Beginner’s Guide To Volcanoes
I assume you’re here to read about what goes into volcanic eruptions? or you want to know, how and what causes earthquakes? Or are earthquakes and volcanism (the process of volcanic eruptions) interconnected? There are many questions which arise when we listen to the word volcano. The questions which have intrigued your curiosity time and again, let me tell you that You’re at the right place so, today i will tell you all these answers.
Reading this article will help you get the knowledge of volcanoes and its history. How the religious people tie it with the wrath of God. There are Some of the ancient Greek mythology regarding volcanoes. In some of the Greek mythologies, the flow of lava is considered as the huge fire from the god’s forge.
The word “Volcano” is derived from “Vulcano”. Aeolian Island is an island in Italy that is volcanic, whose name in turn comes from Vulcan, the god of fire in Roman mythology. Around a century ago, the people who were living in this area used to believe that Volcano was the chimney of the forge of Vulcan.
What Is A Volcano?
Your ears are tired of listening to the word Volcano but your mind doesn’t recognize it. No worries, I’m here to teach you, let’s take an example of Pepsi. Pepsi contains carbon dioxide gas and when we shake it, the gas inside the bottle is disturbed, this increases the kinetic energy of the molecules, and as a result then they want to escape the bottle. Similarly, the gases under the earth’s crust want to escape as a result of movement of tectonic plates, we get to see volcanic eruptions.
If we look up its definition then it would be like;“the escaping of gases, magma, and volcanic ash from the Earth’s crust is known as Volcano and The study of volcanoes is called Volcanology”.
You must’ve heard the word magma when it comes to discussing the lava you might have wondered, what is Magma? What has it to do with the lava? Magma is the molten rocks in the earth’s crust in liquid form. In the Earth’s crust, below the volcano, when the tectonic plates create a movement which results in the rising of magma through the crack, called fissure. When this magma erupts onto the Earth’s surface it is called Lava.
When Magma rises or blasts, its pressure decreases and it allows the gases to form bubbles. The behavior of lava, when it reaches the earth’s surface, depends on gas content and chemical composition. Magma contains silica which is responsible for it’s thickness and thinness.
Lava which contains a low amount of silica has a low amount of viscosity and it flows freely, it allows any gas bubbles to escape promptly, whereas the lava which has a high amount of silica and a high amount of viscosity resist flowing freely and its gases are trapped which cannot escape gradually. The temperature of the lava when it initially comes out of the earth’s crust is about 1300° F and 2,200° F (700° and 1,200° C). There were some tales about the lava in the ancient time which is further described in the next caption.
History Of Volcanoes
Human beings in ancient times were very inquisitive of the significance and behavior of Volcanoes. The giant fire-breathing mountains were very scary and awful when they spewed noxious fumes and flaming rocks. Some people who belonged to the early civilization were particularly located in an area where vigorous tectonic activity usually happened. The distant predecessors had plenty of opportunity to observe and reflect on Volcanic phenomena.
However, the ancient inhabitants of vast alluvial plains of the Nile, Tigris, Euphrates, and Indus Rivers had little acquaintance with Volcanoes. While the citizens of ancient Greek and Rome including Israelites who were living near the junction of tectonic plates were familiar with Volcanism. These civilizations explanations of volcanic phenomena were mythological, philosophical, or naively scientific in nature.
Ancient People used to interpret volcanism in mythological terms. Let’s take an example; The prominent Ancient Roman poet and writer, whose name was Virgil (70–19 B.C), mentioned in his book “Epic Aeneid” about the graphic description of the eruption of Mount Etna which is the great volcano of Sicily Italy.
In his book “Epic Aeneid”, Virgil was describing terrifying crashes, black clouds smoking with pitch-black eddies or whirl, glowing ashes balls of flame licking the stars, and the violent spewing of molten rocks which were boiling up from the depth, so Virgil linked these phenomena to the tale about the giant Enceladus (Typhon to the Greeks) being injured by a thunder strike of Jupiter and then dropped it down under the mass of mount Etna.
Whenever the giant changed the position, Virgil said, the territory moaned, trembled, and veiled the sky in smoke. Virgil also located the entrance to the underworld in the region of Lago Averno (Lake Avernus) in the volcanic ground known as the Phlegraean Fields (Volcano) in Italy. The lake also occupies a volcanic crater. The ancient Greek denominated Hephaestus (the god of fire in Greek mythology), and subsequently, Roman myths denominated Vulcan, as the God of Fire. The mythological doctrine of volcanism were not only restricted to the primitive people but these myths also exist contemporary in Tonga, Samoa, Indonesia, Iceland, and among the Aztecs of Mexico.
The myths about volcanoes persist in Japan and Hawaii. Many Inhabitants of Hawaiians still visualize eruptions of Kilauea as the manifestation of the Wrath of the goddess Pele, who is said to reside in the caldera (a large volcanic crater) of Kilauea. They envision that the goddess Pele is able to make mountains and islands, melt rocks and demolish forests. Now for you to deeply understand how the volcanic earthquakes happen we will proceed into the next heading.
Volcanic Earthquakes
All Volcanic Phenomenons are not catastrophic,lava may be disastrous and bury a land but soil and vegetables can eventually develop. Volcanic earthquakes are the earthquakes that are produced by some Vibrations which are generated by the disturbance of magma beneath the earth’s surface or some other fluid in the volcano.
The movement of magma disturbs the internal environment and increases the pressure of gasses and lava, due to which the surrounding rock fails to resist the pressure which results in a magnitude of 1–5 and in between earthquakes.
The volcanic earthquakes may have some hazards including cracking the grounds, as well as ground demolition and damage to the man made structures such as building and homes made by humans. The earthquake is classified into two types which are Volcano-tectonic earthquakes and long-period earthquakes. So what are Volcano-tectonic earthquakes? And what are long- period earthquakes? Volcano-tectonic earthquakes are produced by the stress in Magma which changes in the solid rock. The earthquake happens because the rock moves to fill spaces where magma is no longer present. Volcanic-tectonic earthquakes don’t alert about the eruption of the volcano but happens suddenly.
The second type of volcanic earthquake which we discussed earlier is long-period earthquakes which happen when the magma injects into the surrounding rock. These earthquakes are the result of pressure that changes during the unsteady transport of the magma. A lot of earthquakes occur when magma injection is sustained. This kind of activity alerts that a volcano is about to erupt.
Do you know what Seismographs are? Seismographs or Seismometers are the source which scientists which is use to record the signal from these earthquakes. These signals are called volcanic tremor. The volcanic tremor signal had been successfully utilized for the prediction of the 1980 eruption of Mount St. Helens Washington and as well as for the 1991 Pinatubo eruption.
The houses of people who live near the active volcano start shaking and windows rattling from many earthquakes that happen each day when a volcanic eruption occurs. These people are very aware of volcanic earthquakes. For instance the inhabitants of Pompeii Italy daily feel the earthquake caused by volcanism.Similarly in 1991, when the Pinatubo in the Philippines erupted, windows and nerves both were rattling because of the earthquake.
Do you know what was the largest eruption in history? Let me tell you about Mount Tambora which is a stratovolcano in Indonesia. It erupted on the 10th 0f April 1815, which is the largest eruption known on the earth for the past 10000 years. More than 31 cubic miles of Magma erupted from that volcano which collapsed subsequently and formed 6 km wide and 1250m deep Caldera (crater created by the volcano). Furthermore, let’s see how many types of volcanoes there are? You’ll learn ahead in the next heading.
Major Types Of Volcanoes
Now we will look for some of the major types of volcanoes which I briefly discussed below.
Pyroclastic Cones
The first type of volcano we’ll get to know is pyroclastic cones, these are mainly cinder-sized, when they erupt the smithereens cool sufficiently when they are in the air, so they do not weld together when they hit one another. The craters from which the smithereens eject are located in the middle of the cone.
Stratovolcanoes
Here we go for the second type of volcano which is composed of Volcanic rock that types which means that it changes from Basalt (enriched in iron and magnesium) to rhyolite (with very high silica content), but its composition is andesite (between basalt and rhyolite).
There are chances that these volcanoes erupt thousands of times over a lifetime of millions of years. This kind of eruption starts with an explosion of ash while the end with the extrusion of thick lava fluid.
Shield Volcanoes
The shape of this lava is like a large circle shape called dome-shaped mountains which are full of Lava. These volcanoes are mainly composed of Basalt. There are also types of shield volcanoes. The first type of shield volcano is small while another type of shield volcano is large.
Small shield volcanoes form quickly from continuous eruption while the large shield volcano is formed over a duration of 1 million years by thousands of effusive eruptions of lava fluid from the elevation (height) and rift (crack) area.
Submarine Volcanoes
This kind of volcano is mainly coned-shaped seamounts (rises from the ocean floor but that does not reach to the water’s surface). Most of the active volcanoes of submarines are known, which happen at shoal depths beneath the sea. Hydrophones are the device to detect the sound or listen beneath the water.
These hydrophones can also be used for the submarine volcanoes. Hydrophones can detect their location and explosive eruption. The active submarine volcano which erupts 1000 meters beneath the sea level is hard to detect because the water pressure at these depths reduces explosive boiling.
Types Of Volcanic Eruption
You may be surprised to know that there are volcanic types which are categorized according to their shape and size, however, they can also be sorted by their eruptive nature. Eruptions may be of two types as either effusive or explosive. Let’s see, what is the effusive and explosive eruption?
The effusive eruptions are those eruptions in which the outpouring or outflow of the Basaltic Magma (enriched in iron and magnesium) is relatively low in gas content and viscosity, while explosive eruptions have magma, which is more viscous and has a high gas content.
This kind of magma usually shatters into pyroclastic (rapidly moving gases in the form of clouds) smithereens (small pieces) due to combustible gas expansion at the time of the eruption. Subsequently, Volcanic activities and volcanic regions are further classified into six significant kinds which are briefly discussed below.
Icelandic Eruption
This type of volcano is characterized by the effusion of molten basaltic lava (enriched in iron and magnesium) which flows from the long parallel crack called cleft. This kind of eruption usually builds lava plateaus (craters or a big hole).
Hawaiian Eruption
This kind of volcano is quite similar to the Icelandic sort. However, In this case, runny lava flows from the Volcano’s summit and radial cleft to form shield volcanoes (discussed ahead in major types), which are quite enormous and consist of gentle slopes.
Strombolian Eruption
Stromboli volcano is located on Stromboli Island in Italy which is off the northeast coast of Italy. In this kind of eruption,the spreading gases explode due to this explosion it expels the coagulated (the lava which is gradually cooling down; semisolid) from the blazing lava which recurs or nearly continues tiny eruptions. Because of such tiny frequent flare-ups, Stromboli volcano has been called the “lighthouse of the Mediterranean”.
The Vulcanian Eruption
The Vulcanian eruption is named after “Vulcano Island” which is located in Italy and close to the stromboli. In general, it involves the fair explosion of gas loaded with volcanic ash. This mixture organizes dark disruptive eruptive clouds that quickly ascend and spread in convoluted (complex) shapes.
The Pelean Eruption
Pelean eruption is associated with an explosive eruption which generates pyroclastic flows, a dense mixture of hot volcanic smithereens, gas and ashes. In 1902 Pelean eruption was listed for the catastrophic eruption of Mount Pelee on the Caribbean island of Martinique (a french department).
The fluidized sludges (wet mud) formed from these eruptions are heavier than air but have low viscosity and pour down to the valleys and slopes at great velocities. They are more catastrophic.
The Plinian Eruption
This Volcanic eruption is an intense violent type of volcanic eruption. For instance the outburst of Mount Vesuvius in 79 C.E in Italy which killed a notable Roman scholar Pliny the Elder and was described as a bystander explicated by his nephew the Historiographer Pliny the Younger.
In this kind of eruption, gases boil out of gas-rich magma which generates large and closely continuous jetting (violent flow of liquid) explosions that empty the magma conduit (the channel of magma) and rip it apart. The surging gases and volcanic Smithereen resemble a mammoth (huge) rocket explosion, directed vertically upward.
The clouds which are formed from the Plinian eruption can reach up to the stratosphere and are often continuously produced for several hours.
Final Thoughts
This article is a beginner’s guide to volcanoes. All the content in this article is well researched from official sources. Thanks for investing your precious time in this article. I hope this article has helped your mind and cleared all the questions which you had regarding volcanoes.
