EES 1030 1st Edition Lecture 10Intro to Earth ScienceStructural Geology:Studying rocks and their geometry IS important to society because it pertains to ground stability for building, groundwater flow, tracing surface coal and ore deposits, gas and oil traps, and construction sites.Field observation by geologists: describe and map the orientations and lithology of rock units. This can be limited by outcrops.Outcrops: Sites where bedrock is exposed at surface.Strike: (trend) compass direction of the line produced by intersection of an inclines rock layer or fault with horizontal plane.Dip: (inclination) angle of inclination of the surface of a rock unit or fault measured from a horizontal plane.Deformation: general term for all changes in the original form or size of a rock unit. The most common types of deformations are brittle and ductile.Stress: force applied to a given areaFracture: changes in the shape or size of a rock unit, caused by stress.Elastic deformation: the rock returns to nearly its original size and shape when the stressis no longer being applied. Once the elastic limit is reached for a rock one of 2 things will happen. The first is:Brittle deformation: the rock fractures and cracks like a plate being dropped.Ductile deformation: the rock squishes into a new flow shape like dough being squishes. What controls brittle vs ductile formation? Different factors that influence the strength of a rock .- Temperature: high temperatures allow room for stretching and make rocks more ductile.Low temperatures will be more brittle. - Rate of deformation: (composition) different minerals are more resistant to deformation.Quartz is more brittle and micas are more ductile. - Confining pressure: high confining pressure minerals are less likely to fracture because the pressure around them hinders it. Less confining pressures with be more brittle.- Strain rate: high strain rate minerals tend to fracture and be more brittle where as low strain rates are more ductile.Joints: common rock structures that concentrate effects of chemical weathering, control location of ore deposits, and represent a risk to construction projects. Slip: sudden movement along a faultTypes of faults: dip slip and strike slipDip-slip fault: movement is mostly parallel to the dip of the fault surface. Dip-Slip faults are normal faults. Reverse fault: dip slip fault with an angle of more than 45 degrees.Thrust fault: dip slip fault with an angle of less than 45 degrees- Hanging wall: rock surface above the fault- Footwall: rock surface below the faultStrike-slip fault: dominant displacement is horizontal and parallel to the strike of the fault.Left-lateral: as you face the fault the opposite side of the fault moves to the left. Ductile deformation: during crystal deformation rocks are often bent into a series of wave-like undulations called folds as compressional stress shortens and thickens the crust.Syncline: a trough or fold of stratified rock in which the strata slope upward from the axis.Anticline: a ridge-shaped fold of stratified rock in which the strata slope downward from the crest.Blind thrust faults: no signs of the fault on the earths surface.Dome: older rocks in the centerBasin: Younger rocks in the