| Pahvant Butte | |
|---|---|
 Pahvant Butte, 2021 | |
| Geography | |
  Pahvant Butte | |
| Country | United States |
| State | Utah |
| Region | Black Rock Desert volcanic field |
| District | Millard County |
| Range coordinates | 39°07′54″N112°33′08″W / 39.13167°N 112.55222°W |
| Topo map | USGS Pahvant Butte North, Utah and Pahvant Butte South, Utah |
Pahvant Butte (also Pavant Butte) is a tuff cone volcano in the west-central portion of Utah, United States. [1]
The butte, sometimes called "Sugarloaf Mountain" by locals, [2] is located in the Sevier Desert in the Pahvant Valley 15.7 miles (25.3 km) south of Delta and five miles east of Clear Lake and the Clear Lake Wildlife Management Area. [3]
The butte has two peaks. The north peak has an elevation of 5,751 ft (1,753 m) and the south peak reaches 5,486 ft (1,672 m). The peaks are about 1000 feet above the surrounding valley floor. The butte is about 1.5 mi (2.4 km) in diameter at the base. [4]
It formed in an active area of volcanism on top of pahoehoe and aa lavas. Originally a subaqueous volcano, it erupted out of the floor of Lake Bonneville approximately 15,500 years ago.
Along the southeast rim of the inner depression of the volcano is an unfinished structure consisting of a concrete building embedded in the hill surrounded by two rings of concrete obelisks. The structure was apparently begun by a man named A. H. Hood, with the intention of generating wind power, in 1923. [5] [2]
Part of the Black Rock Desert volcanic field of the Pleistocene-Holocene age, Pahvant Butte formed above older pahoehoe and aa lavas of the Pahvant field. [6] The volcano was originally a subaqueous volcano formed under Lake Bonneville by a large eruption about 15,500 years ago. The water depth at the time of eruption is estimated to have been 85 m (279 ft). [7] This eruptive activity probably ejected steam, ash, and other materials out of the lake, enveloping the surrounding area with ash and spawning large waves in the lake. The eruption released particles of basaltic lava into the air, which fell back to form tuff. [8]
A raised beach, or lacustrine terrace, formed by waves surrounds most of the volcano's lower rock. A vertical cliff, known as the Lace Curtain, is present on the north flank of the volcano, formed as a result of storm wave action. This name originated from the distinct white, lace-like pattern seen on the cliff face, caused by partial cementation of the tuff by minerals deposited by groundwater. [8]
Pahvant Butte was overlapped by the lava flows of the Ice Springs eruption between 1140 and 1440 AD. [9]
The Pahvant Butte volcano consists of an asymmetrical tuff cone with a breach on its southwestern side — and a platform area that extends to the southeast of the cone, formed of beds of tephra dipping steeply away from the cone, and partly concealing a mound of near horizontally-bedded sideromelane tephra beneath. [7]
The mound of sub-horizontally bedded tephra represents the first stage of the eruption. The ash grains are variably vesiculated, a texture typical of material erupted during phreatomagmatic activity, which involves direct interaction between magma and water. The layers of ash and lapilli, incorporating some clasts of deformed lake sediments, were deposited by sediment gravity flows. Some large ejected blocks have bedding sags beneath them, indicating a ballistic emplacement. The uppermost part of the mound consists of moderately vesicular ash with lapilli, passing up into ripple-marked beds at the base of the overlying cone deposits. These beds are interpreted to represent the result of wave reworking. [7]
The cone consists of steeply dipping layers of mainly palagonite, formed by the alteration of the original basaltic glass. The cone is typical of tuff cones, which form during eruptions in the presence of standing water or abundant groundwater. This part of the volcano was constructed sub-aerially.
The platform consists of deposits formed by the erosion of the cone. These built out into the lake as a prograding delta or beach, forming large cross bedding foresets. [7]
Lava Beds National Monument is located in northeastern California, in Siskiyou and Modoc counties. The monument lies on the northeastern flank of Medicine Lake Volcano, which is the largest volcano by area in the Cascade Range.
Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.
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Newberry Volcano is a large, active, shield-shaped stratovolcano located about 20 miles (32 km) south of Bend, Oregon, United States, 35 miles (56 km) east of the major crest of the Cascade Range, within the Newberry National Volcanic Monument. Its highest point is Paulina Peak. Newberry is the largest volcano in the Cascade Volcanic Arc, with an area of 1,200 square miles (3,100 km2) when its lava flows are taken into account. From north to south, the volcano has a length of 75 miles (121 km), with a width of 27 miles (43 km) and a total volume of approximately 120 cubic miles (500 km3). It was named for the geologist and surgeon John Strong Newberry, who explored central Oregon for the Pacific Railroad Surveys in 1855.
Lapilli is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. Lapilli is Latin for "little stones".
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Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C. The volcanic rock resulting from subsequent cooling is also often called lava.
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