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Cataclastic Flow
A cataclastic rock is a type of fault rock that has been wholly or partly formed by the progressive fracturing and comminution of existing rocks, a process known as ''cataclasis''. Cataclasis involves the granulation, crushing, or milling of the original rock, then rigid-body rotation and translation of mineral grains or aggregates before lithification. Cataclastic rocks are associated with fault zones and impact event breccias. Classification Various classification schemes have been proposed for the cataclastic rocks, but changes in understanding of the processes involved in their formation and better knowledge of the variety of such rocks has made a simple classification difficult, particularly where distinctions cannot be made in hand specimens. Sibson's 1977 classification of fault rocks was the first to include an understanding of the deformation mechanisms involved and all subsequent schemes have been based on this. Fault breccias have been further classified in terms of thei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comminution
Comminution is the reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, cutting, vibrating, or other processes. Comminution is related to pulverization and grinding. All use mechanical devices, and many types of mills have been invented. Concomitant with size reduction, comminution increases the surface area of the solid. For example, a pulverizer mill is used to pulverize coal for combustion in the steam-generating furnaces of coal power plants. A cement mill produces finely ground ingredients for portland cement. A hammer mill is used on farms for grinding grain and chaff for animal feed. A demolition pulverizer is an attachment for an excavator to break up large pieces of concrete. Comminution is important in mineral processing, where rocks are broken into small particles to help liberate the ore from gangue. Comminution or grinding is also important in ceramics, electronics, and battery research. Mech ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clay Mineral
Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minerals form in the presence of water and have been important to life, and many theories of abiogenesis involve them. They are important constituents of soils, and have been useful to humans since ancient times in agriculture and manufacturing. Properties Clay is a very fine-grained geologic material that develops plasticity when wet, but becomes hard, brittle and non–plastic upon drying or firing. It is a very common material, and is the oldest known ceramic. Prehistoric humans discovered the useful properties of clay and used it for making pottery. The chemistry of clay, including its capacity to retain nutrient cations such as potassium and ammonium, is important to soil fertility. Because the individual particles in clay are less ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroclastic Rock
Pyroclastic rocks are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroclasts. Pyroclastic rocks are a type of volcaniclastic deposit, which are deposits made predominantly of volcanic particles. 'Phreatic' pyroclastic deposits are a variety of pyroclastic rock that forms from volcanic steam explosions and they are entirely made of accidental clasts. 'Phreatomagmatic' pyroclastic deposits are formed from explosive interaction of magma with groundwater. The word ''pyroclastic'' is derived from the Greek , meaning fire; and , meaning broken. Unconsolidated accumulations of pyroclasts are described as tephra. Tephra may become lithified to a pyroclastic rock by cementation or chemical reactions as the result of the passage of hot gases (fumarolic alteration) or groundwater (e.g. hydrothermal alteration and diagenesis) and burial, or, if it is emplaced at temperatures so hot that the soft gla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brittle–ductile Transition Zone
__NOTOC__ The brittle-ductile transition zone (hereafter the "transition zone") is the zone of the Earth's crust that marks the transition from the upper, more brittle crust to the lower, more ductile crust. For quartz and feldspar-rich rocks in continental crust, the transition zone occurs at an approximate depth of 20 km, at temperatures of 250–400 °C. At this depth, rock becomes less likely to fracture, and more likely to deform ductilely by creep because the brittle strength of a material increases with confining pressure, while its ductile strength decreases with increasing temperature. Depth of the Transition Zone The transition zone occurs at the depth in the Earth's lithosphere where the downward-increasing brittle strength equals the upward-increasing ductile strength, giving a characteristic "saw-tooth" crustal strength profile. The transition zone is, therefore, the strongest part of the crust and the depth at which most shallow earthquakes occur. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crust (geology)
In geology, the crust is the outermost solid shell of a planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be defined based on its phase (solid crust vs. liquid mantle). The crusts of Earth, Mercury, Venus, Mars, Io, the Moon and other planetary bodies formed via igneous processes and were later modified by erosion, impact cratering, volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust. These two types have different chemical compositions and physical properties and were formed by different geological processes. Types of crust Planetary geologists divide crust into three categories based on how and when it formed. Primary crust / primordial crust This is a planet's "original" crust. It forms from solidification of a magma ocean. Toward the end o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Structure
An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the surface expression of an impact structure. In many cases, on Earth, the impact crater has been destroyed by erosion, leaving only the deformed rock or sediment of the impact structure behind.Neuendorf, K.K.E., J.P. Mehl Jr., and J.A. Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. This is the fate of almost all old impact craters on Earth, unlike the ancient pristine craters preserved on the Moon and other geologically inactive rocky bodies with old surfaces in the Solar System. Impact structure is synonymous with the less commonly used term astrobleme meaning "star wound". In an impact structure, the typical visible and topographic expressions of an impact crater are no longer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite
A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a Meteoroid#Fireball, fireball, also known as a shooting star; astronomers call the brightest examples "Bolide#Astronomy, bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and impact event, impact Earth are called meteorite falls. All others are known as meteorite finds. Meteorites have traditionally been divided into three broad categories: stony meteorites that are rocks, mainly composed of sil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tachylyte
Tachylite ( ; also spelled tachylyte) is a form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt. It is a type of mafic igneous rock that is decomposable by acids and readily fusible. The color is a black or dark-brown, and it has a greasy-looking, resinous luster. It is very brittle and occurs in dikes, veins, and intrusive masses. The word originates from the Ancient Greek , meaning "swift". Tachylites have the appearance of pitch and are often more or less vesicular and sometimes spherulitic. They are very brittle and break down readily under a hammer. Small crystals of feldspar or olivine are sometimes visible in them with the unaided eye. All tachylites weather rather easily and by oxidation of their iron become dark brown or red. Three modes of occurrence characterize this rock. In all cases they are found under conditions which imply rapid cooling, but they are much less common than acid volcanic glasses (or obsidians ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass
Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window panes, tableware, and optics. Some common objects made of glass are named after the material, e.g., a Tumbler (glass), "glass" for drinking, "glasses" for vision correction, and a "magnifying glass". Glass is most often formed by rapid cooling (quenching) of the Melting, molten form. Some glasses such as volcanic glass are naturally occurring, and obsidian has been used to make arrowheads and knives since the Stone Age. Archaeological evidence suggests glassmaking dates back to at least 3600 BC in Mesopotamia, Ancient Egypt, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience, which is a form of pottery using lead glazes. Due to its ease of formability int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial planet, rocky planet or natural satellite, moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of volcanism on Venus, Venus, which cover ~80% of the surface, are basaltic; the lunar mare, lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cohesion (geology)
Cohesion is the component of shear strength of a rock or soil that is independent of interparticle friction. In soils, true cohesion is caused by following: # Electrostatic forces in stiff overconsolidated clays (which may be lost through weathering) # Cementing by Fe2 O3, Ca CO3, Na Cl, etc. There can also be apparent cohesion. This is caused by: # Negative capillary pressure (which is lost upon wetting) # Pore pressure response during undrained loading (which is lost through time) # Root cohesion (which may be lost through logging or fire of the contributing plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...s, or through solution) Typical values of cohesion Cohesion (alternatively called the cohesive strength) is typically measured on the basis of Mohr–Co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithification
Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithification is a process of porosity destruction through compaction and cementation. Lithification includes all the processes which convert unconsolidated sediments into sedimentary rocks. '' Petrifaction'', though often used as a synonym, is more specifically used to describe the replacement of organic material by silica in the formation of fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...s. See also * * * * * * References Geological processes Petrology Sedimentary rocks {{sedimentology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
