EARTH INTERNAL STRUCTURE

PRERNA FOR IAS

EARTH INTERNAL STRUCTURE

(GEOGRAPHY)

1. Crust

The crust is the outermost solid layer of the Earth and forms the continents and ocean floors. It is the thinnest layer, ranging from about 30–70 km beneath continents and 5–10 km beneath oceans. Continental crust is mainly composed of granite-rich rocks, while oceanic crust consists largely of basalt-rich rocks. The crust is broken into tectonic plates that move slowly over the mantle. It is separated from the mantle by the Mohorovičić Discontinuity, commonly called the Moho. The crust supports all terrestrial life, natural resources, mountains, rivers, and human activities on Earth.

2. Mantle

The mantle is the thickest layer of the Earth, extending from the Moho discontinuity to a depth of about 2,900 km. It constitutes nearly 84% of Earth’s total volume and is composed mainly of silicate rocks rich in magnesium and iron. The mantle is divided into the upper mantle and lower mantle. A partially molten zone called the asthenosphere lies within the upper mantle. Heat from Earth’s interior creates convection currents in the mantle, which drive the movement of tectonic plates. These movements cause earthquakes, volcanic activity, mountain formation, and other geological processes shaping Earth’s surface.

3. Core

The core is the innermost layer of the Earth and is composed mainly of iron and nickel. It extends from about 2,900 km depth to the Earth’s center at approximately 6,371 km. The core is divided into two parts: the liquid outer core and the solid inner core. Temperatures in the core range from about 5,000°C to 6,000°C, making it the hottest region of the planet. The core is responsible for generating Earth’s magnetic field, which protects the planet from harmful solar radiation. Understanding the core helps scientists explain Earth’s internal heat and magnetic properties.

4. Outer Core

The outer core lies between depths of approximately 2,900 km and 5,150 km. It is composed primarily of molten iron and nickel and remains in a liquid state due to extreme temperatures. The movement of this liquid metal generates electric currents, which in turn create Earth’s magnetic field through a process known as the geodynamo effect. This magnetic field protects Earth from solar winds and cosmic radiation. The boundary between the mantle and outer core is called the Gutenberg Discontinuity. The outer core plays a vital role in maintaining conditions necessary for life on Earth.

5. Inner Core