Today’s animated Google doodle celebrates the 127th birthday of Inge Lehmann. Most of you, like me, won’t know who she is, but Google is trying to bring to our attention accomplished but unsung women scientists. Lehmann (1888-1993; she lived to 104!) should certainly be of note, for she discovered the nature of the Earth’s core. As Wikipedia notes:

Inge Lehmann (ForMemRS; May 13, 1888 – February 21, 1993) was a Danish seismologist and geophysicist who discovered the Earth’s inner core.In 1936, she postulated from existing seismic data the existence of an inner core with physical properties distinct from the outer core’s and that Earth’s core is not a single molten sphere. Seismologists, who had not been able to propose a workable hypothesis for the observation that the P-wave created by earthquakes slowed down when it reached certain areas of the inner Earth, quickly accepted her conclusion.

Vox has a great explanation of how she used fast seismic waves (P waves) to discover that, contrary to what people thought, the Earth wasn’t just a mass of rock surrounding a fully molten core, but that the core itself had a solid inner nucleus:

Over the next few years, she closely analyzed this and other data sets. In the pre-digital age,her cousin later recalled, Lehmann would record the data on pieces of cardboard torn from boxes of oatmeal, and sometimes sat surrounded by them in her garden, puzzling over the numbers. Eventually, she had an idea: a solid inner core inside the soft, molten outer core, which would reflect some P-waves, causing them to end up in the shadow zone.

Her subsequent calculations, published in a 1936 paper simply titled P’ (as P-waves were then called), confirmed that the idea. “I then placed a smaller core inside the first core and let the velocity in it be larger so that a reflection would occur when the rays through the larger core met it,” she wrote, years later. “The existence of a small solid core in the innermost part of the earth was seen to result in waves emerging at distances where it had not been possible to predict their presence.”

And she lived long enough to do this as well:

In her later years, she used seismological data on underground nuclear explosions to discover another, subtler discontinuity in the upper mantle, at roughly 136 miles below the surface. Scientists still don’t fully understand this boundary, now called the Lehmann discontinuity.

She faced the usual barriers to women in science, and even in the 1950s they wouldn’t appoint her as a professor in Copenhagen. As Time Magazine notes:

Lehmann was educated at a progressive school that valued equal treatment between genders. But when her professional career took off she often faced discrimination for being a woman, once being quoted as saying, “You should know how many incompetent men I had to compete with — in vain.”

Click on the screenshot below to see the animation:

Reader Stephen Q. Muth (Butter‘s staff) sent me a link to the Australian Broadcasting Corporation’s video and report of a big eruption of the Colima volcano (Volcán de Colima) in southwest Mexico. It’s erupted several times in the last year, and the Spanish title of the video notes that this eruption happened yesterday. The ABC’s notes:

The active but isolated volcano is located approximately 500 kilometres west of the capital Mexico City and has erupted at least 30 times since 1585.

The vision was recorded on a permanent fixed webcam operated by Webcams De Mexico, which had placed a series of cameras in the area since the volcano’s last major eruptions in 2013 and 2014.

Colima experienced several significant eruptions in the late 1990s and scientific monitoring of the site began two decades ago.

Ash fell on towns up to 25 kilometres away from the volcano, but no lives or properties were under immediate threat.

Note what appears to be a pyroclastic flow moving down the volcano’s flanks. Nothing could survive that avalanche of hot gas and debris.

I’d dearly love to see something like this. I’ve watched the red molten lava from the volcano on Hawaii’s Big Island flow into the sea, making a huge cloud of steam and building up the island, but it wasn’t nearly as dramatic as the video above.

Over at Bad Astronomy, Phil Plait has posted a stunning video of a volcano exploding, and gives some background. The eruption was of Mount Tavurvur on the island of New Britain in Papua, New Guinea, and it occurred on August 29th. It was captured on video by Phil McNamara, and is now on YouTube.

Phil’s take:

This eruption was smaller in comparison, but holy cow. It was still amazing. In the video you can see lava blasting upward hundreds of meters, falling apparently slowly due to distance. Given the timing delay of the shock wave — 13 seconds or so — so the folks on the boat were just over 4 km away (2.5 miles).

This video was posted two days ago, and already has more than 3 million views. No surprise!

Here are before and after photos from NASA’s Earth Observatory website: notice all the green that has disappeared. The site also gives a lot more information about the eruption.

Before:

After:

h/t: Marcel

The Earth is 4.54 billion years old. We know that not from radiometric dating of rocks on our planet, as the oldest rocks haven’t yet been found, but from dating meteorites that fall on earth from the solar system, which formed around the time Earth did.

But of course that’s not fodder for creationist, for we also have old homegrown rocks, clearly showing that the earth is far older than, say, 10,000 years.

And now we’ve found the oldest bit of Earth yet. As ZME Science and a new paper reported yesterday, it’s a zircon crystal from Australia dated at 4.37 billion years.  The paper with the original report is in Nature Geoscience (reference and link below; free download [I think]).

Here it is.

And it’s not big:

The geological relic indicates, for one, that Earth’s crust formed shortly after the planet stabilized and formed. John Valley, a University of Wisconsin geoscience professor who led the research, said the findings suggest that the early Earth was not as harsh a place as many scientists have thought.

No doubt, this is an extraordinary find, however, the untrained eye would have surely missed it. Measuring about  200 by 400 microns, or roughly two times the width of a human hair, the tiny gem was luckily retrieved by geologists in 2001 from a rock outcrop in Australia’s Jack Hills region.

The researchers used two ways to check the date: radiometric uranium-lead dating and atom-probe tomography, which uses the actual position of individual atoms in the crystal to check the accuracy of the U/Pb method. I’ll let the readers enlighten us about how this method works, as I don’t fully understand it myself; but the upshot is that the APT dates comport with the uranium lead dates, making hash of the creationist objection that dating methods are unreliable, even in the hands of experts.

The APT was used because of worries that U-Pb dating might be off because lead might have moved within the crystal.  This shows that scientists do know the ways that dating could be off, and have checks for them. And APT showed no evidence of such movement. I’ll show that by simply posting part of the paper’s abstract:

h/t: Ant

______

Valley, J. W. et al. 2014. Hadean age for a post-magma-ocean confirmed by atom-probe tomography. Nature Geoscience. doi:10.1038/ngeo2075