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Transcript
TECTONICS ROCK A Facilitator's Guide to Earth Sciences Our Vision Canadians recognize that 1 Science is intrinsic to their lives and acknowledge the fundamental importance of a quality Science education to prepare young people for our rapidly changing world. Our Mission Let’s Talk Science is striving to improve Science literacy through innovative educational programs, research and advocacy. We exist to motivate and empower young Canadians through Science education. 1 Our Science includes life and physical sciences, technology, engineering and mathematics. Let’s Talk Science, National Office 1584 North Routledge Park London, Ontario, Canada N6H 5L6 Tel: 519-474-4081 Fax: 519-474-4085 Email: [email protected] www.letstalkscience.ca Charitable Number: BN88540 0846 RR0001 Developed by Susan O’Leary, Karen Quinn and Darren Thompson For ©2001 Let's Talk Science Current Edition ©2003 Let's Talk Science National Cornerstone Supporters: National Founding *Registered trademark of Imperial Oil Limited. Used under License. To make a tax-deductible donation to improve Science literacy in Canada, please call Toll Free: 1-866-352-3060 or 519-474-4084 or visit our web site: www.letstalkscience.ca All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from LET'S TALK SCIENCE. A. Description of Workshop Overview of Workshop Grade for Workshop/ Appropriate Age This activity is designed for use in Grade 7-9 classrooms or with children ages 12 to 14. This workshop takes your class from magma to mountains. Drifting back in time, students will use scientific evidence to put together a puzzle of „Pangaea‟. Students gain an understanding of plate tectonics by demonstrations of convergent, divergent and transform plate movements. After creating model mountains, students become cartographers by designing and drawing their own topographic map. Overall Objectives Science Topics Composition of the Earth‟s Crust Pangaea Plate Tectonics/ Continental Drift Topographical Mapping To explore the different layers of the Earth. To introduce Pangaea and the continental drift theory. To discover plate tectonics and the three different types of plate movements. To learn about topographical mapping. Page 3 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science B. How to Run This Workshop Physical Requirements Students will do activities at their desks in groups of two. Materials and Set-Up Note: For more detail, see Kit List Introduction Activity #1 – Pangaea Cross section of Earth‟s composition (laminated) 16 bags of fun foam continents (1 per every pair of students) 1 bag of fun foam continents with magnets on the back (For demonstration on chalk board) Beach ball globe (OPTIONAL) Activity #2 – Plate Tectonics Map of Earth‟s Tectonic Plates (overhead) Map of Different Geological Activities to overlay on the plates (overhead) (OPTIONAL) Plate Boundary Movement pictures (laminated with magnets on back for board OR on overheads) Laminated map of Canada (1 per every pair of students) Pangaea Puzzle Task Cards (16) Washable markers (16) Pangaea creatures (16 sets plus extras) *Geological Times Data Sheet (1/student) 1 bag of: -fun foam tectonics plates -fun foam land and water accessories Activity #3 – Topographic Map Sample topographic maps (1 set/kit) Picture of mountains (1 set/kit) 16 placemats for making the mountains (OPTIONAL) Sample Styrofoam model of mountain OR fun foam model of a mountain Laminated example map with parts (Velcro™) *Map worksheet (1/student) 16 bags of: -1 block of plasticine -10 toothpicks -30 cm of heavy fishing line and 2 craft sticks -1 ruler -Coloured markers Topographical Map Task Card *Consumable items Page 4 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Timing of Activity Part of Workshop: General Introduction Introduction to Topic and Explanation of Activities Activity #1 Activity #2 Activity #3 Wrap-up Suggested Timing: 5 min. 10 min. Cumulative Timing: 5 min. 15 min. 20 min. 30 min. 60 min. 5 min. 35 min. 65 min. 125 min. 130 min. C. Introduction to Topic Objectives of Introduction To introduce Earth Sciences. To discover that the Earth has many layers. Suggested Discussion, Q & A Today we are going to talk about the Science of the Earth. Why is this information important to you? We live on Earth and need to know about what is happening in the area we live. For instance, it is important to know if a volcano or earthquake is expected to take place close to us so we can take necessary safety precautions. Sometimes we can’t predict when things like this will happen. What do you know about the Earth? The Earth is made up of layers. Some are liquid, some are solid. The Earth is made up of plates. The Earth is a dynamic and changing place – plates are always moving. Page 5 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science CHOICE: You can use this analogy or come up with one of your own. It may be helpful to have an example of this chocolate in your kit or draw what it looks like on the board. You can think of the Earth as a Ferrero Rocher chocolate -the gold wrapping represents our protective atmosphere. The outer layer of the chocolate is hard and has many different heights. This “crust” is similar to the Earth‟s crust. Inside, is a softer chocolate much like molten lava and the core of the Earth is hard much like the nut in the middle of the chocolate. Can anybody tell me which scientist studies the Earth? A geologist studies the Earth. DELIVERY HINT: While you are talking about the different parts of the Earth (crust, mantle, core), if you mention thicknesses etc., be sure to emphasize that these are estimates only (provide a range) and that we are providing this information based on what we have found. What are the different parts of the Earth? (Use the map of the cross section.) There is a layer around the entire Earth called a crust. It ranges from 6 km to 90 km in thickness. It is thicker where the continents are and thinner where the oceans are. Beneath the crust is a layer of hot rock called the mantle. The mantle is 3,000 km thick (that would be like driving from Vancouver to Regina and back to Vancouver or driving from Toronto to Halifax and back to Toronto) and ranges from 500 to 4,150 degrees Celsius. The top part of the mantle is solid and this part in combination with the crust is called the lithosphere. Below the mantle is the Earth’s core. It is mostly made up of iron and nickel. It is solid in the centre with liquid on the outside. The liquid outer core is approximately 2,100 km thick and the solid core is about 1,300 km (Toronto, Ontario to Fredericton, New Brunswick) in diameter. The temperature at the centre of the Earth is 4,000 degrees Celsius and it is solid because the pressure is too great for the iron and nickel to melt. (Use the classroom map or laminated maps to point to places mentioned.) Page 6 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science D. Activities ACTIVITY #1a: Put Pangaea Together (10 min.) Oral instructions Objective of Activity To introduce Pangaea and explore the continental drift theory. Suggested Instructions, Q & A The first activity we‟re going to do today is a „world puzzle‟ from about 200 million years ago. In 1915, a German meteorologist named Alfred Wegener made some interesting conclusions about how the Earth would have looked 200 million years ago based on a scientific theory called continental drift. Does anyone know what a continent is? A continuous mass of land. This is how we divide the land in our world – Europe, Asia, South America, North America etc. What is a theory? A theory is a scientifically acceptable idea developed to explain a phenomenon. The continental drift theory suggested that about 200 million years ago, there existed a super continent called Pangaea – meaning “all lands”. According to Wegener‟s theory, this continent broke into smaller parts each of which drifted to their present locations. (Ideas relating to this theory date as far back as 1620 when an English philosopherscientist named Francis Bacon was the first person to recognize that the continents fit together. As well, in the early 1900s, Robert Taylor, a geologist who was trying to explain how mountains were formed was the first to put forth the theory of continental drift.) Page 7 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science In groups of two, see if you can solve the world puzzle from 200 million years ago by using the pieces you have to put the continents back together in one piece. (Each of the continents will be labeled with North America, South America, etc.) DELIVERY HINT: Go over directions (north, south, east and west) before you begin this activity by writing a diagram on the board. Some students may not be comfortable with this. ACTIVITY #1b: Put Pangaea Together Using Clues (10 min.) Use Pangaea Puzzle Task Card Oral instructions What sorts of clues did you use to put together your puzzle? Shape, colour, patterns etc. When Alfred Wegener published his theory of continental drift, he used geological and meteorological clues to prove his theory. What do geological clues relate to? History, fossils and structures of the Earth. What do meteorological clues relate to? Weather and the atmosphere. Using the clues provided check your Pangaea Puzzle (in your groups of 2) to see if the clues provide evidence for your original puzzle solution. DELIVERY HINT: Go over the first question together as a group using your fun foam magnetic continent pieces at the front of the class (Refer to the Pangaea Puzzle Task Card.) *Discuss using the large fun foam magnetic continent pieces at the front of the class. You can also use the beach balls to display the 3-D view of the Earth. Page 8 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Page 9 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science ACTIVITY #2: Plate Tectonics (30 min.) Use Geological Times Data Sheet Use laminated Map of Canada Objective of Activity To introduce the theory of plate tectonics. To demonstrate the three plate movements in plate tectonics. Suggested Instructions, Q & A Scientists have been studying the Earth for hundreds of years. As the technology has advanced, so has our knowledge about the Earth; what it is made up of, how it moves and how it will continue to change. We have been looking at Pangaea and how the continents have moved to their current locations. Years ago, scientists called this theory “Continental Drift” because they thought ONLY the continents were moving. However, as they continued to study the Earth they discovered that the continents, the land we live on, is connected to the land underneath the oceans (the sea floor). Let‟s take a closer look at this connection. [Refer to the cross section of the Earth.] The Earth‟s crust covers the entire Earth. You can see that the Earth‟s crust is the land under the oceans and has been pushed upwards to become the land above sea level, the land we live on. Have you ever dropped a hard-boiled egg? What happens to the shell? It cracks into pieces, some large and some small. The Earth‟s crust is also broken into several pieces, although it wasn‟t dropped like the hard boiled egg. [Refer to the diagram of the Earth‟s plates.] Page 10 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Does anyone know what we call these pieces? Plates (show overhead of Earth‟s tectonic plates) (Point out a few plates that are relevant to where you are – don‟t list them all). The Earth‟s crust has 15 plates, they are: Eurasian, Australian, Cocos, South American, African, North American, Antarctic, Nazca, Caribbean, Indian, Pacific, Philippine, Scotia, Arabian and Juan de Fuca. Some plates, like the Pacific plate are entirely under water. Other plates, like the North American plate have both land and water on them. [Refer to the cross section of the Earth‟s composition.] Once scientists realized that the sea floor and the continents were connected, they figured that when the continents were moving, the sea floor must be moving as well. They re-evaluated the theory of continental drift and they came up with a new scientific theory that discusses the plates of the Earth‟s crust. This new and current theory is called plate tectonics. Can anyone guess what tectonics means? Tectonics in Greek (tektonikos) means ‘to build’ or ‘to put together and take apart’. The edges of each plate, where they meet other plates, are called plate boundaries. CHOICE: There is a lot of information included on the 3 kinds of plate boundaries. It is your choice how much detail you give the class – this will depend on their prior knowledge and level of interest. Also, feel free to add role-playing activities or any other demonstration or analogy that you find helps students understand. Demonstration: There are 3 kinds of plate boundaries we are going to focus on in our next activity. (Use the fun foam model or pictures on board to demonstrate the 3 different kinds of plate boundaries.) Page 11 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science 1) A CONVERGENT BOUNDARY is one where two plates are moving towards each other. When two continental plates meet or collide the plate material (Earth‟s crust) gets buckled and folded upwards into mountain ranges (i.e. Himalayas: Indo-Australian plate crashing into the Eurasian plate). Earthquakes also result. This is similar to two cars crashing head-on. The metal wrinkles fold, as the Earth does, forming mountains or rips like an earthquake. When a continental plate collides with an oceanic plate, the oceanic plate gets subducted/pushed under the continental plate. The oceanic plate reheats and melts as it comes into contact with the molten mantle. As the continental plate moves over the oceanic plate, it begins to peel the top layers off the surface. These layers pile up at the edge of the plate. This is how the Rocky Mountains were formed. Earthquakes (Marianas trench) and volcanoes (subduction of the Juan de Fuca plate beneath the North American plate) also result from this type of convergent boundary. When two oceanic plates collide, one usually subducts. The sinking plate remelts and, as it is subjected to much pressure, the remelted material comes to the surface in volcanoes, forming island arcs (i.e. Japan). 2) A DIVERGENT PLATE BOUNDARY is one where plates move away from each other. When this occurs underwater (i.e. Mid-Atlantic ridge) hot magma instantly comes to the surface and spreads out, creating a new ocean floor. When plates move away from each other under a continent, the crust splits open to allow magma out. Magma movement may be slow to the surface (warm areas and geysers/hotsprings) OR the magma might explode, bringing into existence a new volcano where there was only cool Earth before (i.e. East African Rift Valley). Divergent Boundaries may result in volcanic eruptions and earthquakes. 3) The third type of plate movement is called a TRANSFORM BOUNDARY. If plates do not come together nor move away from each other, how do you think they move in relation to each other? They slide alongside each other. Don‟t be fooled by the word slide! When two plates meet there is great stress on the surface of the Earth. Earthquakes occur at transform boundaries, but volcanoes are NOT common. Rocks at the Page 12 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science plate edges (called faults) may be pulverized into powder. (i.e. San Andreas fault in California: North American plate and the Pacific plate). Mountains can be formed from transform faults. Grinding stop and start movement generates great pressure in the plates and can cause cracking. Activity – Geological Times Hand out the Data Sheet and give oral instructions for this activity. Answer the questions on the Data Sheet after reading each article and use the erasable markers to mark your laminated map. The only thing each student will keep is the Data Sheet. Students will not keep the maps. Activity Wrap-up For a review, what are the three types of plate movements? Divergent, convergent and transform boundaries. * Take up the “Geological Times” activity using answers from the data sheet. Canadian Scientist One of the Great Leaders Transform boundary New Island Created! Divergent boundary – volcanic eruption and lava build-up. Rocky Roads Ahead Convergent boundary – subduction of the Pacific Plate underneath the North American Plate. Safest Place to Live in Canada Transform boundary – Queen Charlotte Fault (Pacific Plate and North American Plate) or Convergent Boundary Page 13 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science ACTIVITY #3 – Topographical Maps (60 min.) Use laminated Topographical Demonstration Map Use Map Worksheets Use Topographical Map Task Cards Objective of Activity To create a topographical map. To discover the different parts of a topographical map. Suggested Instructions, Q & A With the last activity we learned about the movement of different plates. In this part of the workshop, we will focus on mountains. Does anybody remember what kind of plate movements can create mountains? Convergent boundaries (plates that push together) are the plate movements that usually create mountains. Does anybody know where we can find the tallest mountain in the world? Mount Everest in the Himalayas found in Nepal. It is growing all the time because the plates are pushing together to make it taller. If you count from the bottom of the ocean, the Hawaiian islands from base (under water) to top are higher. Does anybody know where we can find the tallest mountain in Canada? Mount Logan in the Yukon. What are some mountain ranges in Canada? The Rockies, the Laurentians and the Appalachians How can we illustrate a tall mountain on a flat piece of paper? Colours, symbols (∆∆∆) or special maps called topographic maps. [Compare 3-D model of a mountain made of layers of Styrofoam to a 2-D model of a topographical map.] Page 14 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science How do you think we can represent the height of a mountain using a topographic map? There are special lines on topographic maps called contour lines. Contour lines are labelled to show the height of land. In a topographic map, 0 metres is sea level. If a contour is labelled 100 metres we know that every place along the line is 100 metres above sea level. [Split apart 3-D mountain into its different segments –6 segments total.] Let‟s say that each one of these segments (or contour lines) is 100 metres. If there are 6 segments or contour lines, how tall would my mountain be? 600 metres. [Use the 3-D mountain and the laminated hand-made map (it would be taped to the board)] As you can see from the map on the board, we don‟t need a 3-D model of a mountain to understand the height of a mountain. (If you need, show how you would trace the contour line by placing the 3-D map segments on the hand-made map.) Each contour line represents an increase in elevation by regular intervals (100 m, 200 m, 300 m etc.). If we know that each contour line on our map represents 100 m, how tall is our mountain? By counting the contour lines, we can see that there are 6 lines. Therefore, the mountain is at least 600 metres (the actual peak may be higher than 600 m but it is less than 700 m). Why do you think that we need topographic maps? We can use topographic maps for hiking, camping, canoeing, fishing and orienteering. Topographic maps are also used for urban planning, resource development and surveying. Topographic maps are important because they represent the Earth‟s features accurately and to scale on a two dimensional surface. (Point to the hand-made topographic map on the board.) Page 15 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science On our map we have our contour lines and a map border. What parts of the map are we missing? The components are north arrow, title, date, author, scale, contour interval and legend. (Additional information about scale, legend and north arrow are provided in section F.) * as students mention the different parts – you can attach these parts to the map. Activity DELIVERY HINT: You could suggest to the teacher that they may want to collect these maps as a form of assessment. DELIVERY HINT: You may want to emphasize that for their own mountains, the contour interval will be a made-up number that they decide on (i.e. 100 m, 500 m). Also, clearly explain the difference between SCALE and CONTOUR INTERVAL (see background information section). (Show students bags of supplies for topographic map making.) As you can see, each group will be given a plastic bag with some plasticine and other supplies. With the plasticine you will design a model of a mountain. What is a model? In this case, it is a small-scale representation of the real mountain. Working with a partner, each of you will create a topographic map using the materials provided. One group member will create a STEEP MOUNTAIN and the other member will create a GENTLE SLOPE. Hand out Topographical Map Task Cards but go over them with the class first. Don‟t forget to include a north arrow, scale, legend, authors, title, contour interval and date – you can refer to the map on the board for help. Please don‟t squash your model mountain. We will need them for later. Page 16 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science (Hand out bags with supplies and blank photocopied map.) Activity Wrap-up What does it mean when the contour lines on a topographic map are close together ? It means that the mountain is very steep. What does it mean when the contour lines on a topographic map are very far apart? It means that the mountain has a very gentle slope. * Demonstrate this by comparing two different plasticine mountains (i.e. the steep mountain and the gentle slope) and the topographic maps they have made. Being close to a mountain can affect the people around it and their lifestyle. Often times, these people can use a topographic map to make their life easier. For example: How might you use a topographic map if you were selecting a route for a hike? Choose a route that’s not too steep. How might you use a topographic map to find the best location for an airport? Make sure that airplanes have plenty of room to take off and land before the ground rises. How might you use a topographic map to find a route for a new road? Choose an area that has a gentle slope rather than a steep slope. Try to think of the people that live near mountains. What could they do as jobs? What could they do for fun? How do you think the mountain affects their lifestyle? Jobs: ecotourism (park naturalist), instructors for climbing and skiing etc., search and rescue. Fun: skiing, hiking, climbing. There are many, many examples for both. Page 17 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science E. Wrap-Up What was your favourite activity today? Do you think Science is fun? Do you like Science? Do you have any questions for me? F. Glossary Continental Drift The slow movement of the continents across the surface of the Earth due to the motion of the underlying tectonic plates. Convergent Boundary When two plates are moving towards each other. This can occur with two continental plates collide OR when a continental plate collides with an oceanic plate OR when two oceanic plates collide. Divergent Boundary When plates move away from each other. This can occur underwater OR under a continent. Earthquakes Sudden movements of the Earth‟s crust caused by the plates moving against one another. Earth’s Crust The outer “skin” of the Earth, consisting of large plates of rock which are floating on the mantle. Hot Spot A location on Earth where the temperature of the material under the crust is much higher than elsewhere. As a result, lava or magma is forced upward through cracks in the crust. This is how Hawaii was formed. Lava Hot molten rock that is above the surface of the Earth. Page 18 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Magma Hot molten rock that originates from the Earth‟s mantle. Mantle A thick layer of dense, semi-liquid rock which extends some 3000 km below the Earth‟s crust. Plate Boundaries Areas of volcanic and earthquake activity where tectonic plates meet. Richter Scale A logarithmic scale of 1 to 10 used to compare the magnitude of earthquakes. Subduction The dipping of one plate below another at a convergent plate boundary. Tectonic Plates Huge sections of the Earth‟s crust which move across the underlying mantle. Transform Boundary When two plates slide alongside of each other. G. Background Information Pangaea/Theory of Plate Tectonics With the advent of improved world maps, a few people looked at the world and thought that there were some places that looked like the continents would fit together like puzzle pieces. In 1915, a meteorologist named Alfred Wegener published his theory of Continental Drift. He suggested that about 200 million years ago there existed a super-continent that he called Pangaea (meaning all-land). It broke into smaller pieces and drifted to its present locations. To prove his theory he used the fit of Africa and South America, climatic data, rock structures and fossil evidence. Wegener's idea was NOT well accepted in the scientific community. When he died in 1930 most still did not believe his theory because he still could not explain HOW the continents moved. Page 19 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science In the 1950s and 60s, scientists started using continental shelf edges to examine the fit of the continents. It was VERY close. There were also great advances in exploring the sea floor. They found rifts and earthquakes on the sea floor. But they did NOT find any old rock. This led to the theory of sea floor spreading, as the ocean always seems to be creating new rock. In 1968, continental drift and sea floor spreading were combined to help form the plate tectonics theory. A Canadian named John Tuzo Wilson was one of the main scientists working on the theory. Plate tectonics states that the outer rigid lithosphere (crust and part of mantle) are made up of individual segments, or plates. These plates often include some oceanic and some continental crust, unlike continental drift where the continents themselves were thought to be the only things moving. What causes the plates to move? Scientists are not exactly sure. One explanation is that convection currents in the mantle cause the Earth‟s crust (plates) to move. Heat and pressure cause the molten rock beneath the Earth‟s crust to boil and flow. The energy to cause these convection currents and in turn plate movements may come from several sources within the Earth: Radioactivity within the Earth Meteoric bombardment of Earth Gravity and the pressure it puts on Earth‟s interior If the ocean floor spreads, why doesn’t the water fall into the holes? Water can‟t fall into the holes because tremendous pressure forces molten rock from the mantle to erupt through the rifts and doesn‟t stop to allow even a drop of water in. A totally new plate boundary appears when a continent starts to rift apart. Today, the continent of Africa is splitting apart along the African Rift Valley to make a new plate boundary. Continental lithosphere has broken right through. Sometime in the future, a new ocean may separate East Africa from the rest of the continent. Earth‟s plates move at a rate of approximately 2-12 cm per year. Earthquakes Occur all over the world Most occur on active faults that define the major tectonic plates Page 20 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science The „ring of fire‟ circling the Pacific Ocean (incl. Canada‟s west coast) is one of the most active areas in the world. Largest earthquake ever recorded – 9.5 magnitude off the coast of Southern Chile on May 22, 1960. Most earthquakes that occur in Canada occur along the active plate boundaries off the B.C. coast and along the Northern Cordillera (SW corner of the Yukon Territory and the Richardson Mountains and Mackenzie Valley) and Arctic margins (incl. Nunavut and N. Quebec) Magnitude is determined using a seismograph, recording the amplitude of the ground shaking and correcting this distance from the earthquake source. Intensity refers to how the quake is felt at various locations Human activities can trigger earthquakes! – filling in reservoirs and the injection of fluids into wells for oil recovery or waste disposal Difference between continental crust and oceanic crust Oceanic crust is very dense (basaltic) Continental crust (granitic) is not as dense as the oceanic crust. It extends out into the ocean 200 miles/320 km before sloping off. The continental crust under the water is known as the continental shelf Volcanoes A volcano is a gap in the Earth‟s crust from which molten rock, ash and gases (steam, carbon and sulfur dioxides, carbon monoxide, hydrogen chloride) flow or burst depending on the type of volcano and the pressure involved. Some volcanoes occur at the edge of tectonic plates. As the plates collide, one is subducted (pushed underneath the other). The rock that is subducted remelts to form magma. It can burst up through the surface, creating a volcano. Other volcanoes form under the oceans, when magma gushes up from underneath the oceanic crust. The molten rock in the magma chamber is lighter than the surrounding rock because solid rock expands when it melts. As it expands, the molten rock (magma) moves upward. When the magma reaches the Earth‟s surface it is called lava. The lava cools and solidifies (sometimes slowly and sometimes quickly). Volcanic activity can create earthquakes, avalanches, landslides, mudslides and tsunamis (tidal waves). Page 21 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science An extinct volcano, if such a thing exists – and only time will tell – is a truly dead volcano. The volcano isn‟t located in an area of likely activity and there is no record of activity in years!!! Because of constant plate movement, an extinct volcano might always roar back to life. Where are volcanoes located? Most volcanic sites are areas where the Earth‟s tectonic plates come together/move apart. The Pacific region hosts the largest concentration of volcanoes, called the „ring of fire‟. Is there a link between earthquakes and volcanoes? YES! The movements of Earth‟s tectonic plates cause both earthquakes and volcanoes. Are there volcanoes in Canada? Yes, there are many volcanoes in and near B.C. Volcanoes occur where the Earth‟s crust is being stretched and pulled apart, and new crust is formed, such as along the undersea Juan de Fuca Ridge west of Vancouver Island. These areas of stretching can also occur on the continents. Such a region is found in north western British Columbia and forms a chain of volcanoes referred to as the Stikine Volcanic Belt. One of the most notable volcanoes in this chain is Mount Edziza, now a provincial park because of its incredible beauty. The third type of volcanic area forms where ocean crust is pushed down below continental crust in a subduction zone. A subduction zone runs along the coast of North America from northern California to the northern end of Vancouver Island. The most recently active volcano in this chain is Mount St. Helens in Washington State. Volcanoes in Canada which are part of this chain include Mount Garibaldi, Mount Cayley and Mount Meager. Of these, the most recently active is Mount Meager which had a very large eruption (probably similar to the 1980 eruption of Mount St. Helens) about 2,300 years ago. This eruption spread ash across British Columbia into Alberta. Page 22 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Heights of Mountains The website that lists (in order) the world's highest mountains is: http://infoplease.lycos.com/ipa/A0001771.html Mountain peak Everest K2 (Godwin Austen) Range Himalayas Karakoram Location Nepal/Tibet Pakistan/China Height ft. m 29,035 28,250 8,850 8,611 North Arrow Even if there is no north arrow on the map, it is convention that north is always at the top of the page unless otherwise indicated. There is a difference between true north and magnetic north. Since most topographic maps are used for orienteering, they have both the directions of true north and magnetic north. That way people can make adjustments with their compass. Scale To make the map a more convenient size, features on a map must be proportionally smaller than they really are. The proportion chosen for a particular map is its scale. The scale is the relationship between the distance on the map and distance on the ground. It is usually given in a fraction or a ratio – 1/10,000 or 1:10,000. The first number (map distance) is always 1. The second number (ground distance) is different for each scale. The larger the second number, the smaller the scale of the map. Topography Possible websites for more information: http://www.usgs.gov/education/teacher/what-do-maps-show/WDMS4.html http://mac.usgs.gov/mac/isb/pubs/booklets/symbols The word “topographic” is derived from two Greek words – “topo” meaning “place” and “graphos”, meaning “drawn” or “written”. The distinctive characteristic of a topographic map is that the shape of the Earth‟s surface is shown by contour lines. Contour lines are imaginary lines that join points Page 23 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science of equal elevation on the surface of the land above or below a reference surface such as sea level. Think of a contour line as an imaginary line on the ground that takes any path to maintain constant elevation. Contours make it possible to measure the height of mountains, depths of ocean bottom and steepness of slopes. A topographic map shows more than contours. The map includes symbols that represent such features as streets, buildings, streams and woods. (Contour lines are usually brown and blue lines mean rivers/lakes). Contours that are very close together represent steep slopes. Widely spaced contours, or an absence of contours, means that the ground slope is relatively level. The elevation difference between adjacent contour lines, called the contour interval, is selected to show the general shape of the terrain. A map of a relatively flat area may have a contour interval of 10 feet (3.05 m) or less. Maps of mountainous areas may have contour intervals of 100 feet (30.5 m) or more. Topographic maps are used at all levels of government and industry for food control, forest fire control, real estate planning, development of natural resources, environmental issues, right-of-way, highway planning and depiction of crop areas. H. Suggested Resources Websites www.usgs.gov www.infocan.gc.ca/facts/geography_e.html www.seismo.nrcan.gc.ca/questions/faq_e.html www.extremescience.com/PlateTectonicsmap.htm www.encarta.msn.com Page 24 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science Books Pictures of mountains provided by: Steve Westley Policy & Product Promotion Centre for Topographic Information Natural Resources Canada 711 - 615 Booth Street Ottawa Canada K1A 0E9 Tel: 613-947-0571 Fax: 613-947-2189 <mailto:[email protected]> <http://maps.NRCan.gc.ca/> Kendra, M. and Williams, P. (1992). Science Wizardry for Kids. New York: Barron‟s Educational Series, Inc. ISBN: 0-8120-4766-4 Alvens, C. (1994) Meteorology Today: An Introduction to Weather, Climate and the Environment – 5th edition. Minneapolis: West Publishing Company. ISBN: 0-314-02779-3 Page 25 of 25 In-class workshops, Tectonics Rock ©2003 Let‟s Talk Science