Which of these best describes earth’s mantle? a. most dense layer, consists of the outer and inner parts b. thinnest under the oceans and thickest under continents c. middle layer, density increases with depth as pressure increases d. least dense layer overall, consists of two layers of different thickness

The best description of the Earth's mantle is, It is the Middle layer, density increases with depth as pressure increases.

The Mantle is the layer that is beneath the crust and above the core, it is the middle layer.

Further Explanation;

The Earth is made up of layers which includes;

The CrustIt is the outermost layer of the Earth that is very hard.The Crust is made up of granite and basalt. It is divided into continental plates which drift slowly with time.Mantle  It is the second layer of the earth and takes up to 80 percent of the Earth.The average density of the mantle is 4.5 g/cm^3. This density increases with increase in depth because of an increase in the pressure.The Mantle is divided into the Lithosphere and the Asthenosphere.Convection currents occur in the mantle  Lithosphere  It is made up of Earth’s outermost layer, the crust, and the uppermost portion of the mantle.Lithosphere lies over the asthenosphere such that if a material of the asthenosphere solidifies, it becomes part of the lithosphere.The Lithosphere is comprised of a large number of fragments, each known as the tectonic plate. These tectonic plates are in constant motion and are floating over the plastic material underneath.AsthenosphereIt is the upper portion of the Earth’s mantle which is the middle layer of the Earth.Asthenosphere has a higher temperature compared to the lithosphere and hence its rocks are plastic and can flow.The Asthenosphere is more dense and viscous compared to the lithosphere.Convection currents in the Mantle  In the mantle, convection currents make the mantle move. They occur when the lower mantle heats up and rise, cools down then gets pushed down since it is heavier.Convection currents are due to the density of a fluid that is related to its temperature in the mantle.Hot rocks lower in the mantle are less dense than the cooler rocks below, therefore the hot rocks rise while the cooler rocks sink due to gravity.The CoreOuter coreIt is the third layer of the earth and surrounds the inner core. It is the only liquid layer of the Earth.  This layer is about 2100 miles long and temperatures ranging from 4,000 to 5,000 degrees Celsius.Inner coreIt is the innermost layer of the earth.It contains impure iron that contains sulfur, nickel and other elements in small portions.Its temperatures ranges between 5,000 and 7,000 degrees Celsius.

Keywords: Layers of the Earth, the crust, the Mantle, core, Lithosphere, asthenosphere, mantle convection

Learn more about:Layers of the Earth: Mantle: Lithosphere: Asthenosphere: Mantle convection:

Level: High school

Subject: Geology 

Topic: The Earth

Sub-topic; Layers of the Earth