Palaeomagnetic field intensity variations suggest Mesoproterozoic inner-core nucleation

@article{Biggin2015PalaeomagneticFI,
  title={Palaeomagnetic field intensity variations suggest Mesoproterozoic inner-core nucleation},
  author={Andrew J. Biggin and Elisa J. Piispa and Lauri J. Pesonen and Richard Holme and Greig A. Paterson and Toni Veikkolainen and Lisa Tauxe},
  journal={Nature},
  year={2015},
  volume={526},
  pages={245-248}
}
The Earth’s inner core grows by the freezing of liquid iron at its surface. The point in history at which this process initiated marks a step-change in the thermal evolution of the planet. Recent computational and experimental studies have presented radically differing estimates of the thermal conductivity of the Earth’s core, resulting in estimates of the timing of inner-core nucleation ranging from less than half a billion to nearly two billion years ago. Recent inner-core nucleation (high… 

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References

SHOWING 1-10 OF 31 REFERENCES

Modelling the palaeo-evolution of the geodynamo

Although it is known that the geodynamo has been operating for at least 3.2 Ga, it remains difficult to infer the intensity, dipolarity and stability (occurrence of reversals) of the Precam-brian

Possible links between long-term geomagnetic variations and whole-mantle convection processes

The Earth's internal magnetic field varies on timescales of months to billions of years. The field is generated by convection in the liquid outer core, which in turn is influenced by the heat flowing

Evidence for a very-long-term trend in geomagnetic secular variation

Reconstructions of palaeosecular variation suggest that the Earth’s magnetic field reversed less frequently 2.82 to 2.45 billion years ago, relative to the Cenozoic era. This suggests a long-term

Thermal and electrical conductivity of iron at Earth’s core conditions

TLDR
New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the coremust be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMBHeat flow.

Palaeosecular variation, field reversals and the stability of the geodynamo in the Precambrian

SUMMARY Palaeosecular variation (PSV), as estimated from the scatter of remanent magnetization directions or poles, can be used to shed light to processes in the geodynamo, and potentially, to model

Intensity of the Earth's magnetic field since Precambrian from Thellier-type palaeointensity data and inferences on the thermal history of the core

SUMMARY We present a compilation of palaeointensity data obtained by the Thellier method from magmatic rocks up to 3.5 Gyr old. No apparent very long-term variation occurs from present to Early

Time variations in geomagnetic intensity

After many years spent by paleomagnetists studying the directional behavior of the Earth’s magnetic field at all possible timescales, detailed measurements of field intensity are now needed to

Thermochemical remanent magnetization in Precambrian rocks: Are we sure the geomagnetic field was weak?

[1] Thellier paleointensity determinations from two dikes of the Early Proterozoic (∼2.46 Ga) Matachewan dike swarm (Canada) yield field values of 2.14 ± 0.18 and 9.81 ± 1.65 μT. Corresponding values

Geomagnetic dipole strength and reversal rate over the past two million years

TLDR
It is shown that, at least during this period, the time-averaged field was higher during periods without reversals but the amplitude of the short-term oscillations remained the same, and few intervals of very low intensity are expected during periods with a strong average dipole moment, whereas more excursions and reversals areexpected during periods of weak field intensity.