Loading...
HomeMy WebLinkAboutThe Times Advocate, 2005-01-19, Page 27Wednesday, January 19, 2005 Exeter Times -Advocate 27 The causes and characteristics of tsunamis By Brenna Anstett SPECIAL TO THE TIMES -ADVOCATE (Editor's note: The author is a Grade 12 student at South Huron District High School who wrote the following article for a school project.) EXETER — Due to the recent event along the coastlines of the Indian Ocean, questions have been arising as to what exactly occurred. It has been said that a 9.0 -magnitude earthquake centered off the Indonesian island of Sumatra caused a tsunami to hit the shorelines of nine countries. But what exactly is a tsunami? How did it kill tens of thousands of people? These are the types of questions many people all over the world have been pondering. Since the natural disaster occurred, the lack of pictures and video tapes from the media coverage has not been much help to those wanting to know exactly what happened on the morning of Dec. 26, 2004. To help gain a better understand- ing of the disaster that devastated nine countries along the Indian Ocean, here are some questions and answers on tsunamis. What is a tsunami? The word "tsunami" is pronounced "soo-NAH-mee," and comes from the Japanese language meaning harbour ("tsu") and wave ("nami"). This term originated from fishermen who would return to port to find the area around the harbour devastated, even though there was no sign of waves on the open water. A tsunami is a natural phenomenon which consists of a series of sudden and unexpected, long ocean waves created when a large body of water is displaced at a massive scale. Tsunamis are often incorrectly called tidal waves because of similar character- istics. Tidal waves are periodic move- ments of water produced by the gravita- tional pull of the sun, moon, and planets. Tsunamis have nothing to do with the weather or the tides. Tsunamis are gen- erally associated with earthquakes. How are tsunamis created? There are three main ways in which a tsunami may be created: • an undersea earthquake, often near a subduction zone; • an undersea landslide, which may have been caused by a small earthquake; • and a large meteorite or asteroid hit- ting the ocean. The most common of the three is the underwater earthquake. Tsunamis are generated when the sea floor abruptly deforms and the overlying water is verti- cally displaced. At the plate boundaries, there are large vertical movements of the earth's crust where the denser oceanic plates will slip under the continental plates. This process is called subduction. In an attempt to regain its equilibrium position, waves are formed by the influ- ence of gravity on the displaced water mass. The size of a tsunami is determined by the amount of vertical sea floor deforma- tion. This amount is controlled by the earthquake's magnitude, depth, fault characteristics and the coincident slump- ing of sediments or secondary faulting. A large earthquake that occurs near or under water can lift thousands of square kilometres of sea floor which is what causes the formation of huge waves. Characteristics of tsunamis Tsunamis are known as shallow -water waves which are different from wind - generated waves (waves observed at the beach). Wind -generated waves have a period of five to 20 seconds between two succes- sional waves and have a wavelength of 100-200 metres (300-600 ft.), which is the distance between two successional waves. For a tsunami, the period can last at a range of 10 minutes to two hours and it can have a wavelength of 500 km (300 miles) or more. A wave is characterized as a shallow - water wave when the ratio between the wavelength and the water depth gets very small. This is why tsunamis are shallow -water waves — they have long wavelengths. In deep ocean waters, tsunamis may have wavelengths as much as several hundred kilometres and may reach speeds of up to 720 km/h. The waves will appear small, though, with a height of less than one metre (3 ft.), which is why many ships do not notice a tsunami is occurring while on open waters. As the waves reach shallow waters, they slow down and begin to "pile-up" (the waves become steeper and taller and there is less distance between them). Since the speed of the tsunami is related to the water depth, when the depth decreases, the speed diminishes. The total energy of the tsunami remains con- stant due to its enormous wavelength. By the time the tsunami reaches the shore, the speed has diminished and the height of the wave has increased. Because of this process, a tsunami can grow to be several feet in height as it hits the shore. How big do tsunamis get? The smaller waves that come in off the ocean have a tremendous amount of energy associated with them and as a result, these waves can become gigantic as they approach the shorelines. The height that the waves reach depends on the underwater features of that area. They can reach heights as high as 30 m (100 ft.). The largest tsunami ever recorded happened in July 1958 in Lituya Bay, Alaska, where a huge rock and ice fall sent waves surging up to 500 m (1640 ft.). There may be a series of waves to hit the shores, and the first wave is not always the largest. A tsunami's waves can happen between five minutes to one hour of each other, which amplifies its destruction. With the recent tsunami along the Indian Ocean, the initial wave came washed over a series of Thai resorts, and people came out onto the beaches afterwards to help out the injured. During this time, a second wave hit which claimed even more victims. The speed of a tsunami works the opposite of its height. The height begins small and grows, while the speed begins fast and decreases. The height and speed working together is what causes the tsunami to become so destructive. When out in open water, the speed of a tsunami may reach the speed of a jet aircraft which is about 890 km (500 mph or more). As the tsuna- mi approaches the shore, its speed will decrease to about 75 km/h (45 mph). How much destruction do they cause? Tsunamis are known to cause both the destruction of life as well as massive physical damage. Tsunamis have killed many people and left others with emo- tional damage. On the physical side, tsunamis have destroyed entire buildings and towns as well as several fishing vil- lages. Such things as parking meters are bent all the way to the ground. It takes an enormous amount of time for a place to recover from a tsunami. With the tsunami along the Indian Ocean, the streets of the coastlines of nine countries were flooded, hotels and resorts were destroyed, and houses, fishing villages and towns were demolished. About 150,000 people have been killed. Below is a comparison chart of the 10 deadliest recorded tsunamis (notice the recent Indonesian tsunami is the highest on the list).: • 155,000 — (UN estimate ongoing) Indian Ocean earthquake with tsunami in 2004; • 100,000 — Lisban, Portugal, Morocco earthquake, tsunami and fire in 1755; • 100,000 — Awa, Japan tsunami in 1703; • 70,000 — Messina, Italy earthquake and tsunami in 1908; • 40,000 — South China Sea tsunami in 1782; • 36,000 — Krakatoa volcano and tsunami in 1883; • 30,000 — Japan in 1707; • 27,000 — Japan in 1826; • 25,674 — Chile in 1886; • 22,070 — Sanriku, Japan in 1896. For more information on tsunamis, check out these Web sites: en.wikipedia.org/wiki/Tsunami; www.ussartforg/tsunamis.htm; clearly- explained.com/nature/earth/disasters/ts unamis.html; www.cbc.ca/news/back- ground/forcesornature/tsunamis.html Lay leader conducting this week's Sunday services By Rhoda Rohde THAMES ROAD CORRESPONDENT THAMES ROAD — The January meeting of the United Church Women was held Tuesday evening Jan. 11 in the church basement. Helen Kadey welcomed everyone and gave the theme, `What's An Epiphany?' and also led in prayer. Joan Morgan read the Scripture, Ephesians 3:1-19. The women sang 'The Wise May Bring Their Learning' accompa- nied by the pianist Jean Hodgert. Janis Richardson gave the meditation, 'On Epiphany'. Passmore and Richardson received the offering with prayer by Helen Kadey. The women sang, 'We Three Kings of Orient Are'. Joan Morgan closed the worship service with prayer. New president Carolyn Johns opened the business with, 'A Moment That Happened' and 'A New Year's Greeting'. Everyone repeated the UCW Purpose. New secretary Diane Jeffery took the roll call which was answered by 'A memorable moment from the holiday sea- son.' Jeffery read the previous minutes and the correspon- dence. The women of the Standing Committees each gave a report. The visiting committee for the next four months are group U Marilyn Pym, C Shirley Kerslake, W Helen Weston. The meeting closed with the UCW Prayer. A delicious lunch pre- pared by Anne Bray, Melonie Miller, Passmore, and Virginia Warwick was enjoyed. There were 35 women in attendance. Church service Dave Williams was in charge of the regular church service on Sunday morning. Everyone sang the Introit. Larry Lynn came for- ward and introduced Dave Williams of Woodham who is a licensed lay leader and his wife Eleanor who was in the audi- ence. People shook hands and Williams led in the Call to Worship and the Gathering Prayer. 'All People That On Earth' was sung. Affirmation of Faith was read in unison. The children's hymn was `It Only Takes A Spark'. Williams lit the Christ Candle and told the children a story. Williams explained the symbolism of the fish in Christian history. The choir sang `I've Got A Mansion Over the Hilltop' accompanied by the organist Marilyn Vandenbussche. Psalm 40:1-11 was read responsively. Williams read Isaiah 49:1-7 and the title of his message was `Ordinary People Face Extraordinary Challenges.' `Spirit, Spirit of Gentleness' was sung. Helen Weston and Nancy Smith received the offer- ing and also were the greeters. 'Sent Forth By God's Blessing' was sung. Williams gave the Commissioning and pronounced the Benediction. 'May The God of Hope Go With Us,' was sung to close the service. After the service a congrega- tional meeting was called for the reasons of Pastoral Relations Joint Needs Assessment Committee. A committee was named and then there was a short council meeting. Announcements Dave Williams, who is a licensed lay worship leader, will be conducting our Sunday ser- vices. Williams will be available Tuesday morn- ings in the office (235-2803) from 9:30 a.m. to noon or in case of an emergency at 229-8200 or at Willy@Quadro.net. Contact Helen Weston, Outreach Committee at 229-6281 for someone in hospital, ill at home, etc. Donate to the Tsunami Appeal for Relief and Reconstruction by calling 1-800-465-3771 or online at www.united-church.ca. Indicate that your donation (eli- gible for tax receipt) is for the Tsunami Appeal. You can also send a cheque, payable to The United Church of Canada marked Tsunami Appeal, to Tsunami Appeal, The United Church of Canada, 3250 Bloor THANES ROAD NEWS St., W., Suite 300, Toronto, ON M8X 2Y4. Personal Jane Cann, Justin and Hayden arrived home on Monday after visiting her mother Shirley Hewitt of Hopper's Crossing, Australia Farewell service The following information was inadvertently omitted from last week's Farewell Service for Rev. Marilyn Carter report. After Rev. Marilyn Carter's sermon, Larry Lynn called Rev. Carter forward and read on July 1, 1998 the Thames Road- Elimville Pastoral Charge and Huron Perth Presbytery, and Rev. Carter entered into a covenant ministry. Sharon Passmore put a Bible on the Communion table and Rev. Carter read about the Bible being a symbol of the ministry of the Word among us. Alexander Gallant helped Rev. Carter pour water in the font a symbol of baptism. Alexander portrayed the baby Jesus in the Bethlehem Walk in December 1999. Karen Etherington pre- sented the loaf and Marilyn Pym the wine goblet and were put on the communion table as symbols of our Communion in Christ. Helen Weston presented a towel and basin as symbols of our call- ing to justice and service, according to the example of Jesus. Murray Dawson present- ed keys to Rev. Carter as a sym- bol of daily duties and the work of the administration and of this building. After the service was over, Evelyn Johns played the piano and the Sunday School members played instruments as they walked up the aisles. They also put on a dialogue with the let- ters MARILYN spelling Rev. Marilyn's name. They also sang a catchy tune, In Retrospect' the choir sang humourous words to the tunes of Battle Hymn of the Republic. 'The Grumblers', 'Song About the Bats' and Sharon Lynn had a pole with a fake bat on it and Beatrice Dawson killing with a broom. Also about the strawber- ry supper to the tune of 'My Bonnie' also about Tim Horton's to the tune `There's a Tavern In The Town' also about her home, her cat and about moving on. Robert Bray spoke a few words between each song. Sharon Passmore spoke a few words and Barry Miller called Rev. Carter to the front. Judith Parker read a wonderful address and Barry presented Rev. Carter with a beautiful clock, cards and note pad. Marilyn replied and she asked grace before we went down- stairs for our lunch which brought a very memorable occa- sion to a close.