Dr Marco Maffione is a geoscientist who specialises in palaeomagnetism - the record of the magnetic field preserved in rocks. His research tracks the history of these rocks in the flipping of the magnetic field and the movement of tectonicplates. This has taken him all across the world and even into the open sea.

Why do scientists study rock magnetism?

Rocks retain the direction and strength of the Earth’s magnetic field at the time they were formed. This ‘signal’ that remains is the only method to track the movement of the tectonic plates in latitude. Drawing the maps of the tectonic plates in the past is a bit like a puzzle where you have to deduce those longitudes based on what makes sense. The rocks also undergo other processes long after their formation. It can reveal how the rocks were deformed, helping us understand the forces that are shaping our planet.

How far back can we ‘see’ with palaeomagnetism?

We have some samples with magnetism pre- served, dating back 3.5 billion years. The age of the Earth is 4.5 billion years, so palaeomagne- tism can provide essential information on the evolution of our planet almost since its for- mation. We can also use magnetic intensity to keep track of time. Instead of counting the flips – or reversals – in the magnetic field, the fluc- tuation of its intensity can provide an incredibly accurate constraint on the age of the rocks.

How is studying meteorites useful to understanding the Earth?

Some meteorites have properties similar to rocks on Earth. Of particular interest are those that form deep in the Earth’s mantle, which are difficult to get samples of, such as peridot-
ite. Studying meteorites can tell us about the core constituents of other planets of the solar system and their magnetic properties. Mete- orites and associated impact craters are also important to understand the magnetisation
of rocks under the extreme pressures of an impact.

Is palaeomagnetism still a cutting-edge science?

Yes! Although it’s an old technique, palaeo- magnetism is still developing. In the 1980s, research focused on the fundamentals of magnetic minerals. In the 1990s, this shifted to understanding tectonic processes. Now, we are beginning to use this to study environmen- tal processes, like pollution of water and air. New tools, such as quantum magnetic micro- scopes, are opening up research by allowing the study of magnetism in individual grains.