May 15, 2019
Cosmos Recap: The One With Geology And Also Too Global Warming
This week’s episode of Cosmos: A Spacetime Odyssey, “Lost Worlds of Planet Earth,” is about time travel — the path of all the life that clings to the thin habitable crust of our planet, and the forces that have shaped both. Neil deGrasse Tyson starts us off with a visit to the Carboniferous period, roughly 350 million years ago, at the point where trees began to cover the planet, the result of a newfangled plant molecule, Lignin, which allowed trees to grow higher — and so, with nothing getting in their way, they did. With all that photosynthesis going on, there was more oxygen than at any time in the planet’s history, arthropods were huge, and virtually all the planet’s land mas was a supercontinent, Pangea. All those trees ended up getting buried without decaying much, since bacteria and fungi hadn’t yet evolved a means of digesting lignin. And so eons of forests were buried, their carbon eventually becoming coal. This got messy eventually — twice.
But first, we take a quick jaunt to Nova Scotia’s Joggins Cliffs, where millions of years’ of sediment can be seen as you move along the beach. He shows us a petrified tree, upright in the rock strata, and damned if the first thing I thought of was the young-earth creationist claim that such fossilized trees somehow create a problem for the idea that rock strata formed over millions of years — how can one tree protrude through supposedly eons of layers huh? The answer is a bit more boring — the “fossil forests” may have been covered fairly rapidly, then the trees slowly fossilized; later, over longer periods, other layers of sediment built up over time, eventually surrounding an already-fossilized tree. Sorry, creationists — it didn’t all happen during Noah’s Flood.
More to the point, all those buried trees contributed to the “Great Dying” of 250 million years ago, which nearly wiped out life on Earth — we revisit the “Halls of Extinction,” the notional museum to the great mass extinctions of prehistory, that Tyson introduced in the second episode. As Siberian volcanoes erupted for thousands of years, the coal deposits also burned, releasing deadly toxic gases, and methane trapped in ice was also released. Millennia of alternating global warming, punctuated by years of freezing cold, killed off most life on earth.
The circulatory system of the world’s oceans shut down; the stagnant waters became oxygen starved, killing almost all the fish in the sea, but one kind of life flourished in this brutal environment: bacteria that produced deadly hydrogen sulfide gas as a waste product. That was the last straw — the poison gas killed almost all the remaining plants and animals on the land. This was the Great Dying — the closest that life on Earth has ever come to annihilation.
Luckily, some teensy, very resilient shrewlike
mammals protomammals survived. Say hello to your ancestor, you lucky humans. Little booger lived near Newark, New Jersey, Tyson tells us.
Next, we’re off to the Guadalupe mountains of Texas and New Mexico, the fossilized skeleton of a reef in an inland sea, to illustrate that the Bible actually is correct about the valleys — or sea floors — being exalted and the mountains made low, though the part about the crooked ways being made straight tends to be a bit too linear for geology. And suddenly we’re looking at the Earth of 220 million years ago from space, when “New England and North Africa were next door neighbors.” Over millions of years, the continents moved apart, and the Atlantic Ocean filled in the gap, and then eventually humans came along to figure this all out (or if they were creationists, to claim that the entire process took place in the single year of the Flood. Equal time, you know). In an animation, we meet Alfred Wegener, the first geophysicist to make the case for continental drift, which would explain why fossils of the same species could be found both in the Americas and in Africa, and the existence of nearly identical sedimentary layers and mountain ranges between the continents. Wegener hypothesized a single supercontinent, Pangea — unfortunately, his ideas were generally dismissed until the 1950s. Scientists are human, Tyson reminds us, and have blinds spots and biases; but “science is a mechanism designed to ferret them out. The problem is, we aren’t always faithful to the core values of science.”
Which brings us to another animated segment, the story of Marie Tharp, a researcher in the 1950s who worked with Bruce Heezen to map the ocean floor — but who also was not taken especially seriously since she was a woman (and thank goodness, we needn’t worry that “women in science” were all going to be ghettoized in last week’s “Sisters of the Sun” episode). Tharp (voiced by Amanda Seyfried) discovered the Mid-Atlantic Ridge by analyzing sonar data collected by Heezen — Tyson might have added that as a woman, Tharp was actually barred from working aboard research ships. The animated Heezen at first dismisses her discovery as “girl talk,” but eventually was convinced that yes, the ridge was evidence for plate tectonics. And as they smile in triumph, we go to commercial.
Next, a visit to the Marianas Trench, the deepest canyon on Earth, 10 km deep, where the water pressure is 8 tons per square inch — and yet there’s life, a complete food chain, lovingly recorded in HD, with only a few CGI backgrounds. Tyson remarks that, given time and tectonic movement, even undersea mountains could someday be aboveground. We then get a 3-minute review of the structure of the planet: Iron core, liquid iron outside of that, surrounded by a churning molten mantle, and finally the crust, the thin layer that we think of as solid. Also: Earthquakes, which are not punishment for sin, but just the crust being moved along by the mantle, tectonic plates grinding up against each other.
And now we’re on to the
Triassic Cretaceous extinction, thanks to an asteroid thwacking into the Yucatan and wiping out most animals over 100 pounds — bye, dinosaurs — but giving our little Jersey shrew ancestor and other mammals a chance to become dominant. We learn that we owe our own evolution to the coming together of North and South America — the Isthmus of Panama blocked what had been direct ocean currents from the Atlantic to the Pacific, changing global climate yet again, and making Africa a much warmer, drier place, giving the evolutionary advantage to populations of apes that could move faster on two legs and grab stuff with their hands. “Think of it,” says Tyson:
A change in the topography of a small piece of land half a world away reroutes ocean currents. Africa grows colder and drier. Most of the trees can’t withstand the new climate. The primates who lived in them have to seek other homes, and before you know it, they’re making tools to reshape the planet.
Ah, but it turns out that Earth’s changes aren’t the only factors that shaped life — even other planets influenced us. Not via astrology, but because their gravity changed Earth’s orbit, and made the planet wobble on its axis, causing the great ice ages. And lucky for us clever ape descendants, 10,000 years ago, the fluctuations of the ice ages ended, so we got a chance to do the whole civilization thing, and the inter-glacial period is expected to last another 50,000 years. As a species, we’ve pretty much got it made.
Except there’s one hitch: We’ve been burning up all those forests that turned to coal, all those organisms that became oil and gas, and that’s added a dangerous amount of greenhouse gases to the atmosphere at a rate to rival the “great climate catastrophes of the past,” which Tyson pointedly reminded us resulted in mass extinctions. “We just can’t seem to break our addiction to the kinds of fuel that will bring back a climate last seen by the dinosaurs.” And yet we don’t seem all that interested in changing, because it would be really bad for the nice people whose wealth depends on not changing. “The dinosaurs never saw that asteroid coming,” Tyson says. “What’s our excuse?” And back we go to the Halls of Extinction, with an empty, unnamed corridor that Tyson gestures to like the Ghost of Christmas Future. Do we want to be the ones to go on display as both the cause and the victims of the next great extinction?
After a commercial, we get a reprise of the abbreviated evolution animation from the original Cosmos series, as Tyson says, “Congratulations. You’re alive. There’s an unbroken thread that stretches across three billion years that connects us to the first life that ever touched this world.” And here we are, a whole population of humans descended from a long line of survivors. And could we please not screw it up please? If Carl Sagan’s Cosmos was a plea to not blow ourselves up with nuclear war before we could become a spacefaring species, then Neil deGrasse Tyson’s variation on the theme is just as urgent in its call to stop choking the planet with greenhouse gases. Who’d have guessed that avoiding a global nuclear war turned out to look comparatively easy?
And before we close, a couple of notes: In what is being described as a purely random technical glitch, the Fox affiliate in New Orleans accidentally interrupted the entire discussion of how climate change led humans to evolve in a colder, drier Africa. There were some commercials, a news promo, and a couple of public service spots on the screen instead. This, after a similar accidental programming glitch in March led a discussion of evolution to disappear for viewers in Oklahoma City. Talk about well-timed glitches at TV stations in the Bible Belt! Maybe CNN should look into it.
The other digression, brought to our attention by the Cosmos discussion thread at Reddit, is this beautiful commercial by Google, which premiered during this week’s episode to mark Teacher Appreciation Week, but which I zapped through on the DVR:
You’re made of sterner stuff than I am if you managed not to get a bit weepy at the end. (And of course, as I’ve mentioned, Cosmos kind of primes me to sentimentality anyway, dammit.) Freakin’ Google.
Cosmos: A Spacetime Odyssey airs on Fox 9:00 Sundays Eastern/Pacific, 8:00 Central/Mountain. Reruns Monday on National Geographic Channel 10:00 Eastern. Episode 9, “The Lost Worlds of Planet Earth,” online at CosmosOnTV.com