标签 火山口 下的文章

阿克拉曼火山口, 澳大利亚 The Acraman crater, Australia (© USGS/NASA Landsat data/Orbital Horizon/Gallo Images/Getty images)

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阿克拉曼火山口, 澳大利亚 The Acraman crater, Australia (© USGS/NASA Landsat data/Orbital Horizon/Gallo Images/Getty images)

Will we be ready for the 'big one'? 我们准备好迎接“大挑战”了吗?

Asteroid Day

Today is Asteroid Day, and it's a reminder that as our planet follows its path around the sun, it encounters a lot of stuff. Science tells us that, every day, Earth's atmosphere is hit with roughly 100 tons of dust and particles the size of a grain of sand. And every year, at least 30 small meteors make it through, only to burn up before touching the ground. NASA says it's pretty much guaranteed that at least one of them will be about the size of a car. As time progresses, the likelihood increases that even larger celestial rocks will hit the ground and cause significant damage.

Across the globe, there are plenty of reminders of this in the form of craters, like the one in today's photo. The Acraman crater is a point of impact in South Australia. It's believed to have been created about 590 million years ago when hit by an asteroid with a diameter that could have been as large as 56 miles across. For comparison, the asteroid thought to have killed the dinosaurs 66 million years ago was 6.2 miles across. NASA says that an asteroid the size of a football field would cause significant damage. One that could really threaten civilization hits every few million years. Hopefully, with Asteroid Day being observed across 78 countries since its inception in 2015, we'll be prepared when the 'big one' shows up.




Manicouagan火山口, 魁北克加拿大 Manicouagan Crater in Québec, Canada (© Universal History Archive/Universal Images Group via Getty Images)

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Manicouagan火山口, 魁北克加拿大  Manicouagan Crater in Québec, Canada (© Universal History Archive/Universal Images Group via Getty Images)

An impactful day

We'll be the ones to drop the news on you: It's Asteroid Day! Today you're invited to explore a realm of science usually encountered only through white-knuckle action flicks: Asteroid impact avoidance, or the study of what the heck we do if we spot a big chunk of space junk hurtling right at Earth. That's right, don't worry: People somewhere are coming up with plans for this.

Good thing, because as our photo shows, asteroid impacts do happen. Manicouagan Crater, aka the 'eye of Québec,' was formed by a 3-mile-wide meteorite that hit Earth about 215 million years ago. Much more recently, an explosive meteoroid leveled 800 square miles of Siberian forest in what's called the Tunguska event. It was 113 years ago today, and Asteroid Day's date was chosen in recognition.

So, if you find yourself casting paranoid glances at the sky today, maybe do a little searching on how scientists are learning to prevent potential impacts. Proposed plans involve everything from altering an asteroid's course via a gravitational field, to delaying its approach by attaching rocket thrusters, to good old-fashioned blowing it up. Yay science!





火山口湖,俄勒冈州 Crater Lake in Oregon (© Steve Bloom Images/Alamy)

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火山口俄勒冈州 Crater Lake in Oregon (© Steve Bloom Images/Alamy)

Travels to the Oregon deep

We're looking out on the deepest lake in the US. Crater Lake, the centerpiece and namesake of the only national park in Oregon, goes down to depths of 1,943 feet—that's enough room to stack three-and-a-half Washington Monuments end to end. Fed mainly by snowfall, this pristine, crystal blue lake came into this world with a bang. Sometime around 5700 BCE, Mount Mazama erupted, losing roughly 3,000 feet of its height. The volcano blew out so much molten rock that it left a giant depression that gradually filled with water, giving us this serene scene today.

Crater Lake National Park is open to visitors year-round, but in the winter many of the facilities as well as the road circumventing the lake are closed. But, as our picture captures so beautifully, the snowy view is worth a (socially distant) trip.