Temperature at the centre of the earth
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Temperature at the Centre of the Earth
Understanding the temperature at the center of the Earth is crucial for insights into the planet's internal processes, including its geodynamo and thermal history. Various studies have provided estimates and constraints on this temperature, utilizing different methodologies and theoretical models.
Geothermal Methods and Temperature Estimates
Geothermal methods have been employed to estimate the temperature at the Earth's center. One study suggests that a temperature of 76,000°C at the center is consistent with observed temperature gradients and the potential melting of rocks at a depth of 500 kilometers due to radioactive heat1. This highlights the significant role of radioactive decay in influencing the Earth's internal temperature.
Melting Curve of Iron and Core Temperatures
Iron, being the primary constituent of the Earth's core, has been extensively studied to determine its melting curve under high pressures. Measurements indicate that the melting temperature of iron at the core-mantle boundary (136 gigapascals) is approximately 4800 K, while at the inner core-outer core boundary (330 gigapascals), it reaches around 7600 K. After accounting for impurities, the inferred melting temperature for an iron-rich alloy at the inner core-outer core boundary is about 6600 K, with a maximum temperature of 6900 K at the Earth's center2. This provides an experimental upper bound on the central temperature, suggesting it is significantly lower than some earlier estimates.
High-Pressure Melting-Point Measurements
Further high-pressure experiments on iron and iron-oxygen compounds have provided additional constraints. Extrapolations from these measurements suggest a temperature of approximately 4850 K at the inner-core boundary3. These findings are crucial for understanding the temperature gradient within the core and its implications for the Earth's heat budget and geodynamo models.
Theoretical Studies and Density Functional Theory
Theoretical studies using density functional theory have also contributed to our understanding of the core's temperature. These studies predict that the temperature at the boundary between the solid inner core and the liquid outer core (the ICB) is likely in the range of 5400 to 5700 K. Additionally, they suggest that the outer core contains a significant fraction of light impurities, such as oxygen, which play a role in the convective motions driving the Earth's magnetic field4.
Historical and Alternative Theories
Historical theories have proposed various temperature gradients and conditions within the Earth's interior. For instance, one theory suggested a temperature gradient of one degree per 90 feet of depth, leading to extremely high temperatures ranging from 44,000°C to 105,000°C at depths between 750 and 1,800 miles. This theory also posited that the Earth's center might be gaseous due to the inability of known elements to liquefy or solidify under such extreme conditions8. However, these estimates are significantly higher than those derived from more recent experimental and theoretical studies.
Conclusion
In summary, the temperature at the center of the Earth is a subject of ongoing research, with estimates ranging from around 4850 K to 76,000°C depending on the methodology and theoretical models used. The most recent and reliable estimates suggest a central temperature of approximately 6900 K, derived from high-pressure melting-point measurements and theoretical studies. These findings are essential for understanding the Earth's internal dynamics, including its thermal history and magnetic field generation.
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Most relevant research papers on this topic
GEOTHERMAL METHODS OF ESTIMATING THE AGE OF THE EARTH.
The age of the Earth can be accurately estimated using a simple mathematical method, leading to unexpected results like a 76000°C core temperature and rock melting at a depth of 500 km due to radioactive heat.
The Melting Curve of Iron to 250 Gigapascals: A Constraint on the Temperature at Earth's Center
The melting curve of iron to 250 gigapascals constrains the temperature at Earth's center to 6900 K, suggesting the lower mantle's temperature is significantly less than the outer core.
Highly CitedTemperatures in the Earth's core from melting-point measurements of iron at high static pressures
The inner-core boundary temperature is 4,850200 K, indicating a temperature of 4,850200 K at 3.3 Mbar, which is consistent with current estimates of the Earth's core temperature.
Highly CitedTemperature and composition of the Earth's core
The Earth's core has a temperature of 5400-5700 K and a significant fraction (8-13%) of oxygen, which helps drive the Earth's magnetic field through convective motions in the liquid core.
Highly CitedWhere is the centre of the Earth
The Earth's core is a molten mass that begins halfway down from the surface, and its temperature is more than 3000°C, making it impossible for humans to reach it.
Surface Temperature of the Planet Earth from Satellite Data
The Earth's surface temperature increased by 0.021 0.001°C/year from 2003 to 2019, corroborating climate models and improving the comparison with global annual air temperatures.
Formation of the Earth's Core
Core formation is a major event in the thermal evolution of the Earth, with radioactive heating melting iron and drained iron forming the core, increasing the average temperature by 2,000 K.
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