Layers of the Earth
The Earth is divided into three main layers: the crust, mantle, and core. Each of these layers has unique physical and chemical properties that affect their role in Earth’s overall structure.
The Crust
The crust is the Earth’s outermost layer, composed primarily of rocks and minerals. It is the thinnest layer, ranging from about 5 km (in oceanic regions) to 70 km (in continental regions). The crust can be further divided into two types:
Oceanic Crust
The oceanic crust is relatively thin (about 5-10 km thick) and is composed mainly of basalt. It forms the ocean floors and is denser than the continental crust. As described by Francheteau (1983), the oceanic crust is continually formed at mid-ocean ridges through volcanic activity, where molten material from the mantle rises, cools, and solidifies. Over time, the oceanic crust moves away from the ridges due to the process of plate tectonics.
Continental Crust
The continental crust is thicker (up to 70 km in some areas) and less dense than the oceanic crust. It is composed mainly of granite and supports the Earth’s landmasses. Unlike oceanic crust, which is relatively young, some parts of the continental crust are billions of years old.
The Mantle
Beneath the crust lies the mantle, which extends to a depth of about 2,900 km. The mantle is primarily composed of silicate minerals and can be divided into the upper mantle and lower mantle.
Upper Mantle and Lower Mantle
The upper mantle, which extends to about 660 km beneath the Earth’s surface, is partially molten, giving rise to the phenomenon of mantle convection. The lower mantle, which extends from 660 km to 2,900 km, is more rigid due to the high pressures at these depths.
Mantle convection, as Kerr (1991) discussed, is the process by which heat from the Earth’s core causes the movement of mantle material. This movement is essential in driving the tectonic plates’ motion on the Earth’s surface.
The Core
At the Earth’s center lies the core, which is divided into the outer core and inner core.
Outer Core
The outer core, extending from 2,900 km to 5,150 km, is composed primarily of molten iron and nickel. The movement of the liquid iron in this layer generates the Earth’s magnetic field, a critical factor in protecting the planet from harmful solar radiation.
Inner Core
The inner core, extending from 5,150 km to the Earth’s center at 6,371 km, is solid due to the immense pressure despite its high temperature. Composed primarily of iron and nickel, the inner core plays a vital role in maintaining the Earth’s magnetic field.