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:''This article is about volcanoes. For the action movie, see [[Volcano (movie)]]. For other meanings of the word eruption, see [[eruption (disambiguation)]]''
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!Australian Cattle Dog
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|[[Image:AustrCattleDogBlue_wb.jpg|thumbnail|250px|none|Blue coat color; this dog's tail is docked.]]
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!Alternative names
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|Australian Heeler
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|Blue Heeler
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|Red Heeler
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|Hall's Heeler
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|Queensland Heeler
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|- align=center bgcolor=pink
!Country of origin
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|[[Australia]]
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!Common nicknames
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|Bluey, ACD, Cattledog
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!Classification and breed standards
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{| align=center
|[[Fédération Cynologique Internationale|FCI]]: ||Group 1 Section 2 #287
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|[[American Kennel Club|AKC]]: ||Herding
|[http://www.akc.org/breeds/australian_cattle_dog/index.cfm Std]
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|[[Australian National Kennel Council|ANKC]]: ||Group 5 (Working Dogs)
|[http://www.ankc.aust.com/austcat.html Std]
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|[[Canadian Kennel Club|CKC]]: ||Group 7 - Herding Dogs
|[http://www.nwstar.com/~acdcc/standard.htm Std]
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|[[Kennel Club (UK)|KC(UK)]]: ||Pastoral
|[http://www.the-kennel-club.org.uk/discoverdogs/pastoral/p835.htm Std]
|-
|[[New Zealand Kennel Club|NZKC]]: ||Working
|[http://www.nzkc.org.nz/br504.html Std]
|-
|[[United Kennel Club|UKC]]: || Herding Dog Breeds
|[http://www.ukcdogs.com/breeds/herdingdogs/australiancattledog.std.shtml Std]
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The '''Australian Cattle Dog''' (ACD), also known as the '''Queensland Heeler''', '''Blue Heeler''', and '''Red Heeler''', is a [[herding dog]] developed in Australia for controlling [[cattle]]. It is a medium-sized dog with a lot of energy and an independent streak.
==Appearance==
[[Image:AustrCattleDogBlueFace_wb.jpg|thumbnail|left|One variant of Blue face markings]]
The Cattle Dog's coat comes in a variety of markings, sometimes quite striking. The basic coat colors are ''blue'' and ''red speckle''. For dog owners whose interest is primarily in their qualification for [[dog show]]s, even markings are preferred over uneven markings, and large solid-color marks on the body are undesireable. For owners who are more interested in their dogs' performance in activities such as [[herding]] or [[dog sports]], the breed's strong work ethic and intelligence are of more importance than the exact coat markings.
The mask is one of the most distinctive features of an ACD. This mask consists of a darker red patch over one or both eyes (for the red speckle coat color) or a black patch over one or both eyes (for the blue coat color). These are called, respectively, ''single mask'' and ''double mask''. ACDs without a mask are called ''plain-faced''. Any of these is correct according to the breed standard, and the only limitation is the owner's preference.
A '''volcano''' is a [[landform|geological landform]] (usually a [[mountain]]) where [[magma]] (rock of the Earth's interior made molten or liquid by extremely high temperatures along with a reduction in pressure and/or the introduction of water or other volatiles) erupts through the surface of the [[planet]]. Although there are numerous volcanoes (some very active) on the [[solar system]]'s rocky planets and moons, on [[Earth]] at least, this phenomenon tends to occur near the boundaries of the [[plate tectonics|continental plates]]. However, important exceptions exist in '''[[hotspot (geology)|hotspot volcanoes]]'''.
[[Image:Mahameru-volcano.jpg|thumb|right|300px|Smoking Bromo and Semeru volcanoes on [[Java (island)|Java]] in [[Indonesia]].]]
[[Image:AustrCattleDogRed_wb.jpg|thumbnail|left|Red speckle coat color with undocked tail]]
The name "volcano" has its origin from the name of [[Vulcan (god)|Vulcan]], a god of fire in [[Roman mythology]].
Many Australian Cattle Dogs have a stripe of white hair in the center of the forehead, usually 1/2 inch to 1 inch by 2 inches to 3 inches (about 2 cm by 7 cm) called the ''Bentley Mark''. This is similar in appearance to the blaze markings sometimes found on [[horse]]s. According to legend, a popular dog owned by Tom Bentley passed on this distinctive mark to all Australian Cattle Dogs.
The study of volcanoes is called [[vulcanology]] (or ''volcanology'' in some spellings).
A female Australian Cattle Dog should measure about 17 to 19 inches (43 to 48 cm) at the [[withers]]. A male Australian Cattle Dog should measure about 18 to 20 inches (46 to 51 cm) at the [[withers]]. An ACD is a well-muscled, compact dog with a short, dense coat and a naturally long tail. An ACD in good condition should weigh roughly 40 to 50 pounds (18 to 23 kg).
==Volcanoes==
===Types of volcanoes===
[[Image:Mauna loa.jpg|thumb|right|300px|Eruption of [[Mauna Loa]], March [[1984]]]]
One way of classifying volcanoes is by the type of material erupted, which affects the shape of the volcano. If the erupting magma contains a high percentage (>65%) of [[silica]] the lava is called '''[[felsic]]''' or "Acidic" and tends to be very [[viscosity|viscous]] (not very fluid) and is pushed up in a blob that will solidify relatively quickly. [[Lassen Peak]] in [[California]] is an example. This type of volcano has a tendency to explode because it easily plugs. [[Mount Pelée]] on the island of [[Martinique]] is another example.
Some breeders [[docking|dock]] ACD's tails. This is a controversial practice and, in some countries, is illegal or is prohibited for dogs in the [[dog show|show ring]].
If, on the other hand, the magma contains relatively small amounts (<52%) of silica, the lava is called '''[[mafic]]''' or "Basic" and will be very fluid as it erupts, capable of flowing for long distances. A good example of a mafic lava flow is the Great Þjórsárhraun (Thjórsárhraun) flow produced by an eruptive fissure almost in the geographical center of Iceland roughly 8,000 years ago; it flowed all the way to the sea, a distance of 130 kilometers, and covered an area of 800 square km. Note that the terms ''felsic'' and ''mafic'' are sometimes substituted by the older chemistry terms "acidic" and "basic", respectively. The latter were thought to be a little misleading, however, and are slowly falling into disuse.
Docking Australian Cattle Dogs' tails is a practice peculiar to the United States - ACD tails are not docked in their country of origin, Australia. This is not to be confused with the Stumpy-tailed Cattle Dog, which is born with a naturally docked, or 'bobbed' tail; this animal strongly resembles the ACD in colouring, but has a slightly taller, leaner conformation.
==Temperament==
[[Image:Shield volcano.jpg|thumb|Shield volcano structure]]
Like many [[herding dog]]s, Cattle Dogs have high energy levels and active minds. They need plenty of exercise and a job to do, such as participating in [[dog sports]], learning tricks, or other activities that engage their minds. Some individuals find repetitive training frustrating and dull, so owners should aim to make training sessions varied and more exciting in order to keep their Dog intrested. Cattle Dogs who do not receive the appropriate exercise and entertainment will invent their own, often destructive, activities. These Dogs are, by nature, timid or wary. They are naturally cautious, and grow more so as they age.Their aggresive nature on strangers make them perfect gaurd dogs.
*'''[[Shield volcano]]''': [[Hawaii]] and [[Iceland]] are examples of places where volcanoes extrude huge quantities of lava that gradually build a wide mountain with a shield-like profile. Their lava flows are generally very hot and very fluid, contributing to long flows. The largest lava shield on [[Earth]], [[Mauna Loa]], is 9,000 m tall (it sits on the sea floor), 120 km in diameter and forms part of the [[Island of Hawai'i]]. [[Olympus Mons]] is a shield volcano on [[Mars (planet)|Mars]], and the tallest mountain in the known solar system.
*Smaller versions of the "lava shield" include the '''lava dome''' ('''''tholoid'''''), '''lava cone''', and '''lava mound'''.
Cattle Dogs drive cattle by nipping at their heels, but they have also been known to herd other animals, such as ducks or chickens without instruction when left to their own devices. When around people, their instinct to herd is sometimes hard to suppress and they can nip at people to herd them. If these dogs will be around children, they and their owners must have sufficient training to know how to manage or avoid such situations.
[[Image:Cinder cone volcano.jpg|thumb|Cinder cone volcano structure]]
*'''[[Volcanic cones]]''' or [[cinder cone]]s result from eruptions that throw out mostly small pieces of rock that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 300 m high.
[[Image:Stratovolcano.jpg|thumb|Stratovolcano structure]]
*'''[[Stratovolcano]]es''' or '''composite volcanoes''' are tall conical mountains composed of both lava flows and ejected material, which form the [[stratum|strata]] which give rise to the name. Classic examples include [[Mt. Fuji]] in Japan and [[Mount Mayon]] in the [[Philippines]].
*'''[[Supervolcano]]es''' is the popular term for large volcanoes that usually have a large [[caldera]] and can potentially produce devastation on a continental scale and cause major global weather pattern changes. Potential candidates include [[Yellowstone National Park]] and [[Lake Toba]], but are hard to identify given that there is no formal definition of the term.
*'''[[Submarine volcano]]es''' are common features on certain zones of the ocean floor. Some are active at the present time and, in shallow water, disclose their presence by blasting steam and rock-debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them results in high, confining pressure and prevents the formation and explosive release of steam and gases. Even very large, deepwater eruptions may not disturb the ocean surface.
==Australian Cattle Dog activities==
*'''[[Mud volcano]]es''' are formations which are often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano. This article describes igneous volcanoes.
[[Image:Acd_diving.jpg|thumbnail|left|ACDs need and enjoy any activity, such as diving and swimming.]]
Australian Cattle Dogs not only tolerate a high level of physical activity, they almost demand it. Like many other [[herding dog]] breeds, they have active and fertile minds that turn mischievous if not properly channeled. ACDs are highly intelligent and can be very bossy.
Volcanoes are usually situated either at the boundaries between [[tectonic plates]] or over [[hot spot]]s. Volcanoes may be either dormant (having no activity) or active (near constant expulsion and occasional eruptions), and change state unpredictably.
Volcanoes on land often take the form of flat [[cone]]s, as the expulsions build up over the years, or in short-lived [[volcanic cone#cinder cone|cinder cone]]s. Under [[water]], volcanoes often form rather steep [[pillar]]s and in due time break the [[ocean]] surface in new [[island]]s.
When not active, an ACD can be kept occupied with mental puzzles such as a [http://www.kongcompany.com Kong] stuffed with treats or a [http://www.sitstay.com/store/toys/toysd.shtml Buster Cube].
===Behavior of volcanoes===
Among the most popular activities for Australian Cattle Dogs is [[dog agility]]. While the ACD is ideally suited for this work, since it is a [[herding dog|herding breed]] and thus very reactive to the handler's body language, some ACDs become easily frustrated at the repetition and routine necessary to hone agility skills. As for many breeds, frequent brief training sessions are more effective than infrequent long training sessions.
[[Image:Volcano q.jpg|thumb|right|250px|A volcanic eruption can be devastating for the local [[wildlife]], as well as the human population.]]
For this reason, many handlers find training an ACD to be challenging. It is important to always change the methods and exercises and not allow the dog or handler to get into a rut. ACDs thrive on change and new experiences.
There are many different kinds of volcanic activity and eruptions:
* [[phreatic eruptions]] (steam)
* explosive eruption of high-[[silica]] [[lava]] (e.g., [[rhyolite]])
* effusive eruption of low-silica lava (e.g., [[basalt]])
* [[pyroclastic flow]]s
* [[lahar]]s (debris flow)
* [[carbon dioxide]] emission
All of these activities can pose a hazard to humans.
[[Image:Acd_scent_articles.jpg|thumbnail|right|An ACD finding a scent article as part of obedience competition.]] Only a few ACDs, therefore, have excelled in [[obedience training|obedience competition]]
Volcanic activity is often accompanied by [[earthquake]]s, [[hot spring]]s, [[fumarole]]s, [[mud pot]]s and [[geyser]]s. Low-magnitude earthquakes often precede eruptions.
For example, the [[American Kennel Club]] awards an "Obedience Trial Championship" (OTCh) to the dog-and-handler team that defeats a large number of other teams in open competition. A handful of ACDs have reached this level. While ACDs enjoy the challenge of obedience competition, such as retrieving a scented article, the majority of ACDs are easily bored with precision drilling.
====Active,Australian Dormant,Cattle orDogs Extinct?=in movies===
* ''mad dog'' (blue) and a Dingo (red) in ''[[The Sundowners]]'' ([[1960 in film|1960]])
* ''Dog'' in ''[[Mad Max 2: The Road Warrior]]'' ([[1981 in film|1981]])
* ''Zip'' in ''[[Last of the Dogmen]]'' ([[1995 in film|1995]])
==External links==
Surprisingly, there is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of activity. Given the long lifespan of such volcanoes, they are very active. By our lifespans, however, they are not. Complicating the definition are volcanoes that become restless but do not actually erupt. Are these volcanoes active?
*[http://www.acdca.org Australian Cattle Dog Club of America website]
*[http://www.acdcc.ca Australian Cattle Dog Club of Canada website]
Scientists usually consider a volcano active if it is currently erupting or showing signs of unrest, such as unusual earthquake activity or significant new gas emissions. Many scientists also consider a volcano active if it has erupted in historic time. It is important to note that the span of recorded history differs from region to region; in the [[Mediterranean]], recorded history reaches back more than 3,000 years but in the Pacific Northwest of the United States, it reaches back less than 300 years, and in [[Hawaii]], little more than 200 years.
*[http://www.cattledog.com CattleDog.com Centralized repository for all things ''"Cattledog"'']
*[http://www.acdagility.com ACD Agility website]
Dormant volcanoes are those that are not currently active (as defined above), but could become restless or erupt again.
*[http://www.australiancattledog.com Australian Cattle Dog website: Breed FAQ, Photos, Breeders]
*[http://www.cowdogz.com/ CowDogz.com]
Extinct volcanoes are those that scientists consider unlikely to erupt again. Whether a volcano is truly extinct is often difficult to determine. Since [[caldera]]s have lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct.
For example, the [[Yellowstone Caldera]] (considered a [[Supervolcano]]) in [[Yellowstone National Park]] is at least 2 million years old and hasn't erupted violently for approximately 640,000 years — although there has been some minor activity as relatively recent as 70,000 years ago. For this reason, scientists do not consider the [[Yellowstone Caldera]] as extinct. In fact, because the caldera has frequent earthquakes, a very active geothermal system (i.e., the entirety of the geothermal activity found in [[Yellowstone National Park]]), and rapid rates of ground uplift, many scientists consider it to be a very active volcano.
===Volcanoes on Earth===
:''Main article: [[List of volcanoes]]''
[[Image:Volcano.jpeg|thumb|right|400px|Mount St. Helens erupting in 1980]]
*[[Cold Bay Volcano]] ([[Alaska]], [[United States|USA]])
*[[Mount Baker]] ([[Washington]], [[United States|USA]])
*[[Mount Fuji]] ([[Honshu]], [[Japan]])
*[[Mount Hood]] ([[Oregon]], [[United States|USA]])
*[[Mount Erebus]] ([[Ross Island]], [[Antarctica]])
*[[Etna]] ([[Sicily]], [[Italy]])
*[[Krafla]] ([[Iceland]])
*[[Hekla]] ([[Iceland]])
*[[Kick-'em-Jenny]], ([[Grenada]])
*[[Kilauea]] ([[Hawaii]], [[United States|USA]])
*[[Kluchevskaya]] ([[Kamchatka Peninsula|Kamchatka]], [[Russia]])
*[[Krakatoa]] ([[Rakata]], [[Indonesia]])
*[[Mauna Kea]] ([[Hawaii]], [[United States|USA]])
*[[Mauna Loa]] ([[Hawaii]], [[United States|USA]])
*[[El Misti]] ([[Arequipa]], [[Peru]])
*[[Novarupta]] ([[Alaska]], [[United States|USA]])
*[[Mount Pinatubo]] (Luzon Island, [[Philippines]])
*[[Popocatépetl]] ([[Mexico (state)|Mexico]]-[[Puebla (state)|Puebla]] state line, [[Mexico]])
*[[Santorini]] ([[Santorini|Santorini islands]], [[Greece]])
*[[Soufriere Hills volcano]], ([[Montserrat]])
*[[Mount Rainier]] ([[Washington]], [[United States|USA]])
*[[Mount Shasta]] ([[California]], [[United States|USA]])
*[[Mount St. Helens]] ([[Washington]], [[United States|USA]])
*[[Surtsey]] ([[Iceland]])
*[[Tambora]] ([[Sumbawa]], [[Indonesia]])
*[[Teide]] ([[Tenerife]], [[Canary Islands]], [[Spain]])
*[[White Island]] ([[Bay of Plenty]], [[New Zealand]])
*[[Mount Vesuvius]] (Bay of [[Naples]], [[Italy]])
===Volcanoes elsewhere in the solar system===
[[image:Olympus mons 1998.jpg|thumb|[[Olympus Mons]] ([[Latin]], "Mount Olympus") is the tallest known [[mountain]] in our [[solar system]], located on the [[planet]] [[Mars (planet)|Mars]].]]
The Earth's [[Moon]] has no large volcanoes, but does have many volcanic features such as [[rille]]s and [[Lunar dome|domes]].
The planet [[Venus (planet)|Venus]] is believed to be volcanically active, and its surface is 90% [[basalt]], indicating that volcanism plays a major role in shaping its surface. Lava flows are widespread and many of its surface features are attributed to exotic forms of volcanism not present on Earth. Other Venusian phenomena, such as changes in the planet's atmosphere and observations of lightning, have been attributed to ongoing volcanic eruptions.
There are several extinct volcanoes on [[Mars (planet)|Mars]], four of which are vast shield volcanoes far bigger than any on Earth:
* [[Arsia Mons]]
* [[Ascraeus Mons]]
* [[Hecates Tholus]]
* [[Olympus Mons]]
* [[Pavonis Mons]]
These volcanoes have been extinct for many millions of years, but the European ''[[Mars Express]]'' spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.
[[Jupiter (planet)|Jupiter]]'s [[Natural_satellite|moon]] [[Io (moon)|Io]] is the most volcanic object in the solar system, due to [[tides|tidal]] interaction with Jupiter. It is covered with volcanoes that erupt [[sulfur]], [[sulfur dioxide]] and [[silicate]] rock, with the result that the moon is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1800K (1527C). In February [[2001]], the largest recorded volcanic eruptions in the solar system occurred on Io [http://www2.keck.hawaii.edu/news/archive/eruption/]. See the [[List of geological features on Io#Active Volcanoes|list of geological features on Io]] for a list of named volcanoes on the moon.
The [[Cassini-Huygens]] mission has found evidence of a methane-spewing cryovolcano on the [[Saturn (planet)|Saturnian]] moon [[Titan (moon)|Titan]]. This volcanism is believed to be a significant source of the methane found in its atmosphere. [http://www.newscientist.com/article.ns?id=dn7489]
Many '[[Cryovolcanism|ice volcanoes]]' have been found on [[Triton (moon)|Triton]], a [[Natural_satellite|moon]] of [[Neptune (planet)|Neptune]]; they are believed to eject liquid [[nitrogen]], dust, or [[methane]] compounds.
The [[Kuiper Belt Object]] [[50000 Quaoar|Quaoar]] is also suspected of having ice volcanoes.
==Volcanology==
=== Volcano formation ===
[[image:destructive_plate_margin.png|thumb|left|250px|Diagram of a destructive margin causing [[earthquake]]s and a volcanic eruption]]
Like most of the interior of the earth, the movements and dynamics of '''magma''' are poorly understood. However, it is known that an eruption usually follows movement of magma upwards into the solid layer (the earth's '''crust''') beneath a volcano and occupying a '''[[magma chamber]]'''. Eventually, magma in the chamber is forced upwards and flows out across the planet surface as [[lava]], or the rising magma can heat water in the surrounding landform and cause explosive discharges of steam; either this or escaping gases from the magma can produce forceful ejections of rocks, [[cinder]]s, [[obsidian|volcanic glass]], and/or [[volcanic ash]]. While always displaying powerful forces, eruptions can vary from effusive to extremely explosive.
Most volcanoes on the land are formed at [[destructive plate margin]]s: where oceanic crust is forced below the continental crust because oceanic crust is denser than continental crust. Friction between these moving plates will cause the oceanic crust to melt, and reduced density will force the newly formed magma to rise. As the magma rises it rises up through weak areas in the continental crust, eventually erupting as one or more volcanoes. For example, [[Mount St. Helens]] is found inland from the margin between the oceanic [[Juan de Fuca Plate]] and the continental [[North American Plate]].
[[image:Dikes-large.jpg|thumb|right|250px|Shiprock, New Mexico a volcanic neck in the distance, with radiating dike on its south side. Photo credit: USGS Digital Data Series]]
A volcano generally presents itself to the imagination as a mountain sending forth from its summit great clouds of smoke with vast sheets of flame. The truth is that a volcano seldom emits either [[smoke]] or [[flame]], although various combinations of [[hydrogen]], [[carbon]], [[oxygen]], and [[sulfur]] do sometimes ignite. What is mistaken for smoke consists of vast volumes of fine dust, mingled with steam and other vapors, chiefly sulfurous. Most of what appears to be flames is the glare from the erupting materials, glowing because of their high temperature; this glare reflects off the clouds of dust and steam, resembling fire.
Perhaps the most conspicuous part of a volcano is the [[volcanic crater|crater]], a basin of a roughly circular form within which occurs a ''vent'' (or vents) from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of vast depth. Very large features of this sort are termed [[caldera]]s. Some volcanoes consist of a crater alone, with scarcely any [[mountain]] at all; but in the majority of cases the crater is situated on top of a mountain (the volcano), which can tower to an enormous height. Volcanoes that terminate in a principal crater are usually of a [[cone|conical]] form.
''[[Volcanic cones]]'' are usually smaller features composed of loose ash and cinder, with occasional masses of stone which have been tossed violently into the air by the eruptive forces (and are thus called ''ejecta''). Within the crater of a volcano there may be numerous cones from which vapours are continually issuing, with occasional volleys of ashes and stones. In some volcanoes these cones form lower down the mountain, along rift zones or fractures. When the cone is eroded these rifts or lava filled fractures remain as radial near vertical [[dike (geology)|dike]]s of volcanic rock. For example the radiating dikes at [[Shiprock, New Mexico|Shiprock]] in NW [[New Mexico]].
====Tectonic environments of volcanoes====
Volcanoes can principally be found in three tectonic environments.
[[Image:Tectonic_plate_boundaries.png|thumb|350px|Hotspot and types of plate boundaries.]]
=====Constructive plate margins=====
These are by far the most common volcanoes on the Earth. They are also the least frequently seen, because most of their activity takes place beneath the surface of the oceans. Along the whole of the [[oceanic ridge]] system are irregularly spaced surface eruptions, and more frequent sub-surface intrusions without surface expression. The large majority of these are only known about at surface because of earthquakes as part of the eruptions/ intrusions, or occasionally if passing shipping happens to notice unusually high water temperatures or chemical precipitates in the seawater. In a few places [[oceanic ridge]] activity has lead to the volcanoes coming up to the surface - [[Saint Helena]] and [[Tristan da Cunha]] in the [[Atlantic Ocean]]; the [[Galapagos Islands]] in the [[Pacific Ocean]], allowing them to be studied in some detail. But most activity takes place in considerable water depths. Iceland is also on a ridge, but has different characteristics than a simple volcano.
It could be argued that the volcanoes of the [[Great Rift Valley]] system of East Africa are modified constructive margin volcanoes. However the modifications caused by the presence of thick continental crust are very substantial, and the magmas produced are very different from the typically very homogenous MORB (Mid-Ocean Ridge Basalt) that makes up the huge majority of constructive margin volcanoes.
=====Destructive plate margins=====
These are the most visible and well-known types of volcanoes on earth, forming above the [[subduction zones]] where (oceanic) plates dive into the Earth to their destruction. Their magmas are typically "calc-alkaline" as a result of their origins in the upper parts of altered ocean plate materials, mixed with sediments, and processed through variable thicknesses of more-or-less continental crust. Unsurprisingly, their compositions are much more varied than at constructive margins.
=====Hotspot situations=====
[[Image:Lava_flow_at_Krafla,_1984.jpg|thumb|right|250px|[[1984]] Eruption at [[Krafla]], [[Iceland]]]]
[[Hotspot (geology)|Hotspots]] were originally a catch-all for volcanoes that didn't fit into one of the above two categories, but these days this refers to a more specific circumstance - where an isolated [[Mantle plume|plume]] of hot mantle material intersects the underside of crust ([[oceanic crust|oceanic]] or [[continental crust|continental]]), leading to a volcanic center that is not obviously connected with a plate margin. The classic example is the Hawaiian chain of volcanoes and seamounts; Yellowstone is cited as another classic example, in this case the intersection is with the underside of continental crust. Iceland is sometimes cited as yet a third classical example, but complicated by the coincidence of a hotspot intersecting an [[oceanic ridge]] constructive margin.
There are debates about the simple "hotspot" concept, since theorists cannot agree on whether the "hot mantle plumes" originate in the upper mantle or in the lower mantle. Meanwhile, field geologists and petrologists see considerable variation in the detailed chemistry of one hotspot's magmas versus a second hotspot's magmas. On the third hand, high-resolution [[seismology]] of different hotspots is yielding different pictures of the deep sub-structure of [[Hawaii]] versus [[Iceland]]. There is no detailed consensus about how to interpret these varied results, and it seems plausible that eventually several different sub-types of hotspots will be identified.
===Predicting eruptions===
Science has not yet been able to predict with absolute certainty when a volcanic eruption will take place, but significant progress in judging when one is probable has been made in recent time.
[[image:sthelens3.jpg|thumb|right|200px|[[Mount St. Helens]] erupted explosively on [[May 18]], [[1980]] at 8:32 a.m. PDT]]
Volcanologists use the following to forecast eruptions.
====''Seismicity''====
Seismic activity (small earthquakes and tremors) always occurs as volcanoes awaken and prepare to erupt. Some volcanoes normally have continuing low-level seismic activity, but an increase can signify an eruption. The types of earthquakes that occur and where they start and end are also key signs. Volcanic seismicity has three major forms: short-period earthquakes, long-period earthquakes, and [[harmonic tremor]].
*Short-period earthquakes are like normal fault-related earthquakes. They are related to the fracturing of brittle rock as the magma forces its way upward. These short-period earthquakes signify the growth of a magma body near the surface.
*Long-period earthquakes are believed to indicate increased gas pressure in a volcano's "plumbing system." They are similar to the clanging sometimes heard in your home's plumbing system. These oscillations are the equivalent of acoustic vibrations in a chamber, in the context of magma chambers within the volcanic dome.
*Harmonic tremor occurs when there is sustained movement of magma below the surface.
Patterns of seismicity are complex and often difficult to interpret.
However, increasing activity is very worrisome, especially if long-period events become dominant and episodes of harmonic tremor appear.
In December 2000, scientists at the [[National Center for Prevention of Disasters]] in [[Mexico City]] predicted an eruption within two days from [[Popocatépetl]], on the outskirts of Mexico City. Their prediction used research done by Dr. Bernard Chouet, a Swiss vulacanologist working at the [[United States Geological Survey]], into increasing long-period oscillations as an indicator of an imminent eruption. The government evacuated tens of thousands of people. Forty eight hours later, bang on time, the volcano erupted spectacularly. It was Popocatépetl's largest eruption for a thousand years and yet no one was hurt.
====Gas emissions====
[[Image:Pompeii the last day 1.jpg|thumb|The eruption of Vesuvius in Discovery Channel's ''[[Pompeii: The Last Day|Pompeii]]''.]]
As magma nears the surface and its pressure decreases, gases escape.
This process is much like what happens when you open a bottle of soda and carbon dioxide escapes. Sulfur dioxide is one of the main components of volcanic gases, and increasing amounts of it herald the arrival of more and more magma near the surface. For example, on [[May 13]], [[1991]], 500 tonnes of sulfur dioxide were released from [[Mount Pinatubo]] in the [[Philippines]]. On May 28, just two weeks later, sulfur dioxide emissions had increased to 5,000 tonnes, ten times the earlier amount. Mount Pinatubo erupted on [[June 12]], [[1991]]. On several occasions, such as before the Mount Pinatubo eruption, sulfur dioxide emissions have dropped to low levels prior to eruptions. Most scientists believe that this drop in gas levels is caused by the sealing of gas passages by hardened magma. Such an event leads to increased pressure in the volcano's plumbing system and an increased chance of an explosive eruption.
====Ground deformation====
Swelling of the volcano signals that magma has accumulated near the surface. Scientists monitoring an active volcano will often measure the tilt of the slope and track changes in the rate of swelling. An increased rate of swelling, especially if accompanied by an increase in sulfur dioxide emissions and harmonic tremors, is a high probability sign of an impending event.
==Effects of volcanoes==
The concentrations of different volcanic gases can vary considerably from one volcano to the next. [[Water vapor]] is typically the most abundant volcanic gas, followed by [[carbon dioxide]] and [[sulfur dioxide]]. Other principal volcanic gases include [[hydrogen sulfide]], [[hydrogen chloride]], and [[hydrogen fluoride]]. A large number of minor and trace gases are also found in volcanic emissions, for example: [[hydrogen]], [[carbon monoxide]], and volatile metal chlorides.
[[Image:Volcanic injection.jpg|thumb|300px|right|Volcanic "injection"]]
[[Image:Mauna Loa atmospheric transmission.png|thumb|300px|Solar radiation reduction due to volcanic eruptions]]
[[Image:TOMS SO2 time nov03.png|thumb|300px|Sulfur dioxide emissions by [[volcano]]es.]]
Large, explosive volcanic eruptions inject water vapor (H<sub>2</sub>O), carbon dioxide (CO<sub>2</sub>), sulfur dioxide (SO<sub>2</sub>), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 10-20 miles above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H<sub>2</sub>SO<sub>4</sub>), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the Sun back into space and thus cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys [[ozone]] (O<sub>3</sub>). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of [[carbon]] for biogeochemical cycles.
Gas emissions from volcanoes are a natural contributor to [[acid rain]].
Volcanic activity now releases about 130 to 230 teragrams (145 million to 255 million [[short ton]]s) of [[carbon dioxide]] each year.
Volcanic eruptions may inject an [[aerosol]] of particles and chemicals in the [[Earth's atmosphere]]. Large injections may have visual effects and affect global climate through [[climate forcing]].
==Past beliefs==
[[Image:Kircherearthfires.jpg|thumb|Kircher's model of the [[Earth]]'s internal fires, from ''Mundus Subterraneus'']]
Before it was understood that most of the Earth's interior is molten, various explanations existed for volcano behavior. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface.
[[Society of Jesus|Jesuit]] [[Athanasius Kircher]] (1602-1680), witnessed eruptions of [[Aetna]] and [[Stromboli]], then visited the crater of [[Vesuvius]] and published his view of an Earth with a central fire connected to numerous others caused by the burning of [[sulfur]], [[bitumen]] and [[coal]].
==See also==
*[[Iceland hotspot]]
*[[Prehistoric volcano]]
*[[List of volcanoes]]
*[[List of famous volcanic eruption deaths]]
*[[Volcanic Explosivity Index]]
*[[Black smoker]] (deep sea vent)
*[[Magma]]
*[[Lava]]
*[[Pacific Ring of Fire]]
*[[Geomorphology]]
*[[Earth science]]
*[[Io (moon)|Io]]
*[[Triton (moon)]]
*[[Tsunami]]
*[[Top 10 most deadly Volcanic Eruptions]]
==References==
*Buetow K. ''The Australian Cattle Dog : An Owner's Guide to a Happy Healthy Pet'' ISBN 0876054467.
*Macdonald, Gordon A., and Agatin T. Abbott. (1970). <cite>Volcanoes in the Sea</cite>. University of Hawaii Press, Honolulu. 441 p.
*Ollier, Cliff. (1988). <cite>Volcanoes</cite>. Basil Blackwell, Oxford, UK, ISBN 0-631-15664-X (hardback), ISBN 0-631-15977-0 (paperback).
==Further reading==
* Sigurdsson, Haraldur, ed. (1999) ''Encyclopedia of Volcanoes''. Academic Press. ISBN 012643140X. This is a reference aimed at geologists, but many articles are accessible to non-professionals.
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==External links==
Image:ACDRedChampion.jpg|Champion Red face markings
{{pic}}
Image:Acd_a_frame.jpg|A young ACD at the top of a dog agility A-frame
*[http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html Glossary of Volcanic Terms from USGS]
Image:Acd_jump_chute.jpg|An ACD in a jump chute, practicing [[dog agility]]
*[http://volcano.und.nodak.edu/vwdocs/glossary.html Volcanic and Geologic Terms] from [http://volcano.und.nodak.edu/ Volcano World]
Image:Stripepuppy.jpg|Puppy with blue coat color
*[http://news.bbc.co.uk/1/hi/sci/tech/3183047.stm Television program (BBC) on the prediction of Popocatepetl's 2000 eruption]
</gallery>
*[http://www.volcano.si.edu Smithsonian Global Volcanism Program]
*[http://www.geology.sdsu.edu/how_volcanoes_work Explore the geologic causes of an eruption]
*[http://science.howstuffworks.com/volcano.htm/printable ''How Volcanoes Work'' by Tom Harris]
*[http://www.geology.sdsu.edu/how_volcanoes_work/ How Volcanoes Work] - Educational resource on the science and processes behind volcanoes, intended for university students of geology, volcanology and teachers of earth science.
*[http://www.geonet.org.nz/volcanocam.html '''Volcano Cam''' Geonet's live pictures of 4 of New Zealand's volcanoes]
[[Category:LandformsDog breeds]]
[[Category:Plate tectonics]]
[[Category:Volcanology]]
[[Category:Volcanoes|*]]
[[Category:Geological hazards]]
[[Category:Climate forcing agents]]
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