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21 Cards in this Set
- Front
- Back
continental drift
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Continental drift is the idea that the Earth’s continents have
moved to their present positions after fragmentation of a larger landmass in the geologic past. |
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seafloor spreading
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Seafloor spreading - The hypothesis that ocean basins expand
by addition of new rock from spreading centers, and that older rock is destroyed near the basin margins. |
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Basin
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- A relatively depressed area of the
crust that receives sedimentary deposition. |
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Continental crust
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Solid, outer part of the Earth
underlying the continents and continental shelves, composed largely of granitic rocks. |
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Oceanic crust
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Solid, outer part of the Earth
underlying the ocean basins, consisting largely of basaltic rocks. |
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Pangea
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Late Paleozoic to early Mesozoic supercontinent comprising most of the world’s continental crust.
Alfred Wegener |
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Basis for Wegener’s ideas:
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Jigsaw puzzle
similar geology Glacial striations similarity in ancient organisms |
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Triple junction
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A junction of three spreading plates
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Graben
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Elongate basin formed through downdropping of a fault block, and bounded on both sides by a normal fault
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thermal convection cells
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allows Earth’s mantle capablity of flow and rotation
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Guyot
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A sunken seamount, or undersea volcano, having a flat top due to erosion at sea level.
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Paleomagnetism
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The study of natural remnant
magnetism in rocks to determine properties of the Earth’s magnetic field in the geologic past. |
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Plate boundaries
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At present, there are seven large plates (carrying the
continents and much of the Pacific Ocean), and about 20 smaller plates. Plate motion, typically 1 to 7 cm per year, causes plates to converge, diverge, or slide past one another, and this movement is the source of many earthquakes. Also, many volcanoes line up along or close to plate boundaries. |
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The basic forms of tectonic boundaries
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1) Transform boundaries occur where plates slide or, perhaps more
accurately, grind past each other along transform faults. 2) Divergent boundaries occur where two plates slide apart from each other. Mid-ocean ridges and active zones of rifting are examples. 3) Convergent boundaries (or active margins) occur where two plates slide towards each other commonly forming either a subduction zone (if one plate moves underneath the other) or a continental collision (if the two plates contain continental crust). |
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Passive margin
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The trailing edge of a tectonic plate, where active tectonic interaction with another plates is not occurring.
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Aulacogen
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A failed continental rift that has filled with sediment
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Subduction zone
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Long, narrow belt, usually including a
deep-sea trench, along which subduction occurs. |
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subduction zone
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a slab of cool, dense oceanic crust
comes in contact with the margin of another plate, and it descends beneath that plate, eventually reaching depths where melting occurs under elevated temperature and pressure conditions. The rock will be remelted into magma and recycled. |
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Subduction
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occur when one oceanic slab collides
with another or with continental crust creates volcanoes |
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Volcanic arc
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Arcuate line of active volcanoes and igneous plutons associated with a convergent plate margin where
subduction is occurring |
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Orogenesis
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The process of building mountain chains and consequently deforming granitic crust (continental-type crust).
1. where continental collision occurs; 2. in volcanic arcs adjacent to subduction zones; and 3. along mid-ocean rifts. |