In a break from the ‘all Bernie, all the time’ mode that this blog has been in recently, I want to alert readers to the PBS documentary series Nova that has produced a fascinating two-hour documentary titled Polar Extremes about how the polar regions have experienced dramatic shifts during the history of the Earth. There have been periods when the poles had warm climates and consisted of swamps and forests and at other times when the entire Earth was covered with a sheet of ice.
In this two-hour special, renowned paleontologist Kirk Johnson takes us on an epic adventure through time at the polar extremes of our planet.
Following a trail of strange fossils found in all the wrong places—beech trees in Antarctica, hippo-like mammals in the Arctic—Johnson uncovers the bizarre history of the poles, from miles-high ice sheets to warm polar forests teeming with life. What caused such dramatic changes at the ends of the Earth? And what can the past reveal about our planet’s climate today—and in the future?
I cannot embed the video link but you can see the documentary in full here.
What I liked most about the show was its structure. Johnson would take a surprising finding in the Antarctic, such as a fossil of a leaf from deciduous tree, and ask how it got there. Searching for an answer to that question leads to more questions, that leads to more exploration and testing, that leads to more discoveries, and so on. It looks at how scientists investigate the conditions that far back in time and what they can infer about what might happen in the future. It is a beautiful example of scientific research and inquiry-based learning.
The documentary also does a fine job of blending spectacular footage taken from all over the world with computer-generated recreations of what the Earth was like during the various periods when the poles fluctuated from being frozen to having temperate climates.
The first two-thirds looks at what we know about the deep history of the Earth and the final third takes a more somber turn as it examines the current trends in global warning and where it might lead if we do not take action now.
I have already watched the show twice and plan to watch it more times because there is a lot of rich information in it that I cannot absorb with just one or two viewings.
I can’t help but wonder if this “variable climates at the poles” is ignoring the effects of continental drift. The land masses which are currently at the poles may not have been there when the fossils were laid down. In addition to heating/cooling cycles there are other forces at work.
machineintelligence:
It’s an obvious thing to wonder about, but no, they’re not ignoring that. There are many different types of evidence to consider. Of course I’m not expert on this, so I’m curious about it too….. But paleomagnetic and geological data (and I don’t know what) can help to determine how the plates were moving or what the approximate latitude was for a given sample. What you don’t do is just say “I see signs of a hot/cold climate, which tells me where to put this on the globe.”
So, yeah…. at times the poles (and other places) were hot, while at other times the tropics (etc.) were cold. I think that is pretty certain, although I don’t know how confident we ought to be about many of the details (but that’s just my ignorance).
Also keep in mind that the sorts of things they’re mentioning (beech trees, mammals, etc.) aren’t all that old in a geological sense. We’ve got more and better records of “recent” stuff, and there has also been less time for the plates to move into the current configuration. (It’s still significant, but it isn’t much compared to, say, a 2 billion year period.)
mahineintelligence@#1,
They explicitly examine that hypothesis because it seems so plausible but rule it out because we know where the poles were at various times and their location does not fit with the timeline of when they were tropical.