Chapter 13, Problem 1LC

To determine

To define: The characteristics of the Earth’s lithosphere and asthenosphere.

Answer to Problem 1LC

Lithosphere comprises the uppermost region of the mantle and crust. They consist of tectonic plates and are referred to as the whole solid Earth.

The asthenosphere is found below the lithosphere, and it is referred as the plastic layer of the upper mantle. The rocks present in asthenosphere are very hot and mechanically weak and hence can be collapsed easily.

Explanation of Solution

Features of the Earth’s lithosphere:

Lithosphere comprises the uppermost region of mantle and crust. They consist of tectonic plates and are referred to the whole solid Earth. Pedosphere is the uppermost part in the lithosphere that reacts chemically with atmosphere, biosphere, and hydrosphere by soil-forming process. Lithosphere is made of igneous, metamorphic, and sedimentary rocks.

Lithosphere is divided into two types such as oceanic and continental. Oceanic lithosphere comprises oceanic crust, and it exists in ocean basins. It has a mean density of 2.9 grams per cubic centimeter. Continental lithosphere is made of the continental crust. It has a mean density of 2.7 grams per cubic centimeter.

Features of the Earth’s asthenosphere:

The asthenosphere was named by Joseph Barrel, a British geologist. He divided the interior of the Earth into three parts namely centrospheres, asthenosphere, and lithosphere. Asthenosphere is found below the lithosphere, and it is referred as the plastic layer of the upper mantle.

The rocks present in asthenosphere are very hot and mechanically weak, and hence can be collapsed easily. Even though tectonic plates are found in the lithosphere, it is that movement of the rocks in asthenosphere that causes shaking. Deep earthquakes are an indication of the breaking apart of the rocks in the asthenosphere.