Question

Statement: The Earth's outer core is liquid, while the inner core is solid. - Assertion: The immense pressure at the Earth's center forces the inner core into a solid state despite its high temperature .- Which of the following is correct?

• A. Both the Statement and Assertion are true and the Assertion is the correct explanation of the Statement
• B. Both the Statement and Assertion are true, but the Assertion is not the correct explanation of the Statement
• C. The statement is true but assertion is false
• D. The statement is false but assertion is true

Answer 1

Answer:

A. Both the Statement and Assertion are true and the Assertion is the correct explanation of the Statement

Understanding Earth's Core

• The Earth's interior is composed of several distinct layers: the crust, mantle, outer core, and inner core.
• These layers differ significantly in their chemical composition, temperature, pressure, and physical state.

The Outer Core: A Liquid Layer

• The outer core is located approximately between 2,900 km and 5,150 km below the Earth's surface.
• It is primarily composed of liquid iron and nickel, along with traces of other lighter elements.
• The temperature in the outer core ranges from about 4,400°C to 6,100°C.
• The convective flow of this liquid metallic outer core is responsible for generating Earth's geomagnetic field through a process known as the geodynamo.

The Inner Core: A Solid Enigma

• The inner core extends from about 5,150 km to the Earth's center, at roughly 6,371 km depth.
• Despite extremely high temperatures, estimated to be similar to the surface of the Sun (around 5,200°C to 6,200°C), the inner core remains in a solid state.
• It is also primarily composed of an iron-nickel alloy.

The Role of Immense Pressure

• The assertion highlights the critical role of immense pressure at the Earth's center.
• Although the inner core's temperature is well above the melting point of iron at surface pressure, the colossal pressure prevents the iron and nickel atoms from moving freely and forming a liquid.
• Pressure raises the melting point of a material; at the Earth's center, the pressure is so immense (over 3.5 million times atmospheric pressure) that it forces the iron-nickel alloy into a solid, crystalline structure.
• This phenomenon demonstrates that pressure can override the effect of temperature in determining the physical state of matter.

Key Facts for Competitive Exams

• The Earth's core (both inner and outer) accounts for about 15% of the Earth's volume but nearly one-third of its mass due to its high density.
• The density of the inner core is estimated to be around 13 grams per cubic centimeter.
• The boundary between the outer core and the inner core is known as the Lehmann Discontinuity, discovered by Inge Lehmann in 1936.
• Seismic waves (P-waves and S-waves) are crucial for understanding the Earth's interior. S-waves cannot travel through liquids, which is how scientists deduced the outer core is liquid. P-waves can travel through both, but their speed changes at boundaries.