The odds are quite expert that you have never seen magma – apart from photographs or mayhap on a nature testify on boob tube. Withal, depending on where you live or have traveled you may very well accept interacted with its byproducts without even knowing it (for example, when you walk on a volcanic landscape, or on a granite floor).
Just put, magma is liquefied, molten (which, in this case, is synonymous with melted) rock which exists beneath the surface of the planet. With just a few exceptions (lightning, which can actually exist hotter than the surface of the dominicus, being the most well known), magma is the hottest naturally occurring thing that ever reaches the surface of the earth in whatsoever form. Depending on its type and composition, magma can range from 700 degrees Celsius (1300 degrees Fahrenheit) upwards to 1250 degrees Celsius (almost 2300 degrees Fahrenheit). In the earth’due south distant past, it is believed that magma reached a temperature of over 1600 degrees Celsius (over 3000 degrees Fahrenheit).
Magma is merely found beneath the earth’due south surface – and in recent years testify has been institute which suggests that it may exist, or take existed in the distant past, on other planets – and only in specific areas beneath the surface. When magma comes to the globe’due south surface – usually, but not always, as the consequence of a volcanic eruption – information technology is called lava. When lava cools it forms volcanic, or extrusive, igneous rock which accounts for about fifteen% of the surface expanse of the earth. It should be noted that non all magma makes it to the surface of the globe every bit lava; a great deal of magma cools before it reaches the surface, in the upper layers of the earth’south crust – in which case it forms what is called plutonic, or intrusive, igneous stone.
While people have certainly known about (and even, in some cases, worshiped) volcanoes for thousands of years, and had at to the lowest degree a general idea nearly lava for several centuries, a true understanding of magma – both what it is and where it actually comes from – is a relatively recent thing in human history. Even less than a century ago the technology did non be to actually measure out the heat and composition of magma, much less empathise how and where it was formed. Equally technology continues to accelerate more is understood almost magma – but in that location is still a lot to learn.
Where Does Magma Come From?
Opposite to what many people think, magma does not come from the center of the earth. In order to understand where magma actually does come from – and how it is formed – it is necessary to understand a bit well-nigh the basic structure of the globe itself (the stuff most of usa daydreamed through when it was being taught to usa in high school).
The earth has four basic levels: the inner core, the outer core, the drape, and the crust. The inner core is believed to be comprised primarily of solid atomic number 26 and nickel and is the hottest of all the levels, at over 5500 degrees C (near 10,000 F). The outer core is made upward of generally liquefied iron and nickel and is a chip ‘cooler’, at effectually 4400 degrees C (8000 F). The mantle is divided into an upper and lower part (called the lithosphere and the asthenosphere respectively); the lower part of the mantle is comprised of much the same materials equally the outer cadre, has a plastic-similar liquid consistency and is only slightly cooler, while the upper drapery is fabricated of very dense solid rock and is considerably cooler – usually betwixt 300 and 500 degrees C (most 600 to 900 F). The crust is the top layer of the earth; the lower portions of the crust will range from 200 to 400 degrees C (about 350 to 750 F) while the upper part of the chaff is the surface of the planet where all known life – including humans – exist.
Simply put, magma is formed when solid stone and other constituents in the upper pall or lower crust melts as the result of heat and pressure exerted upon them over a considerable length of time by a number of factors including ‘hotspots’, which are areas where the much hotter lower mantle effectively superheats the cooler material of the upper drapery and lower crust above and melts them. There is no evidence to suggest that magma is produced in any part of the earth other than the lower crust and upper mantle. While the lower mantle and outer core are both comprised of extremely hot liquefied elements, their chemic limerick is unlike from the substance that we normally call magma.
Magma is not evenly or generally distributed at any level within the earth, and is non found ‘everywhere’ at a certain depth; specific conditions must be present for the product of magma to occur. Once magma has been formed, it is forced upward into and through the crust by pressure from below – traveling through cracks in the existing solid stone – and will frequently melt some of the rock information technology passes, creating more magma. Eventually, information technology will either cool beneath the globe’due south surface and turn dorsum into rock or be stored in its liquefied form in ‘magma chambers’ (discussed below) which are found at varying depths beneath the surface of the crust, oft straight beneath volcanoes.
What is Magma Made Of?
Generally speaking, magma has a high silica content – in most cases over l per centum – then silica can be said to form the base of magma. Silica (silicon dioxide) is one of the virtually common naturally occurring elements and is a major component of sand, as well every bit quartz. The basic types of magma (discussed in depth below) are classified based in large part on their silica content.
Other components of magma volition normally include oxygen (as a constituent of silica), iron, aluminum, magnesium, calcium, potassium, phosphorus, and sodium. About magma will also include relatively minor amounts of other gasses that accept dissolved which can include h2o vapor, sulfur, and carbon dioxide amidst others.
The silica and other mineral content in magma will generally determine both the temperature and the viscosity of the liquid, and therefore both its thickness and the rate at which it flows. Magma with a very loftier silica content volition normally exist cooler and have a higher viscosity (in other words, be thicker) and therefore slower moving than magma with low silica content.
Bones Types of Magma
While they all have a number of things in mutual (for example, they’re hot!), not all magmas are the aforementioned, and there are different classifications used by geologists and other scientists to classify them. The different types of magma are by and large determined by the chemical composition, which is based on what materials have been melted or otherwise incorporated into the magma. This chemical composition – and peculiarly the mineral and gas content – will determine the temperature range of the magma, its viscosity, and rate of menstruum, and its general ‘behavior’.
The exact temperature of the different types of magma is extremely difficult to determine, in big part due to the danger and difficulty involved in taking exact measurements. As tin can be seen below, the temperatures of the various magmas listed are normally expressed as ranges and are determined in large part by estimates based on the magma’s behavior as well as their ‘eruption temperatures’. It is not uncommon for the basic types of magma discussed below to overlap or to switch back and forth between ‘types’ due to a number of possible factors (temperature, mineral content, etc.) during its existence.
Also frequently referred to as Malfic, Basaltic magmas are the hottest of all the magma types currently in existence, with temperatures ranging from yard to 1200 degrees C (about 1800 to 2200 F). The silica content of Basaltic magmas is betwixt 45 and 55 percent, which is lower than any other magma type. Because of the relatively low silica content and high temperature, Basaltic magmas take the everyman viscosity of all magma types, meaning that they are ‘thinner’ and more free-flowing – although it is still commonly between xv,000 and 100,000 times less fluid (or free-flowing) than water.
Basaltic magmas have relatively loftier fe, calcium, and magnesium content (in some cases equally much as 19 percent) just are generally low in potassium and sodium. Due to their high temperature (and the respective relatively low corporeality of trapped gasses), Basaltic magmas are considered to exist ‘gentle’ when forced to the surface in the form of a volcanic eruption. Although in its lava-course information technology can be quite fast-moving and cover a considerable amount of territory in a relatively curt time, eruptions of Basaltic magmas/lava are less explosive than the other types of magmas. When Basaltic magmas cool and harden, they form basaltic and malfic igneous rock.
Basaltic magmas more often than not occur at or near divergent or convergent tectonic plate boundaries and hot spots, and a meaning percentage of Basaltic magmas/lava eruptions take place below the surface of the oceans. Volcanic eruptions in the US State of Hawaii are an example of Basaltic eruptions on land. It is believed in nigh scientific circles that Basaltic magmas – and periodic eruptions (in the past or present) – are present on the moon, Venus, Mars, the asteroid Vesta, and Io (the third largest of Jupiter’south moons).
Andesitic magmas are also sometimes referred to as Intermediate, due to the fact that they autumn in between Basaltic and Felsic (discussed below) magmas in terms of temperature and viscosity. Andesitic magmas volition unremarkably accept temperatures ranging from 800 to 1000 degrees C (about 1500 to 1800 F) and a silica content that will range from 55 to 65 percent. Equally a result of the lower temperature and college silica content, Andesitic magmas take a higher viscosity than Basaltic and are, therefore ‘thicker’ and slower moving.
Andesitic magmas take what has generally referred to as intermediate (hence the nickname) levels of magnesium, iron, potassium, calcium, and sodium – meaning that, again, they fall in betwixt Basaltic and Felsic. As they are libation and slower moving than Basaltic, Andesitic magmas have a higher volume of gasses – especially sulfur and carbon dioxide – trapped within them which, in turn, aid to make them significantly more volatile. They are by and large considered to be moderately explosive types of magma. Andesitic magmas frequently puddle in magma chambers in the earth’s crust, where they volition either cool and form rock or build up pressure.
Andesitic magmas are mostly establish around convergent plate boundaries and well-nigh island arcs including the Aleutians off the Alaskan coast and the Philippine Islands in the Western Pacific Ocean. Andesitic magmas can be released to the surface of the earth by earthquakes (many of which have place beneath the surface of the bounding main in what are known as ‘reverse fault’ areas), besides as via volcanic eruptions such as the May eighteenthursday, 1980 eruption of Mount St. Helens in the US Country of Washington. When it cools, Andesitic magmas form andesite igneous rock, which is named after the Andes Mountain range in South America.
Felsic magmas are the ‘coolest’ of all magma types, normally ranging from nigh 650 to 800 degrees C (roughly 1200 to 1500 F) and also accept the highest silica content, coming in at anywhere between 65 and 75 percent. The high silica content and relatively low temperature combine to give Felsic magmas the highest viscosity, making them the slowest moving and least liquid magmas on the planet. They tend to be quite low in fe, calcium and magnesium content, and quite high in potassium and sodium – effectively the reverse of Basaltic magmas. They are besides high in gas content – especially water vapor (H2O) and carbon dioxide (C02); sulfur, chlorine and fluorine gas may also be present.
There are two master types of Felsic magma: Rhyolitic and Dacitic. Dacitic magma is at the upper terminate when it comes to both silica content and temperature, and is closer in temperature and composition to Andesitic magmas, while Rhyolitic magma tends to be the cooler and thicker of the ii. Both magmas are extremely volatile; volcanic eruptions of these types of magma can be highly explosive due in large part to the high gas content and can rip solids from the sides of the volcano. When these magmas cool, they form felsic igneous rocks, including pumice, ryolite and granite.
Felsic magmas seem to be formed when parts of the globe’s chaff melt in conjunction with seawater – which serves to lower the temperature of the magma immediately following the melt – usually about continental rifts and hotspots in the continental chaff. Felsic magmas tin can often be found in huge calderas, which are cauldron-shaped hollows that form at or near the earth’s surface, usually following the emptying of a magma chamber or reservoir via a volcanic eruption. The most famous caldera in the continental U.s. tin can exist plant at Yellowstone National Park.
Ultramafic (too sometimes called komatiite or picritic) magmas no longer exist today, probably condign extinct right around the time the earth’s crust had cooled sufficiently following its initial creation to allow the ancestry of life to develop on the planet – somewhere in the vicinity of 2.5 to 3.five billion years ago. Based on the bear witness found in ultramafic rock samples, Ultramafic magmas were very depression in silica content (probably effectually 40 percent or lower) and very high in atomic number 26, magnesium, and calcium (perhaps running as high as 32 percent). They were likewise quite hot – often reaching a temperature of 1600 degrees C (nearly 3000 F). Due to its chemical limerick and farthermost heat, Ultramafic magmas had an extremely low viscosity – far lower than any of the magmas establish on world today – significant that they were probably able to motility very apace.
A considerable percentage of the earth’due south upper curtain is believed to be composed of ultramafic rock, leading some experts to believe that this was, at one fourth dimension, the most common type of magma on the planet. Today, both the upper mantle and the lower chaff have cooled to a signal where conditions are such that information technology is impossible for Ultramafic magmas to develop. It is believed that Ultramafic magma may currently exist nowadays on Io – the third largest of Jupiter’due south moons – and on the planet Mercury.
Magma chambers are large pools that exist beneath the surface of the earth and which – non surprisingly – concur magma. Magma travels up through and across the world’s mantle and crust through cracks in the existing rock; when information technology can no longer find a way up or across, over fourth dimension it will pool and create a magma bedchamber.
While a magma chamber can exist almost anywhere in the earth’s upper drapery or chaff, they are very hard to detect at smashing depths fifty-fifty with the most modern equipment, and so most of the currently known magma chambers are between ane and 10 kilometers (a little over half a mile to roughly six miles) beneath the world’s surface. Many of the world’southward volcanoes – both below the oceans and on land – are situated well-nigh or directly above a magma chamber. In some cases, a large magma chamber may exist below a smaller bedroom or magma reservoir which, in plough, might exist beneath a volcano.
Any of the existing types of magma tin can puddle in a magma bedchamber and once it has pooled, it comes nether great pressure and will usually begin to absurd. Depending on the rate of cooling, the number of trapped gasses in the magma, and several other factors, the magma will either form intrusive igneous stone – such as granite and diorite – or information technology will fracture the stone around it and continue its journey upwardly, often resulting in a volcanic eruption. During an eruption, the rock surrounding the magma bedchamber will unremarkably collapse and, in some cases, will form a depression at the surface which can issue in the formation of a caldera (discussed higher up).
A Few Words About Lava
As has been stated before, lava is basically what magma becomes when (and if) information technology reaches the surface of the earth. While lava volition sometimes pick up a few extra components such as some sold rock or sediment forth the way, the composition of lava will normally exist substantially the same every bit the magma which forms its base of operations.
There are four basic types of lava (and their names, not surprisingly, stand for with the names of the major magma types): Basaltic, Andesitic, Dacitic and Rhyolitic (the final two beingness the names of the major Felsic magmas). The type of lava volition decide both the explosiveness of its entry to the surface (force of eruption) and its catamenia. Once it has cooled and hardened, it will besides assistance to make up one’s mind the brand-up of the volcano – both inside and outside – as well every bit the surrounding land area.
In most cases, Dacitic and Rhyolitic lavas will produce the most explosive eruptions – in some rare instances literally bravado the tops off of volcanic mountains – and the slowest flow; in some cases then tedious that they will actually seal off the passageways and the opening out of which it is flowing, cooling faster than it can catamenia. Andesitic lava will normally exist thinner and less explosive – and therefore period further – but an eruption tin still pack one hell of a wallop. An andesitic lava flow is most commonly found in the Andes Mountains in S America (later on which it is named) and in eruptions well-nigh island arcs.
Basaltic lava is by far the most mutual type of lava constitute on earth today. It is both the hottest of all lava types and produces the fastest and about sustained flows – due primarily to the fact that, every bit the hottest, information technology takes the longest to cool and so will menses the farthest. Basaltic lava eruptions occur both beneath the surface of the oceans and on dry land. Eruptions that occur on the sea flooring are often the result of ‘hot spots’ in the earth’s crust; over the course of millions of years and countless lava flows, islands formed primarily of cooled lava can somewhen rising above the surface of the ocean. The US Country of Hawaii was created in this mode over the course of an estimated 70 1000000 years, and today the islands are domicile to some of the nearly active (and spectacular) Basaltic volcanoes in the earth. As a result of a continuing lava catamenia, several of the Hawaiian Islands continue to grow in landmass with the passing years.
There are three bones types of Basaltic lava: Pillow, Pahoehoe, and A’a.
Pillow lava is mostly believed to be the virtually mutual blazon of lava. Pillow lava is formed every bit a result of the subaqueous extrusion of Basaltic lava; in other words, when a volcanic or fissure eruption occurs nether water or water ice. The temperature difference between the h2o and lava causes the outer layer of the lava to cool quite quickly, and form rounded tubular masses of lava that volition resemble a pillow after it cools rather than a continuous lava flow. As more lava erupts, more pillows are formed. Pillow lava volition usually be anywhere from iii to 5 feet in bore and can be institute in many places on the ocean floor, as well as beneath glaciers and in ‘pillow formations’ on dry land. Pillow lava that is found on land is usually a good indication that the surface area where information technology is located was at one time beneath the surface of the body of water.
Mostly considered to exist the 2d nearly mutual type of Basaltic lava, Pahoehoe lava flows are what virtually people tend to associate with volcanic eruptions. Pahoehoe lava is both the hottest and most liquid (and, consequently, the fastest moving) type of lava. Pahoehoe lava will normally take an eruptive temperature of around 1100 degrees C (about 2000 F) and volition mostly have a smooth, continuous period at the start that volition form landscapes that can range from more often than not smooth and level near the mouth of the volcano to beautiful and bazaar designs that accept been said to resemble stone sculptures further away. In some cases, Pahoehoe lava will form tunnels as it flows that volition comport the lava all the fashion to the sea where – in the case of the Hawaiian and some other island chains – will cause the island to increase in size over time. In one case the lava flow ceases, the tunnels will sometimes become lava caves.
Pronounced ‘ah-ah’ and significant ‘stony with rough lava’ in Hawaiian, A’a lava is very closely related to Pahoehoe in its composition; in fact, Pahoehoe that travels over land for a particularly long altitude will sometimes go A’a lava. It is cooler and more pasty (thicker) than Pahoehoe and consequently flows at a slower charge per unit. When it cools (which can take weeks or even years), A’a lava tends to form a very rough, jagged, and ‘spiny’ mural of rock that can be extremely difficult to walk across. Examples of cooled A’a lava can exist institute in abundance on the Big Island of Hawaii.
Lisa has a Bachelor’s of Scientific discipline in Communication Arts. She is an experienced blogger who enjoys researching interesting facts, ideas, products, and other compelling concepts. In addition to writing, she likes photography and Photoshop.
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