The Painted Hills is a geologic site in

Wheeler County, Oregon Wheeler County is a county in the U.S. state of Oregon. As of the 2020 census, the population was 1,451, making it Oregon's least populous county. It is named in honor of , an early settler who owned a farm near Mitchell. The county seat is ...

that is one of the three units of the

John Day Fossil Beds National Monument John Day Fossil Beds National Monument is a U.S. national monument in Wheeler and Grant counties in east-central Oregon. Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved l ...

along with Sheep Rock and Clarno. It totals and is located northwest of

Mitchell, Oregon Mitchell is a city in Wheeler County, Oregon, United States. The population was 130 at the 2010 census. It was founded in 1873 and was named after John H. Mitchell, a politician. The Painted Hills unit of the John Day Fossil Beds National Monume ...

. The Painted Hills are listed as one of the Seven Wonders of Oregon. The layers of color for which the site is named can be traced back to cycling periods of wet and dry climate conditions associated with the transition from the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

epoch to the cooler, more temperate

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

epoch. The different layers of colors are due to the soil being composed of a combination of

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

and

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

Geology

Formation

The Painted Hills began to form 35 million years ago when pumice and ash from volcanic eruptions in the

Cascade Mountains The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

traveled 100 miles east and settled over the area. Once there, the ash and other sediments were mixed by natural processes including the flow of water, growth of plants, and the movement of animals. Over time, this led to oxidation of the ash on the surface. Buried under new layers and deposits, the ash turned into soils by way of compaction and cementation. With more time and weathering, the exterior surfaces of The Painted Hills were worn into clay. Now, they are primarily made of hard

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

layers.Painted Hills Viewpoint
from the John Day Fossil Beds National Monument National Park Service.

Layers

The colors of the Painted Hills come from the combination of elements including

Aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

Silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...

Iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

Magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

Manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

Sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

Calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

Phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

Titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

Potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

Oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

, and

Hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

, among others, which arrived with the initial ash fall. Originally light in color, the ash mixed with soils and other elements to form the minerals that give the hills colors such as red, yellow, and black. The alternating red and tan layers within the hills are the result of cycling climate conditions, which were alternately warm and wet or cool and dry for a period of time between 34 and 28 million years ago. As the mild, humid

epoch gave way to the

, the tropical climate shifted, becoming cooler and drier.Bestland, E.A., Hammond, P.E., Blackwell, D.L.S., Kays, M.A., Retallack, G.J., & Stimac, J. (2002).
Geologic Framework of the Clarno Unit, John Day Fossil Beds National Monument, Central Oregon
(PDF). Red soils came from floodplain deposits during the more tropical periods, and are made up of

laterite Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...

s, or soils rich in

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

and

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

. These rust-colored layers are full of

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

in the form of

iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...

. The yellow layers are from a drier and cooler time and take on their yellow hue from

and

magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...

s. The darker, black soil is

that was once vegetative matter that grew along the floodplain. The grey coloring is

, and

. The black marks on the hills get their color from

manganese oxide Manganese oxide is any of a variety of manganese oxides and hydroxides.Wells A.F. (1984) ''Structural inorganic chemistry'' 5th edition Oxford Science Publications, . These include * Manganese(II) oxide, MnO * Manganese(II,III) oxide, Mn3O4 * Mang ...

Fossils

Fossils are rare in the Painted Hills. The original deposits of ash arrived irregularly, creating poor conditions for

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

ization, and most organic matter decayed. Still, it is possible to find leaf fossils from ancient lake beds throughout the hills. Many of the fossilized leaf impressions that have been found indicate the presence of plants and trees including

redwood Sequoioideae, popularly known as redwoods, is a subfamily of coniferous trees within the family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affini ...

cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, breakfa ...

fig The fig is the edible fruit of ''Ficus carica'', a species of small tree in the flowering plant family Moraceae. Native to the Mediterranean and western Asia, it has been cultivated since ancient times and is now widely grown throughout the world ...

, and

alder Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...

, which correspond to the warmer, more humid climate that predominated during the early formation of the hills. An abundance of fossil remains of early horses, camels, and rhinoceroses in the larger Painted Hills unit makes the area particularly important to vertebrate paleontologists.

Recreation

The Painted Hills are listed as one of the Seven Wonders of Oregon. The Painted Hills unit is open year-round with access for all visitors, but recreation can take a toll on the landscape; visitors who step off the trails can disrupt the naturally-occurring mineral layers, and damage the hills' visible features. There are several well-marked trails for visitors, who are encouraged to take a pledge to stay on the trails at all times: 'Don't Hurt the Dirt', and 'Leave No Trace'. On any given day, depending on the weather and the moisture in the hills, visitors might find variations in the colors of the Painted Hills. Light reflects differently when they are wet, causing the shades of color to vary in brightness and hue. In 2015, the annual visitor count at the Painted Hills rose from 45,849 to 74,873. On August 21, 2017, the Great American Eclipse passed directly over the park, allowing visitors a duration of totality of just over 2 minutes, 4 seconds.

Gallery

File: Painted Hills 2009.08.13.11.08.19.jpg File: Painted Hills 2009.08.13.11.08.52.jpg File: Painted Hills 2009.08.13.11.08.56.jpg File: Painted Hills in the John Day Fossil Beds National Monument near Mitchell Oregon.ogv, Bands of

give Painted Hills in the John Day Fossil Beds National Monument near Mitchell, Oregon their colorful appearance.

References

External links

* * Travel Oregon
/ref> – Painted Hills {{National Register of Historic Places Oregon John Day Fossil Beds National Monument Protected areas of Wheeler County, Oregon Articles containing video clips Landforms of Wheeler County, Oregon