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Structure labs/drawing • Recent labs often “sloppy” • Not taking time to draw contacts properly – Units must maintain thickness – Contacts should be parallel and “smooth” – Contacts should be in the right place – Angles should be approximately correct (use a protractor if you cannot draw angles to within 10°) and consistent Drawing a strike and dip symbol What is the orientation determined? 115/37 NE Drawing a strike and dip symbol 115/37 115 37 NE What is the strike? N Done! Remember that if it is a cleavage measurement, the symbol like dip this…direction? What is the What is isthe dip? Geological maps …and on the CROSS-SECTIONS Wolfville map …on the Information is available on the: LEGEND MAP Also some more detailed information in the “Descriptive Notes” Section A • 11 (relatively straightforward) questions. • Some hints – Use the legend and cross-sections – “a deep well” means hundreds of metres (scale of the cross sections) – Contacts are: • Conformable (bedding) • Cross cutting (faults, intrusions, unconformities) – For question 10, think of the rule of vees – For question 11, think of your fieldtrip to Black River At a spreading ridge Away from the ridge segments Plates are moving BUT in the same direction and thus faults are not tectonically active (a “fracture zone”) Between the ridge segments Active relative motion on the fault BUT in the opposite sense to the “offset” of the ridge Right lateral fault… • Fault on which the “other side” appears to have moved to the right. Symbol for right lateral fault Left lateral fault… • Fault on which the “other side” appears to have moved to the left. Symbol for left lateral fault Plate tectonic animation Features on the ocean floor… (6e: 32–34; 5e: pp. 227–234) • Abyssal plain = flat portion of the deep ocean (away from spreading ridges) • Continental shelf = portion of the continental crust that is submerged • Continental slope = the marked change in slope of the ocean floor that indicates the change from continental crust to oceanic crust • Deep sea fan = a “fan shaped” pile of sediment off shore of major rivers (Amazon, Ganges, etc.) Features on the ocean floor… (6e: 32–34; 5e: pp. 227–234) • Mid-ocean ridge = the high range of mountains that runs under the oceans and is the site of “spreading” • Seamount chain = line of undersea peaks that extends from a “hot spot” in the mantle (only one end of the chain can be volcanically active and there is no associated “trench”) Features on the ocean floor… (6e: 32–34; 5e: pp. 227–234) • Transform fault = fault that offsets spreading ridges • Trench = the over deepened portion of the crust where an oceanic plate is “diving” into the mantle (associated with a volcanic arc) • Volcanic arc = A (usually arcuate) line of volcanoes (all can be active at any one time) usually associated with a trench