Study Guide for Exam 3

Physical Geology Study Guide for Exam 3 An accurate, complete, and well-written assignment is worth up to 10 points that will be added to your total points for the exam. This study guide must handed in as a PDF file through an attachment on a Blackboard Message. The study guide must be handed in within one hour of finishing the exam. Answer the following questions: 1) Define Metamorphic Rock. Where Metamorphism generally occur? Metamorphic Rocks are forms by the alteration of preexisting rock due to the effects of pressure, high temperature and or chemically active fluids Metamorphism generally occurs well below the surface of the earth but at shallower depths and temperatures than would cause rocks to melt 2) Describe Metamorphism. What are the three agents of metamorphism? What types of rock can be metamorphosed? Metamorphism conditions within the earth tthat result in the changing of the texture and mineral content of a solid rock without melting it Any type of rock may be metamorphosed- igneous, sedimentary or even metamorphic 3) Define Parent Rock. Why are parent rocks important? Parent rocks: the original rock before metamorphism takes place. Parent rock helps determine what metamorphic rock forms. 4) Describe what can be changed during the process of metamorphism. Process of Metamorphism can change both the texture and the mineral composition of the parent rock 5) What is the parent rock for marble? Describe what occurs when this metamorphosis takes place. Does the mineral content change during this process? What happens to fossils? Limestone is the Parent Rock of Marble When limestone is metamorphosed into marble the crystal size of it changed but not the chemical composition it will recrystallize usually forming larger crystals 6) What is the parent rock for quartzite? Describe what occurs when this metamorphosis takes place. Does the mineral content change during this process? Why is quartzite a very resistant rock? Quartz Sandstone is the parent rock of Quartzite Both sandstone and quartzite are composed of SiO2 When sufficient heat and pressure are applied to a sandstone the grain fuse together to form the very resistant rock quartzite 7) Describe what happens to shale as it undergoes the process of metamorphism. What rocks are formed at low grade metamorphism, medium grade metamorphism, and high grade metamorphism? Does the mineral content change during this process? Which of these metamorphic rocks has the finest grain size and which of these metamorphic rocks has the coarsest grain size? • It will create new minerals in response to the escalated heat and pressure conditions • Slate; Schrist; Gneiss • Yes • Slate has the finest grain size, while Gneiss has the coarset grain size

8) Can slate be formed from any parent rock? Explain why or why not. No It can only be made from shale. 9) What minerals are almost exclusively found in metamorphic rocks? Kyanite, Sillimanite, and some garnett 10) List and describe (in detail) the three basic types of metamorphism. Contact metamorphism occurs when magma comes into direct contact with the parent rock • Changes in the parent rock are primarily due to very high temperatures but not increased pressures • Immediately next to the magma intense metamorphism results in the formation of coarse grained crystals • Moving away from the magma the results in the formation of coarse grained crystals • Moving away from the magma the resulting rock becomes progressively finer grained • A contact metamorphic zone occurs when a parent rock is intruded by molten magma Sheer- • Shear Metamorphism results from the intense pressures that exist along active fault zones where rock units slide past each other • Mechanical deformation and recrystallization of the minerals result from the heat pressure and movement of fluids as rock units slide or shear past one another Regional- • Regional Metamorphism affects extremely large areas and is caused by a combination of both high temperature and high pressure • Most areas that are affected by regional metamorphism are areas undergoing intense deformation due to mountain building processes 11) Describe how metamorphic rocks are classified. Describe the two types of textures. •Metamorphic rocks are classified by texture and mineral composition • Textures include: • Foliated- rock exhibits layering or color banding • Nonfoliated - rock is nearly uniform throughout 12) Describe how and where foliation occurs. • The enormous pressure that accompany regional metamorphism cause the newly formed mineral grains to align themselves in a distinctly parallel arrangement • Foliated- the prominent layering in a metamorphic rock • Only rocks that are metamorphosed under intense pressure will exhibit foliation • Metamorphic rocks that form almost entiremly due to high temperatures will not have foliation 13) Describe the progressive patterns of foliation that develop in metamorphosed shale. The progressive patterns of foliation that develop in a metamorphosed shale serves as a good example of foliation types • Slaty cleavage- develops when a shale undergoes mild metamorphism • Schistosity- is found in foliated metamorphic rocks with larger, visible crystals. Generally the result of the parallel arrangement of platy (micas) and ellipsoidal mineral grain. • Gneissic- layering forms under intense regional metamorphism and displays color banding

elastically However, once the stress exceeds the elastic limit of a rock, it deforms permanently • Ductile deformation involves bending plastically • Brittle deformation involves fracturing 22) How are rock structures determined, how are they represented on a map, and what are some of the common structures? Rock structures are determined on the ground by geologist observing rock outcrops Outcrops are placed where bedrock is exposed at the surface • Geologic maps use standardized symbols and patterns to represent rock types and geologic structures, such as tilted beds, joints, faults and folds 23) Describe dip and strike. How are they used? Timed beds, joints, and faults are planar features whose orientation is described by their strike and dip • Strike is the compass direction of a line formed by the intersection of an inclined plane with a horizontal plane • Dip is the direction and angle from horizontal in which a plane is oriented 24) What are folds, axial plane, hinge line, and limb? Describe the two types of horizontal folds. Folds are wavelike bends in layered rocks. Represent rock strained in a ductile manner, usually under compression • The axial plane do fold into its limbs • The surface trace of an axial plane is called the hinge line ( or axis) of the fold 25) What are plunging folds? Describe the types. Plunging fold are folds in which the hinge line is not horizontal. • Where surfaces have been leveled by erosion, plunging folds form V- or horseshoes- shaped patterns of exposed rock layers beds 26) Describe domes, basins, joints, and faults. Domes: are structures in which the beds dip away from a central point, Sometimes called doubly plunging anticlines Basins: are structures in which the beds dip toward a central point, Sometimes called doubly plunging synclines Joints: fractures in bedrock along which no movement has occurred, Multiple parallel joints are called joint sets Faults: fractures in bedrock along which movement has occurred, Considered "active" if movement has occurred along them within the last 11,000 years, Categorized by the type of movement as dip-slip, strike-slip, or oblique-slip 27) Define fault plane, hanging-wall, foot-wall and upthrown side. Fault plane: an approximately planar surface along which the actual movement takes place Hanging wall: this is the fault block that is on the uppermost side of an incline fault plane Foot wall: this is the fault block that is on the lowermost side of an incline fault plane Upthrown side: The fault block that has moved up relative to the other side is termed the upthrown side 28) What are dip-slip faults? Describe the two basic varieties and thrust faults.

Dip- slip faults have movement parallel to the dip of the fault plane. • In normal faults, the hanging-wall block has moved down relative to the footwall block. • In reverse faults, the hanging- wall block has moved up relative to the footwall block 29) Describe fault blocks, horsts, and grabens. Fault blocks, bounded by normal faults, that drop down or are uplifted are known as grabens and horst, respectively • Grabens associated with divergent plates boundaries are called rifts • Thrust fault are reverse faults with dip angles less than 30% from horizontal 30) What are strike-slip faults? What is a right-lateral strike-slip fault? What is a left-lateral strike-slip fault? Which variety is the San Andreas Fault? What are oblique-slip faults? Strike-slip faults have movement that is predominantly horizontal and parallel to the strike of the fault planes • A viewer looking across to the other side of a right-lateral strike-slip fault would observe it to be offset to the right • A viewer looking across to the other side of a left-lateral strike-slip fault would observe it to be offset to their left. • Oblique-slip fault have movement with both vertical and horizontal components 31) Define earthquake. In general, what causes earthquakes? Where do most of the earthquakes occur? An earthquake is a trembling or shaking of the ground caused by the sudden release of energy stored in the rocks beneath earth surface • Causes of the earthquake=movements of lithospheric plates generally cause fault in the crustal material 1. A few small or medium of the earthquakes are vocanic in origin 2. Earthquakes can also result from human cause explosions or football games • Almost 95% of the earthquakes occur at the edge of interacting plates 32) Describe the elastic rebound theory. Stresses are exerted on the rock formation in adjacent plates, as movement occurs. Sine rock have elastic properties, energy Is stored until the stresses can overcome the friction between the two plate. At the moment energy releases, the rocks along the fault suddenly move, the energy is released, and an earthquake occurs. Energy is released during earthquakes in the form of seismic waves 33) How are earthquakes associated with the “ring of fire”? Earthquake occurrences closely follow the volcanic ring of fire 34) Define fault and where do most of the faults occur in the world? • Transform plate boundaries are the location off many of the world's largest continuous faults • The san andreas fault is the master fault of an intricate fault zone that runs along the coastal area of south and central California 35) Describe (in detail) the San Andreas fault. In 1906 a major earthquake occurred in the San Francisco area, resulting in hundreds of lives lost and million of dollars of damage • In 1989 a major earthquake in the area caused severe bridge, building, and highway damage • In about 10 million years Los angeles will move far enough north to be adjacent with san Francisco

• Faster (4 to 7 km/sec) wave that is the first or primary wave to arrive at recording station following earthquake pass through solids and fluids • S waves- sharing(transverse) body wave in which rock vibrates back and forth perpendicular to the direction of wave propagation • Surface waves • Love waves- side to side motion of the ground surface • Can't travel through fluids • Rayleigh waves - ground to moves in an elliptical path opposite the direction of wave motion • Rayleigh waves are the most destructive 41) Describe how the size of displacement affects the size of the earthquake. o The rocks on opposite sides of a fault are offset or displaced in proportion to the size of the earthquake In a small quake, the fracturing stops within a few seconds and the displacement may be as a fraction of a inch In the largest quakes, the fracturing may last several minutes, and the displacement may be more than 50ft 42) Describe what is felt during an earthquake. o During an earthquake , an observer experiences an initial jolt, caused by P waves, and then a second larger jolt caused by an S wave After this double shaking, the observer experiences a rolling and swaying motion that is caused by Surface Wave. 43) Describe how scientists locate an earthquake. Plotting distance from 3 stations on a map , as circles with ratio equaling the distance from the quake, locate earthquake epicenter 44) Describe the depth of focus for earthquakes. • Shallow focus (0-70 km deep) • Intermediate focus (70-350 km deep) • Deep focus (350-670 km deep) 45) Where in the United States do most of the earthquakes occur? What is seismic risk and what areas in the U.S. have a high risk? Earthquakes occur through out the U.S, But are much more common in the western states and Alaska • Largest seismic risk or hazard exist near the plate boundaries along the U.S Pacific coast (e.g San Andreas fault) and around New Mandrid, Missouri 46) Where in the world do most of the earthquakes occur? Most Earthquakes occur in narrow geographic belts which mark tectonic plate boundaries, the most important concentrations in, circum-Pacific (about 90%) and Mediterranean- Himalayan belts 47) Where do shallow-focus, intermediate-focus and deep-focus earthquakes occur? 48) Describe (in detail) the relationship between earthquakes and plate tectonics. 49) Describe the famous earthquakes that we went over in class.

50) Describe how we predict earthquakes and earthquake precursors. An earth quake prediction is a precise statement, location, and size of the future quake. Thousands of lives could be saved each year if such predictions could be made accurately. Unfortunately, the field of quake prediction is still in its infancy 51) Describe how scientists have interpreted the internal structure of the earth using seismic waves. • Seismic waves travel through the earths interior • S waves do not travel through the liquid outer core • P waves are refracted at density boundaries 52) List and describe the four layers of the Earth. • Inner Core • Outer core • Mantle crust • Crusts 53) Describe the two types of crust. What is the Mohorovicic discontinuity? • The Earth's crust ranges in thickness from 5-11 kilometers for continental crusts • A sharp compositional boundary exists between the base of the crusts and the upper mantle this boundary is called the Mohorovicic discontinuity, simply MOHO • Crust and upper mantle- physical properties the crust and upper mantle can be divided differently if we take into account its physical property and behavior 54) Describe the lithosphere and the asthenosphere. Lithosphere: outermost rigid, brittle layer, composed of the entire crust and uppermost mantle, most faults and earthquakes occur in the lithosphere Asthenosphere: lies beneath the crust extending down to approximately 70km due to its high temperature this layer is plastic, mobile, and is essential for tectonic plate motion.