No, not moss, lichen, and grass.
Plate tectonics!
That split in the ground of Iceland shown above is where two tectonic plates are spreading apart. One side is headed eastward as part of Eurasia while the other side moves west along with the rest of the North American plate.
We know so little, it’s not yet possible to rule out the existence of extraterrestrial life, either now or in the past. But Earth does seem to be the only planet in the Solar System with an outer crust broken up into plates that jiggle around** as heat from the planetary core reaches the surface.
Opinions vary as to whether plate tectonics is necessary for the evolution of life, or not.
However, careful research over almost half a century has shown how the continents that seem eternally stable to us have actually wandered across Earth. It’s even possible to get an idea of where they’re going in the future.
**Mercury is active but a one-plate planet.
For reference, mammals and dinosaurs started out together in the Triassic. The avian dinosaurs are still around, as are mammals. Pay particular attention to India’s position when you see “K/T boundary” in this video; we’re going there tomorrow.
How can they reconstruct these movements? It’s complicated, but tracking what are called “magnetic anomalies” — the rocky record of Earth’s magnetic pole reversals — has helped a lot.
A pole reversal is not the end of the world in real life; it’s quite common, actually.
In the following video, which was made by and for nerds, these paleomagnetic anomalies, when they get to that part, show up as black bars for “normal” pole orientations (like today’s) and as white bars for “reversed” orientations, which is exactly what it sounds like — modern compasses would point south.
And as they say, the matching magnetic “stripes” on each side of the spreading ridge did prove that continents (and ocean seafloor) do move. It was quite a revolution in geology at the time!
As part of tomorrow’s Sunday Morning Volcano post, we’ll see how paleomagnetic data played a role in another geological paradigm, this one having to do with what might have killed off the dinosaurs 66 million years ago.
Featured image: Jen Robinson, CC BY 2.0.
Flight To Wonder 