Breaking Through the Seafloor

Glomar was the primary research vessel of the Deep Sea Discovery Project (DSDP), an international mission created to investigate the history of the Earth’s oceans. Almost everything about Glomar was unprecedented: its drilling rig could probe water depths of more than 7km; it could recover continuous cores of rock over 1700m long; and it was a place for East-West collaboration at the height of the Cold War.

Geologists are historians of deep time, but piecing together the history of the Earth before the DSDP was like trying to understand Tudor England without Henry VIII. The 1870s Challenger Expedition of made great advancements in the science of oceanography, but it took nearly a century for any further developments. For most of the 21st Century, the deep ocean would remain ‘here be dragons’ territory.

One of the earliest DSDP expeditions tested Alfred Wegener’s 1912 theory of continental drift. Wegener had observed that the landmasses either side of the Atlantic matched up neatly, and hypothesised that they were once connected. If Wegener’s theory was correct, then new oceanic crust should be created in the centre of the ocean and the oldest crust should be found at the margins. In 1970, Glomar drilled a series of holes across the full width of the Atlantic Ocean, from South America to Africa. Glomar’s fndings exactly matched the predictions of the theory, and one of the most revolutionary ideas in the Earth Sciences was fnally validated.

The DSDP created the science of palaeoceanography – the study of the ancient ocean. One of the key ways of doing this is

by recovering the microscopic remains of phytoplankton, the plants of the sea. These organisms live in the shallow ocean and gain their energy from photosynthesis – laying down the entire basis of marine food webs. When these creatures die, their bodies can settle through the depths of the ocean, forming a constant rain to the seafoor known as marine snow. Each organism alone is thinner than a human hair, but on geological timescales they fall in their trillions, coating the entire ocean in layers of sediment up to several kilometres thick. This debris provides a continuous record of the ocean over the last 200 million years. By investigating the chemical composition of these organisms, scientists can elucidate information about ancient ocean temperature, elemental makeup, salinity, and a vast array of other details. Scientists can even estimate the total volume of the polar ice caps at any point in geological time by analysing only a handful of these skeletons.

Whether establishing the pacing of Ice Ages or examining the crater that wiped out the non-avian dinosaurs, deep sea drilling is a tool that allows us to shine a light into the darkness of the Earth’s past. Perhaps most poignantly for our modern times, discoveries about past episodes of environmental change allow researchers to contextualise the human-induced changes we are living through today. 17 years after launching, having covered almost 700,000km, Glomar returned to port for the fnal time in 1983. Glomar’s retirement in 1983 also signalled the end of the DSDP. The spirit of Glomar lives on today through the Integrated Ocean Discovery Program (IODP), a collaboration between 24 nations with guaranteed funding through to 2023. IODP’s slogan is ‘Illuminating Earth’s Past, Present, and Future’, and no doubt it will continue to live up to the legacy of discovery laid down over fve decades ago. Matt Sutton is studying for a DPhil in Paleontology at St Anne’s College. I n March 1968, the Glomar Challenger set sail from the dockyards of the Texan town of Orange. Thus began a journey that would fundamentally challenge our understanding of the history of the Earth.

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