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Cambridge University Science Magazine
For centuries, observing the Earth has meant collecting earth. Minerals, rocks, and ores were collected from around the world and gathered into vast collections. One such collection with hundreds of thousands of specimens is housed at Cambridge University’s Sedgwick Museum of Earth Sciences. Rock collections played a crucial role in the foundation of modern geology as a scientific discipline and have been important for its development ever since.

In the past, rock collections were crucial to be able to compare rocks from many different locations. This helped researchers work out the different periods of the geological timescale and what the Earth looked like billions of years ago. Careful comparison of rocks from different continents provided important evidence to build the scientific theory of plate tectonics. More recently, researchers have revisited the collection equipped with new measurement techniques. A team led by Professor John Maclennan re-examined rocks that were collected from volcanic islands in the 1800s. Using electron beams to study the rocks’ composition enabled them to understand the conditions and processes in the Earth’s mantle. Having rocks from so many volcanic islands already neatly arranged in museum drawers made their study much easier — they didn’t have to travel to remote locations around the world to retrieve their own specimens. In this way, the rock collections that shaped the beginnings of modern geology continue to enable scientific advances today.

The Dirty Past of Geology

Collecting and analysing rocks has always been closely tied to economic interests. Knowledge of the layers of rocks in a particular region helps assess the potential for exploitation of resources like coal, oil, and valuable minerals. This is a major driver behind funding for geological surveys and expeditions in the 19th century and to this day. Geologists are frequently employed by mining, oil, and gas companies to gauge prospects for resources.

In the 1800s, Britain and other Colonial powers commissioned geological surveys around the world. They brought back rocks which helped grow collections around the country. The knowledge they gained enabled the British Empire and individual imperialists to target specific regions to bring under colonial control and exploit the local resources. Typically, this went along with the exploitation of the indigenous population who were made to do the labour to extract the resources from the ground. The geologists conducting these surveys also gathered information about the local people and their politics, making it easier to force them under imperial control. Many of the rocks in today’s collections were brought back from such colonial expeditions. The collectors didn’t pay any attention to who might own the specimens they were shipping back to museums in the UK and elsewhere in Europe. There are now several cases in which formerly colonised countries have issued repatriation requests for fossils that were taken during colonial times. An important discussion about how to proceed with specimens that were taken without consent is ongoing.

In the 20th and 21st century, geology played an important role in locating and exploiting fossil fuels around the world. This has led to close ties between oil companies and museums. For example, until 2017 the Natural History Museum in London did consultancy work for oil companies to help them locate underground oil and gas reserves.

The History of The Sedgwick Museum

The Sedgwick Museum of Earth Sciences is the oldest of the University of Cambridge museums, but its rock collections are actually older than the museum itself - private collectors bequeathed parts of their rock collections to the University as early as 1728. In the 19th century, Adam Sedgwick began to more systematically expand the collection and used it for scientific studies. He was particularly interested in how different types of rock layer on top of each other and used these layers to propose several new periods of the geological timescale, including the Cambrian and Devonian periods. His systematic collecting and studying of rocks and minerals made him one of the founders of modern geology and also the founder of what grew into the Sedgwick Museum. He was also a teacher of the young Charles Darwin, but later vehemently disagreed with Darwin’s theory of evolution. Nevertheless, rocks collected by Darwin during his Beagle voyage are now part of the Sedgwick Museum’s collection. In Sedgwick’s time, the fields of geology and paleontology were closely linked and rock collectors were often also fossil collectors. Sedgwick bought rocks and fossils frequently, including from Mary Anning, the prolific fossil collector who was famous for collecting and describing fossils from the cliffs along the English Channel.

The new field of geology attracted many keen students, and soon debates arose about who was allowed to study and work in this new field. Adam Sedgwick strongly disagreed with the efforts of women to obtain full student status at Cambridge, calling these women ‘nasty forward minxes’. His successor, Thomas McKenny Hughes, was more open towards the academic pursuits of women and from the 1870s frequently took women on his geology research field trips. This was enabled by his wife Mary Hughes, a geologist in her own right, who acted as their chaperone. She participated in those field trips for the benefit of her own research, which she published independently as well as with her husband. Several of the women whom she and her husband taught on these field trips went on to become the first female fellows to be admitted to the Geological Society of London.

Today, the rock collections are housed in the Sedgwick Museum, which like all Cambridge Museums, is currently closed due to the COVID-19 pandemic. But if you could visit it, in the Mineral Gallery you would find display case after display case filled with stones. Some are shiny and colourful eye-catchers; others are dull and in muted colours. The Mineral Gallery houses only a small fraction of the vast collection of rocks that the museum owns. In addition to the mineral collection, the museum is also in charge of a petrology collection and a separate collection of building stones. The rocks are used to study how the Earth’s crust has formed and changed over billions of years, as they reveal information about the history of the earth and its current condition. Pick up the right set of rocks, and you might just be able to work out where ancient oceans used to be, when a volcano erupted, or where to dig for gold!

Launching Geology’s Future

Today, we are able to collect rocks from locations that Sedgwick could have only dreamed of. Diving robots can retrieve rocks from the bottom of the ocean and space missions are bringing rocks from the moon (and soon Mars) back to Earth — some of which have made their way into the Sedgwick Museum’s collection. In 1969, rocks collected during the Apollo 11 mission were analyzed in Cambridge and continue to be used for research into the geology of the moon.

The bigger shift for the field of geology is likely to come from the need for an energy transition away from fossil fuels.With the push towards more sustainable energy sources, the role of geological knowledge is shifting. Now, rocks are analyzed to determine where the geological layers below our feet are suitable for the construction of geothermal power plants, where to store carbon after capturing it from the atmosphere, and where to find the right materials to build the wind turbines, solar panels, and batteries needed for a sustainable future. Geology remains critical to understanding our relationship with the world around us, and as the subject evolves then so will the Sedgwick Museum — perhaps one day we will see special exhibits on the geology of renewable energy sources and Martian rocks settled amongst Sedgwick's initial collection.

Juliane Borchert is a postdoctoral researcher in optoelectronics. Artwork by Josh Langfield.