What you’re looking at is a geological formation called Dry Falls, in the Sun Lakes-Dry Falls state park in my home state of Washington. The Dry Falls are a series of escarpments and cliffs near Grand Coulee, deep in Eastern Washington’s channelled scablands region. These are four hundred foot high cliffs in the middle of the desert, how did they get here? What secrets does this terrain hold? What can the strange rock formations and alien landscapes of eastern Washington state tell us about the future of our planet?

During the end of the last ice age, a massive amount of glacial ice in continental Europe and North America melted away. During the period from 25,000 to 10,000 years ago, the Laurentide, Cordilleran, and Fennoscandian ice sheets completely melted, leading to a 120 meter rise in the global sea level. The rise in sea levels from this melting is estimated to have averaged in at roughly one meter per century while being augmented by two intense periods of melting between 15,000 and 13,000 years ago, and between 11,000 and 9,000 years ago.

While the current consensus among paleoclimatologists is that this melting was relatively gradual and steady, occurring at a linear rate over the course of 15,000 years, there is some evidence beginning to surface both in our current ice sheets and in the geologic records on the last one, that a gradual and linear melting rate is not what we should expect to see going forward.

In this post, I’ll look at recent melting trends in Antarctica and Greenland as well as at paleoclimate data from ice and seabed cores to propose a model of continental ice sheet collapses as rapid and potentially cataclysmic historical events which we should be aware of as potentially civilization destabilizing. Most of our current population, our largest cities, and most of our power and industry facilities, are all located in low lying areas susceptible to coastal flooding. If the water levels rise at a rate faster than can be mitigated by a slow withdrawal from the coastline over the course of many decades and centuries, it could cripple human civilization and bring an end to our current way of life.

The first piece of evidence to note here is that the geologic record of the last ice age is littered with superfloods and seemingly cataclysmic sea level rise events. Water topped over earthen berms and flooded into lowlying areas, Doggerland and Sundaland vanished beneath the waves and the Bering Strait cut Asia and North America apart. These events have left scars on the surface of the Earth which you can see from space, you just need to know what to look for.

This is the North Fork of the Toutle River as it flows across the soft dried mud and ash of the Mount Saint Helens lahar zone, I provide this image just to given an example of stream braiding, the lahar zone gives a nice canvas on which you can really see how the water carves all these winding channels through the surface material. This happens in rivers around the world though, there are dozens of examples of this sort of river braiding I could show you. The important thing to note here though is the scale of this landform. The lahar zone is less than a kilometer across, and we can see roads and trees and houses at this level of zoom.

So now lets zoom out and look east across the Cascade range.

This is the channelled scablands from far above. At the height which satellites orbit, the mass scouring of hundreds of square kilometers can clearly be seen. braids tens of kilometers across and hundreds of kilometers long draw tracks across all of eastern Washington before spilling into the Columbia River Valley to flow onward toward the Pacific. This event, or events, geologists aren’t sure, is referred to as the Missoula Megafloods, and was the source of the Dry Falls pictured at the beginning of this post. At their peak flow, the Dry Falls were twice the height of Niagara Falls and five times the width. So much water poured into the Columbia River that it backfilled and flooded most of the Willamette Valley.

According to current consensus, these massive floods were caused when a proglacial lake formed in what is now Missoula, Montana. The leading theory is that a fifty mile long ice dam formed across the Clark Fork River which caused the waters of the receding Cordilleran Ice sheet to back up and pool around Missoula. This presents the first problem with the current consensus and is where a rather peculiar group of individuals become involved.

There are a group of slightly kooky geologists and historians who call themselves the Catastrophists. They hold that a moderately advanced civilization in North America was destroyed during the Younger Dryas period around 12,000 years ago and have found all sorts of interesting things to lend credence to their theory.

The Catastrophists looked at the story of the Missoula Megafloods and said, “That doesn’t work.” They pointed out that an ice dam the size of the one proposed cannot possibly have held back the amount of water under the head pressure that Glacial Lake Missoula was under, long enough for the lake to each its maximum historical depth of over 600 meters. Glacial Lake Missoula is estimated at having held 2,500 cubic kilometers of water, and the catastrophists say that there’s no way that could have happened with an ice dam triggered outburst flood, the ice would give before that much water could build up.

Instead, the Catastrophists propose that glacial lake missoula wasn’t a long term lake, but formed temporarily as a result of water flowing in from further north pooling and backfilling around Missoula as it interacted with the chokepoint in its flow along the Clark Fork River Valley.

The Catastrophists also have other evidence of rapid melting which they have found from seabed cores. Most of the seabed is composed mostly of decaying organic material, crushed up tiny organisms that rain down to the bottom in an ever present snow. However, there are notable strata lines within seabed cores, which contain mostly rocks, pebbles, sand, and other inorganic debris. These layers are called Heinrich Events, and it is believed that they are caused by large masses of icebergs breaking off, carrying rocks and sediment with them, and then dropping these bits of rock and sediment as they melt away. All of these things come together, according to the catastrophists, to seemingly support their theory of a cataclysmic event during the Younger Dryas period, 12,900 years ago.

So the Catastrophists look at all the data for speed of melting, heating from sunlight, atmospheric C02 levels, and conclude that the melting just happens too fast to be explained without an outside source. They claim there simply wasn’t enough energy available for the math to work out unless you added a bunch of extra energy from somewhere outside the climactic system.

The solution to this problem, they say, is that around 12,900 years ago, a comet or asteroid struck the top of the Laurentide Ice Sheet, triggering a massive pulse in melting which we observe in the form of megafloods and Meltwater Pulses and Heinrich Events. The evidence for this is shaky, but I sincerely hope they end up being correct. And they might actually be, late last year a 19 kilometer wide impact crater was discovered under the Hiawatha Crater in greenland. This impactor, if it occured at the right time period, might actually be the catastrophists smoking gun.

However, I am not particularly confident that they are correct. Because it’s under a glacier, we don’t yet know how old the crater at Hiawatha actually is. It could be significantly older than 12,000 years, and if it is, than we’re once again left with too much melting to fit our model and no discernible cause. The currently dominant theory is that a combination of increased insolation on the glaciers and high C02 levels at the time caused their final retreat and collapse. However, the effect seems to have exceeded the cause and the extremity of the events, especially the large pulses of meltwater, seem to imply some other mechanism was present. 

Without invoking some outside event like a volcanic eruption or an extraterrestrial impact, the only explanation we’re left with is the ill-understood climate feedback mechanisms which we are currently engaged in setting off en-masse.

The impact theory is in some senses comforting. We have big telescopes, we can see into space now, in theory, if we knew an impact event was coming, we could prevent it. If it takes an impact to cause a catastrophic melting and sea level rise event, then we’re mostly safe from it happening. If the melting was caused by an impact, then it means our current climate models which estimate around a meter of sea level rise by the year 2100, are largely accurate. 

But if these melting spikes were not caused by an impact, then it means something on earth which we currently do not understand triggered them. Something caused the ice sheets to suddenly and rapidly destabilize and release a large quantity of meltwater over a relatively brief period. If such an event were to occur today, the effects would be globally catastrophic. If an event caused a one-meter sea level rise over the course of a few years, it would render many of the world’s coastal cities uninhabitable. 

Scientists have posited that the West Antarctic Ice sheet, which is sitting on bedrock below sea level, could potentially experience a catastrophic collapse event if sea water was able to access the roots of this glacier. Although computer models have been unable to construct the timeline of events in detail, the possibility remains that the entire ice sheet could collapse over a period as short as a few years, which, if the entire thing went, would lead to 6 to 9 meters of sea level rise, enough to submerge a large number of urban cores around the world and utterly remake coastlines. 

The possibility of this catastrophic melting event is often left out of the climate change conversation, with the assumption being that melting will be a nuisance and force the eventual abandonment of low-lying areas or construction of new seawalls, but is not an existential threat to civilization by itself.

If the entire West Antarctic ice sheet was to collapse over a five year period, it would lead to a global crisis as populations were forced to relocate and cities were rendered unlivable. In many ways, the predictions that the ice sheets will last for centuries more and take a thousand years to melt away are overly optimistic and based on older and less accurate models of past climate events. A recent paper has provided evidence that melting may not be linear in nature but exponential, and if recent trends in accelerating melting are extrapolated out, we could see multimeter sea level rise within the next fifty years.

This would not by itself be an X-Risk, but would represent a major case of cranking up the pressure that humanity is put under, and make other X-Risks such as nuclear wars and pandemics more likely. It is my opinion that the possibility of catastrophic ice sheet collapse should be carefully considered and studied as a real possibility. It’s unlikely we could prevent such a collapse from occurring, but by anticipating such an event we may be able to save many lives and livelihoods.

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1 comment, sorted by Click to highlight new comments since: Today at 1:38 PM
It is my opinion that the pos­si­bil­ity of catas­trophic ice sheet col­lapse should be care­fully con­sid­ered and stud­ied as a real pos­si­bil­ity.

Is it not already? I kind of assumed it was already seriously considered and studied. I do not follow climate science very closely and mostly just read what comes across my RSS feeds on the subject. I've heard of the possibility of catastrophic ice sheet collapse a large number of times in the last...say...5 years.

  • What's the right amount of resources to expend on thinking about this?
  • Is my previous exposure to articles and people talking about the subject indicative of sufficient or insufficient interest and study of this possibility?
  • How do we assess the current amount of resources expended on the subject?