 Show
Updated April 23, 2018 By Andrea Helaine
Each layer in the Earth's crust changes in fundamental ways the closer it is to the planet's core. There are four layers of the Earth, and each layer has a different density, composition, and thickness. Three hundred years ago, English scientist Isaac Newton created the foundation for current scientific thought about the density of the Earth’s layers.
Four layers make up the Earth: the crust, the mantle, the outer core, and the inner core. They all have different densities and makeups depending on their proximity to the core.
Around 1687, Isaac Newton concluded that the Earth’s interior must be composed of a dense material. Newton’s based this conclusion on his studies of planets and the force of gravity. Although much has changed in scientific thought, Newton’s theories about density remain relatively unchanged.
Studies of earthquakes — and their waves — laboratory experiments on minerals and rocks, and studies on pressure and temperature inform today’s conclusions about the increase in density in the Earth's layers and their proximity to the planet core. Scientists used this and other data sets to determine both pressure and temperature.
The Earth’s crust — the outer layer of the Earth — remains the most studied part of the planet's layers because it is easily accessible to scientists. The thickness of the crust varies from 5 km to 60 km, depending on the location. For instance, the crust under mountain ranges tends to be thicker than that under oceans. The crust normally consists of layers of sedimentary rock that covers granite rock, while the crust of the ocean is composed of basalt rock with sediment on top.
The Earth’s mantle is divided into two portions. The upper portion is the location where convection currents occur; denser rock makes up the second, lower portion. The mantle of the Earth is approximately 2,800 km in thickness in total — including both the upper and lower mantle. The upper mantle is made of olivine, pyroxene, and other crystalline minerals, while the lower mantle consists of silicon, magnesium, oxygen — it probably contains iron and other elements.
Liquid in nature, the Earth's outer core is composed of sulfur, oxygen, iron and nickel alloy. The temperature of the outer core is above the melting point of these elements, meaning that the outer Earth’s core remains liquid, never hardening into a solid. The outer core is approximately 2,259 km in thickness.
The Earth’s inner core is a solid mass, composed of sulfur, iron, oxygen, and nickel. As the deepest layer, it has the greatest density of the four layers that make up Earth. The inner core is approximately 1,200 km thick. Though the inner core is the hottest layer, it is solid due to the massive amounts of pressure exerting forces on the elements that comprise it.
It’s the largest and densest of all terrestrial planets. Terrestrial planets like Mercury, Venus, Earth and Mars tend to be rich in metals and silicate rocks. If you crunch the numbers, Earth is mostly:
Finally, nickel (2%), sulfur (2%), calcium (1%), and aluminum (1%) make up most of the remaining. So now we know what Earth is made of in terms of its composition. What is Earth density? And how do you calculate how dense Earth is? Earth density by core, mantle, and crustIf you average density throughout the whole planet, then Earth density is about 5.513 g/cm3. But if you compare Earth density by its layers, density steadily increases as you go inwards from the crust to core.
Finally, the crust consists of rocks rich in silica with a density of about 2.5 g/cm3. The crust rides on a plasticky layer called the asthenosphere. This fluid-like layer with a density of about 3.3 g/cm3. How to calculate Earth density by handDensity is mass divided by volume. Mass is the physical matter of something in a total number of atoms. And volume is the amount of space an object encloses. If you know the mass and volume of an object, then you can measure density by dividing the two. For example, Earth is not a perfect sphere. But we can approximate come to by using the volume of a sphere which is 4/3πr3. Based on a radius of 6,371 km, Earth’s volume would be 1.08 trillion cubic kilometers. Given the mass of Earth is 5.972 × 1024 kg, we can divide by its volume as noted above. After converting kilograms and cubic kilometers to grams and cubic centimeters, Earth density is about 5.519 g/cm3. And this roughly checks in with the general consensus of Earth density at about 5.513 g/cm3. If you account for Earth shape, you can get a better estimate of Earth density. What is the Earth Made Of?The Earth is a fascinating planet, filled with a variety of structures and systems. The Earth’s surface is made up of crust, mantle, and core with different densities. Do you want to learn more about the concepts of Earth Science? If so, there are a lot of career opportunities available as well. These online courses can help!
We want to hear what you have to say! Please use the comment form below and let us know what your thoughts are.
Convection is a term describing the flow of heat in a fluid that is driven by buoyancy derived from horizontal density gradients. Density gradients in the mantle are largely derived from horizontal temperature gradients (and also chemical/compositional horizontal gradients). In the thermal boundary layers (across which the temperature varies continuously from the surface value to the mean mantle temperature) this buoyancy causes instabilities, allowing fluid to leave the boundary layer and rise or fall throughout the system interior. The mantle is a visco-elastic solid, meaning it behaves both viscously and elastically in response to a stress. The viscous nature of the mantle is evident in the slow creep of the mantle manifesting itself as plate tectonics on the surface of the Earth. The elastic nature of mantle rock is evident in the seafloor flexure around ocean island chains (e.g. Kearey, 2009). By assuming a fully elastic crustal layer overlying a fluid, the height of flexure in response to a load can be determined. These theoretical values can be compared with oceanic crust response to seafloor mounts to determine the elastic response of the mantle. Heat is removed from the interior of a planet by thermal conduction as well as subsolidus convection. Subsolidus convection occurs from diffusion or dislocation creep in a solid material. The temperature difference between the interior and cooling surface of a planet maintains the thermal gradient necessary for convection. Heat is the main source of energy driving convection in the mantle. Heat in the mantle is derived from internal sources (radioactive decay of the el- ements uranium, thorium and potassium), heat released from the core and secular cooling of the planet as a whole (residual heat left over from planetary formation and a higher production of radioactive heating in the past). Mantle convection manifests itself at the surface of the Earth. Mid-ocean ridges correspond to the site of passive upwelling mantle material while ocean trenches correspond to the location of convective downwellings (subduction). The cycle of upwelling and downwelling convection helps recycle lithosphere into the mantle, producing new lithosphere at ridges and removing it at subduction zones. Figure 2 shows a depiction of a mantle convection cell, with a hot upwelling plume (red) and cold subducting slab (blue). Figure 1 shows a depiction of mantle convection with an upwelling plume, passive upwelling at a mid-ocean ridge and subducting slabs (downwellings). It also shows large-low shear velocity provinces, ultra-low-velocity-zones and areas of post-perovskite. |
How does density relate to each layer of earth?
Postagens relacionadas
direito autoral © 2024 ihoctot Inc.
