Alex Halliday is an isotope geochemist known for novel mass spectrometry techniques and their applications to the Earth and planetary sciences. He is particularly recognized for his research on the early development of the terrestrial planets. Halliday comes from Cornwall, in the UK. He graduated in geology followed by a doctorate in physics, both from the University of Newcastle-upon-Tyne. He spent ten years at the Scottish Universities Research and Reactor Centre, then twelve years as a professor at the University of Michigan, followed by six years at ETH Zürich. He has been at Oxford University since 2004. Halliday has been President of the Geochemical Society, the European Association of Geochemistry, and the Volcanology, Geochemistry and Petrology Section of the American Geophysical Union. He has experience with a range of science boards and advisory panels including those of the Natural Environment Research Council, the Max Planck Society and the American Geophysical Union. His honors include Fellowship of the Royal Society and Foreign Associate of the National Academy of Sciences. At Oxford he was the dean of science and engineering from 2007 to 2015. He was elected Vice President (Physical Secretary) of the Royal Society in 2014.

Research Interests

Alex Halliday is an isotope geochemist who develops mass spectrometry techniques and applies them to the origin and early evolution of the terrestrial planets. He also conducts studies of mantle melting, magmatic systems, mineral and hydrocarbon deposits, ocean chemistry, continental erosion and the origins of planetary volatiles. Recognising the potential of multiple collector inductively coupled mass spectrometry in particular, his group developed methods for determining precise levels of natural mass dependent fractionation in silicon, vanadium, nickel, tungsten, thallium and uranium, in addition to developing other isotopic systems. Among diverse discoveries, Halliday and others found, by using the decay of hafnium-182 to tungsten-182, that Earth took tens of millions of years to accrete, culminating in the Moon forming event after more than thirty million years. In contrast asteroidal sized objects and Mars formed within just a few million years. Halliday also demonstrated that silicon is a likely light element in Earth's core based on the first evidence of metal-silicate isotopic fractionation. He also showed that the oxygen isotopic composition of Earth and Moon are indistinguishable to very high levels of precision providing evidence endorsed by other isotopic systems, that the Moon's atoms were derived from, or equilibrated with, those of Earth.

Membership Type

International Member

Election Year


Primary Section

Section 15: Geology

Secondary Section

Section 16: Geophysics