Inspired by the other topic that involved the word core but had nothing to do geologically.
So, after careful thought I'm curious, are there layers for the flat earth? I did some research about the layers of the RE and found out quite a lot. All of it makes sense too. I'm wondering what the FE take on this is.
For RE we have 3 layers:
The CrustThe Earth's outermost surface is called the crust. The crust is typically about 25 miles thick beneath continents, and about 6.5 miles thick beneath oceans. The crust is relatively light and brittle. Most earthquakes occur within the crust.
The MantleThe region just below the crust and extending all the way down to the Earth's core is called the mantle. The mantle is relatively flexible so it flows instead of fracturing.
The CoreBeneath the mantle is the Earth's core. The Earth's core consists of a fluid outer core and a solid inner core. Because the outer core contains iron, when it flows it generates a magnetic field. This is the source of the Earth's magnetic field.
However, those are just light descriptions with crappy pictures. Here's a better one before I continue.
Now, we know these layers exist because of volcanos.
A volcano is a rupture in the earth's surface or crust, allowing hot, usually molten rock, ash, and gases originating deep below the surface to periodically escape. Volcanic activity involving the extrusion of rock tends to form mountains or mountain-like features over time.Volcanic activity can also occur from mantle plumes, the so-called hotspots, which occur at locations far from plate boundaries.
*some background definitions*
A
mantle plume is an upwelling of abnormally hot rock within the Earth's (or another planet's) mantle. As the heads of mantle plumes can partly melt when they reach shallow depths, they are thought to be the cause of volcanic centers known as hotspots and probably also have caused flood basalts. It is a secondary way that Earth loses heat, much less important in this regard than is heat loss at plate margins (see Plate tectonics). Some scientists think that plate tectonics cools the mantle, and mantle plumes cool the core.
In geology, a
hotspot is a location on the Earth's surface that has experienced active volcanism for a long period of time.
*continuing*
Let's talk more about the RE layers.
The Crust AgainIn geology, a crust is the outermost layer of a planet, part of its lithosphere. Planetary crusts are generally composed of a less dense material than that of its deeper layers. The crust of the Earth is composed mainly of basalt and granite. It is cooler and more rigid than the deeper layers of the mantle and core.
On stratified planets, such as Earth, the lithosphere is floating on fluid interior layers. Because of convection in the plastic, although non-molten, upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. Oceanic crust is different from that of the continents. The oceanic crust (sima) is 5 to 10 km thick and is composed primarily of a dark, dense rock called basalt. The continental crust (sial) is 20-70 km deep and is composed of a variety of less dense rocks. The crust's temperature ranges from the air temperature to about 900°C near the upper mantle.
Earth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core, and lies directly beneath the Earth's thin crust. The term is also applied to the rocky shell surrounding the cores of other planets. Earth's mantle lies roughly between 30 and 2,900 km below the surface, and occupies about 70% of Earth's volume.
More on the MantleEarth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core, and lies directly beneath the Earth's thin crust. The term is also applied to the rocky shell surrounding the cores of other planets. Earth's mantle lies roughly between 30 and 2,900 km below the surface, and occupies about 70% of Earth's volume.
The boundary between the crust and the mantle is the Mohorovici discontinuity, named for its discoverer, and is usually called the Moho. The Seismic Moho is a boundary at which there is a sudden change in the speed of seismic waves, which can be detected by sensitive instruments at Earth's surface. At one time some people thought that the Moho was the structure along which the Earth's rigid crust moved relative to the mantle. Current research considers the motion of the crust associated with plate tectonics as the surface manifestation of a much deeper mantle circulation. The uppermost mantle just below the crust is composed of relatively cold and therefore strong material. This strong layer of mantle and the crust forms the lithosphere, and cools mainly by convection.
The subregion of the mantle extending about 250 km (155 mi) below the lithosphere is called the asthenosphere, this cools mainly by convection. In some regions of the earth, this subregion of the mantle is partly associated with a region of the mantle that passes seismic waves more slowly. This region is called the low-velocity zone. The cause of this low velocity zone is still debated. Currently theories include the influence of temperature and pressure or the existence of a small amount of partial melt.
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.
In the mantle, temperatures range between 1000°C at the upper boundary to over 4,000°C at the boundary with the core. Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting.
The subregion of the mantle extending about 250 km (155 mi) below the lithosphere is called the asthenosphere; this cools mainly by convection.
Due to the temperature difference between the Earth's surface and outer core there is a convective material circulation in the mantle. Hot material ascends as a plutonic diapir from the border with the outer core, while cooler (and heavier) material sinks downward. This is often in the form of large-scale lithospheric downwellings at plate boundaries called subduction zones. During the ascent the material of the mantle cools down adiabatically. The temperature of the material falls with the pressure relief connected with the ascent, and its heat distributes itself over a larger volume. Near the lithosphere the pressure relief can lead to partial melting of the diapir, leading to volcanism and plutonism.
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. 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. The movements of the lithosphere and the underlying mantle are coupled since descending lithosphere is the dominant driving force for 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. The convection of the mantle is not yet clarified in detail.
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 . 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"). D"; may consist of material from subducted slabs that descended and came to rest at the core-mantle boundary.
Due to the relatively low viscosity in the upper mantle one could reason that there should be no earthquakes below approximately 300 km depth. However, in subduction zones, the geothermal gradient can be lowered, 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 (1.4 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, with permanent plastic deformation accommodated by the movement of point, line, and planar defects through the solid crystals comprising the mantle. The viscosity of the upper mantle ranges between 1019 and 1024 Pa·s, depending on depth. 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.
The second attempt to retrieve samples from the Earth's mantle is scheduled for 2007 . As part of the Chikyu Hakken mission, it will use the Japanese vessel 'Chikyu' to drill up to 7000m (23,000 ft) below the seabed. This is nearly three times as deep as preceding oceanic drillings, which are preferred over land drillings because the crust at the seabed is thinner. The first attempt, known as Project Mohole, was abandoned in 1966 after repeated failures and ever rising costs. The deepest they managed to penetrate was about 180m (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.
Finally, The CoreThe average density of Earth is 5515 kg/m3, making it the densest planet in the Solar system. Since the average density of surface material is only around 3000 kg/m3, we must conclude that denser materials exist within Earth's core. Further evidence for the high density core comes from the study of seismology. In its earliest stages, about 4.5 billion (4.5×109) years ago, melting would have caused denser substances to sink toward the center in a process called planetary differentiation, while less-dense materials would have migrated to the crust. As a result, the core is largely composed of iron (80%), along with nickel and one or more light elements, whereas other dense elements, such as lead and uranium, either are too rare to be significant or tend to bind to lighter elements and thus remain in the crust (see felsic materials).
Seismic measurements show that the core is divided into two parts, a solid inner core with a radius of ~1220 km and a liquid outer core extending beyond it to a radius of ~3480 km. The solid inner core was discovered in 1936 by Inge Lehmann and is generally believed to be composed primarily of iron and some nickel. Some have argued that the inner core may be in the form of a single iron crystal. The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements. It is generally believed that convection in the outer core, combined with stirring caused by the Earth's rotation (see: Coriolis effect), gives rise to the Earth's magnetic field through a process described by the dynamo theory. The solid inner core is too hot to hold a permanent magnetic field (see Curie temperature) but probably acts to stabilise the magnetic field generated by the liquid outer core.
Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet. In August 2005 a team of geophysicists announced in the journal Science that, according to their estimates, Earth's inner core rotates approximately 0.3 to 0.5 degrees per year relative to the rotation of the surface.
While the scientifically mainstream explanation for these temperature gradients is that the heat is simply left over from the planet's initial formation, a theory espoused by J. Marvin Herndon states that fast breeder nuclear reactor type reactions occur in the core of Earth.
Great, now that we know about the layers of the RE, what's it like for the FE?