Earth's outer core temperature

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Earth's Outer Core Temperature Estimates

Research on the temperature of Earth's outer core shows a range of estimates, depending on the methods and assumptions used. Most studies agree that the temperature at the core-mantle boundary (CMB) is between 3,300 K and 5,000 K, while the temperature at the inner core boundary (ICB) is higher, ranging from about 4,800 K to over 7,000 K 126710.

Core-Mantle Boundary (CMB) Temperature

Several studies estimate the temperature at the CMB to be around 3,500 K to 5,000 K. The exact value depends on factors like heat production in the core and the presence of a density gradient in the lowermost mantle. Higher heat production leads to higher CMB temperatures, up to about 5,000 K, while lower heat production or inhibited convection can result in temperatures closer to 3,500 K . Some older estimates suggest even lower values, around 2,650 K, but these are less consistent with more recent experimental and theoretical work .

Inner Core Boundary (ICB) Temperature

The temperature at the ICB is generally estimated to be between 4,800 K and 7,100 K. Experimental studies on the melting point of iron at high pressures suggest that the ICB temperature is likely in the range of 5,400 K to 6,600 K, with some estimates reaching up to 7,100 K depending on the assumed composition and presence of light elements 6710. The presence of impurities like oxygen, sulfur, or silicon can lower the melting point, leading to slightly lower temperature estimates 356.

Temperature Gradient and Distribution

The temperature gradient through the outer core is significant, with estimates of about 1,250 K from the CMB to the ICB . The temperature distribution is thought to follow the melting curve of iron alloys, which inhibits large-scale convection in the outer core . The outer core is mostly liquid, and its temperature must remain above the melting point of iron at the relevant pressures to maintain this state 27.

Implications of Recent Measurements

Recent high-pressure experiments have found that the melting temperature of iron at the ICB is 500 to 1,000 K lower than some previous estimates, suggesting that the Earth's core may be cooler than once thought . This supports the idea that the lower mantle has remained solid for at least a billion years .

Conclusion

In summary, the temperature of Earth's outer core ranges from about 3,300 K to 5,000 K at the core-mantle boundary and rises to between 4,800 K and 7,100 K at the inner core boundary. The exact values depend on core composition, heat production, and the presence of light elements. Recent experimental advances continue to refine these estimates, but the consensus is that the outer core is extremely hot, with temperatures sufficient to keep iron and its alloys in a liquid state under immense pressure 12345679+1 MORE.

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Most relevant research papers on this topic

Thermal regime of the Earth's core

The Earth's core is believed to be at an equilibrium between a solid (FeNi) inner core and a liquid layer containing only a small amount of sulfur, with the temperature T i at the inner-core boundary being about 6000-6500°K for high Q and T c 4

1973·

59citations

·J. Verhoogen

The adiabatic gradient and the melting point gradient in the core of the Earth

The outer core of the Earth must be liquid at temperatures significantly above the temperature in adiabatic equilibrium with the inner-outer core boundary for it to be liquid.

Highly Cited

1971·

192citations

·G. Higgins et al.

Chemical compositions of the outer core examined by first principles calculations

The outer core's chemical composition may be hydrogen-dominated at temperatures between 4,800 K and 5,400 K, or oxygen-dominated at temperatures above 6,000 K.

2020·

53citations

·K. Umemoto et al.

A cooler core for Earth

The melting temperature of iron at extreme pressures is 500 to 1000 kelvin lower than previously estimated, suggesting that Earth has had a solid lower mantle for at least the last billion years.

2019·

2citations

·B. Grocholski

Density and sound velocity of liquid Fe-S alloys at Earth’s outer core P-T conditions

The outer core contains no more than 3.5 wt% S, 2.5 wt% O, or 3.8 wt% Si, and the developed thermal equation of state can help model the Earth's outer core.

2020·

5citations

·Jie Fu et al.

Temperature 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 Cited

2007·

100citations

·D. Alfé et al.

Temperatures in Earth's Core Based on Melting and Phase Transformation Experiments on Iron

The Earth's core has a nearly isothermal inner core, with iron melting at 6350 350 kelvin, and a simple model can explain the inner solid core and outer liquid core.

Highly Cited

1994·

114citations

·Surendra K. Saxena et al.

The current status of speculations on the composition of the core of the Earth

The core of the Earth primarily consists of Fe-Ni in the inner core and molten Fe alloyed with 8 to 20% of a light element, most likely S or Si, giving an average atomic number in the outer core of about 23.

1976·

64citations

·R. Brett

Temperatures within the Earth's Core

The melting point in the Earth's core is 2,610° K, lower than previous estimates and about one-half of those using Gilvarry's values.

1960·

0citations

·J. Jacobs

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 Cited

1987·

332citations

·Q. Williams et al.

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