Hidden Earthquakes Found at Doomsday Glacier: Explained
🕐 8 min read | 🌍 Natural Wonders
🔒 Key Takeaways
- Seismometers buried in the snow on Antarctica's Thwaites Glacier recorded hundreds of repeating 'icequakes', most of them smaller than magnitude 1 and too faint for global seismic networks to register.
- Thwaites holds enough ice to raise global sea level by about 65 cm (roughly 2 feet) on its own, and it currently supplies an estimated 4% of annual global sea level rise.
- The glacier's grounding line has retreated roughly 14 km since the late 1990s, with satellite radar measuring retreat as fast as about 0.8 km per year between 2011 and 2017.
- The icequakes cluster at 'sticky spots' where ice is welded to hard bedrock, showing that parts of Thwaites move in millimetre-scale slip-and-stall pulses rather than gliding smoothly.
Bury a seismometer in the ice of West Antarctica and you might expect silence. Instead, researchers listening beneath the Doomsday Glacier picked up a rattle of hundreds of hidden earthquakes at the Doomsday Glacier — tiny, repeating shudders no distant monitoring station ever noticed. Each one marks a small patch of ice tearing loose from the rock below, and together they act like a stethoscope pressed against one of the fastest-changing glaciers on the planet.
Why Thwaites Is Called the Doomsday Glacier
Thwaites Glacier is a river of ice covering roughly 192,000 square kilometres — about the area of Great Britain or the state of Florida — draining a huge basin of the West Antarctic Ice Sheet into the Amundsen Sea. It earned the nickname 'Doomsday Glacier' because of its geometry: much of its bed lies below sea level, in places more than 1,000 metres deep, and slopes downward inland, a reverse-sloped configuration that can allow retreat to speed up once it starts. Thwaites by itself contains enough ice to raise global sea level by about 65 centimetres, and it buttresses neighbouring ice that could add roughly three metres more over centuries. Satellite radar shows its grounding line — the boundary where ice lifts off bedrock and begins to float — has retreated some 14 kilometres since the late 1990s, with rates near 0.8 kilometres per year measured between 2011 and 2017. Warm, salty Circumpolar Deep Water at roughly 0.5–1 °C, several degrees above the in-situ freezing point, funnels into cavities beneath the ice and thins it from below. Together with neighbouring Pine Island Glacier, Thwaites accounts for a large share of Antarctica's total ice loss, and Thwaites alone is estimated to contribute about 4% of global sea level rise each year. Those numbers are why an obscure Antarctic outlet glacier is now studied more intensely than almost any other ice mass on Earth.
How Scientists Found Hundreds of Hidden Earthquakes
The detections came from field campaigns that hauled seismometers, GPS receivers and radar sledges across one of the least accessible surfaces on the planet, much of it under the International Thwaites Glacier Collaboration, a joint US National Science Foundation and UK Natural Environment Research Council programme running from 2018 to 2023. Instruments were buried a metre or two deep in snow pits and left to record continuously through a polar winter in which surface temperatures fall below −40 °C and no crew can remain. Because the events are so small — many below magnitude 0 and few above magnitude 1 — they are effectively invisible to the global seismic networks that catalogue tectonic earthquakes. Only sensors sitting directly on the ice, typically within a few kilometres of the source, can register signals that weak against wind and crevasse noise. Automated detection algorithms and template matching then combed through months of continuous waveforms, extracting hundreds of near-identical events from the background hiss. The repetition was the giveaway: matching waveforms mean the same small patch of ice is slipping over the same patch of bed, over and over. Similar repeating basal signals had already been catalogued on other West Antarctic ice streams, which gave researchers a template library to work from.
🤔 Did You Know?
Some icequakes beneath Thwaites repeat every few minutes for hours with near-identical waveforms — meaning the same patch of ice is slipping over the same patch of bedrock, millimetres at a time, like a rusty hinge grinding open.
What Is an Icequake, and How Does Ice Make One?
An icequake is a brittle failure inside or beneath a glacier that radiates seismic waves, exactly as rock fracture does in a tectonic earthquake. Ice is a strange material: under slow, sustained stress it creeps like extremely stiff honey, following Glen's flow law, but when strained quickly it snaps like glass. That dual personality produces several distinct seismic families — surface crevassing as ice bends over bumps, hydrofracture as meltwater wedges cracks open, calving quakes as icebergs capsize, and basal stick-slip events at the ice–bed interface. Basal events are the most informative, because they originate at a contact no camera can reach: often 800 to 1,200 metres below the surface, where ice meets bedrock and waterlogged sediment. Their waveforms are short, sharp and high-frequency, typically rich in energy between about 10 and 100 hertz, and their repeat intervals can be almost metronomic. By contrast, the 'glacial earthquakes' produced by capsizing icebergs in Greenland reach magnitude 5 and radiate energy at periods of 20 to 100 seconds, low enough for stations worldwide to detect. In effect, Thwaites is broadcasting the mechanics of its own base upward through the ice, and buried seismometers are the receivers.
Sticky Spots: The Bed That Fights Back
Much of Thwaites slides on a lubricated slurry of water-saturated till, which deforms smoothly and almost silently. But the bed is not uniform — in places harder crystalline bedrock protrudes and the ice becomes effectively welded to it. At these 'sticky spots', elastic strain accumulates until it exceeds the frictional limit, then releases in a sudden slip of millimetres to a few centimetres that radiates an icequake. Because the surrounding ice keeps pushing downstream at speeds of roughly 2 kilometres per year near the grounding zone, stress rebuilds and the cycle can repeat within minutes. A dramatic cousin of this behaviour is seen on the nearby Whillans Ice Plain, which lurches forward about half a metre twice each day in slow-slip events with a moment magnitude near 7 — yet releases the energy so gradually that no one standing on the ice would feel it. Mapping clusters of repeating events therefore shows exactly where the glacier's brakes sit and how hard they are gripping. That matters for prediction, because basal friction remains one of the largest uncertainties in ice sheet models and is usually inferred indirectly rather than measured.
What the Tremors Say About Collapse Risk
A glacier that advances in jerks rather than a smooth glide responds to stress differently from the uniform sliding that many models assume. If sticky spots hold, they slow discharge; if warm ocean water, pressurised meltwater or advancing sediment drowns them out, friction drops and flow accelerates. Changes in icequake behaviour can also appear before velocity changes become visible from orbit, since satellites such as Sentinel-1 typically resolve ice speed over repeat cycles of six to twelve days while seismicity tracks friction almost in real time. Several West Antarctic icequake clusters are modulated by the semidiurnal tide, roughly a 12.4-hour cycle, showing that the ocean tugs on the grounding zone twice a day and changes how the ice slips. Others coincide with fracturing of the Thwaites Eastern Ice Shelf, which is laced with rifts that have propagated at kilometres per year and whose loss would remove an important buttress. None of this means Thwaites will collapse imminently — current published projections describe significant retreat unfolding over decades to centuries, with large uncertainty ranges. What the tremors do establish is that the glacier's base is far more heterogeneous and dynamic than a smooth-flow picture suggests.
Listening to the Ice: The Future of Glacier Seismology
Traditional Antarctic seismic stations are costly, sparsely spaced and vulnerable to snow burial and battery failure through months of winter darkness. Newer approaches are changing the economics: distributed acoustic sensing turns a single fibre-optic cable, lowered into a borehole or laid on the surface, into thousands of virtual sensors spaced roughly a metre apart along tens of kilometres of fibre. Autonomous robots complement that view from below — the Icefin vehicle was deployed through a hot-water borehole about 600 metres deep at the Thwaites grounding zone in early 2020, filming melt rates of a few metres per year on flat surfaces but far higher values inside crevasses and terraces. Machine learning classifiers now sift continuous ice-sheet recordings for event families that human analysts would never find by eye, cutting months of manual scanning to hours. The long-term ambition is a semi-permanent seismic stethoscope on Thwaites, feeding measured basal friction into the ice sheet models that inform coastal planning. With an estimated 230 million people living on land within one metre of current high-tide lines, the payoff for hearing the ice early is measured in cities, not just in scientific papers. Each new deployment also builds a baseline: without years of recordings, no one can say whether a burst of icequakes is normal or a genuine change.
How Icequakes Differ From Antarctica's Tectonic Earthquakes
Antarctica does experience true tectonic earthquakes, but they are far rarer than in most continental regions because the plate is largely surrounded by spreading ridges rather than subduction zones. The largest instrumentally recorded event near the continent was the magnitude 8.1 Balleny Islands earthquake of 25 March 1998, which ruptured oceanic lithosphere north of the Ross Sea. Intraplate quakes within the ice-covered interior are small and infrequent, partly because the enormous weight of ice — up to 4,700 metres thick at the deepest point — suppresses crustal faulting. Icequakes, by contrast, number in the thousands each year at instrumented sites and originate within the ice column or at its base, not kilometres down in bedrock. Seismologists distinguish them by depth, frequency content and duration: basal icequakes are shallow, high-frequency and last a fraction of a second, whereas tectonic events radiate lower frequencies from far deeper sources. Because glacial unloading also changes crustal stress, retreating ice can even influence future tectonic seismicity, a process documented in post-glacial Scandinavia. Telling the two apart is essential before any tremor near Thwaites is interpreted as a sign of ice instability.
Final Thoughts
Hundreds of hidden earthquakes at the Doomsday Glacier show that Antarctica's most closely watched ice mass is not sliding silently — parts of it grip, strain and let go on cycles measured in minutes. To follow what happens next, check the International Thwaites Glacier Collaboration's published field results and NASA Earth Observatory's grounding-line updates, and bookmark Kya Tumko Malum? for our next dispatch from the ice. If a glacier can be heard slipping millimetre by millimetre, what else beneath the Antarctic surface is signalling in frequencies we have barely begun to record?
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Frequently Asked Questions
Are there really earthquakes in Antarctica?
Yes — Antarctica experiences both genuine tectonic earthquakes and far more numerous 'icequakes' caused by fracturing and slipping ice. The largest recorded event nearby was the magnitude 8.1 Balleny Islands earthquake in March 1998, while most icequakes are below magnitude 1 and detectable only by seismometers placed directly on the ice.
Why is Thwaites called the Doomsday Glacier?
Thwaites sits on a bed that lies largely below sea level and slopes downward inland, a shape that can allow retreat to accelerate once it begins. It holds enough ice to raise global sea level by about 65 cm on its own and buttresses neighbouring ice worth roughly three metres more.
How much would sea level rise if Thwaites Glacier collapsed?
A complete loss of Thwaites would raise global sea level by roughly 65 centimetres, or about two feet. Because Thwaites also holds back a much larger section of the West Antarctic Ice Sheet, its collapse could eventually contribute up to about three metres of additional rise over centuries.
What is an icequake and how is it measured?
An icequake is a brittle fracture inside or beneath a glacier that radiates seismic waves, usually at frequencies between about 10 and 100 hertz. They are measured with seismometers buried in snow pits or, increasingly, with fibre-optic cables that create thousands of sensing points along a single line.
📚 Further Reading & Research Sources
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NASA Operation IceBridge / NSF & International Thwaites Glacier Collaboration imagery
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