Reading Passage: Volcanoes

Volcanic eruptions are one of the most powerful phenomena on the planet. Their potency has captivated the minds of many ancient cultures whose gods, including Pele and Vulcan, embodied the power of the volcano. There is great magic surrounding volcanoes: they exist on distant planets in our solar system, they are the source of diamonds and lightning storms, and they can even generate electricity.

In early times our knowledge of volcanoes was limited. People could see the smoke and lava that spewed forth from the volcanoes but didn’t understand what caused it. Many cultures explained these powerful forces by telling stories about the gods that lived in the volcano. Greek mythology, for example, was full of references to volcanoes. In their legends, Typhon, a hideous monster with many heads, drooled lava and spat out fiery rocks. To put a stop to this menace, Zeus imprisoned Typhon under Mt. Etna, the world's tallest active volcano. According to legend this is the source of all the mountain's volcanic activity. In addition, the Greeks credited the god Hephaestus for eruptions. He was generally a peaceful craftsman and the master of the forge, but if provoked, he could vent his wrath on the people in a storm of volcanic ash. Hephaestus later became the Roman god Vulcan.

image courtesy of Stromboli online

image courtesy of Classics 10

image courtesy of The Greek Forums

To Hawaiians, volcanoes are a critically important part of daily living. The Big Island of Hawaii owes its entire existence to the volcanic activity of Mauna Loa (the world's largest volcano) and Kilauea (one of the world's most active volcanoes). It is believed that Kilauea emerged from the sea perhaps 50,000-100,000 years ago and has been active ever since with no documented prolonged periods of inactivity. Since January 1983, continuous lava flows have added over 220 hectares to Kilauea's southern shoreline. This violent volcano is the home of Pele, the Hawaiian Goddess of Fire. It is no wonder that she is seen as an angry, aggressive, primal force.

image courtesy of MSNBC

The gods of volcanoes may seem like characters out of a fantasy novel, but real volcanoes may be better suited for a science fiction story. In fact, there are many volcanoes in outer space. The planet Venus and Io, a large moon of Jupiter, have many active volcanoes.

Venus has more volcanoes - over 1600 major volcanoes and tens of thousands of smaller ones - than any other planet in our solar system. They are completely unlike those on earth in three principal ways. First, none of them appear to be active. Second, since there is no evidence of plate tectonics, there are no linear chains of volcanoes and no zones of activity. And finally, the volcanoes on Venus only show evidence of lava flow and no sign of explosive behavior. Venus also has a unique type of volcano called pancake domes which are, on average, 24 kilometers in diameter and 700 meters high.

image courtesy of The Adler Planetarium

Unlike Venus, Io is about the same size and density as the Earth’s moon and is full of active volcanoes. Eruptions happen so often that the entire surface of the moon can be buried under 100 meters of material every million years.

image courtesy of JPL Ambassador Program

image courtesy of Solar System Exploration

Although they are not as exotic as the volcanoes on other planets, or perhaps as mysterious as the mythological stories would lead us to believe, real volcanoes on the planet earth are surrounded by mystery and allure. Volcanoes can create lightning when they erupt, produce diamonds, and can even be a source of electricity.

Volcanoes are places of extremes. They reach temperatures of up to 1200º Celsius and melt rock to the point that they lose their magnetic properties. It takes these kinds of extremes to produce the violent lightning storms mentioned earlier. Electrical discharges are one of the most awesome spectacles during eruptions. Lightning occurs when the potential difference, or voltage, between the negatively-charged falling ash particles and positively-charged gases associated with the volcano's plume exceed the resistance in the air separating them. These displays can light up the sky but rarely strike the ground or cause damage to the surroundings.

image courtesy of Volcano World at the University of North Dakota

The flash of lightning is just as brilliant as the flash of diamonds. Surprisingly, all diamonds come exclusively from old deeply-eroded volcanoes. Diamonds are formed under intense pressure about 150 kilometers or more under the earth’s surface. Specifically, they come from carrot-shaped structures which represent the roots of ancient, small volcanoes called Kimberlite pipes. Inside these pipes, most gem quality diamonds are found in the Diatreme. The largest diamond mines of this type are found in Australia (Argyle mine), Botswana (Orapa mine), Russia (Yakutia mine), Canada (Diavik mine), Zaire (Mbuji-Mayi mine), and particularly in South Africa (Kimberly and Jagersfontein mines) where the DeBeers Company runs its monopoly of the diamond business.

image courtesy of American Museum of Natural History

image courtesy of GeoForum

image courtesy of Diavik Diamond Mines, Inc.

The diamonds taken from volcanoes are often used as a sign of power in today's society, but scientists are extracting real power to run societies directly from volcanoes. Geothermal power is being used to capture the heat energy of the volcano. There are currently three methods of harvesting the heat of the underground magma: dry steam, flash steam, and binary cycles. The Geysers and Yellowstone National Park are the only two places in the United States with known reserves of underground resources of steam. Flash steam plants are more common and use pipes to transport high pressure underground hot water to the surface. As the water rises, the pressure decreases, and steam is collected while the remaining water is recycled back underground. Binary cycles use a "closed loop" system to circulate a gas in sealed tubes down through the underground hot water and return it to the surface where it is then used to create steam. Whichever method is used, the steam then turns turbines to generate electricity. While the details of any of these procedures may be a little complicated, the ramifications are not. Geothermal plants hold much promise. Although there is still some debate over whether geothermal plants create emissions and deplete the underground hot water sources that support geysers, in general, geothermal energy is viewed as a clean and renewable resource.

image courtesy of Lake County Visitor's Guide

Volcanoes are powerful entities with an ability to capture the imagination. They are the origin of many legends, the cause of some scientific research in space, and the source of lightning, diamonds, and electricity. Like diamonds capture our hearts, so too do volcanoes capture our minds.