EXAM 3 REVIEW 1 Define stress and deformation Stress force to a given area Compressional Stress shortens a rock body Tensional Stress tends to elongate or pull apart a rock unit Shear stress slide past pushing a deck of cards over produces a motion similar to slippage that occurs between individual playing cards when the top of the stack is moved relative to the bottom Deformation is a general term that refers to all rock changes in the original form and or size of a rock body 2 What are the different types of stress and how do rocks respond to these stresses Compressional Stress shortens a rock body Tensional Stress tends to elongate or pull apart a rock unit Shear stress slide past pushing a deck of cards over produces a motion similar to slippage that occurs between individual playing cards when the top of the stack is moved relative to the bottom 3 Define strain and know the different types of strain Type of Stains deformation Elastic Strain deformation changes in size and shape of a rock unit that are reversible like a rubber band Plastic Strain deformation changes in size and shape of a rock unit that are permanent or not reversible through folding and flowing Brittle Strain deformation changes in size and shape of a rock unit that are permanent through fracture and faulting pressures weaker bonding Ductile Strain rocks that deform due to folding and flowing high temps and confining Brittle Strain rocks that exceed their elastic limit will behave like brittle solid and fracture low temps confining pressures stronger bonding 4 Know what joints faults and folds are and understand their differences Joints a joint is just a fracture with no movement Dip Slip Fault movement is mainly parallel to the dip of the fault surface consists of hanging wall rock surface above the fault and the footwall rock surface below the fault Normal Fault Type of Dip Slip Faults Reverse and Thrust Faults Reverse faults have dips greater than 45 degrees Thrust faults have dips less than 45 degrees Reverse Fault Thrust Fault right folds Strike Slip Faults Right lateral as you face the fault the opposite side of the fault moves to the Left lateral as you face the fault the opposite side of the fault moves to the left 5 What are the different types of faults and folds During crustal deformation rocks are often bent into a series of wave like undulations called Parts of folds Anticline upfolded arch shape of an A Syncline downfolded arch shape of an U Limbs refers to the two sides of a fold Axis a line drawn down the points of maximum curvature of each layer Axial Plane an imaginary surface that divides a fold symmetrically Dome upwarping of layer to produce a circular or elongate structure Basin downwarping of layers to produce a circular or elongate low 6 Know the basic earthquake location terminologies Focus point in Earth where earthquake energy is released Epicenter the location on Earth s surface directly above the earthquake focus Triangulation is a technique used to determine location of the epicenter 7 Define foreshocks mainshocks and aftershocks Foreshocks small earthquakes that may precede a large earthquake Mainshock is the largest earthquake in a sequence sometimes preceded by one or more foreshocks and almost always followed by many aftershocks Aftershocks adjustments that occur after a major earthquake these adjustments are small earthquakes 8 Know the types of seismic waves and understand their mode of propagation Surface Waves earthquake energy waves that travel along the outer part of Earth Body Waves earthquake energy waves that travel through Earth s interior these are further subdivided into groups P Waves travel through rock with a push pull type of energy propagation that temporarily changes the volume of Earth materials Can travel through solids liquids gases compression waves have faster velocity refract bend S Waves travel through rock with a shake that briefly changes the shape of earth materials these waves will not travel through gas or liquid these substance are not elastic in their behavior reflect bounce back different angle 9 How is earthquake location determined Travel time graph is used to determine the distance of the epicenter of the quake Transgulation is the technique used to determine location of the epicenter 10 What is the difference between earthquake intensity and magnitude Intensity a qualitative evaluation degree of shaking based on observed damage Modified Mercalli Intensity Scale a scale to determine how strong the quake was Magnitude a quantitative evaluation estimate of energy released data from seismographs Ricter Magnitude Scale determines how much energy is released and picks up the amplitude height of the largest seismic wave on the seismogram Both used to describe the strength of an earthquake 11 How is the energy release by an earthquake measured An earthquakes released energy is measured by its magnitude on a Ricter Scale 12 How does an earthquake cause destruction Strength of shaking proximity to epicenter Amount of time shaking longer more damage Type of soil soft thick wet increases damage material amplification Type of construction designed to be resistant or not 13 Know the mechanical and chemical layers of the Earth Mechanical Layers Lithosphere outermost layer about 250km deep Asthenosphere 2nd layer about 660km Mesoshpere 3rd layer extending from 660km depth to the core Outer Core 2 270km thick Inner Core sphere radius of 1 216km changes in the strength and density of Earth s layers due to increases in temperature and pressure with depth in Earth Chemical Layers Crust 1st layer 3km to 70km thick at some points Mantle 2nd shell layer that is about 2 900km deep Core iron rich sphere at Earth s center having a radius of 3 846km 14 What are the geologic features of the ocean floor Continental Shelf Continental Slope Continental Rise Abyssal Plains the most level places on earth Seamounts Isolated volcanic peaks many form near oceanic ridges may emerge an Island Oceanic Ridges broad linear swells along divergent plate boundaries over 70 000km 43 000 miles in length 20 of earth s surface Why are oceanic ridges elevated Because newly created oceanic lithosphere is hot and occupies more volume than cooler rocks 15 Know the different layers of the oceanic crust Four distinct layers Layer 1 sequence of unconsolidated sediments Layer 2 consisting of pillow lavas Layer 3 numerous interconnected dikes called sheet dikes Layer 4 gabbro in a sequence of