Earth cutaway from core to exosphere. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The planetary core consists of the innermost layer(s of a Planet. The exosphere is the uppermost layer of the atmosphere. On Earth, its lower boundary at the edge of the Thermosphere is estimated to be 500 km to

The mantle is a part of an astronomical object. s are significant physical entities, associations or structures which current Science has confirmed to exist in Space. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A terrestrial planet, telluric planet or rocky planet is a Planet that is primarily composed of Silicate rocks Within our A chemical substance is a Material with a definite chemical composition. The mantle is a highly viscous layer directly under the crust, and above the outer core. The interior of Earth, similar to the other Terrestrial planets, is Chemically divided into layers Earth's mantle is a ~2,900 km thick (1,800 miles)^[1] rocky shell comprising approximately 70% of Earth's volume. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 It is predominantly solid and overlies the Earth's iron-rich core, which occupies about 30% of Earth's volume. A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. Past episodes of melting and volcanism at the shallower levels of the mantle have produced a very thin crust of crystallized melt products near the surface, upon which we live. Plate tectonics and hotspots Divergent plate boundaries At the In Geology, a crust is the outermost solid shell of a planet or moon ^[2] The gases evolved during the melting of Earth's mantle have a large effect on the composition and abundance of Earth's atmosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five

Structure

The mantle is divided into sections based upon results from seismology. Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes These layers (and their depths) are the following: the upper mantle (33–410 km) (20 to 254 miles), the transition zone (410–670 km), the lower mantle (670–2798 km), and the D" layer (2798–2998 km)^[2][3][4][5].

The top of the mantle is defined by a sudden increase in seismic velocity, which was first noted by Andrija Mohorovičić in 1909; this boundary is now referred to as the "Moho"^[3][6]. Andrija Mohorovičić (ˈandrija mɔhɔːrɔvitʃiʨ ( January 23 1857 &ndash December 18, 1936) was a notable Croatian Meteorologist The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth 's crust and the mantle. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, an irregular layer with a maximum thickness of perhaps 200 km. The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. Below the lithosphere the upper mantle becomes notably more plastic in its rheology. Rheology is the study of the flow of matter mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically In some regions below the lithosphere, the seismic velocity is reduced; this – so-called – low velocity zone (LVZ) extends down to a depth of several hundred km. Inge Lehmann discovered a seismic discontinuity at about 220 km depth^[7]; although this discontinuity has been found in other studies it is not known whether the discontinuity is ubiquitous. Inge Lehmann ( May 13, 1888 &ndash February 21, 1993) Fellow of the Royal Society of London, was a Danish The transition zone is an area of great complexity; it physically separates the upper and lower mantle. ^[5] Very little is known about the lower mantle apart from that it appears to be relatively seismically homogeneous. D" is the layer which separates the mantle from the core. The core-mantle boundary (or CMB in the parlance of solid earth geophysicists lies between the Earth's Silicate mantle and its liquid Iron - Nickel ^[2][3]

Characteristics

The mantle differs substantially from the crust in its mechanical characteristics and its chemical composition. A chemical substance is a Material with a definite chemical composition. The distinction between crust and mantle is based on chemistry, rock types, rheology and seismic characteristics. The crust is, in fact, a product of mantle melting. Partial melting of mantle material is believed to cause incompatible elements to separate from the mantle rock, with less dense material floating upward through pore spaces, cracks, or fissures, to cool and freeze at the surface. Typical mantle rocks have a higher magnesium to iron ratio, and a smaller portion of silicon and aluminium than the crust. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 WikipediaNaming This behavior is also predicted by experiments that partly melt rocks thought to be representative of Earth's mantle.

Mapping the interior of the Earth with earthquake waves. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer

Mantle rock shallower than about 400 km depth consists mostly of olivine^[8], pyroxenes, spinel, and garnet^[5][9]; typical rock types are thought to be peridotite,^[5] dunite (olivine-rich peridotite), and eclogite. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. Dunite (ˈduːnaɪt or /ˈdʌnaɪt/ is an igneous, Plutonic rock, of Ultramafic composition with coarse-grained or Phaneritic Eclogite (ˈɛklədʒaɪt is a coarse-grained Mafic ( Basaltic in composition Metamorphic rock. Between about 400 km and 650 km depth, olivine is not stable and is replaced by high pressure polymorphs with approximately the same composition: one polymorph is wadsleyite (also called beta-spinel type), and the other is ringwoodite (a mineral with the gamma-spinel structure). Polymorphism in Materials science is the ability of a solid material to exist in more than one form or Crystal structure Wadsleyite is a high-pressure Polymorph of Olivine, an Orthorhombic Mineral found in the Peace River Meteorite in Alberta Canada Ringwoodite is a high-pressure Polymorph of Olivine, and it is stable at high temperatures and pressures like those in the Earth's mantle near 600 km depth The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric Below about 650 km, all of the minerals of the upper mantle begin to become unstable; the most abundant minerals present have structures (but not compositions) like that of the mineral perovskite. A perovskite is any material with the same type of Crystal structure as Calcium titanium oxide (CaTiO3 known as the perovskite structure The changes in mineralogy at about 400 and 650 km yield distinctive signatures in seismic records of the Earth's interior, and like the moho, are readily detected using seismic waves. These changes in mineralogy may influence mantle convection, as they result in density changes and they may absorb or release latent heat as well as depress or elevate the depth of the polymorphic phase transitions for regions of different temperatures. Mantle convection is the slow creeping motion of Earth's rocky mantle in response to perpetual gravitationally unstable variations in its density The changes in mineralogy with depth have been investigated by laboratory experiments that duplicate high mantle pressures, such as those using the diamond anvil^[10]. A diamond anvil cell (DAC consists of two opposing Diamonds with a sample compressed between the Culets Extreme pressure, which can exceed 1000000

Why is the inner core solid, the outer core liquid, and the mantle solid/plastic? The answer depends both on the relative melting points of the different layers (nickel-iron core, silicate crust and mantle) and on the increase in temperature and pressure as one moves deeper into the Earth. At the surface both nickel-iron alloys and silicates are sufficiently cool to be solid. In the upper mantle, the silicates are generally solid (localised regions with small amounts of melt exist); however, as the upper mantle is both hot and under relatively little pressure, the rock in the upper mantle has a relatively low viscosity. In contrast, the lower mantle is under tremendous pressure and therefore has a higher viscosity than the upper mantle. The metallic nickel-iron outer core is liquid despite the enormous pressure as it has a melting point that is lower than the mantle silicates. The inner core is solid due to the overwhelming pressure found at the center of the planet^[12].

Temperature

In the mantle, temperatures range between 500 °C–900 °C (932 °F–1,652 °F) at the upper boundary with the crust to over 4,000 °C (7,200 °F) at the boundary with the core. The interior of Earth, similar to the other Terrestrial planets, is Chemically divided into layers ^[12] Although the higher temperatures far exceed the melting points of the mantle rocks at the surface (about 1200 °C for representative peridotite), the mantle is almost exclusively solid. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. ^[12] The enormous lithostatic pressure exerted on the mantle prevents melting, because the temperature at which melting begins (the solidus) increases with pressure. Overburden pressure, lithostatic pressure, and vertical stress are terms that denote the Pressure or stress imposed on a layer of Soil Melting is a process that results in the phase change of a substance from a Solid to a Liquid. In Chemistry, Materials science, and Physics, the solidus is a temperature (a line on a Phase diagram) below which a given substance is completely

Movement

Due to the temperature difference between the Earth's surface and outer core, and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle^[3]. Convection in the most general terms refers to the movement of molecules within Fluids (i Hot material ascends as a plutonic diapir (somewhat akin to a lava lamp), perhaps from the border with the outer core (see mantle plume), while cooler (and heavier) material sinks downward. A diapir (ˈdaɪəpɪər) ( French, from Greek diapeirein, to pierce through is an Intrusion caused by Buoyancy and Pressure A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. This is often in the form of large-scale lithospheric downwellings at plate boundaries called subduction zones^[3]. During the ascent the material of the mantle cools down both adiabatically and by conduction into surrounding cooler mantle. The temperature of the material falls with the pressure relief connected with the ascent, and its heat distributes itself over a larger volume. Because the temperature at which melting initiates decreases more rapidly with height than does a rising hot plume, partial melting may occur just beneath the lithosphere and causing volcanism and plutonism. Plate tectonics and hotspots Divergent plate boundaries At the

The convection of the Earth's mantle is a chaotic process (in the sense of fluid dynamics), which is thought to be an integral part of the motion of plates. Convection in the most general terms refers to the movement of molecules within Fluids (i In Mathematics, chaos theory describes the behavior of certain dynamical systems – that is systems whose state evolves with time – that may exhibit dynamics that Plate motion should not be confused with the older term continental drift which applies purely to the movement of the crustal components of the continents. Continental drift is the movement of the Earth 's Continents relative to each other The movements of the lithosphere and the underlying mantle are coupled since descending lithosphere is an essential component of convection in the mantle. The observed continental drift is a complicated relationship between the forces causing oceanic lithosphere to sink and the movements within Earth's mantle.

Although there is a tendency to larger viscosity at greater depth, this relation is far from linear, and shows layers with dramatically decreased viscosity, in particular in the upper mantle and at the boundary with the core. ^[13] The mantle within about 200 km above the core-mantle boundary appears to have distinctly different seismic properties than the mantle at slightly shallower depths; this unusual mantle region just above the core is called D″ ("D double-prime" or "D prime prime"), a nomenclature introduced over 50 years ago by the geophysicist Bullen^[14]. The core-mantle boundary (or CMB in the parlance of solid earth geophysicists lies between the Earth's Silicate mantle and its liquid Iron - Nickel Bullen is a surname and may refer to Arthur Henry Bullen (1857-1920 English editor publisher and a specialist in 16th and 17th century literature D″ may consist of material from subducted slabs that descended and came to rest at the core-mantle boundary and/or from a new mineral polymorph discovered in perovskite called post-perovskite. The core-mantle boundary (or CMB in the parlance of solid earth geophysicists lies between the Earth's Silicate mantle and its liquid Iron - Nickel Post-perovskite is a high-pressure phase of MgSiO3 is composed of the prime oxide constituents of the Earth's rocky mantle (MgO and SiO2 and its pressure and temperature

Due to the relatively low viscosity in the upper mantle one could reason that there should be no earthquakes below approximately 300 km depth. An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer However, in subduction zones, the geothermal gradient can be lowered where cool material from the surface sinks downward, increasing the strength of the surrounding mantle, and allowing earthquakes to occur down to a depth of 400 km and 670 km.

The pressure at the bottom of the mantle is ~136 GPa (1. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface 4 million atm). ^[5] There exists increasing pressure as one travels deeper into the mantle, since the material beneath has to support the weight of all the material above it. The entire mantle, however, is still thought to deform like a fluid on long timescales, with permanent plastic deformation accommodated by the movement of point, line, and/or planar defects through the solid crystals comprising the mantle. Estimates for the viscosity of the upper mantle range between 10¹⁹ and 10²⁴ Pa·s, depending on depth,^[13] temperature, composition, state of stress, and numerous other factors. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. Thus, the upper mantle can only flow very slowly. However, when large forces are applied to the uppermost mantle it can become weaker, and this effect is thought to be important in allowing the formation of tectonic plate boundaries. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere

Exploration

Exploration of the mantle is generally conducted at the seabed rather than on land due to the relative thinness of the oceanic crust as compared to the significantly thicker continental crust.

The first attempt at mantle exploration, known as Project Mohole, was abandoned in 1966 after repeated failures and cost over-runs. The deepest penetration was approximately 180 m (590 ft). In 2005 the third-deepest oceanic borehole hole reached 1416 meters (4,644 feet) below the sea floor from the ocean drilling vessel JOIDES Resolution. JOIDES Resolution (Joint Oceanographic Institutions for Deep Earth Sampling is a Scientific drilling ship once used by the Ocean Drilling Program

On March 5, 2007, a team of scientists on board the RRS James Cook embarked on a voyage to an area of the Atlantic seafloor where the mantle lies exposed without any crust covering, mid-way between the Cape Verde Islands and the Caribbean Sea. Events 363 - Roman Emperor Julian moves from Antioch with an army of 90000 to attack the Sassanid Empire, in a Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The Republic of Cape Verde ( Portuguese: Cabo Verde, 'kabu 'veɾdɨ is a Republic located on an Archipelago in the Macaronesia For the region see Caribbean. The Caribbean Sea (kəˈrɪbiən or /ˌkærɨˈbiːən/ is a tropical Sea in the Western Hemisphere The exposed site lies approximately three kilometres beneath the ocean surface and covers thousands of square kilometres. ^[15][16]

A relatively difficult attempt to retrieve samples from the Earth's mantle was scheduled for later in 2007. ^[17] As part of the Chikyu Hakken mission, was to use the Japanese vessel 'Chikyu' to drill up to 7000 m (23,000 ft) below the seabed. Japanese for "Earth Discovery" is the name of the Japan Agency for Marine-Earth Science and Technology, or JAMSTEC 's outreach program to promote it's drilling vessel This is nearly three times as deep as preceding oceanic drillings.

A novel method of exploring the uppermost hundreds km of the Earth was recently analysed using a small, dense, heat-generating probe which melts its way down through the crust and mantle while its position and progress are tracked by acoustic signals generated in the rocks. ^[18] The probe consists of an outer sphere of tungsten ~ 1 m in diameter inside which is a 60Co radioactive heat source. Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 It was calculated that such a probe will reach the oceanic Moho in less than 6 months and attain minimum depths of well over 100 km in a few decades beneath both oceanic and continental lithosphere. The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth 's crust and the mantle. ^[19]

References

External links

• Don L. Nova Publishers is a Publishing house based in Hauppauge New York. Anderson, Theory of the Earth, Blackwell (1989), is a textbook dealing with the Earth's interior and is now available on the web. Retrieved 2007-12-23. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 962 - Byzantine-Arab Wars: Under the future Emperor Nicephorus Phocas, Byzantine troops stormed the city
• The Biggest Dig : Japan builds a ship to drill to the earth's mantle – Scientific American Magazine (September 2005)
• Information on the Mohole Project
• Thinkquest Team (2000). The Mantle. Retrieved on 2007-12-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 274 - Roman Emperor Aurelian