National Geographic explains:

Yellowstone is a volcano, and not just any volcano. The oldest, most famous national park in the United States sits squarely atop one of the biggest volcanoes on Earth . . . The last three super-eruptions have been in Yellowstone itself. The most recent, 640,000 years ago, was a thousand times the size of the Mount St. Helens eruption in 1980, which killed 57 people in Washington. But numbers do not capture the full scope of the mayhem. Scientists calculate that the pillar of ash from the Yellowstone explosion rose some 100,000 feet, leaving a layer of debris across the West all the way to the Gulf of Mexico. Pyroclastic flows-dense, lethal fogs of ash, rocks, and gas, superheated to 1,470 degrees Fahrenheit-rolled across the landscape in towering gray clouds. The clouds filled entire valleys with hundreds of feet of material so hot and heavy that it welded itself like asphalt across the once verdant landscape. And this wasn't even Yellowstone's most violent moment. An eruption 2.1 million years ago was more than twice as strong, leaving a hole in the ground the size of Rhode Island.

It's worth reading the rest of this article - it beautifully captures the pyrotechnic scientific mystery that is Yellowstone Park. Photographer Mark Thiessen captured the blowholes where Yellowstone lets off scalding, mineral-rich water.

via National Geographic (Thanks Marilyn Terrell!)

Over at Discovery News, io9 pal Michael Reilly reports on a study about the exact ingredients required to whip up a mass extinction event like the one in the Permian-Triassic, which destroyed 90 percent of life on the planet. Researchers Nan Arens and Ian West argue that a mass extinction is caused by a combination of "pulse" events - short, sharp shocks like meteor strikes - and "press" events like millennia-long climate change from constantly-erupting volcanoes. Arens and West base their assertions on intensive study of mass extinction events in Earth's past.

Asks Reilly:

Can researchers come up with a "Grand Unified Theory" of ancient apocalypse?

West and Arens think so. They combed the last 300 million years of geologic record, noting impact craters, massive eruptions, periods of ancient climate change, and then comparing them to extinctions. The rate at which species die off spiked dramatically, they found, when a "pulse"-type event occurred within a million years or so of a "press."

The theory fits well for the dinosaurs. Around the time of their demise 65 million years ago, a comet slammed into the Yucatan Peninsula and a huge volcano, the Deccan Traps, was erupting in what is today India.

But other extinctions are problematic. The greatest dying in geologic history, the Permian-Triassic extinction, killed 90 percent of all life on Earth, but there is no record of an impact. Instead, all signs point to a 200,000-year-long volcanic eruption in Siberia as the murder weapon.

Arens and West's work also suggests that Earth may be headed for a new mass extinction, because climate change is a common form of press event, and all we really need is one big pulse event to reach the total apocalypse tipping point.

SOURCES:
Discovery News

Paleobiology

This week in San Francisco, researchers at the annual meeting of the American Geophysical Union presented a case for Titan's cryovolcanism, which is today's awesome term of art from the world of geophysics. According to Yahoo News:

Scientists believe methane gas breaks up in the atmosphere and forms clouds that rain methane.

The source of methane remains a mystery. Scientists favoring the volcanic theory say methane eruptions from Titan's interior could explain the moon's smoggy atmosphere.

Data from the spectrometer instrument on Cassini found bright spots on two regions on Titan. In one of the regions, scientists found evidence of ammonia frost that they interpreted as coming from the interior.

You can see one of those dark spots in the image from Titan above.

[via Yahoo News]

Reporting for the Anchorage Daily News, Beth Bragg captures the odd excitement of local volcano researchers:

"Things are very hopping," research geophysicist Peter Cervelli of the Alaska Volcano Observatory said Monday afternoon. "We've been ramped up 24/7 for nine days because of Okmok, and to have Cleveland suddenly go off keeps us busy. I'm not sure I'd describe it as fun, but it's certainly exciting."

I love any geophysicist who describes a volcanic eruption as "very hopping." Images via AP.

Dueling Volcanoes [Anchorage Daily News via Knight Science Journalism Tracker]

Mercury is about twice as big as pluto, but still is the smallest object called a "planet" orbiting the Sun. The question is: how much smaller will it get? It will never get anywhere near as small as the former ninth planet, but will the IAU see fit to demote it too as it continues shrinking? Only time will tell.

Meanwhile, Mercury's molten iron core continues to cool, shrinking the planet from the inside. Small particles of solid iron 'snow' rain down toward the ever-widening solid core. But even as the solid grows it's denser than the liquid and so takes up less space. This has been going on probably for billions of years and over time the shrinkage has caused Mercury's crust to buckle and fold up on itself, as seen here (that y-shaped fracture in the left side of the image is a huge fracture in the rock. The whole picture is about 200 kilometers wide):

(from NASA)

On the right hand side of the image, the craters with the soft-looking rims appear to be old impact basins that have been filled in with lava, indicating the Mercury once had some serious volcanoes exploding on its surface. Why did the volcanoes die off? Mercury cooled off. Just like on Mars and the Moon, Mercury was fiery when it first came into being, but lost its heat in the roughly 4.5 billion years since, silencing is volcanic activity. Earth is cooling in a similar way and in a few billion years it will get too cold for volcanoes too. When it does it will go quiet forever.

Source: Science, NASA, via LA Times