Presentation on theme: "Science on the Leading Edge: Plate tectonics on Canada’s West Coast"— Presentation transcript:
1 Science on the Leading Edge: Plate tectonics on Canada’s West Coast The Bamfield Marine Sciences Centre is located on the outer edge of Vancouver Island’s west coast. The Public Education Program works with teachers and students to promote science learning with a focus on the ocean and connections to the ocean.Bamfield Marine Sciences Centre, Public Education ProgramTeachers Workshop, October 24, 2008Pacific Geosciences Centre
2 Thanks to www.bms.bc.ca Kim Juniper (for the idea) Western Canadian Universities Marine Sciences SocietyBamfield Marine Sciences CentreNatural Sciences and Engineering Research Council (NSERC)PromoScience (Funding)EdGeo (funding for teachers workshop, we hope)NRCANGeological Survey of Canada,Pacific Geosciences Centre, (Jane Wynne, Mike Schmidt in particular)University of VictoriaNEPTUNE CanadaUNAVCOAll the pilot teachers and students from Calgary Science School, Robert Bateman Sec.,Summerland Sec., St. Michaels Univ. School, Mark Islfeld Sec., Crestwood SchoolAnd many others…Thanks go out to all the groups and individuals who made the SOLE learning material available for teachers and students.
3 ObjectivesLink plate tectonics to British Columbia’s current geologic situationVisualize the movement of local tectonic platesMake connections between plate movement, sub-sea ridges, divergence, subduction, earthquakes, tsunamis and volcanoesUse real-time data to plot the movement of GPS stations at Victoria and Seattle
4 Where in the world is the Juan de Fuca plate? Tectonic PlatesThe Earths crust is made up of tectonic plates that slowly move on currents of molten rock or magma. Continental plates are less dense and tend to float over dense metal laden oceanic plates.Where in the world is the Juan de Fuca plate?Hint: it is very small.
5 ‘Creation and destruction’ of plates. Divergence: two plates moving away from each otherSubduction: a dense, heavy oceanic plate “slides” under a lighter continental plate
6 Seafloor SpreadingMagma rises to the seafloor through a series of fracturesCools, then sticks to walls forming vertical sheetsOcean crust spreads in both directions away from the ridgeUniversity of Washington& NOAA
7 Juan de Fuca ridge, underwater volcanoes. Juan de Fuca Ridge: Deep Sea Vent
8 VolcanoesVolcanoes lie above the deep subducting crust which is hot enough to melt the mantle aboveHot, buoyant magma rises up to erupt at the surfaceImage: Google Earth
9 Juan de Fuca Plate http://cgc.nrcan.gc.ca/geodyn/images
10 Block diagram of Southwest B.C., showing features. Sub-sea ridge, divergence, Pacific Plate (dense), Juan de Fuca Plate (dense), spreading at ridge, size of Earth not increasing, North American Plate (more buoyant), movement, subduction zone, brittle part sticky, melting part, volcanoes, (use lasagna analogy)Turner, R. J. W., Clague, J. J., Groulx, B. J.,1998: Geoscape Vancouver,living with our geological landscape; Geological Survey of Canada, Open File 3309
11 EarthquakesSouthwestern British Columbia Earthquakes in the last 30 days (from nrcan.gc.ca)
12 Not all months are created equally. Earthquakes Aug 14 - Sept 13
13 There’s a whole lot of shaking going on. Five years worth of shaking.
14 Vancouver Island Earthquakes Epicenters are located along plate margins and above subduction zones (faults)Earthquakes are mostly magnitude 2-4 on the Richter scaleEg. magnitude 3 would move the ground about one millimetreThe Cascadia Subduction fault is locked at a depth of 20km – brittle rock and rock above are being flexedEventually a slip will occur causing another large earthquake
15 wood-block print, the Great Wave off the Coast of Kanagawa, Tsunami, Adapted from awood-block print, theGreat Wave off theCoast of Kanagawa,by Hokusai.The December 2004, Sumatra, Indonesian Islands earthquake rupture area is similar in size to the Cascadia subduction zone. The last megathrust earthquake here was in January The tsunami from that quake was devastating to coastal communities here and in Japan.Mt. St. Helens, USGS
16 The great 1700 EarthquakeThis mathematical model of the January 26, 1700 megathrust earthquake shows the wave as it reaches Hawaii. .
17 Is there evidence the plates are actually moving? Data collected by a network of GPS (Global Positioning System) receivers track the exact position of nodesCompare moving GPS nodes to stationary nodes further inlandMeasure how far and in which direction the crust is deformingWe will have a look at the data and graph the location vectorsThe Geological Survey of Canada runs the permanent GPS tracker network that investigates crustal deformation in British Columbia. It is called the Western Canada Deformation Array and it produces measurements for Canadian and International scientists.
18 Western Canada Deformation Array (WCDA) Permanent GPS Tracker NetworkGeological Survey of CanadaMeasures plate deformation in the CascadiaSubducation ZoneSeismic hazard in densely populated region ofBritish Columbia
19 GPS technology used to measure continental crust movement. Latitude (north/south)Longitude (east/west)Elevation
20 Movement of Victoria GPS Station (East-West) and Correlation with Tremor Activity
21 What the data looks like. Download as a .csv file, save as an Excel file, use Excel to graph and calculate regression line and slopeUse the slope of the line (mm/day) to calculate average yearly movementThe UNAVCO web-site (Outreach & Education) has current data that can be down-loaded so that the class is working with near real-time data
22 Remember, when looking at graphs: Check the axes and the unitsLook for trendsThe slope of line is simply rise/run (or change in y over change in x)Let’s look at some near real-time GPS data from Victoria & Seattle
23 We are going to plot vectors for Victoria and Seattle GPS nodes You have a data table with four boxesVictoria eastward is already calculatedUse the slope (mm/day) X days/year to calculate average annual velocityExample:
27 This is the last graph for this exercise. What is missing? Seattle northY = xWhat is the slope of the line?
28 How to plot a vector.Start at zeroMark how far east and and how far northMake a pointDraw a line from 0 to the pointPut an arrowhead on the pointNorthPointWestEastCongratulations! You made a vector that shows magnitude and direction of movement.SouthNow, draw the Victoria & Seattle vectors
29 Discussion Compare the vectors Why do Ucluelet and Neah Bay vectors have so much more velocity?Predict the vertical movement at Ucluelet and Neah Bay vs more Eastern nodes?What are some sources of error?
30 What’s next? Extending the network to the seafloor. NEPTUNE Canada will provide real-time data on seismic activity to shore via a powered fiber-optic cable.Cabled-laying system on ROPOSROPOS Canada copyright