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The next decade offers the potential for building on and integrating the recent
observational, computational, and experimental advances noted above into a robust
model for evolution of the inner and outer cores. The thermo-chemical evolution of
the core dynamic system is manifested not only in the geomagnetic field but also in
the thermal history of the planet; the rate of inner core growth is determined by how
rapidly the core cools, which is controlled by the mantle. Thus, a bounty of
fundamental results can be harvested by developing a quantitative understanding of
core evolution. The NSF's Cooperative Studies of the Earth's Deep Interior (CSEDI)
program is structured to support interdisciplinary coordination on this topic, and
community organizations such as the Cooperative Institute for Dynamic Earth
Research (CIDER) enhance communications across the disciplines and training of
graduate students in the diverse arena of core studies.
Box 2.3
New Opportunities in Rock Magnetism in the 21st century
Figure B2.3 Example of current scanning SQUID microscopy with submillimeter (~100
micrometer) resolution (A) showing geomagnetic reversal stratigraphic dating of alternating
polarities recorded by magnetite crystals in submillimeter layers of a seafloor manganese
nodule (B). The nodule is only 35 cm thick, and the alternating magnetizations can be fit to a
known polarity reversal timescale (C). SOURCE: Reprinted from Oda et al. (2011) with
permission of Geological Society of America.
Rock and mineral magnetism constitute the essential connection between
geomagnetic records of the past and the answers to the Grand Challenges (NRC, 2008) to
understand the origin and evolution of Earth and the other planets. One such broad challenge
is: How strong or weak have the internal geomagnetic and planetary magnetic fields been
over the past 4.5 billion years? In particular, what can we learn from magnetism of ancient
rocks that can illuminate the intertwined record of the geomagnetic field during the first billion
years of Earth's existence and the formation and growth rate of the solid inner core? In the
past decade the rock and paleomagnetic community have proven the feasibility of extracting
reliable values of paleomagnetic intensity from one-billion-year-old single silicate crystals
containing magnetite grains that have been protected from subsequent chemical alteration.
Figure B2.3 shows an example of magnetic signals now being studied using current scanning
Superconducting Quantum Interference Device (SQUID) sensors. But to advance the science
to more precise and higher (temporal) resolution records of paleointensity, the use of
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