Podcast episode 32 - Published 01 February, 2018 by Nicholas O'FlahertyTweet
Scott’s ‘geologising’ on the Beardmore Glacier
It’s February 8th, 1912. Robert Falcon Scott and his four companions are returning from the South Pole, beaten, dejected. At 90 degrees South, they had found Amundsen’s tent with the Norwegian flag flying. It’s been three weeks since they left the Pole.
They have begun thankfully, to descend from the high altitude and incessant wind of the polar plateau. Starting down the Beardmore Glacier, they’re retracing their route back to ‘the Barrier’ as they called it, or what today we know as the Ross Ice Shelf.
On that day, Scott directed his party towards the moraine below Mount Buckley to get out of the wind. He noted in his diary ‘the delight of setting foot on rock after 14 weeks of snow and ice.’ It was ‘like going ashore after a sea voyage’.
While resting on the sheltered moraine that afternoon, members of his party carried out ‘geologising’, collecting in the process 16kg of rock samples, which included plant fossils.
Scott wrote that among the specimens was ‘a piece of coal with beautifully traced leaves in layers, and some excellently preserved impressions of thick stems, showing cellular structure’.
Nine months later, these very rock samples were found with the bodies of Scott, Wilson and Bowers, when the rescue party discovered their tent on the Barrier.
In the many books written about that ill-fated expedition, there has been much commentary on Scott’s so-called folly of adding that additional 16kg of rocks to their burden in such dire circumstances. What is undeniable however, is their significance.
The first plant fossils found in Antarctica
Plant fossils in Antarctica weren’t new. It was Norwegian Carl Anton Larsen, the pioneer of Antarctic whaling, who was the first to find fossils of petrified wood in Antarctica. He found them on Seymour Island, off the tip of the Antarctica Peninsula, in 1892. Larsen went on to become the first person to ski in Antarctica, on the ice shelf that would later bear his name.
A decade later, in 1902, Swedish geologist Otto Nordenskjöld discovered Jurassic plant fossils, also on Seymour Island. He became one of the first to suggest that Antarctica must have experienced a much warmer climate in the past, covered by forests of ferns and tropical plants.
A year later, in 1903, there was another find of plant fossils, this time on the other side of the continent, during Scott’s first visit to Antarctica, the Discovery expedition. It was the geologist Hartley Ferrar who discovered fossilized plant remains in the upper Taylor Valley, one of the famous dry valleys west of McMurdo Sound.
Shackleton too got in on the act. During the Nimrod expedition in 1908, he discovered impressions of leaves in sandstone boulders, while making the first ascent of the Beardmore Glacier.
Identifying the Glossopteris flora
However, the plant fossils Scott’s party found on that day in 1912 led to a breakthrough in the geological understanding of Antarctica. It would feed into the burgeoning debate at that time on Gondwanaland, Continental Drift, and Antarctica’s role in the formation of the continents.
The samples were taken back to Britain, and in 1914 at Cambridge University, botanist Albert Seward identified among them, the ancient Glossopteris flora. It was the first time evidence of this extinct plant species had been found in Antarctica.
Glossopteris was the name first used by French botanist, Adolphe Brongniart in 1828 to describe the tongue-shaped fossilised leaves that had been discovered in India and Australia up to that time. Through the 19th Century, more and more of these glossopteris fossils were discovered in other locations, in Southern Africa and South America.
Gondwanaland and Continental Drift
Finally in 1885, the Austrian geologist Edward Suess proposed that all these lands where the glossopteris fossils were being found, must have once been connected as part of a supercontinent which he named Gondwanaland.
Almost three decades later, in fact at the very same time that Scott was making his attempt on the South Pole in January 1912, German scientist Alfred Wegener was publishing his first thoughts on what he termed, Continental Drift. It became the basis for what today we know as plate tectonics.
Seward’s identification of the glossopteris flora among Scott’s rock samples, not only confirmed that Antarctica had been part of Gondwanaland, it would be subsequently used by Wegener as further proof of his theory of Continental Drift.
Dating the Glossopteris
Today we know that the Glossopteris plant group succumbed in the largest mass extinction the Earth has ever known, 251 millions years ago. It’s called the Permian Mass Extinction event.
Up until 2016, the oldest forest fossils found in Antarctica were dated to just before that extinction event, some as old as 260 millions years. There are plant fossils (but not full forest fossils) that date to the Devonian period, 380 million years ago, when the forests were first appearing.
The oldest forest fossils yet
This week on The Antarctic Report podcast, we speak to Assistant Professor Erik Gulbranson, of the University of Wisconsin Milwaukee. In December 2016, he led a group of geologists conducting field work in a remote location near the Shackleton Glacier in the Transantarctic Mountains.
They unexpectedly discovered the fossilized remains of an ancient forest. Tests showed the trees were 280 million years old – they are the oldest remains of a forest anyone has ever found in Antarctica to date.
Click here for more information on Erik Gulbranson’s discovery of the oldest forest fossils in Antarctica.