Seeing what was done here in the matter of days make you realize how things like the Grand Canyon formed over millions of years - then wonder how it isn't bigger. Can't imagine the wealth of knowledge that has been been gained by just watching the erosion patterns as the failure evolved.
First, you went from a prolonged severe drought to a very intense rainfall in a very short amount of time, extremely not helped by the massive surface runoff when the emergency spillway was put in use. I don't know all of the geological processes involved, but the upper soil layers were probably made far more mobile and less stable by the drought.
Second, the massive erosion is happening on a slope, whereas the Grand Canyon is (comparatively) flat. A steeper gradient means less force is needed to set sediment in motion.
If you want impressive floods, the Bonneville and Missoula floods are the largest known floods in history. Imagine floods with hundreds or thousands of times the flow rate of Niagara Falls, which cumulatively scoured the Columbia river region by hundreds of feet.
Yeah, the ice age water flows were quite something: similar to the spillway in question just slightly bigger, a natural spillway of Lake Agassiz, River Warren have first cut the Traverse Gap, a mile wide and 130 feet gap into the Big Stone moraine and then created a riverbed five miles wide (!!!) and 250 feet deep.
Tell me about it! I was cycle-touring in the USA many decades ago and maps back then were Rand McNally, not Google... So it was always a matter of guessing where the hills were. So, I get to Colorado, cycling down through Four Corners with the 'Mittens' etc, hope to get to the camp sites in Grand Canyon. So I follow the 'Little Colorado'. My geography skills told me that the road going next to the river would be going downhill, but I wasn't thinking properly!!!
So I follow the Little Colorado expecting an easy drift into camp but instead I have a gale force headwind and serious bits of uphill. So I didn't get there and I had to sleep in the tent held up by rocks with no let up in the wind, with an electrical storm to follow, one where I was the highest metal object around...
Next morning I woke up rough and set off on my bike, literally 1/2 mile away up the road were a group of cycle tourists from Yugoslavia and they pitched up in one of the roadside stalls. Had I not given in so easily the previous night I would have had a fun time meeting up with them and drinking properly... I was also oblivious to the time zone change so the next day came with a 'free' hour too.
I did go down to the very bottom of the Canyon and up the other side to continue my cycle tour of the wonderful U.S.A. These crazy dams (every river is dammed) were a huge part of my time there, riding across them and camping by them.
The land might have uplifted, but the river still had to carve the same depth nonetheless. I don't think the land happened to raise just on both sides of the river and not below it.
Yes, of course the river has to erode away the rising land but it is staying roughly where it is rather than digging down through land that isn't rising.
"U.S. Geological Survey hydrologist Jim O'Connor and Spanish Center of Environmental Studies scientist Gerard Benito have found evidence of at least twenty-five massive floods, the largest discharging ≈10 cubic kilometers per hour (2.7 million m³/s, 13 times the Amazon River). Alternate estimates for the peak flow rate of the largest flood include 17 cubic kilometers per hour and range up to 60 cubic kilometers per hour."
The specific mechanisms of those is pretty fascinating: During glaciation periods, ice dams would form, creating massive headwaters. The dams themselves would fail, as Hemming way, gradually, then suddenly: water would first start trickling through, then both erode and melt the dam, until its integrity was compromised and the entire face would fail.
Fascinating geology and scarily impressive traces. Makes me wonder what will happen on Greenland or Antarctica.
We're about to see a new piece of ice cleave off about the size of Delaware in Antartica. As ridiculous as that is, I think the most worrisome part is that it will further destabilize the ice shelf and the rate of it falling apart is only supposed to increase by this.
As such things go, the West Antarctic Peninsula calving is not particularly significant in terms of being or enabling large-scale changes in sea level. The shelf is a shelf, that is, it is already floating in the ocean, and its status as solid or liquid doesn't affect net sea levels. The peninsula itself is a long and thin landmass, which contains relatively little ice. Loss of the shelf does not, of itself, create the risk of greatly accellerated large scale icecap loss.
The symbolic and scientific significance are large. This is an exceedingly large ice mass, it may persist for years, possibly decades, in the Southern Ocean. It may pose a threat to shipping (though there's comparatively little through the region), and may have impacts on local biology and ecosystems (habitat loss, habitat gain, habitat change).
The mechanisms of loss, calving, migration, persistence, and of resulting changes to land-based glacial flow, will be fascinating.
But in terms of portending a drastic increase of ice flows local to it, the calving has little impact, as compared to, say, a shelf loss proximate to the primary Antarctic land mass -- the Ross or Weddel shelves, for example, which have behind them a thousand kilometers and more of kilometer-thick ice. That will be an interesting occurrence.
Or the formation and destruction, say, of ice dams, on the Antarctic continent or Greenland, creating meltwater pools, perhaps hundreds of kilometers in extent, and suddenly releasing those, as the dams erode, into the oceans. Similar mechanisms created a badlands landscape in eastern Washington State as the prehistoric Lake Missoula formed and drained, perhaps dozens of times, releasing cubic kilometers of water in massive scours. A similar mechanism, probably in Canada, triggered a catastrophic sea-level rise, measured as I recall in meters, over the course of days to a month.
That would also make for an interesting news cycle.
Contextualisation of these types of events in the press is exceedingly poor, with a small handsful of exceptions. I've already mentioned Brad Plumer's Vox coverage in this thread, he's among the exceptions.
