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| a geologic structure in which strata are bent into an upfold or arch |
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| apparent polar wandering path |
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| the zone between 50 and 250 kilometers below the surface of the Earth, where shock waves of earthquakes travel at much reduced speeds, perhaps because of less rigidity. The ___ may be a zone where convective flow of material occurs. |
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| a depressed area that serves as a catchment area for sediments (___ of deposition). A structural ___ is an area in which strata slope inward toward a central location. Structural ___ tend to experience periodic downsinking and thus receive a thinker and more complete sequence of sediments than do adjacent areas. |
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| convergent plate boundary |
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| An upfold in rocks having the general configuration of an inverted bowl. Strata in a ___ dip outward and downward in all directions from a central area. |
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| A fracture in the Earth's crust along which rocks on one side have been displaced relative to rocks on the other side |
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| An assemblage of fossil plants found in rocks of late Paleozoic and early Triassic age in South Africa, India, Australia, and South America. |
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| The great Permo-Carboniferous Southern Hemisphere continent, comprising the assembled present areas of South Africa, India, Australia, Africa-Arabia, and Antartica |
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| the differences between the observed value of gravity at any point on the Earth and the calculated theoretic value |
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| The boundary separating the mantle of the earth from the core below. The Gutenberg discontinuity lies about 2900 below the surface |
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| lateral fault (strike-slip fault) |
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| a fault in which th emovement is largely horizontal and in the direction of the trend of the fault plane. |
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| A hypothetic supercontinent composed of what is now Europe, Asia, Greenland, and North America |
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| the outer shell of the Earth, lying above the asthenosphere and comprising the crust and upper mantle |
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| a body of intricately folded, faulted, and severely metamorphosed rocks, examples of which can be seen in the Franciscan rocks of California. |
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| Mohorovicic discontinuity |
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| a plane that marks the boundary separating the crust of the Earth from the underlying mantle. The "moho," as it is sometimes called, is at a depth of about 70 kilometers below the surface of continents and 6-14 kilometers below the floor of the oceans. |
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| a fault in which the hanging wall appears to have moved downward relative tot he footwall; normally occurring in areas of crustal tension. |
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| An associationo f radiolarian cherts, pelagic muds, basaltic pillow and flow lavas, gabbros, and ultramafic rocks such as periodotite regarded as surviving masses of former oceanic crust largely destroyed in former subjection areas |
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| The Earth's magnetic field and magnetic properties in the geologic past. Studies of paleomagnetism are helpful in determining positions of continents and magnetic poles. |
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| In Alfred Wegner's theory of continental drift, the supercontinent that included all present major continental masses |
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| The great universal ocean that surrounded the supercontinent Pangea prior to its breakup |
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| passive continental margin (trailing edge) |
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| The theory that explains the tectonic behavior of the crust of the Earth in terms of several moving plates that are formed by volcanic activity at oceanic ridges and destroyed along great ocean trenches |
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| primary seismic wave (P-wave) |
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| Seismic waves that are propagated through solid rock as a train of compressions and dilations. Direction of vibration is parallel to direction of propagation |
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| a fault formed by compression in which the hanging wall appears to move up relative tot he foot wall |
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| ridge-push, slab-pull model |
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| the process by which new sea-floor crust is produced along midoceanic ridges (divergence zones) and slowly conveyed away from the ridges |
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| secondary seismic wave (S-wave) |
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| a seismic wave in which the direction of vibration of wave energy is at right angles to the direction the wave travels |
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| an inclided planar zone, defined by high frequency of earthquakes, that is thought to locate the descending leading edge of a moving oceanic plate |
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| seismic or earthquake waves that move only about the surface of the Earth |
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| a geologic structure in which strata are bent into a downfold |
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| A great east-west trending seaway lying between Laurasia and Gondwanaland during Paleozoic and Mesozoic time and from which arose the Alpine-Himalayan Mountain Ranges |
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| a "hot spot" inteh upper mantle believed to exist where a huge column of upwelling magma lies in a fixed position under the lithosphere. ___ are thought to cause volcanism in the overlying lithosphere |
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| a low-angle reverse fault, with inclination of fault plane generally less that 45A7 |
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| a strike-slip fault bounded at each end by an area of crustal spreading that tends to be more or less perpendicular to the trace of the fault |
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| Wadati-Benioff seismic zone |
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