INTRODUCTORY GEOLOGY USING THE AUGMENTED REALITY SANDBOX Terri Woods <[email protected]> East Carolina University BACKGROUND Spatial thinking is often challenging for introductory geology students. The Augmented Reality Sandbox (AR Sandbox) is a powerful tool for bridging the gap between 2-­‐D representations and real landscapes. The AR Sandbox can be used in undergraduate physical-­‐geology courses to teach topographic maps and surficial features and processes. Instructors can demonstrate topographic concepts (contour lines, topographic profiles, etc.) and students can engage in model-­‐building of coastal and fluvial environments (drainage basins, cut-­‐offs, longshore transport, sea-­‐level rise, spits, flooding, etc.). The sandbox’s water-­‐flow model can elucidate impacts of moving water on surface features. TIME Prep Time: 45 minutes Classroom Time: 5 hours Cleanup Time: 15 minutes MATERIALS • AR Sandbox filled with sand • Computer running AR Sandbox software • Auxiliary display monitor • Transparency film, markers, and tape • Whiteboard along the back of the sandbox, to record sand elevations as students create a topographic profile of a three-­‐dimensional sandbox landscape. A cork board and push pins would serve the same purpose. • Supplementary topographic maps and landform images • Large pieces of wood to smooth sand throughout the entire box • Small shovels and buckets 1 • Very thin sticks with cardboard squares taped to the end to generate rainstorms on limited areas • Wooden models of buildings • Rollers for smoothing sand • Rocks and wood for jetties and groins • String • Dowels of various length to fit all the way across and within sandbox • Student camera phones ASSESSMENT Student submissions: Students use camera phones to capture landscape models they build and submit them via email for grading. For the purposes of grading, small details of the shapes of the features and their absolute reliefs were not of primary concern. Instead, the accuracy of the following were evaluated: • general shape of the feature(s) (i.e., oval versus round versus square) o are oval features elongated properly with respect to sides of box? • general location and relief of individual features o are the features with higher and lower elevations located approximately where they should be with respect to one another? o do these higher and lower features show the correct steepness in the right places around the features? o are the stream valleys oriented properly as to where the headwaters and mouths are? o are the tops of features flat where they should be and “pointed” where they should be? o are the proper numbers of valleys and ridges present? o are the smaller feature(s) in the correct spot(s) when located on top of larger features? o are the relative sizes of smaller/larger features correct? Classroom discussion and feedback: As time allowed, the instructor also checked with students working in the sandbox to address questions or misconceptions that arose as they worked. 2 ADDITIONAL RESOURCES • Download sandbox software: https://tinyurl.com/sandbox-­‐download • Sandbox construction and calibration guide: https://tinyurl.com/sandbox-­‐
instructions • Community forum for troubleshooting sandbox issues: http://lakeviz.org/forums/forum/ar-­‐sandbox-­‐forum/ • Other sandbox resources: http://3dh2o.org/sandbox/ • Any laboratory manual for an introductory college course in Physical Geology that includes exercises on topographic maps in general, and topographic maps used to investigate coastlines and rivers, in particular. • Additionally, Google Earth Timelapse (which highlights imagery showing the effects of fluvial and coastal processes over time) can be combined with sandbox model-­‐building to help students compare their models with actual processes. (For instance, Google Earth Timelapse portrays the erosion of the Outer Banks: https://www.youtube.com/watch?v=DKUUNgMKGI8. Additional processes can be explored at: https://earthengine.google.org/timelapse.) I. PRE-­‐LAB PREPARATION (Time: 45 minutes) A. Activating the sandbox 1. Boot up the program by FIRST turning on the projector, and then the computer. The computer is programmed to open up the sandbox.sh program for you. After exiting program, to open it again just go to the desktop and: • Double click on sandbox.sh • Click on “Execute to Terminal” 2. To activate water features: • Put cursor approximately in the middle of the sandbox • Push and hold down the 1 key • Put cursor on “Manage Water” • Release 1 key • The dialogue box “Creating Manage Water” will appear • Press 2 key • Push and hold down the 3 key • Put cursor on “Add Water Locally” 3 • Release 3 key • The dialogue box “Add Water Locally” will appear • Press 4 key B. Build a terrain such as the one shown below, making it significantly steeper on one side than the other. Have the mountain fill much of the sandbox so you won’t need to flood the whole sandbox to see the water rise and fall with respect to contour lines. Make sand elevation in the flats all around the mountain relatively uniform. Make your mountain with a good valley that shows a “V”. Try filling the sandbox with water before lab to get an idea of how long to continue flooding. C. Tape a piece of transparency film horizontally to the monitor (i.e., long dimension across the monitor). Mark the edges with tape so there is no chance of writing on the monitor itself. D. Practice activating the water features. E. Place the whiteboard at the back of the sandbox. F. Prepare / print relevant 2-­‐D topographic maps and landscape images (see sample images included in this lesson plan). 4 II. INTRODUCTION (Time: 5 minutes) -­‐ Explain the important components of the sandbox: A. Kinect camera that perceives changes in the distance to the sand surface B. Computer processes data collected by Kinect camera using visualization software and generates contour lines and an elevation color map. C. Lines and colors are projected onto the sand with a short-­‐throw projector. D. The software also includes a realistic flow simulation that projects moving water onto the sand. E. Computer monitor that shows 2-­‐D image of the 3-­‐D terrain in the sand box. III. INTRODUCTION TO TOPOGRAPHIC MAPS (Time: 45 minutes) Motivation Learning to use topographic maps can be challenging for college students but facility with these maps is crucial to developing an understanding of surficial processes associated with rivers, glaciers, oceans, and groundwater. This skill can also help students in their everyday lives when using road maps, property maps, and navigational charts. Learning Objectives After these exercises (IIIA – IIIE), students should be able to: • list the properties of contour lines o Contour lines do not cross, merge, or branch o Closely spaced contour lines indicate steeper slopes than contour lines that are more widely spaced o Contour lines will often (but not always) close on a map o Contour lines “V” upstream around a valley • understand the difference between relief and steepness • construct topographic profiles • envision a simple terrain based on its topographic map 5 A. Contour Lines (In this and later sections important prompts for the instructor are in bold font.) 1. Instructor asks students to make observations about contour lines and prompts them to respond to the questions below. If they don’t volunteer, have some students kneel down until their eye is level with the rim of the sandbox. Tell them to trace a single contour line all the way around the mountain noting that it does not get higher or lower with respect to the rim of the sandbox. Then ask for responses to the following: a. Do contour lines close to form a loop? Then point out that some may not close within the boundaries of the image they see. b. Do contour lines cross or branch? c. Describe changes in the spacing of contour lines around the mountain and correlate this with steepness. d. What happens to contour lines on either side of a valley? e. Which way does the sharp end of the “V” point – up or downstream? f. Make sure to trace contour lines to demonstrate your observations. B. More Contour Lines 1. Instructor uses the “1” key to rapidly “flood” the box as high up the mountain as is practical considering time constraints. (Try this out before lab to get an idea of how long it takes to flood to the desired elevation.) Because this flooding turns the landscape blue it is much better to watch the changes as you dry up the water with the “2” key than to wait for all the water to drain off the mountain as it accumulates during flooding. The supplemental video suggests how this demonstration could proceed. 2. Now ask for a volunteer to use a pen and mark a line on the transparency where the water meets the mountain all around your feature. 3. Next use the “2” to drain some water and have another student trace the line where the water meets the mountain along a lower contour line. 4. Continue process until you have 4 or 5 lines on the transparency film. 5. Finally remove the transparency and show them the contour map that they have created. 6 6. Because virtual water in the sandbox is opaque you can’t get them to estimate depths under a blue water body, but you can ask them to imagine that water is filling a dry valley up to a line you indicate and get them to determine how deep the water is (just counting contour lines will do). C. Relief and Steepness 1. Instructor builds two hills in the sandbox – one much higher and steeper than the other. 2. After defining relief, ask students which hill has the greater relief? a. Ask them again to note and describe the different spacing of the contour lines. 3. Define local and total relief and ask volunteers to show examples. 4. In a “question and answer” session instructor assesses students to make sure they understand the difference between relief and steepness and how to determine them. D. Topographic Profile (The supplemental video provides a good idea of how this demonstration should proceed.) 1. Using the “two hills” you built for the last demo, lay the string across the box in a straight line going up and down over the most interesting part of the topography. 7 2. Starting at one side of the box, get one student to volunteer to use a skinny dowel (we have various lengths so they can fit down in the box or above the rim) and lay it front to back in the box lined up with and parallel to a contour line. 3. Have another student put a mark on the whiteboard where the skinny dowel touches it. 4. Ask various pairs to repeat this process all the way across the box, trying to engage all students at least once. 5. Now have a student connect the dots to complete the profile. 6. Point out they have generated a topographic profile on the whiteboard. E. Student Activities (Time: 20 minutes per student or student team. Students not actively working in the sandbox can pursue exercises using topographic maps.) 1. In the sandbox, have students construct the terrains shown on the simple topographic maps below. They will then take cell-­‐phone pictures of their models and submit them by email to the instructor for a grade. For the purposes of grading, the overall shape of the feature and its absolute relief were not of primary concern. Instead, if the relief at different places on the features was generally correct, if the number of high and low spots and their locations was generally correct, and if the extent of low-­‐ and high-­‐
relief sections was generally correct, students received full credit. 8 IV. RIVERS LABS Motivation Rivers are important features in a range of ecosystems so students seldom find themselves farther than a few hundred yards from a river channel. Understanding fluvial processes and features can help them avoid serious loss of life and property such regions experience during spring floods and hurricanes. All types of streams exist, ranging from high-­‐gradient mountain rivers flowing in narrow, V-­‐
shaped valleys to low-­‐gradient, coastal creeks on broad coastal plains. Students should, therefore, be familiar with the entire spectrum of fluvial systems. This knowledge permits potential property owners to make wise decisions before they purchase and empowers informed citizens to influence municipal officials as they make decisions regarding land use near rivers. As the US population increases, water-­‐supply and water-­‐quality issues will require even more difficult choices to be made about our streams and rivers. Learning Objectives After this laboratory, students should be able to: • predict the impact of gradient on water flow • explain how flooding impacts regions with differing topographies • recognize many erosional and depositional features created by rivers • construct models of fluvial features in the sandbox • envision what a fluvial feature looks like in three dimensions when looking at its representation on a topographic map, and vice versa • envision the process at work to create fluvial features A. Student Activities (Time: 30 minutes per student or student team. Students not actively working in the sandbox can pursue exercises using topographic maps.) During labs, have students construct models of two to three of the following features and processes in the box and use the water-­‐flow model to study the interaction of water and landscape. Allow them to choose the features and processes they want to model. Again, have them take photos and submit. 9 1. Models of Fluvial Features and Processes a. All groups of students build an elongate ridge with markers placed along the location of the drainage divide. 1) Have them generate virtual rain on one side of the divide and then on the other and note where the water goes. 2) Can water from one drainage travel into the neighboring drainage? b. Student groups then choose to model 2-­‐3 of the following features and processes: 1) Fluvial Features a) General outline of the contiguous 48 states and location of the two major continental divides (east and west) and the huge drainage basin of the Mississippi River showing where it flows into the Gulf of Mexico -­‐ include some tributaries and the Great Plains. b) Point bars, relict point bars, and bars within a stream channel c) Cut-­‐off, oxbow lake, and abandoned meander d) Bigger stream with natural levees and a yazoo tributary -­‐-­‐ Flood with the “1” key so the levees show up well. Make the upstream end at a higher elevation so the water actually flows and then “rain” in both the main stream and the yazoo tributary. e) Build two of the following types of drainage patterns: dendritic, rectangular, trellis and radial. o Flooding with the “1” key makes the pattern more obvious. 2) Fluvial Processes a) Model formation of a meander by starting with a straight channel and then putting an impediment in the way so virtual water moves to the side. Rain on your model to show how the water in the stream is diverted sideways by the impediment. b) Using your hands to represent moving river water transporting sand, demonstrate erosional and depositional processes on the outside and inside of a meander and put the model of a house where it would be safest to build a home. 10 c) Using your hands to represent moving river water transporting sand, demonstrate formation of an oxbow lake and fill it with water. d) Make a delta -­‐-­‐ Build a small basin and partially fill it with water. Then push some sediment down the valley to make a delta. Then dry up water (using the ‘drain’ button) and show the resultant alluvial fan that exists in arid regions with short rainy seasons. e) Model headward erosion. f) Model stream piracy and formation of a water gap by headward erosion. g) Model formation of a wind gap when the water level declines due to climate change. h) Floods and Floodplains o Build a stream with a wide floodplain and one with virtually no flood plain and show how far flood water moves away from these two different streams. o Model both a primary and secondary floodplain (i.e., stream terraces). i) Coastal Flooding -­‐-­‐ Model two different paths for a hurricane to move (two different paths at a 90o angle to one another) over two clearly divided streams and show different flooding patterns in the two different drainages that result from the two different (and perpendicular) paths j) Sinuosity -­‐ Model difference between channel length and valley length to explain sinuosity. V. COASTAL LABS Motivation Coastal change has significant political and social consequences around the globe. If current trends in climate change continue, coastal regions will experience profound effects from sea-­‐level rise. Flooding of low-­‐lying coastal areas requires citizens to make hard decisions about preserving infrastructure and property in 11 the coastal zone. As a result, it is important for voters to understand natural coastal processes and the impacts humans have on them. Learning Objectives After this laboratory, students should be able to: • recognize the types of coastal features formed by erosion and deposition • model ways humans have attempted to interfere with natural coastal processes • describe how US barrier islands such as those of North Carolina originated • construct models of coastal features in the sandbox • model coastal processes in the sandbox • envision what a coastal feature looks like in three dimensions when looking at its representation on a topographic map and vice versa • envision the processes at work to create coastal features A. Student Activities (Time: 30 minutes per student or student team. Students not actively working in the sandbox can pursue exercises using topographic maps.) During labs have students construct models of two to three of the following features and processes in the box and use the water-­‐flow model to study the interaction of water and landscape. Allow them to choose features and processes such as the following to model. Again, have them take photos and submit. 1. Coastal Features a. Build a model of a local estuary showing locations of major inlets. b. Build mainland, backshore, foreshore and offshore portions of the coast and document their appearance during high versus low tide. c. Build a model of a rocky coast with sea stacks, headlands, bays, etc. Generate virtual waves and study and describe how they refract at headlands. d. Build a model of the California coast with circulation cells (beach compartments), offshore submarine canyons to bleed off sediment, and rivers within cells to supply sediment. 12 e. Build a coast showing most of these features: tombolo, barrier island, tidal inlet, ebb tidal and flood tidal deltas, baymouth bar, and spit. 2. Coastal Processes a. Build a spit and determine the direction of longshore transport necessary to deposit that feature. b. Model how longshore transport can convert the spit into a baymouth bar. c. Using rocks to represent groins, model a beach that has built out on one side and eroded on the other in response to longshore transport. d. Build a model to show how longshore transport can close the mouth of an inlet. e. Build a model of Cape Hatteras showing where the sand eroded from the old location of the lighthouse goes as it is carried southward by longshore transport f. Model how sea-­‐level rise erodes a shallowly sloping mainland faster than a steeply sloping mainland. Then flood with the “1” key and watch the mainland retreat. g. Represent barrier island migration by the process of overwash in response to rising sea level pushing sand over the islands with your hands. h. Model the formation of an inlet during a hurricane. After making the inlet, flood the box so that inlets appear at the low spots. i. Model barrier-­‐island thinning as sea level rises (i.e., situation where no overwash occurs due to seawalls, roads, etc.) and the shoreline retreats on both sides of the island. j. Model evolution of the Susquehanna River into Chesapeake Bay Estuary as sea level has risen since the Last Glacial Maximum. k. Model construction of ocean front seawall, its eventual collapse, and accumulation of debris on the beach. l. Model straightening of coastline by erosion of headlands and deposition in bays through hundreds of thousands of years. 13 m. Model refraction of waves around coastal features. Also, see if the model allows you to note and describe how waves are affected by an offshore sandbar. n. Model marine terraces and their exposure as sea level changes. VI. ADDITIONAL STUDENT ACTIVITIES A. If time allows, have students construct real terrains from real topographic maps or other images such as the US Geological Survey topographic maps below. 14 GLOSSARY Alluvial fan – a low, fan-­‐shaped deposit of terrestrial sediment formed by a stream either where it issues from a narrow mountain valley onto a plain or broad valley, or where a tributary stream joins a main stream Augmented reality – overlying computer-­‐generated and presented information onto the real world, thereby combining real and virtual images, presenting an interactive image in real time, and displaying a scene in three dimensions where real and virtual objects are accurately aligned Backshore – the zone that lies above the ordinary high-­‐watermark and is, therefore, not traversed by the rise and fall of the tide so that it remains dry under most conditions Barrier island – a sand island built up over the high-­‐water elevation and similar to an offshore bar but differing from it in having multiple ridges, areas of vegetation, and swampy terraces extending toward the lagoon Barrier island migration – the slow (hundreds to thousands of years) landward movement of a barrier island in response to sea level rise and driven by transportation of marine sediment from the ocean side to the lagoon side of the island during storm events Baymouth bar (also bay barrier) – a sediment bar extending totally or partially across the mouth of a bay and severing the bay’s connection with the ocean Beach compartment – a segment of beach that is provided sediment by a stream at one end and/or erosion of local sea cliffs and which loses sediment down a submarine canyon at its other end Continental divide – an imaginary line connecting points of high elevation across a continent and dividing regions whose streams drain into one ocean from regions that drain into another Cut-­‐off (or meander cut-­‐off) – a new, relatively short channel formed when a stream cuts through the neck of a meander or horseshoe bend Delta – a fan-­‐shaped body of sediment deposited in an ocean or lake at the mouth of a stream Drainage basin – a region of land surrounded by drainage divides from which a river or stream derives all its water Drainage divide – the elevated boundary separating adjacent drainage basins (See continental divide) Drainage pattern – the configuration of a natural or artificial drainage system; stream patterns reflect the topography and underlying rock formations in a region 15 Fluvial – pertaining to or produced by the action of a stream or river Foreshore – the zone that lies between the ordinary high-­‐ and low-­‐watermarks and is daily traversed by the rise and fall of the tide Gradient – the rate of descent or ascent (steepness of slope) of any topographic or hydrologic features such as streams, water tables, or hillsides Groin – a wall built perpendicular to the coastline to trap sand that moves down the coast carried by the longshore current (i.e., undertow) Headward erosion – erosion caused by water flowing at the head (origin) of a river valley, which causes the head to move back away from the direction of the stream flow, and causes the stream channel to lengthen Lagoon – shallow body of water that separates the mainland shoreline from a barrier island or barrier reef Last glacial maximum – the last period in Earth’s climate history when ice sheets were at their greatest extent (about 24,500 years ago) Longshore current (littoral current) – a current caused by wave action, that sets parallel to the shore; usually in the nearshore regions within the breaker zone Longshore transport – movement of sand parallel to the shore in the longshore current Marine terrace – a raised beach or perched coastline that is a relatively flat, horizontal or gently inclined rock surface originating by wave abrasion during thousands of years of stable sea level, and elevated above sea level by local tectonic processes Meander – broad semicircular curve in a stream that develops as the stream erodes the outer bank of a curve and deposits sediment against the inner bank Natural levee – an elongate embankment compounded of sand and silt and deposited along both banks of a river channel during times of flood Offshore – zone that lies below the ordinary low-­‐watermark and is not exposed by the normal low tide so that it remains submerged under most conditions Overwash – coastal process by which storm-­‐induced waves exceed the height of coastal sand dunes so that sand is transported over top of the dune and deposited inland Oxbow lake (or oxbow) – a crescent-­‐shaped body of water located alongside a stream in an abandoned meander after a cut-­‐off is formed and the ends of the original bends are silted up Pleistocene – the epoch of Geologic Time extending from about 2,588,000 to 11,700 years before the present 16 Point bar – one of a series of low, crescent-­‐shaped sand and gravel ridges formed on the inside of a growing meander by the gradual addition of sediment Refraction (wave) – the departure of a wave from its original direction of travel when it approaches the coast at an angle so that one portion of the wave enters shallow water before the rest of the wave Relic point bar – a point bar that is no longer actively accumulating sediment Relief (or topographic relief) -­‐ the vertical elevation difference between the highest and lowest points of a land surface. Can apply to the entire area shown on an individual map or just to a specified horizontal distance or limited area (local). Sea stack – a chimney-­‐like mass of rock detached by wave erosion from a cliff-­‐
lined shore and surrounded by water Seawall – vertical structures used to protect backshore areas from heavy wave action which can destroy developed areas Sinuosity – the length of the stream channel divided by the straight-­‐line distance between its ends Spit – a long ridge of sand deposited by longshore transport where the coast takes an abrupt inward turn. It is attached to land at the upstream end Stream Piracy (or capture) – the natural diversion of the headwaters of one stream into the channel of another stream having greater headward erosional activity and flowing at a lower elevation Stream terrace – one of a series of level surfaces on a stream valley flanking and parallel to a stream channel and above the stream level, representing the uneroded remnant of an abandoned floodplain or stream bed Submarine canyon – steep-­‐sided valley winding across the continental shelf or continental slope, probably originally produced by Pleistocene stream erosion, but presently submerged due to sea-­‐level rise Tidal delta (ebb and flood) – sand bar or shoal formed in the entrance of an inlet by the action of reversing tidal currents Tidal inlet – a natural inlet maintained by tidal currents Tombolo – a sand or gravel bar or spit that connects an island with another island or an island with the mainland Topographical profile – a cross sectional view along a line drawn through a portion of a topographic map Yazoo tributary – a tributary stream that runs parallel to, and within the floodplain of, a larger river for considerable distance, before eventually joining it. Joining of these streams is normally blocked by a natural levee along the larger stream. 17