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Asteroid impacts 3.3 billion years ago may have boiled the oceans

The chaos in the early Solar System was fiendish. Even after the planets had coalesced, there was more than enough rubble left behind to cause frequent and violent impacts that would have rocked the Earth’s youthful crust. After a phase of intense bombardment between about 4.1 and 3.8 billion years ago, things on the asteroid collision scene calmed down. Relatively speaking…

We don’t know exactly when life first developed on Earth, but we know it was present by 3.4 billion years ago. We don’t know if life was present to suffer from the earlier period of bombardment, but we know it was around for any impacts that followed. So what kinds of extraterrestrial punches did life take after 3.4 billion years ago?

A new study by Stanford’s Donald Lowe and Louisiana State University’s Gary Byerly examines a fascinating record of major impacts in South African rocks around 3.3 billion years old. Eight impact layers have been identified in these rocks, each containing sand-sized blobs of rock that solidified after the impact vaporized bedrock. The layers also show signs that they were hit by tsunamis shortly afterward.

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How the Indian Ocean ended up stealing the atmosphere’s heat

If you’re climate-curious, you’ve probably seen some of the research revealing why globally averaged surface air temperatures have warmed less quickly over the last decade or so than they did in the 1990s. The oceans are the dominant heat reservoir in the climate system, and they have been in a greedy phase lately, giving up a little less warmth to the atmosphere.

This has largely been the product of a string of La Niñas in the Pacific driven by stronger easterly trade winds. In those conditions, a pool of colder deep water takes the place of warmer surface water in the eastern Pacific. The warmer water that would normally be there is instead moved westward and mixed downward.

But here’s the puzzling thing: while records show a build-up of heat below the surface, the heat's generally not in the Pacific. If that’s where so much downward mixing is taking place, where is the warm water going?

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Hot lava flows in a parking lot—in upstate NY

Back in 2012, we pointed you to an awesome project at Syracuse University that creates artificial lava flows for science, art, and outreach. They don’t use some mild, room-temperature stand-in for lava, they do it the artisanal way:  melting small batches of basalt in a serious furnace and pouring out the incandescent results. I’ve been hoping to see it for myself ever since, and recently I got the chance to tag along with a group of volcanology students from Colgate University, who were designing and running their own lava experiments for class.

The furnace is surprisingly well-insulated, disguising the fact that it holds molten rock heated to over 1,200 degrees Celsius. It does emit a low, ominous roar, however, as it consumes natural gas to feed its fire. Once poured out, the lava quickly loses heat—it solidifies in just a minute or so, though it still remains incredibly hot long after. Because it solidifies so quickly, it forms amber-black volcanic glass riddled with bubbles of gas that were unable to escape.

The lava pours are as mesmerizing and beautiful as they are geologically exciting. And they’ve probably shocked many a bus rider staring dully out the window while passing the art building.

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Bias in satellite measurements hid recent sea level rise acceleration

Measuring changing sea level precisely enough to say something interesting about it is an extremely difficult task. Many places have tide gauges that have been making measurements for ages, but regional sea level patterns are variable, in part because the coastline itself can be rising or subsiding in some locations.

Satellites sound like the ideal technological solution, but we need to measure the change in distance between the sea surface and a satellite hurtling by over 1,300 kilometers overhead very accurately. Getting accurate enough to detect an average change of about three millimeters over the course of a year has its challenges.

Even if a satellite holds its orbit perfectly, you still have to worry about subtle shifts in the measurements reported by your electronics as they bounce radio waves off the planet. Those shifts are called “bias drifts”—gradually increasing errors that mess with the trend you’re trying to reveal.

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Don’t (just) blame Facebook: We build our own bubbles

We’ve all heard (or expressed) the concern that the Internet allows us to choose only those sources that agree with our ideology. The same “echo chamber” concern applies to social media, with an added twist—platforms like Facebook filter the content we’re shown based on what an algorithm thinks we’ll want to see. Is Facebook going to make sure we don’t have to see articles shared by the few friends we have that might challenge our views?

Given the fact that all your actions on Facebook leave a data trail, this is logistically a much easier question to answer than most. Several researchers at Facebook, led by Eytan Bakshy and Solomon Messing, dug into all that data to investigate.

They had plenty to work with. They limited the study to just the US users over 18 who listed political affiliations on their profile, logged in at least four times a week over the latter half of 2014, and clicked on at least one news/politics link. But they were still left with a tad over 10 million people to work with. (Names were stripped from the data, but in case you’re wondering, this is the kind of thing covered by the data policy you agree to when you sign up. Unlike the controversial “mood” study last year, there was no manipulation of content on Facebook for this study.)

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Growing mystery—getting to the bottom of the highest peak in the Lower 48

Visitors to Yosemite National Park in California’s Sierra Nevada Mountains often ask Park Geologist Greg Stock the same questions: “What’s up with this mountain range? Is it growing or shrinking? How old is it?” But 150 years ago, people considered the same questions, though the reason they were asking them happened to be very different—those visitors were out to strike it rich on California gold.

Mountain ranges, those places where the horizon wins its war with the sky, appear so imposing that they demand explanation even to those unaccustomed to geologic curiosity. Many ranges have origins simple enough that school kids can recite the basic sequence of events. Two tectonic plates smash together like an extremely slow-motion car accident, with a crumple zone in the middle. Or in another flavor of convergence, an oceanic plate is subducted beneath its partner, fueling volcanoes. The first can describe the Himalayas; the second, the Andes.

But the Sierra Nevada Mountains, naturalist John Muir’s brilliant muse, remain a geologic puzzle not so easily solved despite the work of generations of geologists. The North American Plate and the Pacific Plate don’t collide along most of the California coast, they slip past each other horizontally. The Sierra is not an active line of rock-pouring volcanoes like the Cascades to the north. Yet there it is, with all the subtlety of a sledgehammer—Mount Whitney, the highest point in the Lower 48, towering 10,000 feet above neighboring Owens Valley, which is just about 50 miles from Death Valley, the lowest point in North America. The Sierra is a defining feature of the most populous state in the US, but we still don't quite understand it.

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Three Pennsylvania wells likely contaminated by fracking

Public arguments about fracking (at least among those who have heard of the natural gas production technique) have become contentious—a situation not helped by the technical and complicated topic. Lots of information and claims fly around, but there's little in the way of an established framework to help make sense of them.

Claims that fracking has contaminated water can be difficult to resolve, and some turn out to be unrelated to fracking. Geology differs from place to place in important ways that have to be taken into consideration when analyzing water. Regulations governing fracking vary from state to state, too. And the practice has been scrutinized at a level we haven’t subjected conventional oil and gas production to, meaning we might be discovering problems that are common to other techniques.

The illusion of simplicity

Still, we occasionally get a relatively simple case, even if its broader implications are minimal. In the summer of 2010, three nearby homes in northeast Pennsylvania started having disturbing problems with their water wells. Methane was seeping up—in one case accumulating to levels that necessitated evacuating a home due to the explosion risk—and the wells were muddy and foaming. (A nearby river even began bubbling a few months later.)

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Ancient Native American city may have been done in by Mississippi floods

Long before Europeans arrived to settle St. Louis, an impressive human construction stood on the eastern side of the Mississippi River. It was the Native American city of Cahokia. At its height, tens of thousands lived in and around Cahokia, leaving behind great earthen mounds as testament. The largest still stands about a hundred feet tall today, minus what was likely a temple that once adorned its crest.

Like all societies that disappear, we naturally wonder what brought this one to an end around 1350 AD, after a run of hundreds of years. Several familiar scenarios have been proposed: drought, over-exploitation of natural resources, and conflict. However, rather than the onset of a drought, it may have been the end of a dry period that did in Cahokia.

Cahokia was built near the Mississippi River and within its floodplain, and it wasn't protected by any of the levees and flood control structures that exist today. Samuel Munoz of the University of Wisconsin-Madison and a group of collaborators set out to find a record of floods on the Mighty Mississippi that might have impacted the denizens of Cahokia. Some previous work with a sediment core from a nearby lake contained what appeared to be a flood-deposited layer from around 1200 AD—the start of Cahokia’s precipitous decline. To find out more, they collected a second core from another floodplain lake about 200 kilometers downstream and focused on reconstructing the flood history in detail.

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Salty groundwater supports life in Antarctica’s extreme Dry Valleys

It’s easy to forget that Antarctica is a desert, given that very nearly the entire continent is covered by a thick sheet of ice. But snowfall is very slow to add to that white mantle, as the cold air and ocean around Antarctica aren't exactly going to provide prodigious production of atmospheric moisture.

As its name implies, one of the driest and weirdest locales in a very weird continent is the McMurdo Dry Valleys. This area near the coast is the biggest chunk of Antarctica not covered by ice. Bare rock is found there, and not a whole lot else.

There is, however, an unusual feature known as Blood Falls. At the end of Taylor Glacier, which spills into one of the Dry Valleys (Taylor Valley, actually), a mysterious red trickle of salty, iron-rich water periodically stains the ice as it spills out like blood from a wound. It’s a good thing that it isn’t a paranormal message from ghosts warning researchers to leave the valley, because it has had the opposite effect—it draws them in. In 2012, for example, biologists looking for signs of life eking out an existence in the Dry Valleys discovered that Blood Falls contained an impressive community of microbial life.

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When did geology open a road for species to move between the Americas?

We recently covered a study indicating that the Isthmus of Panama docked with South America earlier than we once thought, connecting North and South America and separating the Pacific from Caribbean waters. Instead of linking up just 3 million to 4 million years ago, those researchers found evidence that a connection was present by 14 million years ago.

One of the loose ends created by the new result was that the exchange of North and South American species had also been pinned at about 3.5 million years ago. That raised the question of why species waited to migrate. One possible explanation is that migrations were triggered by a climatic cooling around 3 million years ago.

Well, a new study led by Smithsonian Tropical Research Institute and University of Gothenburg researcher Christine Bacon re-examines the evidence for the exchange of species, dubbed the Great American Biotic Interchange, and suggests that there might not be much of a delay to explain.

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