Knowledge Article: World Geography Ring of Fire Plate Tectonics Certain regions of the world are more vulnerable to natural disasters because of where they are located. Tectonic plates beneath the surface of the earth are constantly grinding against each other. This action produces a great amount of energy, which is sometimes released through geologic episodes, including earthquakes and volcanic eruptions. One region of the planet experiences this activity more than any other—the "Ring of Fire." The Ring of Fire The Ring of Fire runs along the edges of the Pacific Ocean, including Southeast Asia. There, the main Pacific Plate and several smaller ones collide with each other. This ongoing collision creates massive mountain chains, volcanic islands, frequent earthquakes, and highly destructive tsunamis. It should also be noted that the Ring of Fire contains some of the largest population centers in the world, including Japan, Indonesia, and the western coast of the United States. As a result, when a natural disaster does occur along this zone, it can cause severe damage and claim many lives. The Pacific "Ring of Fire" stretches around the rim of the Pacific Ocean. 1 © 2013 EDMENTUM, INC. The tectonic plates on Earth’s surface drift over time. Hundreds of millions of years ago, the modern continents were all part of one supercontinent. Slowly, over the course of time, the continents moved to their current positions. As you might imagine, when huge forces such as these plates come together, there is a massive amount of energy produced. In these regions, much of that energy gets released as seismic (earthquake related) or volcanic activity. One of the most commonly seen plate boundaries is a subduction zone. At a subduction zone, an oceanic plate collides with a continental plate, and because the oceanic plate is denser, it slides (subducts) under the continental plate. This subduction results in the creation of continental volcanic mountain ranges and volcanic islands along the plate boundaries. This exact process has played itself out along many of the edges of the Pacific Ocean, creating the Ring of Fire. As the edges of the hard, rocky oceanic plates disappear under the continents, the heat of the Earth melts them back to a molten state. With nowhere to go, this magma forces its way up through the earth. Eventually it spews through volcanoes as lava. The Ring of Fire itself contains more than half of the worlds' volcanoes. Over millions of years, the subduction of tectonic plates has been an unending process in this area of the world. Like the conveyer belt in a grocery store checkout line, the sea floors have constantly been pushing under the continents. Fiery Indonesia The Ring of Fire has created a zone of geological chaos around the Pacific Rim. The ocean is surrounded on virtually every side by sizeable mountains and islands. From New Zealand through the islands of Southeast Asia, to Japan and Eastern Siberia, and along the coast of the Americas from Alaska to the Southern tip of South America, there are active and dormant volcanoes. These geological forms provide the fire in the name “Ring of Fire”. They are, however, by no means the only danger in the region. Earthquakes are especially prominent in Southeast Asia, Japan, and the Pacific Coast of the Americas. These movements deep within the earth are caused by sudden shifts when the continents, constantly grinding against each other, suddenly release pressure. The effects of the Ring of Fire on Southeast Asia can clearly be seen by Major volcanic sites of Indonesia are indicated with red triangles. Marked in green are the approximate looking at a physical map of the sites of Krakatoa and the point where the 2004 region. Thousands of islands dot this earthquake-tsunami began. 2 region from eastern New Guinea to the Indian Ocean. Many of these islands were first created by volcanic activity or other tectonic events. However, the same natural forces that have helped shape the region also threaten it. The islands of Southeast Asia lie on the boundaries of three massive tectonic plates— the Australian, Pacific, and Eurasian plates. The Indian and Philippine plates are also large and actively moving. With all these forces pushing against each other, the region has become a center of seismic and volcanic activity. Often at sea level, and with few natural barriers against waves, many islands of Southeast Asia are easily damaged by tectonic activity. In some extreme cases, islands can literally be washed away or blown apart. The remainder of this article will examine two of the most destructive natural disasters in this area's recent history—the 1883 Krakatoa eruption and the 2004 tsunami. The Deadly Volcanoes of Krakatoa Indonesia is an archipelago in Southeast Asia that lies within the Ring of Fire. The country has a long history of fiery volcanic eruptions, which continue today. In fact, the archipelago currently has more than 100 active volcanoes. Indonesia was the setting for modern history's most powerful volcanic eruption, which took place on the island of Krakatoa in 1883. Although not much is left of this island, originally located between Java and The imposing sight of Krakatoa's south side was Sumatra, its hollowed shell is a obvious to all that saw it. However, its lurking danger was unknown to many at the time. reminder of its important past. Krakatoa's volcanic eruptions had been documented for hundreds of years before the 1800s. By that time, the island had developed an unusual feature: it had three volcanoes that were connected together below the surface. So a single eruption could cause lava to flow out of two or more volcanoes at the same time. After a series of earthquakes struck in May 1883, Krakatoa's volcanoes started to rumble and churn out lava. These eruptions were not especially dangerous: they were small and confined to a small section of the uninhabited island. In fact, people traveled to Krakatoa to watch the volcanoes in action, and some even landed their sea vessels on the island to get a better look. Although it seemed like a magnificent sight, it did not compare to what was about to happen. 3 The mild volcanic activity continued through the summer, until an explosive eruption occurred on August 26. This outburst, which created an ash cloud that was 36 kilometers (22 miles) high, signaled the start of two days of volcanic activity that would slowly grow more powerful, intense, and deadly. Unfortunately, many people lived close enough to Krakatoa to experience this flare-up. They watched in terror as the volcanoes spewed out ash and molten lava. But the worst was yet to come. The next day, August 27, the most explosive eruptions of that summer destroyed Krakatoa. As the volcanoes' fiery energy spread ash and lava all over the region, the huge island collapsed into an underwater crater. Only a third of it remained above the ocean's surface. This volcanic activity was so loud that it was heard nearly 3,000 miles away! To put this distance in perspective, 3,000 miles is greater than the distance between Los Angeles and Washington, D.C. The eruptions of August 26 and 27 combined to form a catastrophe for Southeast Asia. Thousands of people died when pyroclastic flows and tsunamis swept through the region. The pyroclastic flows, or clouds of toxic gas and extremely hot volcanic material, floated out from the volcanoes first. They burned and killed many as they drifted away from Krakatoa. However dangerous they sound, the pyroclastic flows were not responsible for nearly as many deaths as the tsunami which followed. The Killer Waves Shockwaves from the eruptions sent powerful tsunami waves throughout Southeast Asia. The places nearest to Krakatoa were devastated by these waves. They were often submerged under many feet of water, leaving little untouched. On Sebesi, one of the islands closest to Krakatoa, the entire population drowned, and their bodies washed away. Not even the plants or trees on Sebesi were left behind by the sea waves. Other islands around Krakatoa were also hit by massive tsunamis. One eyewitness, who was five miles inland, described the terror of witnessing the water approach: All of a sudden there came a great noise. We...saw a great black thing, a long way off, coming towards us. It was very high and very strong, and we soon saw that it was water. Trees and houses were washed away …The people began to...run for their lives. Not far off was some steep sloping ground. We all ran towards it and tried to climb up out of the way of the water. The wave was too quick for most of them, and many were drowned almost at my side…one after another, they were washed down and carried far away by the rushing waters. You can see the marks on the hill side where the fight for life took place. Some …dragged others down with them. They would not let go their hold, nor could those above them release themselves from this death-grip. --account of a Javanese field hand, from Krakatau, Indonesia,San Diego State University 4 The ocean was no safe place for people to be either. The powerful tsunamis threw ships off course, or even ejected them from the water altogether, carrying them onshore. The waves also battered many ships, leaving them damaged or destroyed. After ravaging Southeast Asia, the energy from the tsunami's waves radiated out and traveled across the world. In Sri Lanka, an island off the coast of India, it was powerful enough to kill one person.