Volume 5 Issue 5
A Facination With Volcanoes
by Laurisa White Reyes
Nine years ago, when my husband and I were engaged to be married, we flew to Guatemala to visit his family. As we approached our destination, I looked out the window and saw half a dozen volcanoes spread out over the lush green landscape. It was the first time I had ever seen a real volcano and I was impressed, to say the least. But the most breath taking moment of our trip occurred a few weeks later while driving outside Guatemala City. At 4:00 in the morning the sky was pitch black except for the distant contour of Pacaya, Guatemala's most active volcano, made visible by the red glow of hot lava flowing down its flank. It was an image so magnificent that it has remained vivid in my memory all these years.
Mankind has had a fascination with volcanoes since the beginning of time. History records their awe-inspiring beauty as well as the power of their destructive forces. There are literally thousands of volcanoes throughout the world. With 130, Indonesia has more active volcanoes than any other country in the world, the most active of which is Merapi which means "Mountain of Fire."
When it comes to teaching children about volcanoes, resources are endless. Books and videos by the dozens are available at every bookstore and library. For younger children, reading picture books and discussing basic facts about volcanoes can be enough to spawn a sincere interest. For older children, it can easily lead to an exploration of an entire branch of scientific study. The fact is, volcanology is a very intricate science. I cannot even begin to offer a particle of the wealth of information available. However, I do hope to provide a glimpse into what amazing discoveries await those who find volcanoes as captivating as I do. FYI, this article is written with older children in mind. However, at the end I do suggest activities and resources for younger children as well.
Classifying the Structure of Volcanoes:
The average volcano has several distinct parts which make up the whole. Below the Earth's surface is the Magma Reservoir, a "lake" of molten lava which travels upward through a Conduit toward the volcano's Vent, or opening. When the magma reaches the Vent, it may erupt in a gentle flow or, if the pressure is great enough, a large explosion.
The outside of the volcano is formed by the Base (bottom), Flank (sides), Summit (top), and finally the Crater which surrounds the vent or volcano opening.
Though most volcanoes have these characteristics in common, every volcano is unique. The systems for classifying volcanoes are actually quite complex. Volcanic classification relies on several factors including size, lava chemistry, geographic location, and level of activity, just to name a few. But the most common method for classification is what is called morphology, or the physical structure of a volcano. Some volcanologists list as many as twenty-six morphological types of volcanoes, but according to the Smithsonian Institute, the majority of volcanoes, as many as 90%, fall into one of the six categories listed below:
Lava Domes form when lava piles up around a volcano's vent and are commonly found on the sides of Strato volcanoes, such as the one that formed on Mount St. Helen's after its eruption in 1980.
Cinder Cones are formed by cinders falling from eruption clouds and can develop singly or in clusters.
Shield Volcanoes are shallow domes made from hardened basalt, a very liquid type of lava. The island of Hawaii is made up of four of these types of volcanoes which are the largest volcanoes in the world.
Strato Volcanoes comprise approximately 60% of the Earth's volcanoes and are easily recognizable by their cone-shaped appearance. These types of volcanoes, when active, can exhibit highly explosive eruptions and have caused more casualties than any other type of volcano. Mount St. Helens is an example of a Strato Volcano.
Caldera are also called inverted volcanoes due to the fact that they are formed by large amounts of magma which build up below the earth's surface then collapse into large circular or oval-shaped depressions. Crater Lake in Oregon was formed this way.
Flood Basalt Plateaus are characterized by large volumes of lava which erupt from fissures covering vast areas.
Classifying Volcanic Eruptions:
While most volcanoes have been dormant or extinct for hundreds of years, approximately 540 are still active today. An average of sixty volcanoes worldwide erupt annually. Most of these eruptions are very small. But every so often a volcano erupts with such force that it causes immeasurable damage. One of the deadliest eruptions in history occurred just under a century ago in that very land in which I saw my first volcano. In 1902 Guatemala's Santa Maria erupted killing nearly 5,000 people. However, that number pales in comparison to Mt. Pelee's ash flows which killed over 29,000 that same year, or the Tsunami (tidal wave) which resulted from Krakatau's eruption in 1883 and took the lives of 36,417 people. But by far the worst volcanic calamity occurred in 1815 when 92,000 died following the eruption of Tambora in Indonesia.
Since volcanic eruptions can range from very minor to catastrophic, scientists have developed a scale of measurement to determine the force of any particular eruption. This scale is called the Volcanic Explosivity Index or VEI and classifies eruptions on a scale of 0 to 8, 0 being non-explosive and 8 being the most forceful. Eruptions can be further classified by placing them into one of the following categories:
Hawaiian eruptions are quiet and have low gas content with thin, fluid lava flows.
Basaltic eruptions are similar to Hawaiian except for their large volume of lava.
Strombolian eruptions are characterized by the ejection of material tens or hundreds of feet in the air. When lava flows are present, they are shorter and thicker than that of Hawaiian eruptions.
Vulcanian eruptions usually begin with steam explosions which remove old layers of rock from the vent. An eruption cloud of ash forms and is commonly accompanied by lightening within the cloud. Lava flows are thick and viscous.
Peleean eruptions begin with the formation of domes and avalanches of glowing lava. Later, magma forms a steep-sided dome or outcropping within the vent which can then collapse resulting in additional ash flows.
Plinian eruptions are named for the Roman naturalist, Pliny the Elder, who died during an eruption of Vesuvius in AD 79. They have two key characteristics: a powerful gas blast and the ejection of large volumes of pumice. Many of these eruptions last a few weeks to a few months and the longer of these include showers of ash and lava avalanches.
Rhyolitic flood eruptions produce large volumes of material spread over large distances producing broad, nearly level plains.
Ultravulcanian eruptions eject solid rock and steam ranging from ash to block-sized material. No magma is present.
Suggested Resources and Activities:
Now, before you start to feel overwhelmed by all this, keep in mind that there is a lot more to volcanoes than morphology and eruptions. From here you might veer off into the history and legends surrounding individual volcanoes, or explore a certain type of volcano that may be abundant in a particular area of the world, or even delve into what exactly causes eruptions. Younger children might enjoy handling samples of igneous (volcanic) rock as part of their study of rocks and minerals. Videos are a great way to capture young imaginations. Some titles to look for include "Volcano: Nature's Inferno" from National Geographic's Disaster video series, "In The Path of a Killer Volcano" or "Hawaii Born of Fire" both from NOVA, "Eyewitness: Volcano" (best choice for very young children), and "Inside Hawaiian Volcanoes."
If you are interested in obtaining some top quality books on the subject, the Smithsonian Institute recommends the following:
Volcanoes of the World, by Tom Simkin and Lee Siebert
Volcanoes, by Seymour Simon (an illustrated book for children ages 8-12)
Volcano & Earthquake, by Susanna Van Rose (written for teenagers & adults)
Finally, there are several kits available that allow you to build your own volcano and/or conduct experiments relating to volcanic activity. I mention only two here:
Science in a Nutshell: Our Changing Earth
This mini-science kit from Delta Education (1-800-442-5444) explores the processes that shape our ever-changing earth including volcanic eruptions and earthquakes. Includes activity guide for 10 or more activities, student journals, specialized equipment, and consumable materials needed for up to six uses. Cost: $35.98 plus shipping & handling
Smithsonian Giant Volcano Kit
Includes quick drying compound and plastic cone for constructing your own volcano, chemicals needed to create "lava," and three samples of igneous rocks (pumice, obsidian, & basalt). This product can usually be found at Toys 'R' Us, Play Co. Toys, Learning Express, Micheal's, K-Mart, and Wal-Mart.
You can also create your own erupting volcano with just a few items from your kitchen.Items Needed: Small Glass Jar Pie Tin or Plate Clay Baking Soda Red or Orange Food Coloring Vinegar
Directions: 1. Stand jar in the center of pie tin. 2. Cover sides of jar with clay. This will be your volcano. 3. Carefully fill the jar half way with baking soda. Add a few drops of food coloring. 4. Add vinegar one spoonful at a time. Stand back and watch the "lava" flow down the sides of your volcano.
Laurisa White Reyes 21408 Alaminos Drive Saugus, CA 91350 (661) 263-0194 email: email@example.comCopyright © 2006 Modern Media