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Topic: Lithostatic pressure

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Hydrostatic equilibrium

Sedimentary rock

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	Pressure (from metamorphic rock) -- Encyclopædia Britannica
		The pressure experienced by a rock during metamorphism is due primarily to the weight of the overlying rocks (i.e.,lithostatic pressure) and is generally reported in units of bars or kilobars.
		The pressure exerted on a floor by a 42-pound box the bottom of which has an area of 84 square inches is equal to the force divided by the area over which it is exerted; i.e., it is one-half pound per square inch.
		pressure exerted by a vapor when the vapor is in equilibrium with the liquid or solid form, or both, of the same substance; increases with increasing temperature; the temperature at which the vapor pressure at the surface of a liquid equals the pressure exerted by the surroundings is called the boiling point of the liquid.
	www.britannica.com /eb/article-80308 (858 words)

	Figure 7. A. Porosity analysis from Hole 975C. The porosity derived from the density log decreases almost linearly with ...
		The lithostatic pressure is derived by numerical integration of the density log.
		The reduced lithostatic pressure is defined as the lithostatic pressure minus the hydrostatic pressure.
		Below the seal, the fluid overpressure is observed to be close to the reduced lithostatic pressure, which indicates the presence of natural fracturing in the transition zone.
	www-odp.tamu.edu /publications/161_SR/chap_10/c10_f7a.htm (622 words)

	Overburden pressure. Who is Overburden pressure? What is Overburden pressure? Where is Overburden pressure? Definition ... (Site not responding. Last check: 2007-11-04)
		Overburden, or lithostatic pressure, is a term used in geology to denote the pressure imposed on a stratigraphic layer by the weight of overlying layers of material.
		It is common for parts of stratigraphic layers to be isolated, or sealed, such that they are no longer in hydrostatic equilibrium.
		In such cases, the layer, or part of layer, is said to be in a condition of overpressure (if local pressure is greater than hydrostatic) or underpressure (if local pressure is less than hydrostatic).
	www.knowledgerush.com /kr/encyclopedia/Overburden_pressure (151 words)

	Pressure prediction from seismic data: implications for seal distribution and hydrocarbon exploitation in the deepwater ... (Site not responding. Last check: 2007-11-04)
		The conventional techniques for pressure prediction are limited by two factors: establishing a "normal" trend of an attribute (usually a porosity indicator) and a set of calibration curves relating "overpressure" to deviation from the normal trend of that attribute.
		Formation pressure or pore pressure, p, is defined as the pressure acting upon the fluids in the pore space of a formation.
		The formation pressure gradient, expressed usually in pounds per square inch per foot (abbreviated by psi/ft) in the British system of units, is the ratio of the formation pressure, p, in psi to the depth, z, in feet.
	www.oilvel.com /Dutta_seal/Dutta_seal.htm (3875 words)

	Patent 4165945: Method for storing fluid underground at maximum pressure p
		In other instances, lithostatic pressure is resorted to for balancing internal pressure in various storage tanks, pressure-sustaining ducts or nuclear reactors (refer, in particular, to "Mecanique des roches et ses applications" published by Dunod, Paris 1967, pages 377 to 389).
		Lithostatic pressure as used in the art is the pressure which may be tolerated by an underground cavity sunk into rock at a certain depth without cracking.
		Pressurized gas is fed into, and from, cavity 1 by means of a duct 14 connecting the tank to filling and exhaust means M' via shaft 2.
	www.freepatentsonline.com /4165945.html (3345 words)

	Patent 4162706: Determining the locus of a processing zone in an oil shale retort by monitoring pressure drop across ...
		Also contributing to changes in pressure drop in the retort during retorting of oil shale can be a decrease in the effective void fraction of the fragmented mass due to absorption of liquid hydrocarbons on the surface of oil shale in the retorting zone and on the advancing side of the retorting zone.
		Superimposed on this tendency of the pressure drop across the fragmented mass to increase with time as the retorting and combustion processing zones advance through the fragmented mass are fluctuations and changes in the pressure drop across the fragmented mass with variations in processing parameters.
		From the samples and the correlation between pressure drop across the fragmented mass and the kerogen content of the formation, the pressure drop and changes in the pressure drop across the fragmented mass can be predicted as a function of the elevation of the processing zone in the fragmented mass.
	www.freepatentsonline.com /4162706.html (7901 words)

	Overpressure - Wikipedia, the free encyclopedia
		Overpressure, in geology, is a term used to describe the pressure regime in a stratigraphic unit that exhibits higher-than-hydrostatic pressure in its pore structure.
		Overpressure in stratigraphic layers is fundamentally caused by the inability of connate pore fluids to escape as the surrounding mineral matrix compacts under the lithostatic pressure caused by overlying layers.
		Fluid escape may be impeded by sealing of the compacting rock by surrounding impermeable layers (such as evaporites, chalk and cemented sandstones).
	en.wikipedia.org /wiki/Overpressure (242 words)

	Metamorphism and Metamorphic Rocks
		Pressure increases with burial from the weight of overlying rock (uniform or lithostatic pressure) and from tectonic forces (differential or directed pressure).
		Lithostatic pressure, which is defined by the relation:
		Rocks are foliated with mineral assemblages characteristic of varying metamorphic temperatures and pressures.
	www.geo.ua.edu /intro03/Meta.html (981 words)

	pressure -- Britannica Concise Encyclopedia - Your gateway to all Britannica has to offer!
		The pressure exerted by a confined gas results from the average effect of the forces produced on the walls of the container by the continual, numerous collisions by gas molecules.
		Lithostatic pressure is the stress exerted on a body of rock in the Earth's crust by surrounding rock, which increases with depth below the surface.
		Vapour pressure is a measure of the tendency of a material to change into the gaseous or vapour state, and it increases with temperature.
	concise.britannica.com /ebc/article-9375860 (948 words)

	Mantle (geology) - Wikipedia, the free encyclopedia
		The convection of the Earth's mantle is a chaotic process (in the sense of fluid dynamics), which is thought to drive the motion of plates.
		The pressure at the bottom of the mantle is ~140 GPa (1.4 Matm).
		There exists increasing pressure as one travels deeper into the mantle, the entire mantle, however, is still thought to deform like a fluid on long timescales.
	en.wikipedia.org /wiki/Earth%2527s_mantle (849 words)

	Metamorphic Rocks (Site not responding. Last check: 2007-11-04)
		Careful analysis of the mineral composition of the rock, or petrologic evaluation, is required, often requiring the use of petrographic microscope or electron microprobe to determine the exact composition of the individual minerals.
		The pressure may be static, as in the lithostatic pressure which results from the weight of the overlying rocks.
		Pressure may also be directed by tectonic forces, which can be tensional, compressional or shear forces.
	www.dmtcalaska.org /course_dev/explogeo/class09/notes09.html (2087 words)

	Sedimentary rock (Site not responding. Last check: 2007-11-04)
		Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in three main ways—by the deposition of the weathered remains of other rocks (known as clastic sedimentary rocks); by the deposition of the results of biogenic activity; and by precipitation from solution.
		Sedimentary rockss are formed from overburden pressure as particles of sediment are deposited out of air, ice, or water flows carrying the particles in suspension.
		As sediment deposition builds up, the overburden (or lithostatic) pressure squeezes the sediment into layered solids in a process known as lithification ("rock formation") and the original connate fluids are expelled.
	www.sciencedaily.com /encyclopedia/sedimentary_rock (475 words)

	GO 568 Fractures & Faults II
		In most cases, the lithostatic P is borne mainly by intergranular P, and hydrostatic P is much less than lithostatic P. However, in some situations, hydrostatic P can approach or equal lithostatic P, in which case the overburdern mass of rock essentially floats on a cushion of high-pressure fluid.
		The necessary fluid pressure may be developed in the crust when porous, mechanically weak strata of low permeability, such as claystone, lignite, chalk, or salt, are subjected to rapid loading.
		The high fluid pressure sufficient to facilitate overthrusting may develop whenever the rate of loading for whatever reason is greater than the rate of fluid escape from compacted, weak strata.
	academic.emporia.edu /aberjame/struc_geo/faults/faults2.htm (972 words)

	Nat' Academies Press, The Role of Fluids in Crustal Processes (1990)
		By hydrostatic pressure what is meant is the pressure resulting from the density of an overlying column of fluid as opposed to the much greater pressure resulting from the density of an overlying column of rock (lithostatic pres- sure).
		Near the Earth's surface fluid pressure is controlled by the extent of the overlying fluid column (hydrostatic pres- sure) while the pressure exerted on mineral grains (lithostatic pressure) is considerably greater owing to the much greater density of the- minerals.
		Note that fluid pressure equal to rock pressure does not imply that fluid is trapped in a static state but that it is possible that the flow of fluid is balanced by permeability changes near fluid pressure equal to rock pressure.
	books.nap.edu /openbook/030904037X/html/64.html (4243 words)

	Pressure (Site not responding. Last check: 2007-11-04)
		Different kinds of pressure (static, dynamic, partial, total, vapor, etc.) are distinguished by the orientation of the surface with respect to mass-flow velocity vectors or by the restriction to a specified set of molecular species crossing the imaginary surface.
		The actual total pressure in a high-vacuum system cannot usually be measured by a single gage, but in vacuum technology the term total pressure is sometimes used to refer to the reading of a single untrapped gage which responds to condensable vapors as well as permanent gases.Symbol p.
		Pressure has been building for several years to modernize the political system, and both the King and the Government recognize that there is a need for political reform, including the drafting of a new constitution and, specifically, a bill of rights.
	www.websters-online-dictionary.org /pr/pressure.html (4159 words)

	Pressure Solution (Site not responding. Last check: 2007-11-04)
		When sediments are subjected to pressure and temperature for a prolonged period, say some millions of years, the sediment grains grow into each other forming a solid rock without breaking.
		Due to this pressure increase the solubility of the grainmaterial rises slightly.
		At the free pore boundary this pressure increase is so small that it will probably not be effective, not even after millions of years.
	www.xs4all.nl /%7Edeboerrb/Flash/PressureSolution.html (199 words)

	GEOBAROMETRY - ARCHEAN LODE-GOLD
		Lithostatic pressure conditions were assumed for meso- and katazonal deposits, whereas a mixed litho-hydrostatic pressure gradient was assigned to epizonal deposits.
		For deeper deposits (> 5 km) lithostatic fluid pressures are assumed based on the lack of evidence for surface water influx and hydrodynamic considerations such as the total load of rocks overlying the deposits.
		Note that for the epizonal gold deposits, pressures may vary between litho- and hydrostatic values; for meso- and katazonal deposits constant lithostatic pressures are assumed.
	www.geology.wisc.edu /flincs/pubs/ecrofi1.html (679 words)

	Geotechnical Sensors
		Tip resistance is a measure of the pressure exerted (force per area) on the tip of the cone as it is advanced at a constant speed.
		Friction and pressure sensors inside the cone are usually connected to a data acquisition system on the surface, either using cables or data transmitters.
		Pore pressure transducers, also known as piezocones, measure the response of groundwater in pores in soil or sediment to the force of the advancing point.
	fate.cluin.org /direct_push/dpgeotech_main.asp (2429 words)

	metamor (Site not responding. Last check: 2007-11-04)
		These pressures are associated with thermo-disequilibrium within the earth that cause plate movement and collisions.
		Burial Metamorphism - metamorphism caused predominantly by lithostatic pressure in a thick accumulation of sedimentary and/or volcanic rocks.
		Deeply buried sedimentary and volcanic rocks are squeezed by directed pressures and subjected to temperature increases due to burial.
	itc.gsw.edu /faculty/tweiland/metamor.html (1205 words)

	Metamorphic Rocks
		Lithostatic pressure is equal in all directions and compresses the volume of rock into a denser material.
		Under great pressure, mineral grains may be smeared and aligned into bands perpendicular to the direction of greatest pressure.
		Temperatures of metamorphism vary widely from 400-1000°C. The amount of metamorphism is governed by a variety of factors, among which are the differences between the temperature of the pluton and the country rock, the heat capacity and conductivity of both magma and country rock.
	www.uwsp.edu /geo/faculty/ritter/geog101/textbook/earth_materials_structure/metamorphic_rocks.html (854 words)

	Solutions to Homework Problem Set #3
		The oil fountain was produced by the lithostatic pressure at the top of the reservoir.
		The oil column of the fountain must be able to produce a weight that equals the lithostatic pressure.
		It is equivalent to approximately the pressure at 1 km depth of ocean.
	www.geology.uiuc.edu /~hsui/classes/geo350/HW-Solutions/soln03F99/soln03.htm (291 words)

	Nat' Academies Press, The Role of Fluids in Crustal Processes (1990)
		Figure 11.3 shows pressure profiles at venous times as the pressure builds to lithostatic for a case in which pe~meability is 10-9 darcies.
		Once lithostatic pressure is reached, permeability is increased 1000 times, simulating the effect of fracturing.
		The pressure once again builds to a lithostatic level at the bottom of the column, a second break occurs, and this sequence continues to repeat itself.
	www.nap.edu /books/030904037X/html/158.html (2534 words)

	GEO THERMAL
		is the isochoric thermal pressure, dT/dz is the geothermal gradient.
		The variation of hydrostatic pressure, pore fluid pressure, lithostatic pressure and pore fluid factor with depth are shown in Figure 4.
		Near the surface, fluid pressure is controlled by hydrostatic pressure and lithostatic pressure is considerably greater than the fluid pressure owing to the higher density of the rocks.
	www.iisc.ernet.in /currsci/nov251998/articles29.htm (2870 words)

	Vertical stress in the ground (Site not responding. Last check: 2007-11-04)
		The magnitude of the pore pressure at the water table is zero.
		The combined effect is a complex relationship involving partial pressures and the degree of saturation of the soil.
		The clay is undrained and the pore pressure increases by 72.0 kPa.
	fbe.uwe.ac.uk /public/geocal/SoilMech/stresses/stresses.htm (1977 words)

	COMPACTION MODEL
		Palciauskas and Domenico (1989) show that compaction by pressure solution in sedimentary basins is irreversible and several orders of magnitude more effective than the corresponding poro-elastic (reversible) compressibility.
		Defining the departure from hydrostatic pore pressure, lithostatic pressure, and porosity by
		The uncompacted porosity and the compressibility are determined in the upper section of the sedimentary column provided that this domain is hydrostatically pressured.
	www-odp.tamu.edu /publications/161_SR/chap_10/c10_4.htm (716 words)

	Abnormal Fluid Pressure (Site not responding. Last check: 2007-11-04)
		Sedimentary basins with overpressures typically consist of 2-3 km of normal pressured sediments with a transition zone and then a deep section of high fluid pressures.
		- rate of pressure generation is sufficiently high so as to maintain abnormal pressures in the presence of low-permeability rocks over geologic time (e.g., very high sedimentation rates).
		Thus, as sediments are heated with burial, the expansion of water generates fluid pressure.
	www.geol.lsu.edu /Faculty/Nunn/gl4182/Geopress.html (282 words)

	Nat' Academies Press, The Waste Isolation Pilot Plant: A Potential Solution for the Disposal of Transuranic Waste (1996)
		Brine pore pressure in both halite and anhydrite marker bed units at WIPP has been found to be approximately 12 MegaPascals (MPa), which is between hydrostatic (6 MPa) and lithostatic (15 MPa).
		When anhydrite is subjected to internal pressures (e.g., by high gas or brine pressures in the waste rooms) approaching lithostatic, its permeability may increase significantly due to the generation of incipient fractures and eventually open macroscopic fractures.
		The hazard of such "pockets" of pressurized gas is considered by the committee to be negligible because of its small volume and small gas pressure energy.
	www.nap.edu /books/0309054915/html/37.html (5401 words)

	Search Results for lithostatic pressure - Encyclopædia Britannica
		The pressure exerted on a floor by a 42-pound box the bottom of which has an area...
		pressure exerted by a vapour when the vapour is in equilibrium with the liquid or solid form, or both, of the same substance—i.e., when conditions are such that the substance can exist in both or in...
		the pressure on a surface resulting from electromagnetic radiation that impinges on it, which results from the momentum carried by that radiation; radiation pressure is doubled if the radiation is...
	www.britannica.com /search?query=lithostatic+pressure (580 words)

	Discussion (Site not responding. Last check: 2007-11-04)
		Since water solubility falls off as the square root of lithostatic pressure [McMillan, 1994], we can expect an enormous viscosity gradient in the shallow portions of a volcanic conduit.
		If magma viscosity increases faster than the decrease in lithostatic pressure, we would expect rise velocities to decrease as gas bubbles climb towards the vent.
		Though we simplify the pressure accumulation by considering a gas foam which collects beneath an immovable, impermeable, high viscosity plug, pressure buildup is probably integrated over a conduit section.
	www.agu.org /pubs/toc/gl/gl/gl9821/1998GL900102/node5.html (459 words)

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