Before I get to the teeth-grinding parts, let me sing some praises. The production values are great! The visuals are outstanding! The three sites selected to illustrate the power and scale of Ice Age megafloods are fantastic!
The location they explored in Iceland, Ásbyrgi Canyon, is exactly what Washington State's Grand Coulee would look like if the climate in the eastern part of the state was colder and wetter. They highlight the similarities perfectly. And when they show a seafloor map of the English Channel, the resemblance to the Channeled Scablands is absolutely unmistakable.
I love that they chose three landscapes with quite similar origins – Ice Age megafloods – but three different triggering mechanisms. In Ásbyrgi Canyon's case, the flooding was caused by gigantic jökulhlaups from Vatnajökull, possibly triggered by volcanic eruptions. For the English Channel, there was probably a ridge of chalk connecting what would become England and France, and a humongous glacial lake where the North Sea is now. When rivers and glacial meltwater filled the lake to the top of the ridge, a spillway formed and rapidly eroded through the soft chalk, unleashing a gargantuan flood of water that quickly carved the Channel. And for our own beloved Channeled Scablands, a lobe of the Cordilleran Ice Sheet blocked the Clark Fork River, creating Glacial Lake Missoula, which grew deep enough to float its ice dam and unleash the mind-boggling floods that carved the Channeled Scablands.
All of this is presented with excellent graphics to help us visualize what our Ice Age ancestors didn't have the technology to record if they witnessed it. Great!
However, I have many problems with how the stories were presented, and what was ignored. I'll be talking only about the Channeled Scablands, which I know quite a bit about, but I can tell from the Nature article I linked above that the program elided important bits about the English Channel, and I have no doubt readers familiar with Ásbyrgi Canyon could also point out many serious flaws.
Problem 1: J Harlen Bretz is missing
They never, not once, mention his name. If all you know of the Scablands comes from this show, you'll walk away convinced we were clueless about how they formed until late 20th-early 21st century geologists took an aerial survey, compared the Scablands to similar features in Iceland, used some fancy dating techniques, and discovered the Truth.
They don't give even a hint that Bretz had figured out the broad outlines of the story in the 1920s, mostly by walking the landscape, mapping it carefully, and trusting what the landforms were telling him. And the huge coulees, immense dry waterfalls, massive ripple marks and gravel bars, and outsized potholes were all saying that floods on a scale never witnessed in written history had roared through, stripping away topsoil and carving bedrock into fantastic shapes.
Now, the geologic community of the 1920s didn't accept Bretz's flood hypothesis, but by the late 1950s, evidence had mounted to the point where it would be pretty silly to deny it. The studies performed in the latter half of that century and the first decades of this have served to refine and reinforce his work, adding details and depth, and enlarging our understanding to include tens to hundreds of flood events, some of which very probably took place during previous ice sheet advances hundreds of thousands of years ago.
Ask my partner B how many snarky remarks I made about them ignoring the painstaking work of J Harlan Bretz, which brought the concept of an Ice Age megaflood to the scientific world. There were many lots, he can tell you. I even had to pause several times to rant.
Problem 2: J.T. Pardee is also missing
You know what Bretz was missing? A water source for his flood. You know what J.T. Pardee found in 1910 and further investigated in the 1930s, confirming it's suitability? The water source for Bretz's flood. He gave a talk about it in 1940. His work bolstered Bretz's Spokane Flood (later, Missoula Floods) story, and went a long way towards convincing very skeptical geologists that sudden, catastrophic floods had created the Scablands. His Glacial Lake Missoula lent its name to the floods. He was a key scientist in this story. And you'd never know he existed from this documentary! His name, like Bretz's, is completely absent.
Don't get me wrong: the experts Nova enlisted to help tell the story were great. They've added some important data. But they weren't, as the documentary implies, the ones who discovered the original evidence for ginormous flood events and the glacial lake that fed them. I'm pretty sure those experts probably mentioned Bretz and Pardee many times during filming. And I seriously, bitterly resent the filmmakers pretending Bretz and Pardee didn't exist, not to mention acting like none of the Glacial Lake Missoula story would be known without extremely recent dating techniques.
Problem 3: The Cascades Volcanoes red herring
So, this is probably just me being all nitpicky, because the filmmakers had thoroughly annoyed me and I wasn't in a generous mood by this point, but the entire red herring sequence where they leap from volcanoes causing jökulhlaups in Iceland to asking if the Cascades volcanoes like Mounts Rainier and St. Helens could have caused the Missoula Floods about undid me.
They're on the west side of the state! The floods came from the east! WRONG BLOODY DIRECTION, PEOPLE!! ARGH!!!
And even if the direction wasn't completely backwards, the Cordilleran Ice Sheet never traveled that far south. None of those volcanoes were ever buried by any ice sheet. Their glaciers, though much more substantial than today, were too danged small to feed floods of that scale. E.V.E.R.
Bad red herring! Bad!
Problem 4: Ice floats in water. The ice dam floated. Why didn't they mention that?!
Dana's being nitpicky again, but this really got up my nose: they talk about the ice dam failing because the Clark Fork River began flowing under it.
The Emmons Glacier called, and would like you to know it's doing justfinethankyou with a river flowing from under it.
Ice in general called, and would like to ask you what it does in lots of water. It would also like you to know it's brittle, even in lobe of an ice sheet quantities.
The Clark Fork River, though engorged by glacial meltwater, wasn't big enough to stop an ice sheet from damming it. But it filled its new lake deeper and deeper until it was deep enough for that extremely large mass of ice to float. And floating, probably plus rushing water suddenly barrelling from under it, caused it to snap and break, releasing 500 cubic miles or so of lake water all in an instant.
This extremely neato fact is not mentioned. And there's just no excuse for it.
Honestly, there's no excuse for any of it. Anybody researching the Missoula Floods, not to mention speaking to many lots of experts, would come across all of the above facts repeatedly. Mentioning them takes mere seconds. Heck, if they needed extra time, they could have dropped the ridiculous red herring!
So, it's a documentary with a lot to offer. But there's an awful lot of fail. Keep that in mind if you decide to watch it, and seek out sources that will tell you the important details they failed to mention.