Question

Which layer of Earth contains the asthenosphere? A) crust C) outer core B) mantle D) inner core

Short answer

The asthenosphere is located in the mantle.

Step-by-step solution

Identifying the Earth's Layers

First, let's identify the main layers of the Earth. These layers are the crust, the mantle, the outer core, and the inner core.

Understanding the Asthenosphere

The asthenosphere is a specific part of the Earth's layers where rocks are able to flow at a very slow rate. It is important for plate tectonics as it allows the tectonic plates to move.

Locating the Asthenosphere

The asthenosphere is located within the layer called the mantle. It is not near the surface like the crust, nor is it deep within the core.

Identifying the Correct Answer

Now that we've identified the asthenosphere as part of the mantle, the correct answer to which layer contains the asthenosphere is B) mantle.

Key concepts

Earth's Layers

Our planet, Earth, is composed of several distinct layers that vary in composition and function.

• The outermost layer is the **crust**, which is where we live and consists of solid rocks.
• Beneath the crust lies the **mantle**, a massive layer with semi-solid rock that varies from rigid to malleable.
• Below the mantle, we find the **outer core**, which is mainly liquid and composed of iron and nickel.
• The center of the Earth is the **inner core**, a dense ball of solid metal.

It’s fascinating how each of these layers plays a significant role in Earth's geology. For example, the movement and behavior of these layers are crucial for understanding phenomena like earthquakes and volcanic activity.
These layers are dynamically interacting with each other, and together, they form the very structure of our planet.

Mantle

The mantle is the layer directly under the Earth's crust and makes up about 84% of Earth's volume. It is primarily composed of silicate rocks which are rich in iron and magnesium. The mantle can be divided into two parts:

• The **upper mantle**, which includes the asthenosphere and is where the rock is partially melted.
• The **lower mantle**, where the rock is more solid and under greater pressure.

The mantle's unique characteristic is its ability to flow very slowly, which is crucial for the movement of tectonic plates located above it. Because of the heat emanating from the core, convection currents are caused within the mantle. These currents drive the movement of the tectonic plates, making the mantle a key player in Earth's dynamic geology.

Plate Tectonics

Plate tectonics is a scientific theory describing the large-scale motion of the plates making up Earth's lithosphere. These plates include the continents and ocean floors, and they ride atop the semi-fluid asthenosphere in the mantle. Here's how it works:

• The lithosphere is divided into several tectonic plates.
• The asthenosphere underneath allows these plates to move due to its semi-fluid nature.
• Interactions at the boundaries of these plates lead to geological phenomena.

Plate tectonics is responsible for major geological events such as earthquakes, mountain formation, and volcanic activity. The movement is typically a few centimeters per year, which may seem slow but has huge implications over geological timescales. Understanding plate tectonics not only sheds light on Earth's past but also helps predict future changes.