Events / History / Year of Carbon

Around the carbon cycle in twelve pioneers

For our last public lecture of the year, Dr Simon Mitton took us on a tour of ‘Carbon’s fundamental role on Earth’ in the stories of twelve pioneering scientists of the past 500 years. Telling the very human stories behind the people who made some of the key discoveries, Simon delivered a unique public lecture about the history of carbon as we know it.

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A diagram from the Deep Carbon Observatory showing the whole Earth carbon cycle as it relates to plate tectonics and dynamics of the mantle. (Orange arrows correspond to outgassing from Earth’s interior. Blue arrows correspond to carbonate precipitation or organic C burial. Curved blue arrows represent terrestrial silicate weathering and seafloor weathering.)

 

Earth as a bar magnet

The very earliest contribution to carbon science is attributed to William Gilbert (1544 – 1603) who undertook a fundamental investigation of magnetism in order to better understand how the magnetic compass worked. He was the first to suggest that Earth’s interior was like a bar magnet, and the first to insist that by conducting the right investigations at the Earth’s surface we can determine many things about its interior. If only he had known then how much our understanding would progress.

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An illustration of the Earth’s interior and magnetic field, Image: Kay Lancaster, University of Liverpool.

 

The world’s first geomagnetic map

With the aim of improving marine navigation, Edmund Halley  (1656 – 1741) made the world’s first geomagnetic map (1700) by taking measurements of the deviation between magnetic and true north. He called upon mariners globally to help him with his research by collecting and submitting measurements of this kind to the Royal Society in what might be thought of as the world’s first citizen science project. Halley’s dataset of geomagnetic deviation was the first to span multiple continents and illustrates the value of collecting accurate, reproducible, open data – at a time when this was not the norm.

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Edmund Halley’s geomagnetic map (1700), Image: UK National Maritime Museum (Wikimedia Commons).

 

Humboldt, influencer of the 1700s

Alexander von Humboldt (1769 – 1859) set an example to the science community of international collaboration. He was an advocate for long-term, consistent measurement of the world’s geomagnetic field which paved the way for much of the geophysical and meteorological monitoring scientists still conduct to this day. As part of the Russian Empire he installed many of the long term monitoring stations around the world still in use. He was one of the first scientists to share concerns over the possibility of human induced climate change, and was a successful populariser of his scientific ideas – a true “influencer” of the 1700s.

 

What’s in a name?

Antoine Lavoisier (1743 – 1794) remarkably changed the course of science in the late 1700s when he began to measure chemistry quantitatively instead of qualitatively. Along with his wife, Marie-Anne (1758 – 1836), they laid the groundwork for the establishment of the metric system, wrote the first extensive list of chemical elements, and therefore also coined the names we now use for such elements, including the sixth element on their list, ‘carbon’.

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Portrait of Antoine-Laurent and Marie-Anne Lavoisier, Image: Metropolitan Museum of Art (Wikimedia Commons).

 

China’s secret ingredient

Jacques-Joseph Ébelmen (1814 – 1852) discovered what we now refer to as the ‘silicate-carbonate cycle’ while trying to discover what made fine china clay so favourable for crockery. The secret turned out to be the clay mineral ‘Kaolin’, which is formed by the decomposition of silicate minerals on exposure to carbonic acid. However, as Ébelmen’s findings were published in ‘Anales des Mines’, the french language journals of the government Mining Authority, his work remained largely uncredited until 1996.

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Kaolinite from the Geisenheim kaolin mine, Germany, Image: Marion Halft – Own work, CC BY-SA 4.0.

 

Diamonds from peanut butter

Percy Brigman (1882 – 1961) and Hatten S. Yoder (1921 – 2003) were pioneers of high pressure petrology who developed the first high pressure experimental systems. They used these to put geologic mixtures under pressures that would mimic the conditions in the deep Earth thus developing our understanding of the chemical and physical processes at play. This research led them to discover that diamonds from within the deep Earth contained geochemical insights into the chemistry of material deep below the Earth’s crust.

In 2014, a team of scientists from the Bayerisches Geoinstitut in Germany used modern iterations of equipment invented by Brigman and Yoder to synthesise diamonds from different carbon rich materials, including one from peanut butter!

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An uncut diamond crystal. Image: Rob Lavinsky (Wikimedia Commons).

 

Some like it hot

The idea that the age of any mineral could be determined using radio-isotopes was first proposed by geologist, Arthur Holmes (1890 – 1965). A discovery that eventually led to major public acceptance of plate tectonic theory. The ability to date subsequent layers of oceanic crust originating from a mid-ocean spreading zone was central to this acceptance. Holmes pioneered ‘geochronology’ or the practice of dating the Earth and materials that it consists of – also leading to one of the first accurate calculations of the age of the Earth.

 

The final piece of the puzzle: 1900 – 2019

Arthur’s theory of ocean floor spreading was further confirmed by work undertaken in the 1900s by Harry Hammond Hess (1906 – 1969), who surveyed the depth from the sea surface to the ocean floor, finding bathymetric highs near mid-oceanic zones parallel to continental edges and lows along the margins where continents met the oceans.

The painstaking task of drawing up cross sections of the sea bed was undertaken by Marie Tharp (1920 – 2006). While constructing these cross sections she noticed a valley in the centre of the Atlantic ocean which led to the discovery of the mid Atlantic ridge rift valley, and further developed our understanding of plate tectonics.

In more recent history, Frederick Vine and Drummond Matthews determined that the alternating pattern of magnetic signatures parallel to the ocean spreading centres, indicated that the Earth’s magnetic field changed over time and these alternating stripes recorded when the magnetic field had switched. Their research, led to widespread consensus about sea-floor spreading theory, and was significant in the acceptance of plate tectonic theory.

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An illustration showing the variation in sea-floor magnetism as noted by Vine and Drummond, Image: The Naked Science Society.

 

These twelve early pioneers of deep carbon science are just a few of the people behind the discoveries that changed the way in which Earth scientists understand the formation, storage, and cycling of carbon in the geosphere. Simon’s book ‘From Crust to Core‘ expands on all of the stories he told in his public lecture, and more! It will take readers on a tour of deep carbon science from the Ancient Greeks up until the start of the Deep Carbon Observatory and will be published next year.

You can find out more about Plate Tectonics on the Society’s website.

You can watch all of this year’s public lectures, including Simon’s, on our YouTube channel.

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