument
Painted Hills Overlook
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| View from the Overlook |
The colorful Painted Hills are part of the lower John Day formations, with layers of the Clarno formations and Picture Gorge Basalts visible nearby. At Sheep Rock and Clarno units, explore other aspects of the John Day Fossil Beds.
Pieces Of The Puzzle
The ground before you is like a puzzle. A long streak of color breaks off, then seems to continue in the next hill, but at a different level. To connect the pieces, look for similar color, thickness, and sequence in a series of layers.
 |
| The colors of the Painted Hills |
The red in the Painted Hills is from rusty iron minerals, oxidized by long exposure. The golden layers reveal a mix of oxidized magnesium and iron, metamorphic claystone minerals. Black hash marks are rich with manganese. Each of the colors represent a different geologic process.
This valley is a gently contoured theater of geologic change, with erosion from rain the latest sculptor.
Deciphering The Forest
Volcanic ash can be gentle and fine enough to preserve a leaf's structure in great detail. Nearby 34 million-year-old "Bridge Creek Flora" fossils reveal many species of an ancient, hardwood forest. This forest had a blend of trees found today only in parts of the Appalachians, China, and spots along the Pacific Coast.
Fossils indicate that some types of trees changed little during the Age of Mammals. From that evidence and comparisons to modern trees and their settings, we have learned a great deal about past ecosystems and climates.
About thirty million years ago there was a period of significant global change. As the air cooled and the seasons became more pronounced, the earlier near-tropical plants of the area retreated southward. Many hardwoods and conifers replaced them, as did a whole new set of forest creatures.
A Matter of Survival
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| View of Painted Ridge from the Painted Hills Overlook Trail |
Here, about 30 million years ago, major shifts in temperature and humidity occurred. Great changes in the plant life inevitably resulted. The animals that survived this transition were those that evolved new behaviors, different bodies, new abilities to survive. Still, long-term survival was not assured, as the fossil record reveals.
Fossils from the John Day country imply more than an odd-shaped mammal or exotic plant. Here they portray a healthy forest ecosystem long gone, and suggest reasons for its disappearance. Gathering such information may help us predict the future of modern species.
Picture Gorge
Sheep Rock Unit
John Day Fossil Beds National Monument
Picture Gorge Basalts
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| Picture Gorge as viewed from Oregon Route 19 |
The bottom two layers of the gorge are the same two that cap Sheep Rock peak, behind you. In recent centuries, American Indian pictographs were drawn upon the rock, giving the gorge its name.
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| Sheep Rock Peak |
Vertical columns formed when the molten lava slowly cooled, contracted and cracked uniformly, upward from the bottom of a layer, forming six-sided pillars. In this region, basalt layers commonly feature both jumbled and columnar patterns, making each layer look like two layers.
Over 70 miles to the south, a violent volcanic explosion sent a fiery torrent of superheated gases, ash, and large particles sweeping across the surface of the land. This surge slowed and settled, welding into hard rock called ignimbrite. The high, flat-topped mesa, capped with this ignimbrite layer, is part of the Rattlesnake Group.
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| Picture Gorge as viewed from the interpretive sign |
Blue Basin
Sheep Rock Unit
John Day Fossil Beds National Monument
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| Blue Basin Tuff on top of the cliff |
The nearby butte is capped by "Blue Basin tuff," a harder rock than the claystone below. The cap still protects the butte, though eventually both will erode away. A layer of "Blue Basin tuff" is also in the high cliff-side to the left of the trail.
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