Science & Technology

Earth rolls over 84 million years ago, new evidence suggests

We know that True polar wander (TPW) can tilt the entire planet or satellite with respect to the axis, but it is not entirely clear how often this happened to Earth.

Currently, new studies provide evidence of such tilting events that occurred about 84 million years ago. dinosaur I still walked the earth.

Researchers analyzed Italian limestone samples dating back to the Late Cretaceous (10.5 million to 65.5 million years ago) and sought evidence of changes in magnetic records indicating the occurrence of TPW.

Bacterial fossils trapped in rocks form chains of minerals Magnetite, Provides some of the most compelling evidence of true polar wander in the Late Cretaceous to date – and it may help resolve decades of scientific debate.

What does true polar wander look like? (Victor C. Tsai / Wikimedia Commons / Public Domain)

“This observation represents the latest documented large-scale TPW and challenges the notion that the spin axis is nearly stable over the last 100 million years,” the researchers explain. .. paper..

The Earth is composed of an inner core of solid metal and an outer core of liquid metal, with a solid mantle and crust (surface) moving slowly over the liquid metal. The Earth’s magnetic field generated by the outer core is recorded in rocks as studied here.

True polar wander is when the geographic poles shift so much that the wrapping outside the Earth tilts.Nothing really changes with respect to the Earth’s magnetic field, but changing rocks record differently. Paleomagnetic data As they move.

The data reveals the distances to the geographical poles of the north and south, allowing researchers to plot where these poles actually are. A perfectly vertical field means that the rock was at the pole, and a perfectly horizontal field indicates that it was at the equator.

“Imagine looking at the earth from space.” Geologist Joe Kirshbink says, From Tokyo Institute of Technology, Japan. “True polar wander makes the Earth appear to be tilted sideways. What is actually happening is the entire planetary rock shell, the solid mantle and crust, rotating around the liquid outer core. That’s what you’re doing. “

tpw 02Part of the extraction work. (Ross Mitchell)

Studies show that there was an inclination of about 12 degrees on Earth about 84 million years ago, which was corrected relatively quickly – within about 5 million years, the equivalent of a “space yo-yo” in the researchers’ words. increase.

This means that these rocks, and Italy itself, traveled towards the equator before falling.another Recent research It suggests that a similar slope is currently underway. Climate change It affects the earth.

The team says it Previous research It only did not collect sufficient data from geological records, implying that true polar wander did not occur in the Late Cretaceous. This cannot be said in the latest research.

“That’s one of the reasons why it’s so refreshing to see this study with abundant and beautiful paleomagnetic data.” Geophysicist Richard Gordon says, From Rice University in Houston, was not involved in the study.

The study is published at Nature Communications..

Earth rolls over 84 million years ago, new evidence suggests Earth rolls over 84 million years ago, new evidence suggests

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