Volcanoes 101

Updated on June 18, 2018
harrynielsen profile image

Science has always fascinated me. This includes not only the ecological sciences, which I studied in school, but other endeavors, as well.

Kilauea in 1959

In 1959, Kilauea volcano in Hawaii produced some spectacular images, like this one here of its abundant and fertile lava flow.
In 1959, Kilauea volcano in Hawaii produced some spectacular images, like this one here of its abundant and fertile lava flow. | Source

Volcanic Effects On the Human Experience

There's no way around it, volcanoes fascinate, intrigue, terrify and mystify us. From the terrifying explosion of Krakatoa back in 1883 to the almost continuous eruptions of Kilauea and Mauna Poa on the Big Island of Hawaii, these magnificent natural events always seem to give us reason to stop and observe their awesome display of firepower.

And at the same time, there is that basic sense of primordial fear and survival that always seems to come with the news that someplace in the world a volcano is erupting, threatening lives and destroying property.

The Earth's Core

A diagram of the earth's core, including the movement of magnetic north between 1990 and 1996.
A diagram of the earth's core, including the movement of magnetic north between 1990 and 1996. | Source

The Earth is Not Solid

Contrary to the popular proverbial expression, it is not feasible or even possible to dig straight down to China. The distance is staggering, 8,000 miles approximately, but the hot, solid iron core of the planet stays at a constant 10,800 degrees Fahrenheit, ( the same temperature as the surface of the sun) a condition which makes the task more than impossible.

Though the inner core is believed to be solid, it is surrounded by a semi-solid, outer core and then a larger, rocky, plastic layer of mantle that sometimes produces magma, the red, fiery liquid that comes poring out of volcanoes as hot lava.

And just in case you are you are interested in the numbers, going from the center outward, they are 760 miles, 1,400 miles, 1,800 and five to 25 miles. That's 760 miles for the radius of the inner core, 1,400 miles for the thickness of the outer core, 1,800 miles for the thickness of the mantle and finally five to 25 miles for the thickness of the crust, depending on whether or not there is an ocean on top.

We Live On The Crust

The outer most layer of the planet earth is called the crust. That's the part that we live on. The crust is shaped into mountains, valleys, plains and plateaus. It varies in thickness and is covered by vast amounts of water, known as an ocean. The ocean (several oceans actually) is not actually considered to be part of the crust.

If the crust was one solid unit with no weak spots, there would be no volcanoes. But since the crust consists of many movable plates of land, cracks can form where the tectonic plates meet and magma can emerge through these cracks and form a volcano. It should come as no big surprise that a majority of the world's volcanoes can be found it concentrated areas, where these sub-continental plates meet.

The Nature of Magma

The earth's mantle is a huge, rock layer that lies underneath the earth's crust. Under most conditions, the material exists in a solid form, but when placed under heavy pressure and heat, the rock strata can form liquid pools that are red hot in temperature. This liquid material is called magma and it is this magma that comes gushing out of volcanoes as lava and then flows down the side of the cone.

Vulcan, The Roman God of Fire

The Roman God of Fire, Vulcan, makes for a near-perfect symbol for a volcano. In this painting by Alessandro Gherardini Vulcan with the aid of Cyclopidae is making a shield  for the son of Venus.
The Roman God of Fire, Vulcan, makes for a near-perfect symbol for a volcano. In this painting by Alessandro Gherardini Vulcan with the aid of Cyclopidae is making a shield for the son of Venus.

Vulcan Symboloizes the Fire of Creation (and Destruction)

Ancient legend has it that Vulcan, the son of Zeus, was tossed into the sea from Mt. Olympus by his father because he was physically deformed. Here he was raised by the sea nymph, Thetis. Eventually, Vulcan left the underwater world of Thetis and discovered a small Greek island. Here, he built a forge that was used to make nearly invincible shields and armaments for Roman deities.

After his fall from the heavens, Vulcan became the craftsman, who could create marvelous objects from many kinds of different metals. His spirit is also manifest in the numerous volcanoes that have risen from time to time along the northern rim of the Mediterranean Sea. Taking all of this mythology into account, it is no surprise that volcanic activity around the world bears his name, as does the the science of studying volcanoes, which is called volcanology.

Paricutin, a Textbook Cinder Cone Volcano

Paricutin volcano (1945) in Mexico was studied from the time it began as a small mound in a farmer's field until it formed a thousand foot high mountain and erupted
Paricutin volcano (1945) in Mexico was studied from the time it began as a small mound in a farmer's field until it formed a thousand foot high mountain and erupted | Source

A Typical Volcano

When we think of a volcano, quite often we are visualizing a cinder cone volcano. This is the most basic type of volcano, where hot magma rises from deep within the earth, forcing the land to rise around the relatively small, column of molten rock. In this type of volcano, one simple cone shaped mountain is formed and when the volcano actually erupts, the magma emerges from the top as lava.

More often than not the liquid lave runs down the side of the cone, but it some situations the lava explosion can be quite spectacular and shoot high into the air.

Mt. Vesuvius

Mt. Vesuvius in Italy is high on any volcano watch list, because of the large number of people that live near the base of the volcano
Mt. Vesuvius in Italy is high on any volcano watch list, because of the large number of people that live near the base of the volcano | Source

Stratovolcanoes

Stratovolcanoes are complicated versions of a cinder cone volcano.They form tall cylindrical shaped mountains like a cinder cone volcano, but instead of having just one central column of magma, there are many routes for the molten material to travel through. These paths branch out like a tree root, creating a network of molten lava flows that can emerge from various points on exterior side of the volcano. Some of the more notorious stratovolcanoes, include Mount Saint Helens, Vesuvius, Pinatubo and Popocatepetl.

Types of Volcanoes

There are three basic types of volcanoes, which are characterized by how the hot lava flows form.
There are three basic types of volcanoes, which are characterized by how the hot lava flows form. | Source

The Shield Volcano

The other type of volcano is called a shield volcano. These volcanoes are less common, but by coincidence, Hawaii houses many of the shield volcanoes, including Kilauea, which during the month of May (2018) has constantly been in the news because of its many small eruptions and hot lava flows.

Basically, these type of volcanoes get their names because they resemble a warrior's shield, lying on the ground. This rocky mound is characterized by having a very large base, shallow-sloping sides and numerous underground magma plumes, which can produce red hot lava flows at the surface.

Volcanoes Basics

Some Scientific Terms About Volcanoes

With volcanoes in the news lately, here is a list of terms that you might want to know.

Active Volcano - any volcano that has erupted in the past 10,000 years and is expected to erupt again

Caldera - a large bowl shaped depression formed at a top of a volcano, when the ground collapses

Lahar - a fast-moving mudflow made of ash and water

Lava - magma that reaches the earth's surface

Laze - mist containing Hydrochloric acid that forms when molten lava flows into sea water

Magma - molten rock below the earth's surface

Pahoehoe - a type of lava that forms a thin wispy crust, when it hardens

Pyroclastic Flow - a high temperature mixture of hot ash and lava fragments that moves out of avolcanic eruption at a high speed

Tephra - any sized material that is ejected during a pyroclastic explosion

Vog - a fog, containg sulfur dioxide that forms near lava vents

Volcanic Ash - lava particles that are less than a tenth of an inch in size

Volcanic Bomb - a mass of molten lava that hardens after it has been ejected into the air by an eruption

Volcanology - the scientific study of volcanoes



Questions & Answers

    © 2018 Harry Nielsen

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      • harrynielsen profile imageAUTHOR

        Harry Nielsen 

        2 months ago from Durango, Colorado

        Thanks. Volcanoes are very in much in the news today and if we want to try to make sense of what's going on, we are going to need the understand the basics, first.

      • lions44 profile image

        CJ Kelly 

        2 months ago from Auburn, WA

        Nice job. Very timely and important with what's going on in Hawaii. Sharing.

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