Volcano – a mountain that spits fire? Volcano basics.

What is a volcano? If you ask kids all over the world to do a drawing, you will get quite similar results. A steep mountain with “fire” erupting from the top and sometimes lava streams running down it´s flanks.

Kids drawing found on the net

Kids drawing found on the net

Let us deal with the very basics about volcanoes. I know it is much more complicated but everyone needs to start with basics first in order to start to understand. This is part of a talk I held at the Ars Electronca Center on April 3rd to explain the origin of volcanism, how volcanoes work and why each of them is different. ( http://www.aec.at/center/2014/03/20/dsl-vulkane-2014/ )

Image Wikimedia Commons

Image Wikimedia Commons

By definition a volcano is a geologic structure formed by magma welling to the surface. The molten rock are called magma as long as it is still below the ground. As soon as the material reached the surface, it is called lava.
The name volcano originates from the Italian Island Vulcano on which the ancient Romans thought their God of Fire Vulcanus would have his smithy.

Volcanism is not unique to earth. Scientists were surprised when the Voyager probe sent back images from Jupiters moon Io and they noticed they saw an erupting volcano in the image. We now know the Mares on the moon are formed by ancient lava. Just a few weeks ago new facts about very recently erupting volcanoes on Venus and why the volcanoes there are so different, made the news. The highest mountain of the Solar Syste, Olympus Mons on Mars is a volcano. Cryovolcanism was detected on several moons like Saturn`s Titan and Enceladus or Neptun`s Triton.

Jupiter´s moon Io

Jupiter´s moon Io

Many scientists think nowadays, that life might have come into existence close to submarine hydrothermal vents. So volcanism might be the culprit for causing life. As long as volcanism seems to exist on so many bodies in the solar system it might very well exist on countless exoplanets and their moons. In case the assumption that life first started on Earth, close to hydrothermal vents, is correct, this heightens the chance to, some day, find life elsewhere in the Universe.

Each volcano is different, The type of lava it produces is different. The shape and height and of course the location is different. In order to start understanding lets take a closer look at our home planet itself.

Below the hard surface of the earth there is the mantle made of liquid material. Please note that the proportion of the surface compared to the rest is not like an oranges skin to the orange but much more like an apples skin compared to the rest of the fruit. So we are effectively walking on rather thin ground.
The layer forming the surface is thicker below continents and much less thick below the oceans. The very first pieces of earth which hardened billions of years ago are called cratons and those are naturally the parts were the crust is thickest.

Lets start why volcanoes exist on Earth. There are basically 2 types of volcanoes. Volcanoes caused by subduction of tectonic plates and volcanoes caused by hotspots. (Other categorizations will follow later.)

We already took a look at the mantle. Scientists found that there are plumes rising upward inside this mantle.

Image from http://faculty.weber.edu/bdattilo/shknbk/notes/htsptplm.htm where you can also find a short discussion of hotspots and mantle plumes.

Image from http://faculty.weber.edu/bdattilo/shknbk/notes/htsptplm.htm where you can also find a short discussion of hotspots and mantle plumes.

Above such a plume you may find volcanoes. Hotspot volcanoes are typically shield volcanoes. Flat mountains with a broad base, not like the steep cones kids like to draw.
As long as the crust moves above the hotspot, island chains are being formed, like the Hawaiian Islands and the Midway Island for example.
The Canary Islands might be due to hotspot volcanism too, but some scientists I talked to when I was there last year, claimed it is probably more complicated.

Nasa. Image of the day

Nasa. Photo of the year 2014.

Some examples for shield volcanoes:
Fernandina Island Galapagos Island

Wikimedia Commons

Wikimedia Commons

Mauna Kea, Hawaai USA

Olympus Mons, Mars

Image Nasa

Image Nasa

Note that Mars has no subduction volcanism as long as it has no moving tectonic plates. )

Subduction zone volcanoes
The concept of tectonic plates and continental drif is fairly new in science. Abraham Ortelius speculated why Afrika´s western coast fits so well to South Amerika´s eastern coast in 1596.

Image Wikimedia Commons

Antonio Snider-Pellegrini’s Illustration of the closed and opened Atlantic Ocean (1858). Image Wikimedia Commons

In 1912 German Scientist Alfred Wegener came up with the idea of continental drift. During his lifetime he was a well known meteorologist but his new idea was debated. In the 1950ies scientist started seeing Alfred Wegeners point and only in the 1970ies the fact of continental drift and tectonic plates became generally accepted and commonly known. Chryphia found a neat movie on this subject.
Paleo Geographic from http://sos.noaa.gov/What_is_SOS/index.html
The illustration shows the plates and where the subduction zones are situated. Subduction happens around the famous Pacific rings of fire. But not only there. Italys active volcanoes are caused because the African plate dips below the Eurasian plate and starts melting. Along the main subduction zones of North and South America you will find chains of volcanoes around 100km inland. The volcanoes there “reuse” material which had been forming a crust millions of years ago. Water is been pulled down along with the sediments. A mixture of water and rock always makes a volcano rather explosive. Subduction volcanoes are typically stratovolcanoes with the well known shape we all associate with the term volcano.


Illustration of a volcano.

Illustration of a volcano.

Examples for strato volcanoes:
Colima, Mexico (Photo by Christian Villicaña, Flickr)

Hassan Dagi, Turkey

Karymsky, Kamtchaka, Russia

Wikimedia Commons

Wikimedia Commons

Parinacota Volcano, Chile

Wikimedia Commons

Wikimedia Commons

ps: There will be more parts of volcano basics which are written to  help newbies understand the very basics of volcanism and why we are so fascinated by the topic.


246 thoughts on “Volcano – a mountain that spits fire? Volcano basics.

  1. no. 5 – Iamelele volcano (also called Iamalele or Iamalele-Fagululu)? don’t think so, but will put it out there anyway.

  2. No 4: Walter Alvarez

    K-T is the Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary. Alvarez was part of a team that identified the boundary; he went on to study Roman volcanics; and, ended up at the Lamont-Doherty Geological Observatory of Columbia University.


    • or if you meander through Lamont-Doherty Geological Observatory website, you find the Heezen and Tharp Fracture Zones and the Pitman Fracture Zone so two faults for the price on one 🙂

          • The 535 Krakatoa thing doesn’t really have any geological evidence that supports it from what I have seen.

            Just supposition based off of kings lists and folklore.

            It makes a nice story, but without tangible evidence its not worth that much.

            • Isnt’ that the approximate time period of the Llopango eruption? Llopango was a huge eruption, it should be a much more well-known eruption in modern history, but I get the impression that due to the lack of eurocentrism, it seems to be forgotten.

            • “Lack of Eurocentrism?”

              Might be better phrased as

              “Lack of interest due to Eurocentrism.”

              At the time, we didn’t really have anyone stomping around over here other than a few Mayan and Mayan derived people. Their focus was principally on surviving whatever came their way. Be it exploding mountains or marauding tribes. Punctuated by hurricanes and other tropical oddities.

            • A bit of Americocentrism there… 🙂
              We had heards of explorers and mapmakers ambling about the world then. Some where Greek christians from the East Roman Empire, and some where arabic merchants. Quite a lot of their travelling journals survive to this date. A few centuries later the Arabic explorers really exploded unto the world in the form of the Moorish Empire. We always forget how enlightened they where while we Europeans mainly had problems with understanding the concept of washing ourselves. 🙂

            • Ya know, there is a saying that one “aw shit” can eliminate scores of “attaboys”

              Torching the Library of Alexander sort of counts as one seriously massive “aw shit”

              I don’t care how “enlightened” someone paints themselves, the wanton destruction of historical information is the ultimate in reprehensible. And yes, the Spanish are just as guilty. Many parts of Central American culture have been forever lost due to the same misogynist mentality.

    • Vitrified hill forts in a line from Edinburgh to South Wales, AD 565 and St Columba moving from Ireland to Scotland and erecting a Celtic Cross with a falling star in the centre, legends of dragons around the stories of King Arthur (that well-known Hungarian Roman horseman and war leader) and the Dark Ages, so called perhaps because the sun was so dark, as well as the disappearance of civilization for a while, would seem to suggest that cosmic events were also happening around this time. Timescales are a bit vague though.

    • 03.05.2014 05:49:35 65.104 -16.394 2.8 km 3.2 90.05 1.9 km NNW of Herðubreiðartögl
      This looks interesting certainly very on going. Magma movement rather than just rifting I feel.

    • It’s not really a line… more of a collection of faults in a step-over fault configuration. To the north is a graben structure where it interfaces with the Wabash and Illinois fault systems. Some sources have called this a failed triple junction. (The rift failed, so it failed)

    • Sissel has allready tried that one, it is not that far off, so do not go into a completely different direction with it.

  3. 3 Jemez Mountains volcanic complex, New Mexico, including the Valles Caldera (or Jemez Caldera) with the Tent Rocks and lava domes.

    • Serendipity, it seems like Herdubreid got a jump on me.
      I was going to publish an article yesterday that she is the fourth likeliest volcano to erupt in Iceland.
      I am not sure if this is the run up yet, but the run up to an eruption is most likely on the way.
      We have to wait on IMOs call on this.

  4. Sadly, I must report that the consumption of Carlsberg beer does not assist with riddle solving.

  5. Do not worry, I am just moving the riddles to the new post that will be published in a few minutes.

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