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Flat Slab Subduction
Flat slab subduction is characterized by a low subduction angle (<30 degrees to horizontal) beyond the and a resumption of normal subduction far from the . A slab refers to the subducting lower plate. A broader definition of flat slab includes any shallowly dipping lower plate, as in western . Flat slab |
Seismometer
A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output of such a device—formerly recorded on paper (see picture) or film, now recorded and processed digitally—is a ''seismogram''. Such data is used to locate and characterize earthquakes, and to study the internal structure of Earth. Basic principles A simple seismometer, sensitive to up-down motions of the Earth, is like a weight hanging from a spring, both suspended from a frame that moves along with any motion detected. The relative motion between the weight (called the mass) and the frame provides a measurement of the vertical ground motion. A rotating drum is attached to the frame and a pen is attached to the weight, thus recording any ground motion in a seismogram. Any movement from the ground moves the frame. The mass tends ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle (geology)
A mantle is a layer inside a planetary body bounded below by a Planetary core, core and above by a Crust (geology), crust. Mantles are made of Rock (geology), rock or Volatile (astrogeology), ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone planetary differentiation, differentiation by density. All Terrestrial planet, terrestrial planets (including Earth), half of the giant planets, specifically ice giants, a number of Asteroid, asteroids, and some planetary Natural satellite, moons have mantles. Examples Earth The Earth's mantle is a layer of Silicate minerals, silicate rock between the Crust (geology), crust and the Earth's outer core, outer core. Its mass of 4.01 × 1024 kg is 67% the mass of the Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly solid, but in Geologic time scale, geological time it behaves as a Viscosity, visc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus, the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the Displacement (fluid), displaced fluid. For this reason, an object with average density greater than the surrounding fluid tends to sink because its weight is greater than the weight of the fluid it displaces. If the objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nazca Ridge
The Nazca Ridge is a submarine ridge, located on the Nazca plate off the west coast of South America. This plate and ridge are currently subducting under the South American plate at a convergent boundary known as the Peru-Chile Trench at approximately per year. The Nazca Ridge began subducting obliquely to the collision margin at 11°S, approximately 11.2 Ma, and the current subduction location is 15°S. The ridge is composed of abnormally thick basaltic ocean crust, averaging 18 ±3 km thick. This crust is buoyant, resulting in flat slab subduction under Peru. This flat slab subduction has been associated with the uplift of Pisco Basin and the cessation of Andes volcanism and the uplift of the Fitzcarrald Arch on the South American continent approximately 4 Ma. Morphology The Nazca Ridge is approximately wide, long, and has of bathymetric relief. The gradient of the slopes is 1-2 degrees. The ridge is located at a depth of below sea level, above the carbonate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pampean Flat-slab
The Pampean flat-slab is the flat slab subduction, low angle subduction of lithosphere, oceanic lithosphere beneath Northern Argentina. The Pampean flat-slab is one of three flat slabs in South America, the other being the Peruvian flat-slab and the Bucaramanga flat-slab. It is thought that the subduction of the Juan Fernández Ridge, a chain of extinct volcanoes on the Nazca Plate, is the underlying cause of the Pampean flat-slab. Effects The shallowing of subducted slab beneath north-central Chile and Argentina is linked to a series of changes in volcanism and tectonics. Deformation of crust The flat-slab has caused an tectonic uplift, uplift of Sierras Pampeanas which begun first in the north and then moved southwards over millions of years. The oldest noted uplift episode associated with Pampean flat-slab is that of Sierra de Aconquija (27 °S) from 7.6 to 6 million years ago (Ma) in the Miocene, Late Miocene epoch. This was followed by the uplift of massifs further south su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seamount
A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form.IHO, 2008. Standardization of Undersea Feature Names: Guidelines Proposal form Terminology, 4th ed. International Hydrographic Organization and Intergovernmental Oceanographic Commission, Monaco. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface, such flat-top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Plateau
An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map). Oceanic plateaus produced by large igneous provinces are often associated with hotspot (geology), hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean large igneous province, Caribbean, Ontong Java Plateau, Ontong Java, and Mid-Pacific Mountains, are located on swell (geology), thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example the Falkland Plateau, Lord Howe Rise, and parts of Kerguelen Plateau, Kerguelen, Mascarene Plateau, Seychelles, and Arctic ridges. Plateaus formed by larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juan Fernández Ridge
The Juan Fernández Ridge is a volcanic island and seamount chain on the Nazca plate. It runs for about in a west–east direction from the Juan Fernández hotspot to the Peru–Chile Trench between the latitudes of 32-34° S before subducting beneath the South American plate near Valparaíso. The ridge forms a deep underwater corridor about below sea level, and was formed by upwelling of hot material from deep underground more than 22 million years ago. The ridge affects the geology of the region, and causes volcanic activity and earthquakes. Location Juan Fernández Ridge is a chain of volcanic islands and seamounts on the Nazca plate. It runs for about in a west–east direction from the Juan Fernández hotspot to the Peru–Chile Trench between the latitudes of 32-34° S before subducting beneath the South American plate near Valparaíso. Geology The ridge was formed by upwelling of a deep plume of hot material from the mantle of the Earth. The ridge forms a deep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bathymetry
Bathymetry (; ) is the study of underwater depth of ocean floors ('' seabed topography''), river floors, or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water depth measurements are from Ancient Egypt over 3000 years ago. Bathymetry has various uses including the production of bathymetric charts to guide vessels and identify underwater hazards, the study of marine life near the floor of water bodies, coastline analysis and ocean dynamics, including predicting currents and tides. Bathymetric charts (not to be confused with '' hydrographic charts''), are typically produced to support safety of surface or sub-surface navigation, and usually show seafloor relief or terrain as contour lines (called '' depth contours'' or '' isobaths'') and selected depths ('' soundings''), and typically also provide surface navigational information. Bathymetric maps (a more general term where navigational safet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Working Hypothesis
A working hypothesis is a hypothesis that is provisionally accepted as a basis for further ongoing research in the hope that a tenable theory will be produced, even if the hypothesis ultimately fails.See in "hypothesis", ''Century Dictionary Supplement'', v. 1, 1909, New York: The Century Company. Reprintedv. 11, p. 616(via ''Internet Archive''] of the ''Century Dictionary and Cyclopedia'', 1911. Like all hypotheses, a working hypothesis is constructed as a statement of expectations, which can be linked to deductive, exploratory research Shields, Patricia and Rangarjan, N. (2013). ''A Playbook for Research Methods: Integrating Conceptual Frameworks and Project Management''. Stillwater, OK: New Forums Press. See Chapter 5. in empirical investigation and is often used as a conceptual framework in qualitative research. The term "working" indicates that the hypothesis is subject to change. History Use of the phrase "working hypothesis" goes back to at least the 1850s. Charles Sande ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Causality
Causality is an influence by which one Event (philosophy), event, process, state, or Object (philosophy), object (''a'' ''cause'') contributes to the production of another event, process, state, or object (an ''effect'') where the cause is at least partly responsible for the effect, and the effect is at least partly dependent on the cause. The cause of something may also be described as the reason for the event or process. In general, a process can have multiple causes,Compare: which are also said to be ''causal factors'' for it, and all lie in its past. An effect can in turn be a cause of, or causal factor for, many other effects, which all lie in its future. Some writers have held that causality is metaphysics , metaphysically prior to notions of time and space. Causality is an abstraction that indicates how the world progresses. As such it is a basic concept; it is more apt to be an explanation of other concepts of progression than something to be explained by other more fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
