The asthenosphere is mostly solid, but it’s able to flow. We call that liquidus. It is a hot weak zone, and it represents the upper mantle. The asthenosphere looks like a liquid, but it’s not liquid. There’s a good reason for this misconception. It is what we refer to as viscoelastic. It means under certain conditions, it’s elastic, and under other conditions, it can deform as a plastic material.
So the earthquake waves are also elastic waves. They’re elastic defamations, and they’re very capable of propagating through the asthenosphere of the earth. And yet, under other conditions, the Asthenosphere is capable of falling. It is one of the important layers of the earth’s surface that maintain other surfaces and keep the earth flexible to move.
What is the Asthenosphere made of?
Astheno comes from the Greek word, which means week, and sphere means surface. So the asthenosphere means weak surface. The asthenosphere is the upper layer of the earth’s mantle. It sits above the boundary between the upper part and the lower part of the mantle. Also, it sits above the outer, inner core but sitting below the lithosphere. The asthenosphere has a relatively low resistance to plastic flow. So it’s a little bit more capable of fluid motion than certainly the solid lithosphere.
When we go into plate tectonics, the lithospheric plates are moving around on a surface. That is fluid which capable of flow. It means that the plates can move relative to one another, not necessarily all in the same direction nor at the same speed. So the convection currents in the asthenosphere are assumed to be responsible for these relative motions.
There is some difference in the composition of the materials, the rocks, and the minerals that make up the crust or upper part of the mantle. The asthenosphere is the sort of middle section of the mantle. The Earth’s asthenosphere is also made up of peridotites, and they are reasonably solid. About 99% of the asthenosphere is solid rock, and the other 1% is a molten-like magma state. The asthenosphere is hot, and that heat that temperature makes it mechanically weak compared to the lithosphere.
The rocks that are less in silica, high in magnesium and iron, and asthenosphere are found. Asthenosphere would be seismic waves like earthquake waves which are generated when a quake is happening. It is also called the low-velocity zone. And why do we call it the velocity zone? It is possible more than in nature because it is partially molten. It is not completely solid, not completely liquid.
- Most of the earth’s mantle are rocks that are regarded as silicates. Silicates are a network structure and a link between silicon and oxygen. Common silicate found in the mantle includes olivine, garnet, and pyroxene.
- Another primary rock type is magnesium oxide.
- Ions are a significant one because it is a key element in the core. Also, It’s the reason why the core is magnetic.
In the asthenosphere, there happen ductile deformation. When something deforms the duct tightly, it is thought as it’s under as the strain is put onto. It doesn’t fracture and more like stretches out and deforms. The asthenosphere does not make up all of the mantle or the remaining part of the mantle. The asthenosphere is thicker than the lithosphere, but together, they make a relatively small mantlepiece.
The lithosphere is very rigid and very hard to deform. The asthenosphere is fairly easy to deform. It sort of works like toffee. If you squash toffee, change its shape and deform it, and that’s called plastic deformation. The same thing happens to rocks in the asthenosphere but much more slowly.
The asthenosphere is malleable, ductile, and impartial mold in a state. That is why we call as asthenosphere as the plastic layer of the surface. Now, its plasticity is why tectonic plates can move on top of the outer sphere. These plates are rigid, solid, and less dense. The asthenosphere is partially molten and higher in density. These plates’ property is floating across the asthenosphere.
The asthenosphere is generally between where the lithosphere ends. They are anywhere between 50 and 200 kilometers in depth. One of the shallowest points at which the lithosphere will end averaged a bit obvious would be lower, mainly in the oceanic crust.
As far as temperature goes, the asthenosphere is down to that point in the mantle, where the temperature increases much more quickly. And the upper boundary is usually around 1300 degrees Celsius. The top of the asthenosphere is 1,300 degrees Celcius. Basaltic lava, which is the hottest type of lava on earth, erupts in Hawaii’s volcanoes. This stuff is 1,200 degrees Celsius. So the asthenosphere is hotter than lava.
Pressure: This layer’s pressure is about 18 GPa and gradually builds up in the thicker regions.
Location: It is located between seventy-two to 250 kilometers beneath the surface.
I hope you understand the asthenosphere layer very well. If you have any questions, then feel free to ask.
- What Is The Lithosphere Made Of With Definition & Structure
- What Is The Troposphere With Composition & Temperature
- How Does Magma Form With Composition & Characteristic
- What Is The Mesosphere With Characteristics & Facts
Barrel. “The strength of the crust, Part VI. Relations of isostatic movements to a sphere of weakness – the asthenosphere.” The Journal of Geology.
Harsh Gupta. Encyclopedia of Solid Earth Geophysics. Springer Science & Business Media.
Lev Eppelbaum; Izzy Kutasov; Applied Geothermics. Springer Science & Business.
Czechowski, L.; Grad. “Two mechanisms of formation of asthenospheric layers.”