Hopi Buttes volcanic field is a monogenetic

volcanic field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

located on the

Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area of ...

mostly on the Navajo Reservation around the town of

Dilkon Dilkon ( nv, ) is a census-designated place (CDP) in Navajo County, Arizona, United States. The population was 1,184 at the 2010 census. The name of the town is said to be derived from the Navajo phrase "Smooth black rock" or "Bare surface.” ...

in northeastern Arizona north of

Holbrook Holbrook may refer to: Places England *Holbrook, Derbyshire, a village *Holbrook, Somerset, a hamlet in Charlton Musgrove *Holbrook, Sheffield, South Yorkshire, a former mining village in Mosborough ward, now known as Halfway *Holbrook, Suffolk, a ...

. The volcanic field covers an area of approximately and contains about 300

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

s and diatremes.Geo-Ecological Study of Historic and Prehistoric Land Use in the Hopi Buttes area, Navajo Nation, Arizona, USGS
/ref> The erosional exposure of the deposits varies with those in the eastern portion exhibiting the shallowly eroded maar deposits and those in the western portion the more deeply eroded feeder diatremes. The maars result from explosive interaction of the hot diatreme material with the groundwater system and result in a mixture of volcanic

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...

material and sediments of the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

–

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58lacustrine sediments of the

Bidahochi Formation The Pliocene to Late Neogene Bidahochi Formation lies at an elevation of about to at the southeast of the Colorado Plateau; the deposits are from Hopi Lake (also called Bidahochi Lake), and the deposits extend southwards to the region at the ...

. In the western portion of the field the buttes consist of the feeder diatremes of

monchiquite Lamprophyres () are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions. They are alkaline silica-undersaturated mafic or ultramafic rocks with high magnesium oxide ...

and

nepheline syenite Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are al ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

s. Most of the volcanic activity occurred between 8.5 and 6 million years ago, with the most recent dated at 4.2 million years ago.Volcano World, ''Coliseum Maar, Hopi Buttes, Arizona''

Notable vents

References

{{DEFAULTSORT:Hopi Buttes Volcanic Field Volcanic fields of Arizona Landforms of Apache County, Arizona Monogenetic volcanic fields Geography of the Navajo Nation Miocene volcanism Pliocene volcanism

Notable vents

See also

References