What On Earth (Sound) Was That #4? Seismic Music From Earth, Of Course…

Last week, we posted our first mystery sound in our latest installment of “What on Earth is That?”> We had some interesting guesses; one reader guessed the noisemaker was an earthquake and another guessed it was a calving ice. The answer is somewhere in the middle.

Giant icebergs may sink ships, but they also have their weaknesses. The sound you heard is the seismic signal recorded in October 2005 when a monstrous iceberg drifting off the coast of Antarctica’s Cape Adare crashed into the previously unknown Davey Shoal and broke apart. (Science News covered the collision in this July article.)  The full length of the audio file, sped up by a factor of 100, can be heard below. Within just 90 seconds, you can experience the full 2.5-hour event.

The “tap, tap, tap” is from cracks propagating through the massive chunk of ice. The effect is similar to what you hear if you drop ice cubes into a glass of water. The cracking noise crescendos until about 1:15, followed by a subtle hum resembling a muffled chain saw. That noise, from the phenomenon of ice pieces rubbing against each other, becomes most noticeable after the breakup. The same saw-like noise heard prior to 1:15 is thought to be the bottom of the berg rubbing on the shoal.

The audio comes from a study published June 18 in Journal of Geophysical Research. Looking at images from the Moderate Resolution Imaging Spectroradiometer on NASA’s Terra and Aqua satellites, the team noticed that between 1989 and 2005, at least three large bergs drifting off Cape Adare had suddenly stopped and broke apart. To discover the cause behind the bergs’ unusual behavior, the team turned to an iceberg called B15A.

Fortunately, plenty of information about the behemoth berg, which measured about 820 feet vertically and spanned some 75 miles by 19 miles, was available. Before the breakup, scientists had deployed an instrument package on B15A that included GPS and a seismometer. Later, a separate research group mapped the seafloor topography within the same area. “We knew from breakup that there ought to be something there,” said Seelye Martin, of University of Washington in Seattle, who led the study.

Overlaying the satellite images on the seafloor map, researchers recreated the series of events. On October 28, the berg hit the top of an underwater shoal 5.6 miles long and 705 feet below the surface at its highest point. The seismic information, heard in this post, matched the collision observed in the satellite imagery. Listening to the seismic music of the Earth is not new; geologists have long listened to the “rock music” of seismic waves from earthquakes. “But the iceberg has a very different signature,” Martin said. “Earthquakes sound like a big boom or slip, while in this case you can actually hear something breaking up.”

So what does it all mean? “It’s an interesting result, but it’s not a world changer,” Martin said. “We now know a little more about the obstacles — and sound — of some ill-fated icebergs leaving the Ross Sea.”

— Kathryn Hansen, NASA’s Earth Science News Team

Images and sound are courtesy of Seelye Martin, University of Washington

What on Earth is That? #2

(Please post your guesses and your name in the comments, and we’ll give the answer next week…)

Here at What on Earth, we’re constantly stumbling across interesting photos, videos, and audio clips from NASA’s exploration of our planet (be it from space, the field, or the lab.) Whether it’s a satellite montage captured from thousands of miles up, the roar of our B-200 research aircraft, or a microscopic view of a cloud droplet, there’s literally always something strange and wonderful passing across our desks.

To have a little fun (and spare all that fascinating stuff from the circular file), we’re going to post snippets of it every now and then, usually on Fridays. What we post will change, but the question to you all will always be the same: “What on Earth is that?”

Our only hints:

1) Our picks will always be related to Earth science in one way or another

2) It will have some relation to what we do at NASA.

We’ll give you a week to post your guesses, and we’ll post the answer the following Friday. In the meantime, check out the answer to What On Earth is That #1 here.  

What on Earth was That #2

Last week, we asked you to identify the flecks in a video posted to What on Earth is That #2, and we received all sorts of replies. The correct answer?

They may look like twinkling stars, but the shimmering flecks in this video are actually some of the tiniest particles in the ocean. This clip shows a complex mixture of the miniscule particles, both organic (living) and inorganic (nonliving) types. The large, fern-shaped specimen on the lower right is a type of phytoplankton. Some of the other flecks are likely bacteria and viruses.

Did you notice the slight vibrating motion that makes all the specks look like they’re flickering? That’s caused by random collisions with atoms, a phenomenon called “Brownian motion.” By measuring the distance each particle is pushed around, it’s even possible to infer particle size, which is important for understanding how the particles scatter sunlight in the ocean and for interpreting what ocean-observing satellites “see.”

Image and video Information: This sample was pulled from the Arctic’s Chukchi Sea on June 29, 2010, as part of NASA’s ICESCAPE mission. Kuba Tatarkiewicz, of the Scripps Institution of Oceanography, captured the action with a NanoSight instrument — a camera, microscope and viewing unit that the team adapted for use during the ICESCAPE oceanographic voyage.

-Kathryn Hansen, NASA’s Earth Science News Team

What On Earth Was That #3 ?

Last week, we showed you this mystery image. What was it? As a number of readers—including Brad Halderman (comment #3), Budi Prasteya (comment #7), and others—correctly guessed, you’re looking at a cropped version of one of the famous “sailing stone” tracks located on the Racetrack Playa in Death Valley National Park.

Since the 1940s, researchers have documented the distinctive furrows behind rocks at a number of dried out lake beds in Death Valley. Yet, nobody has actually seen the rocks move or proven definitively how the tracks form. Animals, earthquakes, and gravity have all been ruled out. Some researchers have suggested that the composition of the rock might be a factor, but tests have shown most of the boulders are run-of-the mill dolomites, basalts, limestones, gneisses, and schists that aren’t unusually slippery.

One of the best theories left standing: a combination of wind, mud, and ice. The area receives strong gusts of wind, and episodic bursts of rain that can create slicks of mud for brief periods. During cold weather, thin layers of ice can carpet the playa, and many scientists believe that wind, with the help of ice and mud underneath—has enough force to slide the boulders.

Though science journalist Brian Dunning has an interesting video that shows the movement of ice on the playa, no one has filmed wind actually moving the rocks. In the meantime, researchers (including a recent group sponsored by NASA) continue to investigate the phenomenon, as a NASA news story reported earlier this summer. 

–Adam Voiland, NASA’s Earth Science News Team

The image above is available through  NASA Goddard’s photo and video flickr feed

What On Earth (Sound) Is That? #4

Regular readers know the drill by now: Every other Friday we post a snippet of one of the many strange and fascinating bits of earth science that pass through our inboxes here at What On Earth, and then you all have a week to show off your science savvy by hazarding a guess (or two or three, if you’d like) in the comments. The last clue was an easy one, but we’re predicting this one–our first sound–will stump most of you.  Listen up, and prove us wrong…

Remember, the answer usually has something to do with….
a) Earth Science

Something on your mind? Email us suggestions and feedback at nasawhatonearth@gmail.com  

What On Earth is That? #3

(Please post your answers and your name in the comments, and we’ll give the answer next week….)

Here at What on Earth, we’re constantly stumbling across interesting photos, videos, and audio clips from NASA’s exploration of our planet (be it from space, the field, or the lab.). We’ve started posting snippets of them every now and then, usually on Fridays. What we post will change, but the question to you all will always be the same: “What on Earth is that?”

We’ll give you a week to mull it over and guess (use the comments), and we’ll post the answer the following Friday. Our only hints:

1) Our picks will always be related to Earth science in one way or another, and…

2) They’ll have some relation to what we do here at NASA.

NASA Earth Buzz: Soot, the Big Melt, and More

What on Earth Was That?
Last week, we asked you to identify the image on the left, and we received all sorts of replies. (Nope, it’s not an ant eating salt, spitting acid, or laying eggs). The correct answer? A microscopic view of soot from a wildfire. Check the original post for more details.

The Big Melt
A massive chunk of glacial ice tumbled from the shores of Greenland on July 6-7. The calving front – where the ice sheet meets the ocean – retreated nearly 1.5 kilometers (a mile) in a day. The mass of ice lost was nearly 1/8 the size of Manhattan. (NASA.gov)

Get a GRIP on This
A group of NASA researchers based in Florida and southern California won’t be sipping lemonade by the beach this summer. Instead, they’ll be chasing hurricanes with three NASA aircraft. (JPL News)

Record Setting Heat Sears Mid-Atlantic Region
After the whopper snowstorms this winter, a broiling heat wave has descended on the U.S. Mid-Atlantic. By June 28, Washington DC had endured 10 consecutive days where temperatures soared above 90°F (32° C). (Goddard DISC)

Climate Connections
Have questions about global warming and climate change? Tired of all the spin? Try these straightforward questions and answers from NASA scientists and science writers. (Earth Observatory)

Coming to a Theater Near You
You’d have to be living under a rock not to know that NASA studies the Moon, Mars, and deep space. But as a rocket-pack clad astronaut points out in a new video short at your local movie theater, a big part of our mission is to study Earth. (NASA Explorer)

A Porthole on the Arctic
Get a glimpse of science in action as NASA-funded researchers cruise the Arctic on an icebreaker. (NASA HQ Flickr)

Tweet of the Week
Floods kill an average of 140 people per year in the U.S., making it the number one severe weather killer. (SciJinks)

Aerosol image (left) from Peter Buseck, Arizona State University. Fire image (right) from Jim Ross, NASA Dryden Flight Research Center.