8/19/2016 What is Structural Geology? Geol 341 Structural Geology Introduction Goals Topics and Logistics • 1. Understand Earth’s structures and • http://www.geo.wvu.edu/~jtoro the processes that create them. • 2. Learn skills used to analyze and interpret geological structures How do Tool to Measure Strike and Dip we explain the major You need to buy one now features of SUUNTO MC2 Navigator the Earth? or Brunton TRUARC15 Mirror Compass with clinometer, Azimuth (360o) $40 to $50 Or a smartphone app (Lambert) Earth Field Notebook $8 each Moon 1 8/19/2016 Why are there mountains? How do faults relate to earthquakes? Active mountain front, Basin and Matterhorn, Swiss Alps Range Province, Nevada Interaction between Structural and It all starts with field observations Sedimentary Processes Brooks Range Foothills, AK Erosion Tectonic Burial Sedimentary burial Basal heat flux A basic tool: the geologic map A structural cross section: Interpret deep structure from surface data 2 8/19/2016 How can solid rock flow like taffy? Strain Field in a Shear Zone Morcles Nappe, Swiss Alps From Ramsay and Hubert, 1983 Microscopic view: How is deformation accomplished? Study structures at all scales 5 mm Looking inside the Earth Seismic Reflection Data from Santos Basin (Brazil) Seismic Acquisition Fossen, 2010 3 8/19/2016 Practical applications of Structure Methods of Structural Geology Where is the oil field? Experiments with Analogue Materials Salt H.M. Cadell, 1887 Mechanics: What happens to the stress field Stress Components when you drill a well? Or when a fault forms? zz z zx xz xz xx xx zx zz x Fracture systems and their role in fluid flow Preparation for Field Camp 4 8/19/2016 Orientation of a Plane Apparent Horizontality Elements of Geology, Lyell 1871 True Dip vs Apparent Dip True Dip vs Apparent Dip Map View N d= true dip True 20 a= apparent dip Dip Apparent True b= angle between strike (d) Line of section and line of section b tan a= tan d . sin b 50o a= atan (tan d . sin b) Line of Strike Apparent Dip Table Take Home Points a b • Structural Geology ranges from field observations to quantitative models and has broad applications • You need to buy a geological compass • Strike and dip describe the orientation and tilt of rock layers • Apparent dip is the tilt seen on a plane that is NOT 90o to strike. It is always less than true dip 5.