# Alexander Halliday
**Alexander N. Halliday** is an isotope geochemist, Professor of Earth and Environmental Sciences and of Climate at Columbia University and Founding Dean Emeritus of the Columbia Climate School, known for developing multiple-collector inductively-coupled plasma mass spectrometry (MC-ICPMS) and applying it to the timing of accretion, core formation, and volatile loss in the terrestrial planets.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) His listed fields of scholarship include isotope geochemistry, mass spectrometry, high temperature geochemistry, planetary sciences, and the evolution of the Earth and Moon.[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) He was elected a Foreign Associate of the US National Academy of Sciences in 2015.[3](https://royalsociety.org/people/alexander-halliday-11563/)
| Fact | Detail |
|---|---|
| Field | Isotope geochemistry, mass spectrometry, planetary sciences[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) |
| Signature method | MC-ICPMS, developed and applied to accretion and core-formation timing[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) |
| Key result | Hafnium–tungsten dating showing Mars and most of Earth formed within 10 million years of the Solar System's birth[4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) |
| Career | SURRC 1976–86; Michigan 1986–98; ETH Zürich 1998–2004; Oxford 2004–18; Columbia 2018–present[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) |
| Honors | FRS 2000; NAS International Member 2015; Academia Europaea 2016; knighthood[3](https://royalsociety.org/people/alexander-halliday-11563/) • [2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) • [5](https://www.st-andrews.ac.uk/graduation/honorands/2023/alexander-halliday/) |
| Current roles | Professor at Columbia; Founding Dean Emeritus, Columbia Climate School; Visiting Fellow, Oxford Martin School[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) |
## Early life and education
Halliday graduated in geology and then took a doctorate in physics, both from the University of Newcastle-upon-Tyne.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) From 1976 to 1986 he was a postdoctoral fellow and then lecturer at the Scottish Universities Research and Reactor Centre in East Kilbride.[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) • [5](https://www.st-andrews.ac.uk/graduation/honorands/2023/alexander-halliday/)
## Career
According to the Academy of Europe, his dated appointments run: Scottish Universities Research and Reactor Centre, postdoctoral researcher 1976–81 and lecturer 1981–86; Associate and Full Professor at the University of Michigan 1986–98; Professor at ETH Zürich 1998–2004, where he was Head of the Department of Earth Sciences 2002–04; Chair of Geochemistry at Oxford from October 2004, and Head of Oxford's Mathematical, Physical, and Life Sciences Division 2007–15; Director of Columbia's Earth Institute 2018–23; Founding Dean of the Columbia Climate School 2021–23; and Founding Dean Emeritus from 2023.[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) • [3](https://royalsociety.org/people/alexander-halliday-11563/) • [1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) At Oxford he was a Professorial Fellow at St Hugh's College (2004–2012) and Wadham College (2012–2018).[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) According to Columbia News, Columbia announced his Earth Institute appointment on December 14, 2017.[4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) Since 2018 he has also been a Visiting Professor in Oxford's Department of Earth Sciences, and since 2023 a Visiting Fellow at the Oxford Martin School.[2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman)
## Representative work
**The hafnium–tungsten chronometer.** According to Eos, Halliday recognized and developed use of the hafnium–tungsten isotope system for dating core formation; the parent nuclide's half-life is 9 million years.[6](https://eos.org/agu-news/alex-halliday-receives-2016-harry-h-hess-medal) Using this method, developed in his lab, his group showed that Mars and most of Earth formed within 10 million years of the [Solar System](https://www.edgepedia.org/solar-system)'s creation.[4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) The results indicate core formation was contemporaneous with accretion, some of it in the first few million years, with a tail extending out to as much as 100 million years.[6](https://eos.org/agu-news/alex-halliday-receives-2016-harry-h-hess-medal) His 2008 paper in *Philosophical Transactions of the Royal Society A*, ["A young Moon-forming giant impact at 70–110 million years"](https://royalsocietypublishing.org/doi/10.1098/rsta.2008.0209), used lunar strontium isotope data to define the Rb–Sr age of the Moon as 4.48±0.02 Ga, or 70–110 Ma after the start of the Solar System, later than earlier tungsten-isotope-based estimates, and reported xenon and lead-lead ages agreeing with it, evidence of catastrophic terrestrial degassing, atmospheric blow-off, and significant late core formation.[7](https://royalsocietypublishing.org/doi/10.1098/rsta.2008.0209) He also named the giant-impact lunar-forming impactor Theia.[6](https://eos.org/agu-news/alex-halliday-receives-2016-harry-h-hess-medal)
**MC-ICPMS.** The technique combines the ionization efficiency of the inductively-coupled plasma source with the precision achievable with magnetic-sector multiple-collector mass spectrometry, enabling precise isotopic measurements of many elements in natural materials for the first time.[8](https://www.earth.ox.ac.uk/people/alex-halliday) The Oxford laboratory suite he established, shared with colleagues in the department, includes five MC-ICPMS instruments, described as the largest suite of its kind world-wide.[8](https://www.earth.ox.ac.uk/people/alex-halliday)
## Honors and memberships
Halliday became a [Fellow of the Royal Society](https://www.edgepedia.org/fellow-of-the-royal-society) in 2000, was made a Foreign Associate of the US National Academy of Sciences in 2015, and joined the Academy of Europe (Academia Europaea) in 2016 within its Earth & Cosmic Sciences section.[3](https://royalsociety.org/people/alexander-halliday-11563/) • [2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) Among his honors are the Geological Society's Murchison Medal, the Bowen Award, and the [American Geophysical Union](https://www.edgepedia.org/american-geophysical-union)'s Harry Hess Medal, the latter given in 2016 for his planetary research, along with the European Association of Geochemistry's Urey Medal, the Institute of Measurement and Control's Oxburgh Medal, and a Knighthood recognizing his services to science and innovation.[3](https://royalsociety.org/people/alexander-halliday-11563/) • [4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) • [5](https://www.st-andrews.ac.uk/graduation/honorands/2023/alexander-halliday/)
## Leadership and advisory roles
He was Vice President (Physical Secretary) of the Royal Society from 2014 to 2018, and Oxford University's dean of science and engineering from 2007 to 2015.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) In the Oxford role he launched building projects, expanded postdoctoral researchers, focused on diversity, and strengthened Oxford's ties with government and the private sector; he also proposed ONE, the Oxford Networks for the [Environment](https://www.edgepedia.org/environment).[4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) He has been President of the Geochemical Society, the European Association of Geochemistry, and the Volcanology, Geochemistry and Petrology Section of the American Geophysical Union; as Geochemical Society president he established the Clair C. Patterson Medal for environmental geochemistry.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) • [4](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute) He has served on advisory and funding boards including the US National Science Foundation, the [Max Planck Society](https://www.edgepedia.org/max-planck-society), the UK's Natural Environment Research Council, the Natural History Museum, Oxford and Cambridge Universities, the Royal Society, and Carnegie Science.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday)
## Recent developments
Since 2023 Halliday has been Founding Dean Emeritus of the Columbia Climate School, while remaining Professor of Earth and Environmental Sciences and of Climate, and a Visiting Fellow at the Oxford Martin School.[1](https://people.climate.columbia.edu/users/profile/alexander-n-halliday) • [2](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman) His 2023 publications include a *Science Advances* paper on liquid solution centrifugation for safe, scalable, and efficient isotope separation (14 July 2023).[9](https://orcid.org/0000-0002-3797-6918)
## References
1. [Alexander N. Halliday, Columbia Climate School profile](https://people.climate.columbia.edu/users/profile/alexander-n-halliday)
2. [Academy of Europe: Halliday Alexander Norman](https://www.ae-info.org/ae/Member/Halliday_Alexander_Norman)
3. [Sir Alexander Halliday FRS, Royal Society](https://royalsociety.org/people/alexander-halliday-11563/)
4. [President Bollinger Names Pioneering Oxford Geoscientist Alex Halliday to Head Earth Institute, Columbia News](https://news.columbia.edu/news/president-bollinger-names-pioneering-oxford-geoscientist-alex-halliday-head-earth-institute)
5. [Alexander Halliday, University of St Andrews honorand citation (2023)](https://www.st-andrews.ac.uk/graduation/honorands/2023/alexander-halliday/)
6. [Alex Halliday Receives 2016 Harry H. Hess Medal, Eos](https://eos.org/agu-news/alex-halliday-receives-2016-harry-h-hess-medal)
7. [A young Moon-forming giant impact at 70–110 million years, Phil. Trans. R. Soc. A](https://royalsocietypublishing.org/doi/10.1098/rsta.2008.0209)
8. [Alex Halliday, Department of Earth Sciences, University of Oxford](https://www.earth.ox.ac.uk/people/alex-halliday)
9. [Alexander Halliday, ORCID](https://orcid.org/0000-0002-3797-6918)
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*Topic: Encyclopedia › Physical world and mathematics › Physical and mathematical scientists › Earth and climate scientists › Researchers in geology, geophysics, geochemistry, and hydrology › Petrology and Geochemistry › Geochemists and isotope geochemists*
*Initially written Sep 21, 2026 · Reviewed: Sep 25, 2026 · Edited: Sep 25, 2026; Oct 15, 2026 · Last review: Sep 25, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license