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Human Noise Reaches to the Deepest Part of the Ocean

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If a ship passes over the deepest part of the ocean but there’s nobody there to hear it, does it still make a sound? It sure does. New audio recordings from the Mariana Trench, the deepest part of the world's oceans, have captured the sounds of whales, distant earthquakes, storms, and even ships passing tens of thousands of feet above.

Challenger Deep is a valley inside the trench, seven miles below the surface of the ocean. To give you some idea of just how deep that is: If you chiseled Mount Everest off its foundation and dropped it into the Challenger Deep, the mountain’s peak would still be a mile underwater.

Image credit: Center for Coastal and Ocean Mapping - Joint Hydrographic Center

The valley is of great scientific interest, but its distance from the surface and the tremendous amounts of pressure down there have made it hard to study. A team of engineers created a special titanium-coated hydrophone, or underwater microphone, but even they weren’t sure it would work.

"We had never put a hydrophone deeper than a mile or so below the surface, so putting an instrument down some seven miles into the ocean was daunting," engineer Haru Matsumoto said in a press release. "We had to drop the hydrophone mooring down through the water column at no more than about five meters per second. Structures don't like rapid change, and we were afraid we would crack the ceramic housing outside the hydrophone." 

Researchers dropped the hydrophone over the side of a ship. More than six hours passed before the equipment reached the valley floor, but once it did, it began recording. When the research team collected the hydrophone, they brought up 23 days' worth of noise from the bottom.

"You would think that the deepest part of the ocean would be one of the quietest places on Earth," chief project scientist Robert Dziak said in the press release. "Yet there really is almost constant noise from both natural and man-made sources. The ambient sound field at Challenger Deep is dominated by the sound of earthquakes, both near and far was well as the distinct moans of baleen whales and the overwhelming clamor of a category 4 typhoon that just happened to pass overhead. There was also a lot of noise from ship traffic, identifiable by the clear sound pattern the ship propellers make when they pass by."

Curious what those “distinct moans” and that “overwhelming clamor” sound like? Listen for yourself:

The Challenger Deep soundtrack is impressive on its own, as both scientific data and a demonstration of human ingenuity. But it’s also an indicator that our effects on the environment reach farther than we could have imagined. Scientists now know that anthropogenic (human-created) sound wreaks havoc on marine ecosystems, from the largest whales to the smallest fish eggs on coral reefs. From city streets to the Challenger Deep, our noise is more than just noise.

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Air Quality in American National Parks and Big Cities Is Roughly the Same
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iStock

National parks usually have more vegetation, wildlife, and open spaces than urban areas, but the two don't look much different when it comes to air quality. As City Lab reports, a new study published in Science Advances found that U.S. national parks and the nation's largest cities have comparable ozone levels.

For their research, scientists from Iowa State University and Cornell University looked at air pollution data collected over 24 years from 33 national parks and the 20 most populous metro areas in the U.S. Their results show that average ozone concentrations were "statistically indistinguishable" between the two groups from 1990 to 2014.

On their own, the statistics look grim for America's protected areas, but they're actually a sign that environmental protection measures are working. Prior to the 1990s, major cities had higher ozone concentrations than national parks. At the start of the decade, the federal government passed the Clean Air Act (CAA) Amendments in an effort to fight urban air pollution, and ozone levels have been declining ever since.

The average ozone in national parks did increase in the 1990s, but then in 1999 the EPA enacted the Regional Haze Rule, which specifically aims to improve air quality and visibility in national parks. Ozone levels in national parks are now back to the levels they were at in 1990.

Ground-level ozone doesn't just make America's national parks harder to see: It can also damage plants and make it difficult for human visitors to breathe. Vehicles, especially gas-guzzling trucks and SUVs, are some of the biggest producers of the pollutant.

[h/t City Lab]

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India's Supreme Court Demands That the Taj Mahal Be Restored or Demolished
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iStock

The Taj Mahal is one of the most recognizable monuments on Earth, but over the years it's started to look less like its old self. Smog and insect droppings are staining the once pure-white marble exterior an unseemly shade of yellow. Now, The Art Newspaper reports that India's Supreme Court has set an ultimatum: It's threatening to shut down or demolish the building if it's not restored to its former glory.

Agra, the town where the Taj Mahal is located, has a notorious pollution problem. Automobile traffic, factory smoke, and the open burning of municipal waste have all contributed to the landmark's increasing discoloration. Insects and acid rain also pose a threat to the facade, which is already crumbling away in some parts.

India's highest court now says the country's central government must seek foreign assistance to restore the UNESCO World Heritage Site if it's to remain open. Agra's state of Uttar Pradesh has taken some steps to reduce pollution in recent years, such us banning the burning of cow dung, which produces heavy brown carbon. In 2015, India's Supreme Court ordered all wood-burning crematoriums near the Taj Mahal to be swapped for electric ones.

But the measures haven't done enough to preserve the building. A committee led by the Indian Institute of Technology in Kanpu reportedly plans to investigate the exact sources of pollution in the area, a process that will take about four months. The Supreme Court plans check in on the status of site every day from July 31.

Air pollution isn't the only factor damaging the Taj Mahal. It was constructed near the Yamuna River in the 17th century, and as the water gradual dries up, the ground beneath the structure is shifting. If the trend continues it could lead to the building's total collapse.

[h/t The Art Newspaper]

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