Precariously-balanced rocks are helping to improve earthquake hazard predictions

Precariously-balanced rocks are helping to improve earthquake hazard predictions
Precariously-balanced rocks are helping to improve earthquake hazard predictions

Precariously balanced rocks, or PBRs, can be found throughout the world, identified by slender rocks balanced on a pedestal boulder.

There are a few ways they can form. PBRs can be the result of landslides or retreating glaciers, which deposit the rocks in the unordinary formations. They can also manifest when softer blocks erode, leaving the stronger ones behind.

While they look delicate, some of them — like the Brimham Rocks in Yorkshire or Chiricahua National Monument in Arizona — have survived countless earthquakes over thousands of years. Now, researchers from Imperial College London are taking a closer look at PBRs, because they are showing promise in helping scientists determine earthquake hazards more accurately.

The study’s authors say the construction of PBRs provides insight on the upper limit of earthquake shaking that has occurred in the area.

It’s this information that

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‘On the Rocks,’ ‘The Glorias’: Movies to Watch This Week

Thursday’s news that President Trump and several in his orbit have tested positive for coronavirus should probably give one pause before heading to cinemas this weekend — or anytime soon. This thing is contagious, people! And I say that as someone who got COVID-19 myself during an early March trip to Broadway.

But that doesn’t mean we don’t need cinematic distractions, and American distributors continue to deliver. I’ll be headed to the Mission Tiki Drive-in tonight to attend a Beyond Fest double feature. (The venue has four screens, and Sofia Coppola-Bill Murray reunion “On the Rocks” just opened on one of them.)

China closed its theaters long before the U.S., and they’ve reopened them earlier as well, which explains why it has taken this long to get what was supposed to be a major blockbuster timed to the Chinese New Year: “Jiang Ziya,” from the animation studio responsible for “Ne

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What wobbling rocks can tell us about nuclear safety

Precariously balanced rocks, or PBRs, record a history of things that haven't happened
Precariously balanced rocks, or PBRs, record a history of things that haven’t happened

We’ve all seen them; we’ve even taken pictures of ourselves pretending to hold them up or to push them over.

These are the precariously balanced rocks on a hill or a coastal cliff. It’s as if the gentlest nudge would send them tumbling.

In truth, the disturbance needed to unsettle the blocks is quite significant, and that got husband and wife geologists Drs Dylan and Anna Rood wondering about how these great stones could be used to decipher earthquake history.

Think about it: if a precariously balanced rock has held its position for 10,000 years without tipping over, it means the land around the stone hasn’t experienced shaking above a certain level in all that time.

“The turn of phrase we’re trying to coin is that these precariously balanced rocks, or PBRs, are an ‘inverse seismometer’,” explains

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Over 15 million years, weathering rocks reduced carbon dioxide levels and cooled Earth — ScienceDaily

The Greenland ice sheet owes its existence to the growth of an arc of islands in Southeast Asia — stretching from Sumatra to New Guinea — over the last 15 million years, a new study claims.

According to an analysis by researchers at the University of California, Berkeley, UC Santa Barbara and a research institute in Toulouse, France, as the Australian continent pushed these volcanic islands out of the ocean, the rocks were exposed to rain mixed with carbon dioxide, which is acidic. Minerals within the rocks dissolved and washed with the carbon into the ocean, consuming enough carbon dioxide to cool the planet and allow for large ice sheets to form over North America and Northern Europe.

“You have the continental crust of Australia bulldozing into these volcanic islands, giving you really high mountains just south of the equator,” said Nicholas Swanson-Hysell, associate professor of earth and planetary science

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Bright rocks on Ryugu reveal the asteroid’s violent past



a close up of a crater: Ryugu is approximately 0.6 miles wide and weighs 450 million tons.


© Provided by Popular Science
Ryugu is approximately 0.6 miles wide and weighs 450 million tons.

Asteroid Ryugu was somewhat of a mystery when astronomers first spotted it back in 1999. But we now know that the spinning-top-shaped body floating some 217 million miles from Earth is a loose assemblage of fragments from a collision between two asteroids held together by their aggregate gravity. Scientists estimate Ryugu formed between 10 million to 20 million years ago—practically yesterday in cosmic time, but how the asteroid came to be has remained largely unknown. Now, new research lays bare Ryugu’s recent violent past.



a close up of a crater: Ryugu is approximately 0.6 miles wide and weighs 450 million tons.


© JAXA/UTokyo/Kochi U/Rikkyo U/Nagoya U/Chiba Inst Tech/Meiji U/U Aizu/AIST
Ryugu is approximately 0.6 miles wide and weighs 450 million tons.

To uncover secrets about this rubble-pile asteroid, the Japan Aerospace Exploration Agency (JAXA) dispatched the fridge-sized spacecraft Hayabusa2 to Ryugu. For the study, published Monday in Nature Astronomy, scientists used

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