The Bighorn Basin is a plateau region and intermontane basin, approximately 100 miles (160 km) wide, in north-central Wyoming in the United States. It is bounded by the Absaroka Range on the west, the Pryor Mountains on the north, the Bighorn Mountains on the east, and the Owl Creek Mountains and Bridger Mountains on the south. It is drained to the north by tributaries of the Bighorn River, which enters the basin from the south, through a gap between the Owl Creek and Bridger Mountains, as the Wind River, and becomes the Bighorn as it enters the basin. The region is semi-arid, receiving only 6–10 in (15–25 cm) of rain annually.
Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrounding atmosphere. New Zealand geologist Patrick Marshall (1869–1950) coined the term ignimbrite from the Latin igni- [fire] and imbri- [rain].
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 layers of fossil plants and mammals that lived in the region between the late Eocene, about 45 million years ago, and the late Miocene, about 5 million years ago. The monument consists of three geographically separate units: Sheep Rock, Painted Hills, and Clarno.
The Sierra Madre Occidental is a major mountain range system of the North American Cordillera, that runs northwest–southeast through northwestern and western Mexico, and along the Gulf of California. The Sierra Madre is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western 'sounds' of North America, Central America, South America, and West Antarctica.
The geology of the Australian Capital Territory includes rocks dating from the Ordovician around 480 million years ago, whilst most rocks are from the Silurian. During the Ordovician period the region—along with most of eastern Australia—was part of the ocean floor. The area contains the Pittman Formation consisting largely of Quartz-rich sandstone, siltstone and shale; the Adaminaby Beds and the Acton Shale.
The Moenkopi Formation is a geological formation that is spread across the U.S. states of New Mexico, northern Arizona, Nevada, southeastern California, eastern Utah and western Colorado. This unit is considered to be a group in Arizona. Part of the Colorado Plateau and Basin and Range, this red sandstone was laid down in the Lower Triassic and possibly part of the Middle Triassic, around 240 million years ago.
The Carmel Formation is a geologic formation in the San Rafael Group that is spread across the U.S. states of Wyoming, Utah, Colorado, north east Arizona and New Mexico. Part of the Colorado Plateau, this formation was laid down in the Middle Jurassic during the late Bajocian, through the Bathonian and into the early Callovian stages.
Cerro Galán is a caldera in the Catamarca Province of Argentina. It is one of the largest exposed calderas in the world and forms part of the Central Volcanic Zone of the Andes, one of the three volcanic belts found in South America. One of several major caldera systems in the Central Volcanic Zone, the mountain is grouped into the Altiplano–Puna volcanic complex.
The John Day Formation is a series of rock strata exposed in the Picture Gorge district of the John Day River basin and elsewhere in north-central Oregon in the United States. The Picture Gorge exposure lies east of the Blue Mountain uplift, which cuts southwest–northeast through the Horse Heaven mining district northeast of Madras. Aside from the Picture Gorge district, which defines the type, the formation is visible on the surface in two other areas: another exposure is in the Warm Springs district west of the uplift, between it and the Cascade Range, and the third is along the south side of the Ochoco Mountains. All three exposures, consisting mainly of tuffaceous sediments and pyroclastic rock rich in silica, lie unconformably between the older rocks of the Clarno Formation below and Columbia River basalts above.
The Rattlesnake Formation is a Miocene to late Pliocene geologic formation found along the John Day River Valley of Oregon, in the Western United States.
The Oregon high desert is a region of the U.S. state of Oregon located east of the Cascade Range and south of the Blue Mountains, in the central and eastern parts of the state. Divided into a southern region and a northern region, the desert covers most of five Oregon counties and averages 4,000 feet (1,200 m) above sea level. The southwest region is part of the Great Basin and the southeast is the lower Owyhee River watershed. The northern region is part of the Columbia Plateau, where higher levels of rainfall allow the largest industry on private land to be the cultivation of alfalfa and hay. Public land within the region is owned primarily by the Bureau of Land Management, which manages more than 30,000 square miles (78,000 km2) including five rivers designated as Wild and Scenic.
This timeline of volcanism on Earth includes a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic explosivity index (VEI) or equivalent sulfur dioxide emission during the Quaternary period. Other volcanic eruptions are also listed.
Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America and the Andes of South America.
Mahogany Mountain is an ancient caldera volcano on the border of Oregon and Idaho, in Malheur County and Owyhee County, respectively. While its early history is largely unknown, its last eruption was probably 15.5 million years ago. This eruption ejected layers of rhyolite and produced tuff, creating formations of rock in the Leslie Gulch.
Lauca is a 5,140 metres (16,860 ft) high andesitic stratovolcano in the Central Volcanic Zone of the Andes on the Altiplano in northern Chile. Administratively it is located in Putre, Arica y Parinacota Region. The volcano was active during the Late Miocene from 10.5 million years ago onwards. A major ignimbrite collapsed the volcano in the Late Pliocene.
Kurile Lake is a caldera and crater lake in Kamchatka, Russia. It is also known as Kurilskoye Lake or Kuril Lake. It is part of the Eastern Volcanic Zone of Kamchatka which, together with the Sredinny Range, forms one of the volcanic belts of Kamchatka. These volcanoes form from the subduction of the Pacific Plate beneath the Okhotsk Plate and the Asian Plate.
Acer taggarti is an extinct maple species in the family Sapindaceae described from a number of fossil leaves and samaras. The species is known from Miocene sediments exposed in central Oregon, US. It is one of several extinct species belonging to the living section Rubra.
Lake Modoc is a former lake in California and Oregon, in the location of present-day Upper Klamath Lake, Lower Klamath Lake and Tule Lake. It existed during the Pliocene and Pleistocene epochs, its formation probably influenced by volcanism and faulting. The bed of the former lake had plentiful resources for early humans, and today it is used for agriculture.
The Nevadaplano was a high plateau that is proposed to have covered parts of southwestern North America during the late Mesozoic and early Cenozoic, located in the present-day US states of Idaho, Nevada, Utah and possibly others. It most likely formed during the Cretaceous as a consequence of subduction dynamics and may have reached elevations of 3 kilometres (9,800 ft) and more, although its elevation is controversial. It was flanked on the west by the Sierra Nevada, which was traversed by various valleys that came down from the Nevadaplano. Closed basins and numerous volcanic calderas covered the relatively flat Nevadaplano; large volcanic eruptions distributed ignimbrites over the plateau and down the valleys draining it.
