Tasa Graphic Arts, Inc.
1210B Salazar Road - Taos, NM USA 87571
Phone: (800) 293-2725 or (575) 758-5535 - Fax: (575) 758-5536
E-mail: info@tasagraphicarts.com
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Tasa Graphic Arts, Inc. 1210B Salazar Road - Taos, NM USA 87571 Phone: (800) 293-2725 or (575) 758-5535 - Fax: (575) 758-5536 E-mail: info@tasagraphicarts.com |
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Tasa Portfolio Volume 3 Captions |
The images on Tasa Portfolio Volume 3 are related to these subjects:
Crustal Deformation Earthquakes Earth's Interior The Ocean Floor Plate Tectonics Mountain Building Energy and Mineral Resources TGA201.jpg Deformation of Earth's crust caused by tectonic forces and associated stresses resulting from the movement of lithospheric plates. A. Strata before deformation. B. Compressional stresses associated with plate collisions tend to shorten and thicken Earth's crust by folding, flowing, and faulting. C. Tensional stresses at divergent plate boundaries tend to lengthen rock bodies by displacement along faults in the upper crust and ductile flow at depth. D. Shear stresses at transform plate boundaries tend to produce offsets along fault zones. The right side of the diagram illustrates the deformation (strain) of a cube of rock in response to the differential stresses illustrated in corresponding diagrams to the left. TGA202.jpg Strike and dip of a rock layer. TGA203.jpg By establishing the strike and dip of outcropping sedimentary beds on a map A., geologists can infer the orientation of the structure below ground B. TGA204.jpg Idealized sketches illustrating the features associated with symmetrical folds. The axis of the fold in A is horizontal, whereas the axis of the fold in B is plunging. TGA205.jpg Block diagram of principal types of folded strata. The upfolded, or arched, structures are anticlines. The downfolds, or troughs, are synclines. Notice that the limb of an anticline is also the limb of the adjacent syncline. TGA206.jpg Plunging folds. A. Idealized view of plunging folds in which a horizontal surface has been added. B. View of plunging folds as they might appear after extensive erosion. Notice that in a plunging anticline the outcrop pattern "point" in the direction of the plunge, while the opposite is true of plunging synclines. TGA207.jpg Monocline consisting of bent sedimentary beds that were deformed by faulting in the bedrock below. TGA208.jpg Gentle upwarping and downwarping of crustal rocks produce domes (A) and basins (B). Erosion of these structures results in an outcrop pattern that is roughly circular or elongated. TGA209.jpg The Black Hills of South Dakota, a large domal structure with resistant igneous and metamorphic rocks exposed in the core. TGA210.jpg The bedrock geology of the Michigan Basin. Notice that the youngest rocks are centrally located, while the oldest beds flank this structure. TGA211.jpg The rock immediately above a fault surface is the hanging wall, and that below is called the footwall. These names came from miners who excavated ore along fault zones. The miners hung their lanterns on the rocks above the fault trace (hanging wall) and walked on the rocks below the fault trace (footwall). TGA212.jpg Block diagrams illustrating a normal fault. A. Rock strata prior to faulting. B. The relative movement of displaced blocks. Displacement may continue in a fault-block mountain range over millions of years and consist of many widely spaced episodes of faulting. C. How erosion might alter the upfaulted block. D. Eventually the period of deformation ends and erosion becomes the dominant geologic process. TGA213.jpg Normal faulting in the Basin and Range Province. Here, tensional stresses have elongated and fractured the crust into numerous blocks. Movement along these fractures has tilted the blocks producing parallel mountain ranges called fault-block mountains. TGA214.jpg Diagrammatic sketch of downfaulted (graben) and upfaulted (horst) blocks. TGA215.jpg Block diagram showing the relative movement along a reverse fault. TGA216.jpg Idealized development of Lewis Overthrust fault. A. Geologic setting prior to deformation. B., C. Large-scale movement along a thrust fault displaced Precambrian rock over Cretaceous strata in the region of Glacier National Park. D. Erosion by glacial ice and running water sculptured the thrust sheet into a majestic landscape and isolated a remnant of the thrust sheet called Chief Mountain. TGA217.jpg Block diagram illustrating the features associated with strike-slip faults. Note how the stream channels have been offset by fault movement. The faults in the diagram are right-lateral strike-slip faults. (Modified after R. L. Wesson and others) TGA218.jpg Earthquake focus and epicenter. The focus is the zone within Earth where the initial displacement occurs. The epicenter is the surface location directly above the focus. TGA219.jpg Elastic rebound. As rock is deformed, it bends, storing elastic energy. Once strained beyond its breaking point, the rock cracks, releasing the stored-up energy in the form of earthquake waves. TGA220.jpg Principle of the seismograph. The inertia of the suspended mass tends to keep it motionless, while the recording drum, which is anchored to bedrock, vibrates in response to seismic waves. Thus, the stationary mass provides a reference point from which to measure the amount of displacement occurring as the seismic wave passes through the ground. TGA221.jpg Seismograph designed to record vertical ground motion. TGA222.jpg Types of seismic waves and their characteristic motion. (Note that during a strong earthquake, ground shaking consists of a combination of various kinds of seismic waves.) A. As illustrated by a slinky, P waves are compressional waves that alternately compress and expand the material through which they pass. The back-and-forth motion produced as compressional waves travel along the surface can cause the ground to buckle and fracture, and may cause power lines to break. B. S waves cause material to oscillate at right angles to the direction of wave motion. Because S waves can travel in any plane, they produce up-and-down and sideways shaking of the ground. C. One type of surface wave is essentially the same as that of an S wave that exhibits only horizontal motion. This kind of surface wave moves the ground from side to side and can be particularly damaging to the foundations of buildings. D. Another type of surface wave travels along Earth's surface much like rolling ocean waves. The arrows show the elliptical movement of rock as the wave passes. TGA223.jpg Typical seismograph. Note the time interval (about 5 minutes) between the arrival of the first P wave and the arrival of the first S wave. TGA224.jpg An earthquake epicenter is located using the distances obtained from three or more seismic stations. TGA225.jpg Distribution of the 14,229 earthquakes with magnitudes equal to or greater than 5 for the period 1980-1990. (Data from National Geophysical Data Center/NOAA) TGA226.jpg Zones of earthquake foci in 1965 in the vicinity of the Tonga Islands. (Data from B. Isacks, J. Oliver, and L. R. Sykes) TGA227.jpg Region most affected by the Good Friday earthquake of 1964. Note the location of the epicenter (red dot). (After U.S. Geological Survey) TGA228.jpg Schematic drawing of a tsunami generated by displacement of the ocean floor. The speed of a wave correlates with ocean depth. As shown, waves moving in deep water advance at speeds in excess of 800 kilometers per hour. Speed gradually slows to 50 kilometers per hour at depths of 20 meters. Decreasing depth slows the movement of the wave. As waves slow in shallow water, they grow in height until they topple and rush onto shore with tremendous force. The size and spacing of these swells are not to scale. TGA229.jpg Tsunami travel times to Honolulu, Hawaii, from selected locations throughout the Pacific. (Data from NOAA) TGA230.jpg Probabilities of a major earthquake between 1988 and 2018 along the San Andreas fault. TGA231.jpg Seismic energy travels in all directions from an earthquake source (focus). The energy can be portrayed as expanding wave fronts or as rays drawn perpendicular to the wave fronts. TGA232.jpg The transmission of P and S waves through a solid. A. The passage of P waves causes the intervening material to experience alternate compressions and expansions. B. The passage of S waves causes a change in shape without changing the volume of the material. Because liquids behave elastically when compressed (they spring back when the stress is removed), they will transmit P waves. However, since liquids do not resist changes in shape, S waves cannot be transmitted through liquids. (After O. M. Phillips, The Heart of the Earth, San Francisco: Freeman, Cooper and Co., 1968) TGA233.jpg A. Seismic waves would travel through a hypothetical planet with uniform properties along straight-line paths and at constant velocities. B. Wave paths through a planet where velocity increases with depth. C. A few of the many possible paths that seismic rays take through Earth. TGA234.jpg Views of Earth's layered structure. The left side of the cross section shows that Earth's interior is divided into three different layers based on compositional differences-the crust, mantle, and core. The right side of the cross section depicts the five main layers of Earth's interior based on physical properties and hence mechanical strength-the lithosphere, asthenosphere, mesosphere, outer core, and inner core. The block diagrams above the large cross section show an enlarged view of the upper portion of Earth's interior. TGA235.jpg Idealized paths of seismic waves traveling from an earthquake focus to three seismographic stations. In parts A and B, you can see that the two nearest recording stations receive the slower waves first because the waves traveled a shorter distance. However, as shown in part C, beyond 200 kilometers, the first waves received passed through the mantle, which is a zone of higher velocity. TGA236.jpg The abrupt change in physical properties at the core-mantle boundary causes the wave paths to bend sharply, resulting in a shadow zone for P waves between about 105 degrees and 140 degrees. TGA237.jpg View of Earth's interior showing P and S wave paths. Any location more than 105 degrees from the earthquake epicenter will not receive direct S waves since the outer core will not transmit them. Although P waves are also absent beyond 105 degrees, they are recorded beyond 140 degrees. TGA238.jpg Travel times of seismic waves generated from nuclear test explosions were used to measure the depth of the inner core accurately. An array of seismographs located in Montana detected the "echoes" that bounced back from the boundary of the inner core. TGA239.jpg Variations in P and S wave velocities with depth. Abrupt changes in average wave velocities delineate the major features of Earth's interior. At a depth of about 100 kilometers, the sharp decrease in wave velocity corresponds to the top of the low-velocity zone. Two other bends in the velocity curves occur in the upper mantle at depths of about 410 and 660 kilometers. These variations are thought to be caused by minerals that have undergone phase changes, rather than resulting from compositional differences. The abrupt decrease in P-wave velocity and the absence of S waves at 2900 kilometers marks the core-mantle boundary. The liquid outer core will not transmit S waves, and the propagation of P waves is slowed within this layer. As the P waves enter the solid inner core, their velocity once again increases. (Data from Bruce A. Bolt) TGA240.jpg Earth's magnetic field is thought to be generated by vigorous convection of molten iron alloy in the liquid outer core. TGA241.jpg Estimated geothermal gradient for Earth. Temperatures in the mantle and core are based on several assumptions and may vary ± 500 degrees C. (Data from Kent C. Condie) TGA242.jpg Echo sounders. A. An echo sounder determines the water depth by measuring the time interval required for an acoustic wave to travel from a ship to the seafloor and back. The speed of sound in water is 1500 m/sec. Therefore, depth = 1/2 (1500 m/sec x echo travel time). B. Modern multibeam sonar obtains a profile of a narrow swath of seafloor every few seconds. TGA243.jpg Major topographic divisions of the North Atlantic and a profile from New England to the coast of North Africa. TGA244.jpg Schematic view showing the provinces of a passive continental margin. Note that the slopes shown for the continental shelf and continental slope are greatly exaggerated. The continental shelf has an average slope of one-tenth of 1 degree, while the continental slope has an average slope of about 5 degrees. TGA245.jpg Active continental margin. Here sediments from the ocean floor are scraped from the descending plate and added to the continental crust as an accretionary wedge. TGA246.jpg Turbidity currents move downslope, eroding the continental margin to enlarge submarine canyons. These sediment-laden density currents eventually lose momentum and deposit their loads of sediment as deep-sea fans. Beds deposited by these currents are called turbidites. Each event produces a single bed characterized by a decrease in sediment size from bottom to top, a feature known as a graded bed. TGA247.jpg Formation of a coral atoll due to the gradual sinking of oceanic crust and upward growth of the coral reef. A. Fringing reef forms around volcanic island. B. As the volcanic island sinks, the fringing reef gradually becomes a barrier reef. C. Eventually, the volcano is completely submerged and an atoll remains. TGA248.jpg A. The structure of oceanic crust is thought to be equivalent to the ophiolite complexes that have been discovered elevated above sea level in such places as California and Newfoundland. B. The formation of the three units of an ophiolite complex in the rift zone of an oceanic ridge. C. Diagram illustrating the site where new ocean crust is generated. TGA249.jpg Reconstruction of Pangaea as it is thought to have appeared 200 million years ago. TGA250.jpg This shows the best fit of South America and Africa along the continental slope at a depth of 500 fathoms (about 900 meters). The areas where continental blocks overlap appear in brown. (After A. G. Smith, "Continental Drift." In Understanding the Earth, edited by I. G. Gass.) TGA251.jpg Fossils of Mesosaurus have been found on both sides of the South Atlantic and nowhere else in the world. Fossil remains of this and other organisms on the continents of Africa and South America appear to link these landmasses during the late Paleozoic and early Mesozoic eras. TGA252.jpg Matching mountain ranges across the North Atlantic. A. The Appalachian Mountains trend along the eastern flank of North America and disappear off the coast of Newfoundland. Mountains of comparable age and structure are found in the British isles and Scandinavia. B. When these landmasses are placed in their predrift locations, these ancient mountain chains form a nearly continuous belt. These folded mountain belts formed roughly 300 million years ago as the landmasses collided during the formation of the supercontinent of Pangaea. TGA253.jpg A. The supercontinent Pangaea showing the area covered by glacial ice 300 million years ago. B. The continents as they are today. The shading outlines areas where evidence of the old ice sheets exists. TGA254.jpg A. Earth's magnetic field consists of lines of force much like those a giant bar magnet would produce if placed at the center of the Earth. B. Earth's magnetic field causes a dip needle (compass oriented in a vertical plane) to align with the lines of magnetic force. The dip angle decreases uniformly from 90 degrees at the magnetic poles to 0 degrees at the magnetic equator. Consequently, the distance to the magnetic poles can be determined from the dip angle. TGA255.jpg Simplified apparent polar-wandering paths as established from North American and Eurasian paleomagnetic data. A. The more westerly path determined from North American data was caused by the westward movement of North America by about 24 degrees from Eurasia. B. The positions of the wandering paths when the landmasses are reassembled. TGA256.jpg Seafloor spreading. Harry Hess proposed that upwelling of mantle material along the mid-ocean ridge system created new seafloor. The convective motion of mantle material carries the seafloor in a conveyor-belt fashion to the deep-ocean trenches, where the seafloor descends into the mantle. TGA257.jpg Schematic illustration of paleomagnetism preserved in lava flows of various ages. Data such as these from various locales were used to establish the time scale of polarity reversals. TGA258.jpg Time scale of Earth's magnetic field in the recent past. This time scale was developed by establishing the magnetic polarity for lava flows of known age. (Data from Allen Cox and G. B. Dalrymple) TGA259.jpg The ocean floor as a magnetic tape recorder. A. Schematic representation of magnetic intensities recorded as a magnetometer is towed across a segment of the Mid-Atlantic Ridge. B. Notice the symmetrical stripes of low- and high-intensity magnetism that parallel the ridge crest. Vine and Matthews suggested that the stripes of high-intensity magnetism occur where normally magnetized oceanic basalts enhance the existing magnetic field. Conversely, the low-intensity stripes are regions where the crust is polarized in the reverse direction, which weakens the existing magnetic field. TGA260.jpg As new basalt is added to the ocean floor at mid-ocean ridges, it is magnetized according to Earth's existing magnetic field. Hence, it behaves much like a tape recorder as it records each reversal of the planet's magnetic field. TGA261.jpg A mosaic of rigid plates constitutes Earth's outer shell. (After W. B. Hamilton, U.S. Geological Survey) TGA262.jpg Most divergent plate boundaries are situated along the crests of oceanic ridges. TGA263.jpg A. Pangaea, 200 million years ago. B. Pangaea, 150 million years ago (Jurassic Period). TGA264.jpg Pangaea, 100 million years ago (Cretaceous Period). TGA265.jpg Pangaea, 50 million years ago (Early Cenozoic). TGA266.jpg Pangaea, present. TGA267.jpg A. Rising magma upwarps the crust, causing numerous cracks in the rigid lithosphere. B. As the crust is pulled apart, large slabs of rock sink, generating a rift zone. C. Further spreading generates a narrow sea. D. Eventually, an expansive ocean basin and ridge system are created. TGA268.jpg East African rift valleys and associated features. TGA269.jpg Zones of plate convergence: Oceanic-continental. TGA270.jpg Zones of plate convergence: Oceanic-oceanic. TGA271.jpg Zones of plate convergence: Continental-continental. TGA272.jpg Distribution of the world's oceanic trenches, ridge system, fracture zones, and transform faults. Where transform faults offset ridge segments, they permit the ridge to change direction (curve) as can be seen in the Atlantic Ocean. TGA273.jpg The ongoing collision of India and Asia, starting about 45 million years ago, produced the majestic Himalayas. TGA274.jpg Diagram illustrating a transform fault boundary offsetting segments of a divergent boundary (oceanic ridge). TGA275.jpg The Mendocino transform fault permits the movement of seafloor generated at the Juan de Fuca ridge to move southeastward past the Pacific plate and beneath the North American plate. Thus, this transform fault connects a divergent boundary to a subduction zone. Furthermore, the San Andreas fault, also a transform fault, connects two spreading centers; the Juan de Fuca ridge and a divergent zone located in the Gulf of California. TGA276.jpg Distribution of shallow-, intermediate-, and deep-focus earthquakes. Note that deep-focus earthquakes occur only in association with convergent plate boundaries and subduction zones. (Data from NOAA) TGA277.jpg Distribution of earthquake foci in the vicinity of the Japan trench. Note that intermediate- and deep focus earthquakes occur only within the sinking slab of oceanic lithosphere. (Data from NOAA) TGA278.jpg The chain of islands and seamounts that extends from Hawaii to the Aleutian trench results from the movement of the Pacific plate over an apparently stationary hot spot. Radiometric dating of the Hawaiian Islands shows that the volcanic activity decreases in age toward the island of Hawaii. TGA279.jpg This map illustrates directions and rates of plate motion in centimeters per year. Seafloor spreading velocities (as shown with black arrows and labels) are based on the spacing of dated magnetic stripes (anomalies). The colored arrows show Very Long Baseline Interferometry (VLBI) data of plate motion at selected locations. The data obtained by these methods are typically consistent. (Seafloor data from DeMets and others, VLBI data from Ryan and others.) TGA280.jpg The world as it may look 50 million years from now. (From "The Breakup of Pangaea," Robert S. Dietz and John C. Holden. Copyright 1970 by Scientific American, Inc. All rights reserved.) TGA281.jpg Proposed models for mantle convection. A. The model shown in this illustration consists of two convection layers - a thin, convective layer above 660 kilometers and a thick one below. B. In this whole-mantle convection model, cold oceanic lithosphere descends into the lowermost mantle while hot mantle plumes transport heat toward the surface. C. This deep-layer model suggests that the mantle operates similar to a lava lamp on a low setting. Earth's heat causes these layers of convection to slowly swell and shrink in complex patterns without substantial mixing. Some material from the lower layer flows upward as mantle plumes. TGA282.jpg Earth's major mountain belts. TGA283.jpg During the first survey of India, an error in measurement occurred because the plumb bob on an instrument was deflected by the massive Himalayas. Later work by George Airy predicted that the mountains have roots of light crustal rocks. Airy's model explained why the plumb bob was deflected much less than expected. TGA284.jpg The development of a volcanic island arc by the convergence of two oceanic plates. Continuous subduction along these Aleutian-type convergent zones results in the development of thick units of continental-type crust. TGA285.jpg Orogenesis along an Andean-type subduction zone. A. Passive continental margin with extensive wedge of sediments. B. Plate convergence generates a subduction zone, and partial melting produces a developing volcanic arc. C. Continued convergence and igneous activity further deform and thicken the crust, elevating the mountain belt, while the accretionary wedge grows. TGA286.jpg Simplified diagrams showing the northward migration and collision of India with the Eurasian plate. A. Converging plates generated a subduction zone, while partial melting of the subducting oceanic slab produced a continental volcanic arc. Sediments scraped from the subducting plate were added to the accretionary wedge. B. Position of India in relation to Eurasia at various times. C. Eventually the two landmasses collided, deforming and elevating the accretionary wedge and continental shelf deposits. In addition, slices of the Indian crust were thrust up onto the Indian plate. (Modified after Peter Molnar) TGA287.jpg Distribution of present day oceanic plateaus and other submerged crustal fragments. (Data from Ben-Avraham and others) TGA288.jpg This sequence illustrates the collision of an inactive volcanic island arc with an Andean-type plate margin. TGA289.jpg Map showing terranes that have been added to western North America during the past 200 million years. Data from paleomagnetic and fossil evidence indicate that some of these terranes originated thousands of kilometers to the south of their present location. (After D. R. Hutchinson and others) TGA290.jpg This sequence illustrates how the combined effect of erosion and isostatic adjustment results in a thinning of the crust in mountainous regions. A. When mountains are young, the continental crust is thickest. B. As erosion lowers the mountains, the crust rises in response to the reduced load. C. Erosion and uplift continue until the mountains reach "normal" crustal thickness. TGA291.jpg One possible mechanism for the uplift that led to the formation of the southern Rockies, Colorado Plateau, and Basin and Range province. A. Nearly horizontal subduction of an oceanic plate initiated a period of tectonic activity. B. Sinking of this oceanic slab allowed for upwelling of hot mantle material that buoyantly raised the crust. TGA292.jpg The multistage process for transforming material from the asthenosphere into continental crust. Once continental crust is generated, its low density apparently keeps it afloat indefinitely. TGA293.jpg The map show the major Precambrian mountain belts (orogens) and cores of ancient continental blocks (cratons) and their ages in billions of years (b.y.). It appears that North America was assembled from crustal blocks that were joined by processes very similar to modern plate tectonics. These ancient collisions produced mountainous belts that include remnant volcanic island arcs which were trapped by the colliding continental fragments. TGA294.jpg Coal fields of the United States. (Courtesy of the Bureau of Mines, U.S. Department of the Interior) TGA295.jpg Common oil traps. A. Anticline. B. Fault trap. C. Salt dome. D. Stratigraphic (pinch-out) trap. TGA296.jpg Major primary pollutants and their sources. Percentages are calculated on the basis of weight. (Data from the U.S. Environmental Protection Agency) TGA297.jpg The heating of the atmosphere. Most of the short-wavelength radiation from the Sun, that is not reflected back to space, passes through the atmosphere and is absorbed by Earth's land-sea surface. This energy is then emitted from the surface as longer-wavelength radiation, much of which is absorbed by certain gases in the atmosphere. Some of the energy absorbed by the atmosphere will be radiated Earthward. This so-called greenhouse effect is responsible for keeping Earth's surface much warmer than it would be otherwise. TGA298.jpg Distribution of oil shale in the Green River Formation of Colorado, Utah, and Wyoming. The areas shaded with the darker color represent the richest deposits. Government and industry have invested large sums to make these oil shales an economic resource, but costs have always been higher than the price of oil. However, as prices of competing fuels rise, these vast deposits may become economically more attractive. (After D. C. Duncan and V. E. Swanson, U.S. Geological Survey Circular 523, 1965) TGA299.jpg Simplified diagram showing the principle of the tidal dam. TGA300.jpg Illustration of the relationship between a parent igneous body and the associated pegmatite and hydrothermal deposits.