Conical hill

Last updated
Milesovka Hill in the Bohemian Central Uplands Milesovka ppost.jpg
Milešovka Hill in the Bohemian Central Uplands

A conical hill (also cone or conical mountain) is a landform with a distinctly conical shape. It is usually isolated or rises above other surrounding foothills, and is often of volcanic origin.

Contents

Conical hills or mountains occur in different shapes and are not necessarily geometrically-shaped cones; some are more tower-shaped or have an asymmetric curve on one side of the hill. Typically, however, they have a circular base and smooth sides with a gradient of up to 30°. Such conical mountains are found in all volcanically-formed areas of the world such as the Bohemian Central Uplands in the Czech Republic, the Rhön in Germany or the Massif Central in France.

Term

The conical hill as a geomorphological term first appeared in the German language, as Kegelberg, coined by Goethe and geologists of his era. From their natural appearance these were mostly basaltic or phonolitic landforms in the shape of a mathematical cone, hence why the term came to be used in the early geological literature.
The first systematic geological mapping of the Kingdom of Saxony, proposed and started by Abraham Gottlob Werner, describes, in his later works, numerous mountains and hills of volcanic or subvolcanic origin as Kegel ("cone") or Kegelberg ("conical hill/mountain"). The term was introduced more definitively by Carl Friedrich Naumann in Notes to Section VII of the Geognostic Charter of the Kingdom of Saxony and its Adjacent Territories (Erläuterungen zu Section VII der geognostischen Charte des Königreiches Sachsen und der angränzenden Länderabtheilungen) thus: "The ordinary form of basalt and phonolitic hills is generally so wonderfully uniform that you can often recognize them even from a distance. They are cones. Of course, this typical form has many variations; the [normally] round base may be elongated, the peak may take the form of a rocky crest or ridge, ... but most forms can be reduced at least to a conical or a cone-segment shape. ... Flat ridges are then arranged in rows, out of which rise only a very isolated basalt or phonolite cones." [1]

In this work, which was published by Naumann and later revised by Bernhard Cotta, the most important hills are described in the relevant map sheets, for example: 33. The Mittenberg, a conical hill in the centre between Tollenstein, Schönfeld and Neuhütte; rock, coarse splinters, with grey feldspar crystals. [2]

Today the descriptors "cone", "conical hill" or "conical mountain" are mainly used as morphological terms in geography for a steep-sided, isolated hill or mountain, because they are not always seen or described in connexion with volcanic processes. [3]

Formation

Mount Damavand, Iran Damavand in winter.jpg
Mount Damavand, Iran

Volcanic cone

Mount Fuji, Japan Kodaki fuji frm shojinko refurb.jpg
Mount Fuji, Japan

All stratovolcanoes and shield volcanoes have a tendency to form a cone at the surface. However, stratovolcanoes are able to form steeper sides whilst shield volcanoes only form very flat cones. The reason for this is that stratovolcanoes are composed largely of solid, eruptive material, whereas shield volcanoes are built up mainly by fluid lava flows.

Over the course of time, after several eruptions, a cone of debris forms from the eruptive material. The natural conical shape so formed is simply a result of the fact that the amount of ejected material decreases with the radially distance from the crater. The layer of debris deposited is greater near the volcano than further away, so the volcano grows more rapidly close to the crater itself. The slope gradient of the resulting volcano is dependent both on the angle of repose as well as the speed at which the volcano is weathered. The angle of repose is, in turn, dependent on the composition of the lava, its viscosity and rate of solidification, and also the amount of ejected loose rock. Many volcanoes tend to produce subsidiary craters or adventive cones. These are new openings formed on the sides of the volcano through which new material is ejected sometimes only on one side. As a result, these mountains lose their ideal conical shape. The formation of an almost perfect conical mountain or hill is only possible where there is a stable, central crater. Many volcanoes are therefore only conical from one direction of view; from other angles they appear to have an irregular shape or bulges.

Karst cones

Chocolate Hills, Philippines Bohol Hills, Chocolate Hills 3, Philippines.jpg
Chocolate Hills, Philippines

Conical hills may form in tropical karst regions, such terrain being known as kegelkarst. A typical example of non-volcanic conical hills are the Chocolate Hills in Bohol on the Philippines.

Erosion-formed cones

In almost all mountain regions of the world, conical peaks may be formed by erosion processes, but they are not usually isolated landforms. Often they arise through the formation of ordinary riverine meanders. But they can also result from the action of an entrenched river that has cut deeply into a plateau. The resulting cutoff meander spur may be cone-shaped.

Artificial cone hills

Former conical tips at the Wismut mining company works in Thuringia Reusterhalden.JPG
Former conical tips at the Wismut mining company works in Thuringia

The artificially created hills or mounds associated, for example, with mining also tend to be cone-shaped. These artificial hills are also free-standing and, once tipping has finished, they may become conical hills overgrown with vegetation. However, as artificial features they are classed as spoil tips rather than natural hills.

See also

Related Research Articles

<span class="mw-page-title-main">Volcano</span> Rupture in the crust of a planet that allows lava, ash, and gases to escape from below the surface

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

<span class="mw-page-title-main">Stratovolcano</span> Type of conical volcano composed of layers of lava and tephra

A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high to intermediate levels of silica, with lesser amounts of less viscous mafic magma. Extensive felsic lava flows are uncommon, but have traveled as far as 15 km (9 mi).

<span class="mw-page-title-main">Volcanic cone</span> Landform of ejecta from a volcanic vent piled up in a conical shape

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.

Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.

<span class="mw-page-title-main">Mount Mazama</span> Complex volcano in the Cascade Range

Mount Mazama is a complex volcano in the western U.S. state of Oregon, in a segment of the Cascade Volcanic Arc and Cascade Range. Most of the mountain collapsed following a major eruption approximately 7,700 years ago. The volcano is in Klamath County, in the southern Cascades, 60 miles (97 km) north of the Oregon–California border. Its collapse, due to the eruption of magma emptying the underlying magma chamber, formed a caldera that holds Crater Lake. The mountain is in Crater Lake National Park. Mount Mazama originally had an elevation of 12,000 feet (3,700 m), but following its climactic eruption this was reduced to 8,157 feet (2,486 m). Crater Lake is 1,943 feet (592 m) deep, the deepest freshwater body in the U.S. and the second deepest in North America after Great Slave Lake in Canada.

<span class="mw-page-title-main">Mount Washington (Oregon)</span> Deeply eroded volcano in the Cascade Range of Oregon

Mount Washington is a deeply eroded volcano in the Cascade Range of Oregon. It lies within Deschutes and Linn counties and is surrounded by the Mount Washington Wilderness area.

<span class="mw-page-title-main">Maar</span> Low-relief volcanic crater

A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption. A maar characteristically fills with water to form a relatively shallow crater lake, which may also be called a maar.

<span class="mw-page-title-main">Crater Highlands</span> Geologic region along the East African Rift in Tanzania

<span class="mw-page-title-main">Kostal Cone</span> Cinder cone in Wells Gray Provincial Park, British Columbia, Canada

Kostal Cone, also called Kostal Volcano and Fire Mountain, is a young cinder cone in Wells Gray Provincial Park in east-central British Columbia, Canada. It rises from the northeast shore of Kostal Lake in the Cariboo Mountains. With an elevation of 1,440 m (4,724 ft), Kostal Cone is one of the lowest volcanoes in the Wells Gray-Clearwater volcanic field.

<span class="mw-page-title-main">Mount Tendürek</span> Shield volcano in eastern Turkey

Mount Tendürek is a shield volcano on the border of Ağrı and Van provinces in eastern Turkey, near the border with Iran. The volcano, which is mostly known for being near the supposed wreck site of Noah's Ark, is very large; its lava flows cover roughly 650 km2 (251 sq mi) across a swath of flat land. The mountain's two main features are the main summit crater Greater Tendürek, and a smaller crater known as Lesser Tendürek which lies to the east of the main crater. The slopes are very gentle and resemble a shield, after which the type is named. Mount Tendürek is known to have erupted viscous lava like that of volcanoes on the island of Hawaii.

<span class="mw-page-title-main">West Crater</span> Lava dome in Washington, United States

West Crater is a small lava dome with associated lava flows in southern Washington, United States. Located in Skamania County, it rises to an elevation of 4,131 feet (1,259 m), and forms part of the Cascade Volcanic Arc. It is also part of the Marble Mountain-Trout Creek Hill volcanic field, a little-known Quaternary volcanic field in the southern Cascades of Washington state. The area can be hiked, and can be accessed by roads in the Gifford Pinchot National Forest.

<span class="mw-page-title-main">Black Crater</span> Shield volcano in central Oregon, United States

Black Crater is a shield volcano in the Western Cascades in Deschutes County, Oregon. Located near McKenzie Pass, the volcano has a broad conical shape with gentle slopes. The volcano likely formed during the Pleistocene and has not been active within the last 50,000 years. Eruptive activity at the volcano produced mafic lava flows made of basaltic andesite and olivine basalt; it also formed a number of cinder cones. A normal fault occurs on the western side of the volcano, trending north–south. The volcano has been eroded by glaciers, which carved a large cirque into the northeastern flank of the mountain, forming its current crater.

<span class="mw-page-title-main">Cinder cone</span> Steep hill of pyroclastic fragments around a volcanic vent

A cinder cone is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is symmetrical; with slopes between 30 and 40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.

<span class="mw-page-title-main">Tequila Volcano</span>

Tequila Volcano, or Volcán de Tequila is a stratovolcano located near Tequila, Jalisco, in Mexico. It stands at a height of 2,920 meters above sea level,. Stratovolcanoes, also referred to as composite volcanoes, are the "iconically" conical-shaped volcanoes, found most commonly along subduction zones. Stratovolcanoes are composed of steeply dipping layers of lava, hardened ash, and other material that erupted from the main vent such as tephra and pumice. Commonly higher than 2500 meters above sea-level, Stratovolcanoes have gentle lower slopes which gradually become steeper the higher you get with a relatively small summit crater. Due to their eruptions, Stratovolcanoes have several distinct variations giving some a specific feature such as calderas and amphitheaters.

Trout Creek Hill is a small Pleistocene basaltic shield volcano in Washington, United States. Located in Skamania County, Trout Creek Hill rises to an elevation of 2,946 feet (898 m). It is part of the Cascade Volcanic Arc, located in the Marble Mountain-Trout Creek Hill volcanic field.

Mount Leura is a 313-metre scoria cone surrounding a dry crater 100 m deep and is the central and most obvious component of a larger volcanic complex southeast of the town of Camperdown located in western Victoria, Australia, 194 kilometres (121 mi) south west of the state capital, Melbourne. The inactive volcano is thought to have last erupted between 5,000 and 20,000 years ago. The name means "big nose" in local aboriginal dialect.

<span class="mw-page-title-main">Volcanic history of the Northern Cordilleran Volcanic Province</span>

The volcanic history of the Northern Cordilleran Volcanic Province presents a record of volcanic activity in northwestern British Columbia, central Yukon and the U.S. state of easternmost Alaska. The volcanic activity lies in the northern part of the Western Cordillera of the Pacific Northwest region of North America. Extensional cracking of the North American Plate in this part of North America has existed for millions of years. Continuation of this continental rifting has fed scores of volcanoes throughout the Northern Cordilleran Volcanic Province over at least the past 20 million years and occasionally continued into geologically recent times.

<span class="mw-page-title-main">Hirtstein</span>

Hirtstein is a mountain of Saxony, in southeastern Germany. It is situated near the village Satzung, in the Ore Mountains, about 1.5 km from the border to the Czech Republic. Its elevation is 890 m.

<span class="mw-page-title-main">Atakor volcanic field</span> Volcanic field in Algeria

Atakor volcanic field is a volcanic field in Algeria. It lies in the Hoggar mountains and consists of a variety of volcanic features such as lava flows and about 450 individual vents which create a spectacular scenery.

<span class="mw-page-title-main">Volcanism on the Moon</span> Volcanic processes and landforms on the Moon

Volcanism on the Moon is represented by the presence of volcanoes, pyroclastic deposits and vast lava plains on the lunar surface. The volcanoes are typically in the form of small domes and cones that form large volcanic complexes and isolated edifices. Calderas, large-scale collapse features generally formed late in a volcanic eruptive episode, are exceptionally rare on the Moon. Lunar pyroclastic deposits are the result of lava fountain eruptions from volatile-laden basaltic magmas rapidly ascending from deep mantle sources and erupting as a spray of magma, forming tiny glass beads. However, pyroclastic deposits formed by less common non-basaltic explosive eruptions are also thought to exist on the Moon. Lunar lava plains cover large swaths of the Moon's surface and consist mainly of voluminous basaltic flows. They contain a number of volcanic features related to the cooling of lava, including lava tubes, rilles and wrinkle ridges.

References

  1. Naumann: Section VII, pp. 61-62
  2. Naumann: Section VII, p. 94
  3. Hartmut Leser (ed.): Diercke Wörterbuch Allgemeine Geographie. Munich, (dtv) 2005, p. 421 ISBN   3-423-03422-X.

Literature