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EASC:Chp. 7- Plate Tectonics
Chapter 7: 'Plate Tectonics: A Scientific Theory Unfolds' Book: Earth Science by Tarbuck, Lutgens, Tasa Ed. 12th
Terms in this set (48)
Profound reversal of scientific understanding.
A theory that originally proposed that the continents are rafted about. It has essentially been replaced by the plate tectonics theory.
The theory that proposes that Earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself, 1968
The proposed supercontinent that 200 million years ago began to break apart and form the present landmass, "all land," coined by Wegener
Evidence of 'Pangea'
The Continental Jigsaw Puzzle
Fossils Match Across the Seas
Transoceanic Land Bridges
Rock Types and Structures Match
continental jigsaw puzzle
Wegener used present day shorelines to make a fit of the continents, it was immediately challenged by Earth scientists
fossils match across the seas
mesosaurus are found only in black shales of the Permian period in Eastern S. American and S. Africa
an aquatic fish-catching reptile
transoceanic land bridges
the most widely accepted explanation of migration
rock types and structures match
Wegener found 2.2 billion year old igneous rocks in Brazil that closely resembled similarly ages rocks in Africa
Wegener found evidence for dramatic global climate changes during the geologic past, evidence was late Paleozoic glaciation presently lies within 30 degrees of the equator in subtropical/tropical climates
When did Wegener's proposal gain attention?
oceanic ridge system
A continuous elevated zone on the floor of all the major ocean basins and varying in width from 500-5,000 kilometers. The rifts at the crests of ridges represent divergent plate boundaries.
The rigid outer layer of Earth, including the crust and upper mantle
A coherent unit of Earth's rigid outer layer that includes the curst and upper unit (plate), moves 5 cm/day, 2 in/year. Distribution of hear is uneven, the largest is in the Pacific, known as "The Ring of Fire."
A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers and in some regions extends as deep as 700 kilometers. The rock within this zone is easily deformed.
All major interactions among individual plates occur among this.
Also known as, constructive margins, where 2 plates move apart, resulting in up-welling of material from the mantle to create new seafloor.
Also known as, destructive margins, where 2 plates move together, resulting in oceanic lithosphere descending beneath an overriding plate, eventually to be reabsorbed into the mantle, or possibly in the collision of 2 continental blocks to create a mountain system.
transform fault boundaries
Also known as, conservative margin, where 2 plates grind past each other without the production or destruction of lithosphere. Discovered 1965 by J. Tuzo Wilson.
Along the axis of some ridge segments is a deep down-faulted structure
Process of producing new seafloor between 2 diverging plates divergent boundaries also called, spreading centers, 2 in/year
The splitting of a continent is thought to begin with the formation of an elongated depression; East African Rift. Not all rift valleys develop into full-fledged spreading centers
An elongated depression in the seafloor produced by bending of oceanic crust during subduction, Peru-Chile trench.
Another name for convergent boundaries; a long, narrow zone where one lithospheric plate descends beneath another.
The process of thrusting oceanic lithosphere into the mantle along a convergent boundary. Low dip angles usually result in considerable interaction between the descending slab and the overriding plate; these regions experience great earthquakes.
The process by which most igneous rocks melt. Since individual minerals have different melting points, most igneous rocks melt over a temperature range of a few hundred degrees. If the liquid is squeezed out after some melting has occurred, a melt with a higher silica content results. Generates 10% molten material, intermixed with unmelted mantle rock, has a basaltic composition (silica-rich magma).
continental volcanic arcs
Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent, Cascade Range.
volcanic island arc (island arc)
A chain of volcanic islands generally located a few hundred kilometers from a tench where active subduction of the oceanic slab beneath another is occurring, Tonga islands.
3 Types of Convergences
Any break or rupture in rock along which no appreciable movement has taken place. Part of prominent linear breaks in the oceanic crust, includes both the active transform faults and their inactive extensions into the plate interior.
To gather sediments just above the igneous crust as a means to dating the seafloor at each site.
Are areas of volcanic volcanism heat flow (high), and crustal uplifting that are a few hundred kilometers across.
A mass of hotter-than-normal mantle material that ascends toward the surface, where it may lead to igneous activity. These plumes of solid yet mobile material may originate as deep as the core-mantle boundary.
hot spot tracks
Chains of volcanic structures, trace the direction of plate motion.
(fossil magnetism) The natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rocks at the time it became magnetized.
The temperature above which a material loses its magnetism. Iron-rich grains cool below the curie point, they gradually become magnetized in the direction of the existing magnetic lines of force.
The magnetic poles had migrated through time, or that lava flows moved, Europe had drifted in relation to the poles.
Rocks exhibit the same magnetism as the present magnetic field.
Rocks exhibiting the opposite magnetism.
Normally and reversely magnetized rocks of a given age in one location matured the magnetism of rocks of the same age found in all other locations.
magnetic time scale
Divisions called chrons, measure magnetic polarity.
Driving the plate's movements.
2 methods used for calculations
Very long Baseline Interferometry (VLBI)
Global Positioning Sustem (GPS)
drives plate motion
-convective flow in the rocky 2,900 kilometer-thick mantle- warm, buoyant rock rises and cooler, dense material sinks under its own weight-underlying driving force for plate movement.
-mantle convection and plate tectonics are part of the same system. Sub-ducting oceanic plates drive the cold downward-moving portions of convective flow where as shallow upwelling of hot rock along the oceanic ridge and buoyant mantle plumes are the upward arm of the convective mechanism
-the slow movements of Earth's plates and mantle are ultimately driven by unequal distribution of heat within Earth's interior
Slab sink into the asthenosphere, they "pull" the trailing plate along, in results because old slabs of oceanic lithosphere are more dense than the underlying asthenosphere and hence "sink like a rock."
Driving force, gravity-driven mechanism results from the elevated position of the oceanic ridge, which causes slabs of lithosphere to "slide" down the flanks of the ridge.
mantle flow tends to "suck" in nearby plates (similar to pulling the plug in a bath tub), even if it becomes detached from the overlying plate, its decent will continue to create flow in the mantle and hence will continue to drive plate motion.
THIS SET IS OFTEN IN FOLDERS WITH...
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