What term describes the rate of temperature increase with depth in the earth?

• A. Geothermal Gradient
• B. Mantle
• C. Igneous Rock
• D. Metasomatism

Answer: (A)

Geothermal gradient is the rate at which temperature increases with depth in the Earth. It is usually expressed in degrees Celsius per kilometer and reflects how heat from the interior conducts through rocks. In the shallow crust, a typical gradient is about 25–30 °C per kilometer, though it varies with location and depth due to heat flow and rock properties. This concept is distinguished from the mantle (a planetary layer), igneous rock (a rock type), and metasomatism (chemical alteration by fluids). Because it specifically describes how temperature changes with depth, it’s the term that best fits the question.