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45-617: Professor Robert W. Webb of the University of Chicago was the first to research the fault in 1936; He found a lava flow (Pliocene age) that covered the northern end of the fault trace where the Little Kern and Kern River coincided. Without any evidence of deformation affecting the hardened lava and without any evidence found previously when investigating the fault line, Webb deemed the fault to be inactive. In 2007, Professor Elisabeth Nadin (University of Alaska Fairbanks) discovered that while mapping

90-480: A Rock = % Δ A = A f − A i A i × 100 {\displaystyle \%\Delta A={\frac {A_{f}-A_{i}}{A_{i}}}\times 100} Where: A i {\displaystyle A_{i}} = Initial Area A f {\displaystyle A_{f}} = Final Area For each of these methods of quantifying, one must take measurements of both

135-430: A change in rock failure mode, at an approximate average depth of 10–15 km (~ 6.2–9.3 miles) in continental crust , below which rock becomes less likely to fracture and more likely to deform ductilely. The zone exists because as depth increases confining pressure increases, and brittle strength increases with confining pressure whilst ductile strength decreases with increasing temperature. The transition zone occurs at

180-561: A layer immediately beneath it. Continental crust is produced and (far less often) destroyed mostly by plate tectonic processes, especially at convergent plate boundaries . Additionally, continental crustal material is transferred to oceanic crust by sedimentation. New material can be added to the continents by the partial melting of oceanic crust at subduction zones, causing the lighter material to rise as magma, forming volcanoes. Also, material can be accreted horizontally when volcanic island arcs , seamounts or similar structures collide with

225-403: A linear stress vs strain relationship past the elastic limit. Ductile deformation is typically characterized by diffuse deformation (i.e. lacking a discrete fault plane ) and on a stress-strain plot is accompanied by steady state sliding at failure, compared to the sharp stress drop observed in experiments during brittle failure . The brittle–ductile transition zone is characterized by

270-456: A lower density compared to the oceanic crust , called sima which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity ), there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character. Most continental crust

315-439: A steady-state hypothesis argue that the total volume of continental crust has remained more or less the same after early rapid planetary differentiation of Earth and that presently found age distribution is just the result of the processes leading to the formation of cratons (the parts of the crust clustered in cratons being less likely to be reworked by plate tectonics). However, this is not generally accepted. In contrast to

360-486: Is a material property that can be expressed in a variety of ways. Mathematically, it is commonly expressed as a total quantity of elongation or a total quantity of the change in cross sectional area of a specific rock until macroscopic brittle behavior, such as fracturing, is observed. For accurate measurement, this must be done under several controlled conditions, including but not limited to Pressure , Temperature , Moisture Content , Sample Size, etc., for all can impact

405-711: Is deformation which exhibits a linear stress-strain relationship (quantified by Young's Modulus) and is derived from Hooke's Law of spring forces (see Fig. 1.2). In elastic deformation, objects show no permanent deformation after the stress has been removed from the system and return to their original state. σ = E ϵ {\displaystyle \sigma =E\epsilon } Where: σ {\displaystyle \sigma } = Stress (In Pascals) E {\displaystyle E} = Young's Modulus (In Pascals) ϵ {\displaystyle \epsilon } = Strain (Unitless) Viscous Deformation Viscous Deformation

450-539: Is dry land above sea level. However, 94% of the Zealandia continental crust region is submerged beneath the Pacific Ocean , with New Zealand constituting 93% of the above-water portion. The continental crust consists of various layers, with a bulk composition that is intermediate (SiO 2 wt% = 60.6). The average density of the continental crust is about, 2.83 g/cm (0.102 lb/cu in), less dense than

495-506: Is governed by both the external conditions around the rock and the internal conditions sample. External conditions include temperature, confining pressure, presence of fluids, etc. while internal conditions include the arrangement of the crystal lattice, the chemical composition of the rock sample, the grain size of the material, etc. Ductilely Deformative behavior can be grouped into three categories: Elastic, Viscous, and Crystal-Plastic Deformation. Elastic Deformation Elastic Deformation

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540-409: Is little evidence of continental crust prior to 3.5 Ga . About 20% of the continental crust's current volume was formed by 3.0 Ga. There was relatively rapid development on shield areas consisting of continental crust between 3.0 and 2.5 Ga. During this time interval, about 60% of the continental crust's current volume was formed. The remaining 20% has formed during the last 2.5 Ga. Proponents of

585-615: Is sub-divided into three different zones; The proto-Kern Canyon Fault Zone, the Kern Canyon Fault Zone, and the late Quaternary active Kern Canyon Fault. The proto-Kern Canyon Zone is an old ductile shear zone found at the northern segment of the fault line. Evidence of mylonitized zones, 90 Ma intrusive rocks, and Mesozoic-metamorphic rocks mention that this was where the Kern Canyon Fault (which shares these same rock specimens) first emerged and had drifted away from due to

630-886: Is when rocks behave and deform more like a fluid than a solid. This often occurs under great amounts of pressure and at very high temperatures. In viscous deformation, stress is proportional to the strain rate, and each rock sample has its own material property called its Viscosity . Unlike elastic deformation, viscous deformation is permanent even after the stress has been removed. σ = η ξ {\displaystyle \sigma =\eta \xi } Where: σ {\displaystyle \sigma } = Stress (In Pascals) η {\displaystyle \eta } = Viscosity (In Pascals * Seconds) ξ {\displaystyle \xi } = Strain Rate (In 1/Seconds) Crystal-Plastic Deformation Crystal-Plastic Deformation occurs at

675-456: The Atlantic Ocean , for example) are termed passive margins . The high temperatures and pressures at depth, often combined with a long history of complex distortion, cause much of the lower continental crust to be metamorphic – the main exception to this being recent igneous intrusions . Igneous rock may also be "underplated" to the underside of the crust, i.e. adding to the crust by forming

720-540: The Cambrian explosion . All continental crust is ultimately derived from mantle-derived melts (mainly basalt ) through fractional differentiation of basaltic melt and the assimilation (remelting) of pre-existing continental crust. The relative contributions of these two processes in creating continental crust are debated, but fractional differentiation is thought to play the dominant role. These processes occur primarily at magmatic arcs associated with subduction . There

765-484: The Mediterranean Sea at about 340 Ma. Continental crust and the rock layers that lie on and within it are thus the best archive of Earth's history. The height of mountain ranges is usually related to the thickness of crust. This results from the isostasy associated with orogeny (mountain formation). The crust is thickened by the compressive forces related to subduction or continental collision. The buoyancy of

810-492: The atomic scale and is governed by its own set of specific mechanisms that deform crystals by the movements of atoms and atomic planes through the crystal lattice. Like viscous deformation, it is also a permanent form of deformation. Mechanisms of crystal-plastic deformation include Pressure solution , Dislocation creep , and Diffusion creep . In addition to rocks, biological materials such as wood, lumber, bone, etc. can be assessed for their ductility as well, for many behave in

855-411: The capacity of a rock to deform to large strains without macroscopic fracturing. Such behavior may occur in unlithified or poorly lithified sediments , in weak materials such as halite or at greater depths in all rock types where higher temperatures promote crystal plasticity and higher confining pressures suppress brittle fracture. In addition, when a material is behaving ductilely, it exhibits

900-417: The constant activity within the batholith. Nadin exhumed the shear zone and recovered that it extended from the northern end of Harrison Pass, CA to the south-eastern arm of Lake Isabella, CA. The Kern Canyon Fault Zone is a north-striking feature that harbored pre-Quaternary crustal deformation such as right-lateral strike slip and east-down normal displacement. These episodes caused bedrock displacement along

945-432: The crust forces it upwards, the forces of the collisional stress balanced by gravity and erosion. This forms a keel or mountain root beneath the mountain range, which is where the thickest crust is found. The thinnest continental crust is found in rift zones, where the crust is thinned by detachment faulting and eventually severed, replaced by oceanic crust. The edges of continental fragments formed this way (both sides of

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990-406: The dominant deformation process. Gouge and Breccia form in the uppermost, brittle regime while Cataclasite and Pseudotachylite form in the lower parts of the brittle regime, edging upon the transition zone. Mylonite forms in the more ductile regime at greater depths while Blastomylonite forms well past the transition zone and well into the ductile regime, even deeper into the crust. Ductility

1035-419: The dominant mode of continental crust formation and destruction. It is a matter of debate whether the amount of continental crust has been increasing, decreasing, or remaining constant over geological time. One model indicates that at prior to 3.7 Ga ago continental crust constituted less than 10% of the present amount. By 3.0 Ga ago the amount was about 25%, and following a period of rapid crustal evolution it

1080-543: The ductility and material properties of a biological substance. Peak Ductility Demand is a quantity used particularly in the fields of architecture, geological engineering, and mechanical engineering. It is defined as the amount of ductile deformation a material must be able to withstand (when exposed to a stress) without brittle fracture or failure. This quantity is particularly useful in the analysis of failure of structures in response to earthquakes and seismic waves. It has been shown that earthquake aftershocks can increase

1125-487: The fault line, allowing the fault itself to dip steeply. It extends from Walker Basin, CA to Harrison Pass and coincides with the proto-Kern Canyon Fault Zone starting from Kernville to Harrison Pass. The late-Quaternary active Kern Canyon Fault extends the ~150 km (99) miles from Walker Basin past Harrison Pass. Its existence exploits both the Proto-Kern and Kern Canyon Fault Zones' weaknesses, resulting in ruptures along

1170-526: The fault's basement rocks. His method of understanding the geology of the fault included surface study, drilling and trenching; using this approach, he was able to discern the rocks affected by this fault zone at 800 feet in width (244m). These specimens include quartzite, olivine, gabbro, sheared granitic rocks, metasedimentary rocks, and diorite. 35°36′N 118°30′W  /  35.6°N 118.5°W  / 35.6; -118.5 Ductility (Earth science) In Earth science , ductility refers to

1215-535: The faults within the Southern Sierra Nevada, there had been several accounts of activity along the Kern Canyon Fault well into the Quaternary Era. Her research continued into 2010, which explicitly entailed the lines of evidence that overturn the proposition that the fault was inactive for more than 3.5 million years. Due to the continued activity of the fault as well as its extension, the Kern Canyon Fault

1260-410: The initial and final dimensions of the rock sample. For Elongation, the measurement is a uni-dimensional initial and final length, the former measured before any Stress is applied and the latter measuring the length of the sample after fracture occurs. For Area, it is strongly preferable to use a rock that has been cut into a cylindrical shape before stress application so that the cross-sectional area of

1305-411: The lumber, lack of defects such as knots or grain distortions, temperature at 20 C, relative humidity at 65%, and size of the cut shapes of the wood samples. Results obtained from the experiment exhibited a linear stress-strain relationship during elastic deformation but also an unexpected non-linear relationship between stress and strain for the lumber after the elastic limit was reached, deviating from

1350-820: The measured ductility. It is important to understand that even the same type of rock or mineral may exhibit different behavior and degrees of ductility due to internal heterogeneities small scale differences between each individual sample. The two quantities are expressed in the form of a ratio or a percent. % Elongation of a Rock = % Δ l = l f − l i l i × 100 {\displaystyle \%\Delta l={\frac {l_{f}-l_{i}}{l_{i}}}\times 100} Where: l i {\displaystyle l_{i}} = Initial Length of Rock l f {\displaystyle l_{f}} = Final Length of Rock % Change in Area of

1395-490: The model of plasticity theory. Multiple reasons were suggested as to why this came about. First, since wood is a biological material, it was suggested that under great stress in the experiment, the crushing of cells within the sample could have been a cause for deviation from perfectly plastic behavior. With greater destruction of cellular material, the stress-strain relationship is hypothesized to become more and more nonlinear and non-ideal with greater stress. Additionally, because

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1440-615: The oldest rocks on Earth are within the cratons or cores of the continents, rather than in repeatedly recycled oceanic crust ; the oldest intact crustal fragment is the Acasta Gneiss at 4.01 Ga , whereas the oldest large-scale oceanic crust (located on the Pacific plate offshore of the Kamchatka Peninsula ) is from the Jurassic (≈180 Ma ), although there might be small older remnants in

1485-437: The peak ductility demand with respect to the mainshocks by up to 10%. Continental crust Continental crust is the layer of igneous , metamorphic , and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves . This layer is sometimes called sial because its bulk composition is richer in aluminium silicates (Al-Si) and has

1530-466: The persistence of continental crust, the size, shape, and number of continents are constantly changing through geologic time. Different tracts rift apart, collide and recoalesce as part of a grand supercontinent cycle . There are currently about 7 billion cubic kilometres (1.7 billion cubic miles) of continental crust, but this quantity varies because of the nature of the forces involved. The relative permanence of continental crust contrasts with

1575-459: The point where brittle strength equals ductile strength. In glacial ice this zone is at approximately 30 m (100 ft) depth. Not all materials, however, abide by this transition. It is possible and not rare for material above the transition zone to deform ductilely, and for material below to deform in a brittle manner. The depth of the material does exert an influence on the mode of deformation, but other substances, such as loose soils in

1620-699: The same manner and possess the same characteristics as abiotic Earth materials. This assessment was done in Hiroshi Yoshihara's experiment, "Plasticity Analysis of the Strain in the Tangential Direction of Solid Wood Subjected to Compression Load in the Longitudinal Direction." The study aimed to analyze the behavioral rheology of 2 wood specimens, the Sitka Spruce and Japanese Birch. In the past, it

1665-400: The sample can be taken. Cross-Sectional Area of a Cylinder = Area of a Circle = A = π r 2 {\displaystyle A=\pi r^{2}} Using this, the initial and final areas of the sample can be used to quantify the % change in the area of the rock. Any material is shown to be able to deform ductilely or brittlely, in which the type of deformation

1710-570: The samples were inhomogeneous (non-uniform) materials, it was assumed that some bending or distortion may have occurred in the samples that could have deviated the stress from being perfectly uniaxial. This may have also been induced by other factors like irregularities in the cellular density profile and distorted sample cutting. The conclusions of the research accurately showed that although biological materials can behave like rocks undergoing deformation, there are many other factors and variables that must be considered, making it difficult to standardize

1755-521: The short life of oceanic crust. Because continental crust is less dense than oceanic crust, when active margins of the two meet in subduction zones, the oceanic crust is typically subducted back into the mantle. Continental crust is rarely subducted (this may occur where continental crustal blocks collide and overthicken, causing deep melting under mountain belts such as the Himalayas or the Alps ). For this reason

1800-494: The side of the continent as a result of plate tectonic movements. Continental crust is also lost through erosion and sediment subduction, tectonic erosion of forearcs, delamination, and deep subduction of continental crust in collision zones. Many theories of crustal growth are controversial, including rates of crustal growth and recycling, whether the lower crust is recycled differently from the upper crust, and over how much of Earth history plate tectonics has operated and so could be

1845-500: The ultramafic material that makes up the mantle , which has a density of around 3.3 g/cm (0.12 lb/cu in). Continental crust is also less dense than oceanic crust, whose density is about 2.9 g/cm (0.10 lb/cu in). At 25 to 70 km (16 to 43 mi) in thickness, continental crust is considerably thicker than oceanic crust, which has an average thickness of around 7 to 10 km (4.3 to 6.2 mi). Approximately 41% of Earth's surface area and about 70% of

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1890-454: The upper crust, malleable rocks, biological debris, and more are just a few examples of that which does not deform in accordance to the transition zone. The type of dominating deformation process also has a great impact on the types of rocks and structures found at certain depths within the Earth's crust. As evident from Fig. 1.1, different geological formations and rocks are found in accordance to

1935-405: The volume of Earth's crust are continental crust. Because the surface of continental crust mainly lies above sea level, its existence allowed land life to evolve from marine life. Its existence also provides broad expanses of shallow water known as epeiric seas and continental shelves where complex metazoan life could become established during early Paleozoic time, in what is now called

1980-480: The zones over the past 15 thousand years. The Kern Canyon fault, according to the early study of Webb, is made up of 90 percent of granodiorite (a phaneritic-textured intrusive igneous rock similar to granite) and although densely covered by soils and brush, Webb discovered traces of sheared breccias and mylonites in specific zones along the fault. While conducting a study of the fault's capability of supporting Isabella Dams, Treaser (1948) recorded in-depth analysis of

2025-457: Was shown that solid wood, when subjected to compressional stresses, initially has a linear stress-strain diagram (indicative of elastic deformation) and later, under greater load, demonstrates a non-linear diagram indicative of ductile objects. To analyze the rheology, the stress was restricted to uniaxial compression in the longitudinal direction and the post-linear behavior was analyzed using plasticity theory. Controls included moisture content in

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