A new study is revealing our planet took a strange turn about 84 million years ago. It tilted by 12 degrees.
"True polar wander (TPW), or planetary reorientation, is well documented for other planets and moons and for Earth at present day with satellites, but testing its prevalence in Earth’s past is complicated by simultaneous motions due to plate tectonics," write the researchers in their study.
"Here we present a new high-resolution palaeomagnetic record from two overlapping stratigraphic (regarding rock layers and layering) sections in Italy that provides evidence for a ~12° TPW oscillation from 86 to 78 Ma. This observation represents the most recent large-scale TPW documented and challenges the notion that the spin axis has been largely stable over the past 100 million years."
How did they come to this conclusion?
Scientists can figure out which tectonic plates were where millions of years ago by looking at what's known as paleomagnetic data. Paleomagnetism is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. This record provides information on the past behavior of Earth's magnetic field.
The study authors collected ancient limestones from Italy and analyzed their magnetic alignment only to discover that Earth's crust was moving about 3 degrees every million years during its tilt and tilt back.
"In this work, we present >1000 palaeomagnetic data from the Scaglia Rossa limestone as a rigorous test of the ca. 84 Ma TPW event. Samples were collected from two parallel stratigraphic sections as a test of reproducibility," write the researchers.
"Modern demagnetization and analytical palaeomagnetic methods were employed, including state-of-the-art rock magnetic experiments that shine new light on the origin of the stable palaeomagnetic remanences of the Scaglia Rossa limestone. Both stratigraphic sections definitively confirm the existence of ca. 84 Ma TPW."
The researchers further write that their data confirms not only a single tilt shift at this time, but a “roundtrip” tilt oscillation where the pole excurses and then returns back to its original pole position. Well, there you have it, folks. Our planet tipped over and came back again!