Tag Archives: crater

Indian lake turns pink almost overnight

The water of Lonar Crater Lake in India is typically deep-green, but it has recently turned pink — almost overnight — and nobody knows why.

Image credits Maharashtra Tourism / Twitter.

I think it goes without saying that large bodies of water don’t typically just change color, but Lonar Lake did. The Indian landmark was a tourist attraction before, but it has now become a hotbed of visitors eager to see its bright pink waters.

Exactly what caused this change, or why it happened so fast, is as of yet unknown. 

Crater lake

The color change was captured best by two NASA images taken on May 25 and June 10 with the Operational Land Imager (OLI) on Landsat 8. The waters changed color over the span of a few days, according to NASA.

“India’s Lonar Crater began causing confusion soon after it was identified in 1823 by a British officer named C.J.E. Alexander,” NASA says of the crater.

“Lonar Crater sits inside the Deccan Plateau—a massive plain of volcanic basalt rock leftover from eruptions some 65 million years ago. Its location in this basalt field suggested to some geologists that it was a volcanic crater. Today, however, Lonar Crater is understood to result from a meteorite impact that occurred between 35,000 and 50,000 years ago.”

Lonar Lake is located in India’s west-central state of Maharashtra, and it isn’t the only pink lake we know of. Lake Hillier in Australia is permanently pink, with the color likely produced by Halobacteriaceae, pink-colored microorganisms that inhabit its salty waters, and a species of single-cell algae called Dunaliella salina. When stressed, D. salina releases carotenoids (a class of molecules that give plants such as carrots their color), including an orange-red colored one.

But Lake Hillier doesn’t change its color — it’s always pink. One possible explanation of the shift in Lonar Lake could be a rise in salinity due to a long period of warm, dry weather promoting evaporation, as is the case with Lake Urmia in Iran (whose color changes seasonally). In other words, it could be going to a very dramatic and pink algal bloom. A chemically-induced change hasn’t been ruled out yet, however.

Lonar Lake is quite visually striking and remote, and as such is dotted with small temples along its rim. Due to its salinity and alkaline nature, the late doesn’t house much wildlife. It was the discovery of maskelynite (a type of natural glass produced during asteroid impacts) revealed its true origin.

The lake has always been unique, and this change in color only adds to its quirkiness. Exactly what caused this change is still unknown — as is whether the colors will switch back or not. But researchers will undoubtedly try to find out what’s going on here, and will keep the lake under observation while drawing samples to analyze.

Monitoring Volcanic Craters with Infrasound “Music”

Volcanic craters act as giant horns that emit intense low-frequency sounds. Changes in this infrasound may be used to track rising lava lakes and identify signals of future eruptions.

Eruption of Villarrica Volcano. Credit: Wikimedia Commons.

Eruption of Villarrica Volcano. Credit: Wikimedia Commons.

Chile’s Villarrica volcano erupted suddenly on 3 March 2015, disgorging a lava fountain more than 2 kilometers high. The eruption—Villarrica’s first in 30 years—was unexpected in terms of its rapid onset and its violence. It was also remarkably short-lived. Within an hour, the explosive activity had ended. Within about a month, the volcano had returned to its usual state, which featured a roiling lava lake situated deep within the steep-walled summit crater.

Forecasting such violent eruptions is the holy grail for applied volcano science. Toward this objective, volcanologists deploy seismometers to detect tremors, tiltmeters and GPS to identify swelling, and multispectral detectors to monitor gas and heat output. Infrasound sensors, which record the low-frequency sounds produced by volcanoes, are an increasingly important component of this diverse tool kit.Volcanologists traditionally have used infrasound surveillance to both count explosions and track eruption intensity, important capabilities when the view of the volcano is obscured [Fee and Matoza, 2013; Johnson and Ripepe, 2011]. Recent studies have demonstrated that infrasound monitoring can also be used to identify important eruption precursors [e.g., Ripepe et al., 2018]. Villarrica gave indications of its unrest through the changing character of its infrasound. We now recognize that Villarrica’s changing sounds provided a warning that lava was rising within the crater [Johnson et al., 2018a].

These observations were made serendipitously as part of a National Science Foundation–sponsored research project, Volcano Acoustics: From Vent to Receiver, that studied the long-distance propagation of the infrasound produced at Villarrica. During the 2015 field expedition, we installed sensors on the summit and flanks of the volcano. Although the 3 March eruption destroyed the summit deployment, sensors outside the damage zone collected data that yielded a full chronology of the volcano’s increasing unrest.

Volcanoes as Giant Musical Instruments

Volcanoes generate infrasound, low-frequency sounds below the threshold of human perception. Despite varied eruptive behaviors, many volcanoes radiate their most intense sounds within a few octaves of 1 hertz, corresponding to sound wavelengths of hundreds of meters. It is no coincidence that this dimension is similar to the dimension of volcanic craters, which play a critical role in modulating the radiated sound [e.g., Kim et al., 2015].

In many ways, a volcano is like a giant musical instrument. As with volcanoes, the size of a musical horn controls the pitch of the sound it makes: Bigger horns make lower-pitched sounds. Musical sounds tend to be pleasing because of the horn’s resonance; air pressure waves sloshing back and forth within a length of brass tube project sonorously from the horn’s bell. The shape of the bell’s flare is important and controls whether a note is sharp and short or rich and reverberating. This quality, which is independent of a note’s frequency or loudness, is referred to broadly as its timbre.As with a musical horn, a volcano’s timbre and pitch are particular to a crater’s shape. Volcanoes with deep craters have a tendency to produce low-frequency sounds, whereas shallow craters radiate higher-frequency sounds [Spina et al., 2014; Richardson et al., 2014]. Narrow conduits often resonate for extended periods, but broad, dishlike craters might not reverberate at all. Although volcanic sound sources can be varied, vents at the bottom of a crater acting as mouthpieces often generate infrasound. The violent expulsion of gas from vents or from a lava lake surface can induce the crater to resonate.

Volcanic Unrest and Changing Sound Quality

Fig. 1. During the few days leading up to Villarrica’s 3 March 2015 explosion, the volcano’s characteristic explosion infrasound changed (top and bottom). Colored disks represent the spatial equivalents of the respective infrasound time series, which were recorded 4 kilometers from the vent; oscillations are mostly absent on 2 March. Waveforms on 27 February had well-defined oscillations that were mostly absent by 2 March (middle). Draped topography was created by the authors from the Shuttle Radar Topography Mission digital elevation model using an image from NASA Earth Observatory. VID and VIC are the stations that recorded the waveform data.

Volcano infrasound merits particular attention when it changes over time. This can happen when volcanoes change their shape as crater walls slump, floors collapse, or a lava lake rises and falls. Villarrica’s lava lake dynamism, for instance, is considered to be responsible for changing infrasound leading up to the violent eruption in 2015. Frequency fluctuations had previously been attributed to oscillating lava lake stages [Richardson et al., 2014], but in 2015, scientists noted a systematic variation that led up to the violent eruption on 3 March. A study by Johnson et al. [2018a] reported two primary observations: The frequency content of the sounds increased around 1 March (from 0.7 to 0.95 hertz), and the timbre changed (Figure 1). Prior to 1 March, reverberations were evident, but afterward, the sound became like a thunk. In other words, the crater’s acoustic source had dampened.

Villarrica’s crater resembles a funnel, with a conical upper section and a narrow conduit beneath. The absence of resonance in early March is important because according to numerical models, it signifies a high stand of the lava lake situated near the flaring section of the crater. During Villarrica’s typical background state, the surface of the lava lake is deeper—and often hidden—within the vertical-walled shaft. By 2 March, the infrasound signals suggest that the lava lake was approaching the crater rim; the horn had become a loudspeaker, as illustrated in the video below.

The trigger for the dramatic 3 March lava fountain, which started at 3:00 a.m. local time, remains enigmatic, but the end result was a violent paroxysm that caused property damage, forced thousands of people to evacuate the area, and made worldwide headlines. Infrasound observations told us that the surface of the lava lake had reached a high level several days before the eruption. These insights may help us to anticipate future eruptions at open-vent volcanoes.

Volcano Resonance on Steroids

Every volcano has a unique infrasound signature. Compared with Volcán Villarrica, whose resonance evolved during a few days from noticeable to absent, infrasound from Ecuador’s Cotopaxi volcano was notable because it rang consistently in 2016 (Figure 2). Villarrica’s infrasound oscillations lasted cumulatively for a few seconds, but a single oscillation at Cotopaxi lasted for 5 seconds. As many as 16 oscillations were detected in some of the infrasound signals, which, incredibly, lasted more than a minute (Figure 3).

Fig. 2. Cotopaxi and Villarrica volcano photos and satellite imagery from NASA Earth Observatory show the relative size of their summit craters, which produce discrete infrasound signals. Yellow squares in both satellite images are 1 square kilometer. Credit: NASA International Space Station photo archive (Cotopaxi satellite photo), NASA Earth Observatory
Fig. 3. The infrasound signal time series illustrates the nature of the resonance at Villarrica and Cotopaxi (top left). Each waveform is a composite stack of 50 events, which occurred during 1 day at Villarrica and during 6 months at Cotopaxi. A detail of the first 10 seconds from this time series shows the contrast in sound signatures from the two volcanoes (top right). Frequency spectra peak at 0.2 hertz for Cotopaxi and 0.75 hertz for Villarrica; damping factors α indicate the time constant for characteristic decay in reciprocal seconds (bottom).


A study of the Cotopaxi events recorded in 2016 refers to these beautiful signals as infrasound tornillos, the Spanish word for screws, because the pressure recording resembles a screw’s profile [Johnson et al., 2018b]. Such waveforms attest to an exceptionally low damping and thus a high quality factor of the crater acoustic source. (Sources with higher quality factors have less damping, and they ring or vibrate longer.)

If Villarrica is like a large trombone, with a leadpipe length that changes over time, then Cotopaxi is like a giant tuba, with relatively unchanging dimensions during much of 2015 and 2016. After explosions in August 2015 opened up Cotopaxi’s crater, the visible conduit extended steeply downward from its 5,900-meter summit. Throughout the first half of 2016, the crater bottom was not visible to aircraft flying over the summit. Aerial observations showed a vertical-walled crater at least 200 meters deep, a dimension corroborated by the modeled infrasound, which suggested a 350-meter shaft.

Sources of Crater Resonance

Infrasound’s journey from volcano source to receiver can be understood only by considering the dramatic modulating effects produced by crater topography [Kim et al., 2015]. It is most plausible that both Cotopaxi’s impressive tornillos and Villarrica’s subdued oscillations are induced by short-duration impulses occurring at the bottom of their craters. An abrupt explosion, or an impulse, contains a broad spectrum of frequencies; however, only those that excite the crater in resonance are well sustained.

Typically, volcano scientists who analyze remote infrasound recordings are generally less interested in the oscillatory “breathing” of the crater outlet (i.e., its infrasound resonance) than in extracting important information about the explosion’s source, such as its duration or mass flux. It is this information that contributes to our growing understanding of how gas accumulates and separates from magma and how it powers volcanic explosions.

However, with recent developments in the understanding of crater acoustic effects, we are better poised to recover important parameters related to the sources of explosions. Cotopaxi and Villarrica represent just two of the dozens of volcanoes active worldwide where infrasound is contributing to our fundamental understanding of eruption dynamics and to our ability to forecast future paroxysms.


This work was funded in part by National Science Foundation grants EAR-0838562 and EAR-1830976 and by the Fulbright Scholar Program.

About the authors: This article was written by Jeffrey B. Johnson (jeffreybjohnson@boisestate.edu), Boise State University, Idaho; and Leighton M. Watson, Stanford University, Calif. The article originally appeared on Eos, 100, https://doi.org/10.1029/2019EO123979. Published on 17 June 2019.


Fee, D., and R. S. Matoza (2013), An overview of volcano infrasound: From Hawaiian to Plinian, local to global, J. Volcanol. Geotherm. Res., 249, 123–139, https://doi.org/10.1016/j.jvolgeores.2012.09.002.

Johnson, J. B., and M. Ripepe (2011), Volcano infrasound: A review, J. Volcanol. Geotherm. Res.206, 61–69, https://doi.org/10.1016/j.jvolgeores.2011.06.006.

Johnson, J. B., et al. (2018a), Forecasting the eruption of an open-vent volcano using resonant infrasound tones, Geophys. Res. Lett., 45(5), 2,213–2,220, https://doi.org/10.1002/2017GL076506.

Johnson, J. B., et al. (2018b), Infrasound tornillos produced by Volcán Cotopaxi’s deep crater, Geophys. Res. Lett., 45(11), 5,436–5,444, https://doi.org/10.1029/2018GL077766.

Kim, K., et al. (2015), Acoustic source inversion to estimate volume flux from volcanic explosions, Geophys. Res. Lett., 42(13), 5,243–5,249, https://doi.org/10.1002/2015GL064466.

Richardson, J. P., G. P. Waite, and J. L. Palma (2014), Varying seismic-acoustic properties of the fluctuating lava lake at Villarrica volcano, Chile, J. Geophys. Res. Solid Earth, 119(7), 5,560–5,573, https://doi.org/10.1002/2014JB011002.

Ripepe, M., et al. (2018), Infrasonic early warning system for explosive eruptions, J. Geophys. Res. Solid Earth, 123(11), 9,570–9,585, https://doi.org/10.1029/2018JB015561.

Spina, L., et al. (2014), Insights into Mt. Etna’s shallow plumbing system from the analysis of infrasound signals, August 2007–December 2009, Pure Appl. Geophys., 172(2), 473–490, https://doi.org/10.1007/s00024-014-0884-x.

Illustration of newly discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Scientists find huge 19-mile impact crater under Greenland’s ice sheet

Researchers recently identified a huge bowl-shaped crater measuring a staggering 19 miles (31 km) across under half a mile of Greenland ice. The immense crater was likely formed by the impact of a mile-wide iron meteorite, which must have unleashed 47,000,000 times the energy of the nuclear bomb dropped on Hiroshima at the very end of WWII. The biggest question on everybody’s mind right now is when it all happened.

Illustration of newly discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Illustration of the newly-discovered immense crater in Greenland. Credit: Nasa/Cryospheric Sciences Lab/Natural History Museum of Denmark.

Kurt Kjær, a Professor at the Natural History Museum of Denmark in Copenhagen, suspected an impact crater might be hidden away under Greenland’s ice after NASA radar images showed a massive depression of the bedrock beneath the Hiawatha glacier, in the northwestern part of the island.

In May 2016, one year after the satellite images were released, scientists flew over the glacier pointing a cutting-edge ice-penetrating radar onto the glacier to map the underlying rock. The 3-D images clearly show all the hallmarks of an impact crater — a 19.3-mile-wide circular feature with a rim around it and an elevated central region.

The crater’s basin is about 300 meters deep, suggesting it was perhaps made by a one-mile-wide meteorite. This immediately classes the impact site among the top 25 largest known craters on Earth. According to the researchers, the impact would have melted and vaporized approximately ~20 km3 of rock.

“There would have been debris projected into the atmosphere that would affect the climate and the potential for melting a lot of ice, so there could have been a sudden freshwater influx into the Nares Strait between Canada and Greenland that would have affected the ocean flow in that whole region,” co-author John Paden, Associate Professor of electrical engineering and computer science at Kansas University, told the AFP.

Kurt Kjær collecting sediment samples from the crater's dranage system. Credit: Natural History Museum Denmark.

Kurt Kjær collecting sediment samples from the crater’s drainage system. Credit: Natural History Museum Denmark.

The meteorite was likely mostly made of iron, judging from geochemical tests performed on particles of shocked quarts collected from a nearby floodplain.

“Beyond the grains in the sediment sample that we interpret to be possible ejecta, no ejecta layer associated with this structure has yet been identified. Despite the absence of such additional evidence, an impact origin for the structure beneath Hiawatha Glacier is the simplest interpretation of our observations,” the authors wrote in their new study.

Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Credit: Science Advances.

Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Credit: Science Advances.

When exactly did the impact actually takes place is not at all certain. Kjær and colleagues are confident that the crater is no older than 3 million years, the time when ice began to cover Greenland.

“The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet,” the authors wrote in the journal Science Advances

As for the lower limit, radar images show that the deepest layers of the glacier that are older than 12,000 years are very deformed compared to upper layers and are filled with lumps of rock. To be sure, researchers will have to use radiometric dating techniques on material from the crater — that means drilling through half a mile of ice. It might take a few years before this happens, however.


AI spots thousands of craters on the Moon — including over 6,000 previously undiscovered ones

Without an atmosphere to protect it, the Moon is under constant assault from meteorites and asteroids, hitting the satellite and leaving behind a horde of craters. Using a novel AI-based technique, a team of researchers has developed a new way to identify and count these craters.

An artificially colored mosaic constructed from a series of 53 images taken by the Galileo Spacecraft. Can you see the craters?

“When it comes to counting craters on the moon, it’s a pretty archaic method,” says Mohamad Ali-Dib, a postdoctoral fellow in the Centre for Planetary Sciences (CPS).

Indeed, while astronomy has benefitted from the automation of many processes, crater counting had lagged behind — but not anymore.

“Basically we need to manually look at an image, locate and count the craters and then calculate how large they are based off the size of the image. Here we’ve developed a technique from artificial intelligence that can automate this entire process that saves significant time and effort.”

Ali-Dib wasn’t the first to come up with this idea. Several projects have attempted to develop algorithms for the detection of lunar craters, but they performed rather poorly. However, the new algorithm, which was trained on a large dataset covering two-thirds of the moon, performed much better. It was so good at understanding the general shape and characteristics of a crater that it was even able to detect craters on other bodies, such as Mercury.

“It’s the first time we have an algorithm that can detect craters really well for not only parts of the moon, but also areas of Mercury,” says Ali-Dib, who developed the technique along with Ari Silburt, Chenchong Charles Zhu, and a group of researchers at CPS and the Canadian Institute for Theoretical Astrophysics (CITA).

They fed 90,000 images of the moon’s surface into an artificial neural network (ANN). ANNs mimic the vast network of neurons in a brain, simulating the biological learning process. After the learning process, the neural network was able to not only identify but also categorize craters larger than five kilometers. The team believes that with further “training” it will also be able to zoom in on smaller craters.

Some lunar craters last for billions of years. Image credits: NASA.

Since the moon also doesn’t have tectonics or strong erosion, the craters can remain visible for extremely long periods of time, with Ali-Dib’s team finding craters as old as four billion years. However, this is also the main drawback of the algorithm: it requires an atmosphere-less body, without erosion, and clearly visible craters.

Journal Reference: Ari Silburt et al. Lunar Crater Identification via Deep Learning. arxiv.org/abs/1803.02192

Scientists zoom into Chicxulub, the “dinosaur crater”

Geologists are getting an unprecedented glimpse into the asteroid that wiped out the dinosaurs and much of life on Earth 65 million years ago.

Gravity anomaly map of the Chicxulub impact structure. The coastline is shown as a white line. Image by USGS.

When two geophysicists discovered a huge crater in the Yucatán Peninsula in Mexico in the late 70s, the entire geologic world was thrilled. The date of the crater coincided precisely with the Cretaceous–Paleogene boundary which marks the end of the Mesozoic. It also offered a great explanation to the massive extinction which occurred at that boundary. But for all the answers it offered, Chicxulub posed even more questions.

The crater is over 180 km (110 miles) in diameter, located next to the village of Chicxulub in Yucatan. We have a pretty good idea of the accuracy, as well as the diameter and the energy released. There’s also a strong case regarding the impact the meteorite impact had on life on Earth – it basically wiped out a large part of it. But how, exactly? Why did some creatures survive and others didn’t? How did life bounce back after it? And perhaps more importantly, what can we learn from it in regards to our current situation?

Those are all questions scientists would like to answer, but in order for that, they need to take core samples from the crater – and that’s deep underground, offshore. Chicxulub is the only known Earth crater with a remaining impact peak ring, but it is under 600 m (2,000 ft) of sediment. The drilling machine already pushed 1,335m below the modern sea floor and now, for the first time, researchers are getting real samples straight from the crater.


“They’re very strange rocks,” explained Prof Jo Morgan, who is involved in the study. “The rocks have formed this feature: it’s called a ‘peak ring’. They’re very, very highly… what we call ‘shocked’. Shock pressures of many tens of gigapascals have deformed the rocks. They’re also highly fractured, and have moved long distances. So, even though they’re made of granite-type rocks, they’re amazingly different to anything else we see in the world.”

The international project has already acquired the hundreds of metres it drilled from beneath the Gulf floor earlier this year to the MARUM Center for Marine Environmental Sciences, at the University of Bremen, Germany. Rock analysis ios a long-term endeavor, but Prof Sean Gulick, from the University of Texas, US, one of the two chief scientists involved, has shared some of his initial thoughts:

“We’ve been able to examine that first 10,000 years after the impact, which is dominated by what we call ‘disaster species’ – dominated by the organisms that love stressed environments. And then we can see evolution coming back in [during] the next few hundred thousands years after that,” he told BBC News.

The ‘disaster species’ he’s referring to are basically small plankton invading the pore spaces and cracks in and around the crater. As they analyze more and more what happened after the impact, we’ll get a clearer picture of life’s re-emergence in the area.

“We’ve got some cell counts and some DNA, but it’s all very early days; we’re very concerned about contamination,” Prof Morgan added. “But the signs are that, yes, this crater was occupied soon after the impact.”


Scientists discover “new” craters on the Moon


Albedo map credit: NASA GSFC/SwRI Topographic map credit: NASA GSFC/ASU Jmoon

Albedo map credit: NASA GSFC/SwRI
Topographic map credit: NASA GSFC/ASU Jmoon

Understanding the Moon’s recent geological history is important and could put the entire solar system into perspective.

“These ‘young’ impact craters are a really exciting discovery,” said SwRI Senior Research Scientist Dr. Kathleen Mandt, who outlined the findings in a paper published by the journal Icarus. “Finding geologically young craters and honing in on their age helps us understand the collision history in the solar system.”

Using LAMP and LRO’s Mini-RF radar data, the team mapped the floors of very large, deep craters near the lunar south pole. The craters are very difficult to study because the Sun never illuminates them directly. However, tiny differences in the craters’ reflectivity (also called albedo) allows researchers to estimate their age.

“We study planetary geology to understand the history of solar system formation,” said SwRI’s Dr. Thomas Greathouse, LAMP deputy principal investigator. “It is exciting and extremely gratifying to happen upon a unique and unexpected new method for the detection and age determination of young craters in the course of nominal operations.”

Space collision played a key role in the solar system’s formation and history, including in the history of the Moon itself. The satellite is riddled with meteorite impact craters, and by dating the craters, the frequency and intensity of collision through time can also be understood. A press release from the Southwest Research Institute reads:

“When a small object collides with a larger object, such as the Moon, the impact creates a crater on the larger body. Craters can be a few feet in diameter or several miles wide. During the impact, the material ejected forms a blanket of material surrounding the crater. The ejecta blankets of “fresh,” relatively young craters have rough surfaces of rubble and a sprinkling of condensed, bright dust. Over millions of years, these features undergo weathering and become covered with layers of fluffy, dark dust.”

To make this discovery even more intriguing, the same technology could be used to study the craters on other objects.

“Discovering these two craters and a new way to detect young craters in the most mysterious regions of the Moon is particularly exciting,” said Mandt. “This method will be useful not only on the Moon, but also on other interesting bodies, including Mercury, the dwarf planet Ceres, and the asteroid Vesta.”

11 Volcanic Craters to Blow Your Mind

Volcanoes are truly amazing – spewing out lava from the depths of the planet, they are a close reminder that our planet is very much alive and constantly changing. Even after they become dormant or extinct, volcanoes are still incredibly majestic – here we’ll take a look at just some of the most spectacular craters they left behind

Diamond Head Crater, Hawaii

Image credits: Eric Tessmer.

Image credits: Eric Tessmer.

Diamond head is a tuff cone located on the Hawaiian island of Oʻahu. Known to local Hawaiians as Lēʻahi, it is part of a system of cones called by geologists the Honolulu Volcanic Series. The volcano is estimated to be 200,000 years old, and has been extinct for about 150,000 years – which is why locals have no fear in building around it, and even inside the crater.


Image credits: Eric Tessmer.

Looking almost too beautiful to be real, Diamond Head has been a touristic attraction for decades, representing a short and relatively easy walk up to the crater. Some say that it isn’t even a proper volcano, but a mere vent of the Ko’olau Range. But even if it ever erupted, its eruption was likely very short, lasting no more than a few days, which is why the cone is so symmetric.

Koko Crater, Hawaii


Image credits: Eric Tessmer.

We’re staying in Hawaii for the next one, as I just can’t take my eyes off the Koko Crater, on the eastern side of Maunalua Bay along the southeastern side of the same Island: Oʻahu in Hawaiʻi.

Image via Wikipedia.

Koko Head’s last eruption was 30,000–35,000 years ago, still long enough to be considered extinct. It lies across from Diamond Head at about 14 km and according to legend, was formed when Pele, the goddess of fires and volcanoes, was chased by Kamapuaa, the pig god. Geologists have a different opinion, believing it is part of the same volcanic series as Diamond Head.

Kelimutu volcano, Indonesia

Image via Wikipedia.

It’s time to move from Hawaii all the way to Indonesia, where Kelimutu thrones over the small town of Moni in central Flores island in Indonesia – the alleged birth place of Homo floresiensisthe “hobbit people” described by some anthropologists. These early inhabitants were likely fascinated by the volcano, which is still somewhat active. The crater now hosts two lakes of different colors.

Image via Wiki Commons.

Kelimutu showed increased seismic activity in February-April 1993, with 318 deep and 196 shallow earthquakes recorded, leading researchers to believe that an eruption in the near future is not out of the question. Interestingly, the color of the lakes formed in the crater vary on a periodic basis. Subaqueous fumaroles are the probable cause, encouraging different types of microorganisms to thrive.

Crater Lake (Okama), Japan

Okama. Image via Wiki Commons.

Crater Lake (or Okama by its Japanese name) is part of Mount Zaō, a complex volcano on the border between Yamagata Prefecture and Miyagi Prefecture in Japan. The whole area includes a cluster of stratovolcanoes and is the most active volcano in northern Honshu. The crater cannot be accessed, but it can be viewed from a distance (in the summertime) through a spectacular road called the Zao Echo Line.

“Snow monsters” – image via Wikipedia.

Among Okama’s spectacular features are the so-called snow monsters. During the winter, strong winds carry water droplets and splash them against trees and their branches, where they freeze, forming near-horizontal icicles. Falling snow settles on this ice, resulting in a ghost-like figure.

Santa Ana, El Salvador

Image via Wikipedia.


At 2,381 metres above sea level, it is the highest volcano in the country. Santa Ana volcano served as an inspiration for Antoine de Saint-Exupéry’s famous French novella (The Little Prince), based on his life with his Salvadoran wife Consuelo de Saint Exupéry, who was The Rose in the story.

Image via Britannica.

The volcano is still active and very dangerous, with an eruption killing two people, injuring seven and forcing many to relocate.

Mount Mazama, Oregon

Image via Wikipedia.

Mount Mazama is another spectacular stratovolcano, located within Crater Lake National Park. It’s much larger than all of the volcanoes we’ve featured on this list so far, with its last eruption being 42 times greater than the eruption of Mount St. Helens in 1980.

USGS Bathymetry Survey of the crater lake.

The summit was destroyed by an eruption that took place almost 9000 years ago, reducing its height by almost 1 km. Much of the volcano fell into the volcano’s partially emptied neck and magma chamber. At 8,159 feet (2,487 m), Hillman Peak is now the highest point on the rim.

Mount Katmai, Alaska

Mount Katmai, Image via Wikipedia.

The world’s largest volcanic eruption of the 20th century broke out at Novarupta in June 1912, with 30 times the volume of magma from the 1980 eruption of Mount St. Helens. Although almost all the magma erupted at the Novarupa vent, most of it was stored beneath Mount Katmai, 10 km away. Most of Mount Ketmai actually collapsed that day.Colorful ash in the Valley of Ten Thousand Smokes. Image via Wikipedia.

The eruption and resulting pyroclastic ash flow formed the Valley of Ten Thousand Smokes, named by botanist Robert F. Griggs, who explored the volcano’s aftermath for the National Geographic Society in 1916.

Seongsan Ilchulbong, South Korea

Image via Wikipedia.

Seongsan Ilchulbong is an archetypal tuff cone formed by hydrovolcanic eruptions five millennia ago. Tuff cones are less common than cinder cones and generally form at magma-water boundaries.

The crater, as seen from the road. Image via Wikipedia.

The eruption took place in very moist conditions, which allowed much water to permeate into the volcano, creating what is called a wet eruption. These conditions lasted for the entire length of the eruption, and consequently, the area has a bowl-like crater unfilled by scoria or lava.

Aogashima, Japan

Image via Flickr.

If you haven’t had enough craters, we’ve got a treat for you – a crater in a crater! Aogashima is a volcanic Japanese island in the Philippine Sea some 358 kilometres (222 mi) south of Tokyo and administered by the city. The area has a very rich volcanic history and the volcano is still considered active, despite not having an eruption for more than 200 years.

The crater in a crater. Image via Wikipedia.

There is a small human settlement on Aogashima with a population of 170. It’s not clear when this settlement began or how it dealt with the record volcanic activity in 1652, and the earthquake swarm in July 1780. It is known however that In April 1783, lava flows from the Maruyama cone resulted in the evacuation of all 63 households on the island, but two years later, in what is the last recorded eruption, over 100 people lost their lives.

Taal Volcano, Philippines

Taal crater, via Wikipedia.

If that somehow still wasn’t enough volcano-ception for you, then I’ve got something even better: Taal Volcano. The crater is pretty spectacular in itself, but what makes it even more mind bending is that it is an island within a lake on an island within a lake on an island. Pretty neat huh? So on Luzon island in the Philippines, you have Taal Lake and Taal Volcano, which is an island in the lake. Inside the volcano crater – you guessed it: there’s a lake with an island.

Taal Volcano's crater before the 1911 eruption with the central cone and one of the lakes on the crater floor.

Taal Volcano’s crater before the 1911 eruption with the central cone and one of the lakes on the crater floor.

But this very neat fact doesn’t diminish the danger posed by this volcano. Because of its proximity to populated areas and its eruptive history, the volcano was designated a Decade Volcano: 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) as being worthy of particular study because of the danger they posed. Taal’s eruptions claimed at least 5000 lives.

Kerid Volcano, Iceland

Image via Wikipedia.

It’s only fitting to end with a volcano from Iceland, one of the most active volcanic areas in the world. Iceland has several hundreds of volcanoes, with some 30 systems being still active today. Kerid is a volcanic crater lake located in the Grímsnes area in south Iceland.


Image via Wiki Commons.

Image via Wiki Commons.

The genesis of Kerid is still debatable, but now the main theory seems to be that it is a  cone volcano which erupted and emptied its magma reserve. After the magma was depleted, the weight of the cone caused the structure to collapse into the empty magma chamber, now hosting a lake. The lake itself is shallow, but due to the abundance of minerals from the soil, is an opaque and strikingly vivid aquamarine.

GeoPicture of the Week: Xico Crater in Mexico

It’s a new year alright, and what better way to start it than with a GeoPicture? This is the Xico volcanic crater in Mexico.

Image via Imgur.

Located in the southern parts of of Mexico City in the municipality of Xico within the Chichinautzin volcanic field. The Chichinautzin volcanic is located in the Trans-Mexican Volcanic Belt, relatively close to the area where the Cocos tectonic plate subducts beneath the North American Plate (about 350 km / 220 miles). The filed is formed mostly from small cinder cones and shield volcanoes.

As you can see here, the crater is slowly being engulfed by urban development as more and more houses are being built around it, even at the base of its slopes. Farmers have even climbed the top of the volcano and used the fertile soil to plow fields.


Scientists 3D print models of impact craters on Moon and Mars

3D printing has not only opened amazing new possibilities for human (and animal) medicine, engineering and even art, but it has ignited our imagination and pushed us to think about things in new, different ways. At the poster presentation at the annual Geological Society of America (GSA) conference in Baltimore, two scientists have presented 3-D models of impact craters on the Moon and Mars, as well as of Mars’s Valles Marineris canyon.

Three-dimensional printing promises to give researchers and students broad access to easily studied, touchable models of structures like Mars’s Valles Marineris–a vast canyon at right center of this photo that resembles scars on the face of the planet. Credit: NASA/JPL

“We’ve had open houses for middle school kids, and we always have a puddle of them staring fixedly” at the models, said Seth Horowitz, who originally trained as a neuroscientist but started collaborating with a Brown University astronomer in 2011 on printing the models. “Students who haven’t been exposed to 3-D printing are just mesmerized by them.”

Indeed, this not only offers new ways to study the craters, but it also has a huge educational value, providing the students a way to directly visualize the craters. Horowitz started collaborating with Peter Schultz, the director of the Northeast Planetary Data Center. Schultz specializes in studying impact craters around the solar system, including on Earth; he’s worked not only with mathematical simulations, but also with 3D models that offer researchers more intimate information about the craters.


Physically printing them and studying them in reality was only the next logical step.

“It’s great to be able to look at a fantastic animation of sunrise over a Martian valley, but being able to pick up a physical model and move it around … all without having to learn another piece of software or needing yet another java update before it works, enhances our understanding of the places,” Horowitz said.

3D printing and real-life modelling can have a number of applications not only in studying alien bodies, but also in studying geological features here on Earth. Visualizing a landscape or geological feature is one thing, but actually holding it in your hand is a completely different experience, especially for students. For students with a physical impairment, this is a potential game changer.

“Having the 3-D model amplifies what we’re trained to see with contour maps [and] surface feature maps,” Schultz said.

A 58-square-centimeter (23-square-inch) 3-D model of the giant Valles Marineris canyon on Mars. Credit: Seth Horowitz, Northeast Planetary Data Center

The data for this model was obtained from the various satellite missions orbiting Mars and the Moon. These satellites mapped the surface using radar or lidar to produce digital models. This data is digitzed and can then be transferred to a 3D printer. Any scientist with a 3-D printer and the right data could print their own models, both for students and for research.

It’s important to note that while printing these models is without a doubt cool and interesting, the scientific potential should not be overlooked.

“The challenge now is to turn this into something more than toys or giveaways,” he continued. “It’s really important to be able to turn this into something usable and I think we’re just at the [edge] of that.”

Have geologists discovered all the big craters on Earth?

Mars has over 250,000 craters created by asteroid impacts, the Moon has millions – too many to count. But the Earth has an atmosphere, which means we’re protected against most threats and we have much to be thankful for. But even the craters that we do have are constantly eroded by wind and water, so finding and identifying them is quite a challenge. Just 128 confirmed large impact craters have been spotted on the Earth’s surface,an extremely low number. But a new study concluded that it’s not that we haven’t searched hard enough – those are simply all the craters that still exist on our planet’s surface.

The Meteor Crater is “only” 1 mile across – craters larger than this are becoming increasingly harder to discover… because we may have discovered them all.

It’s a surprising result.

“I’m definitely surprised.” says Brandon Johnson, a planetary scientist at the Massachusetts Institute of Technology in Cambridge, who was not involved in the study. “It’s the first time anyone has done this kind of thing—taking into account the effects of erosion.”

Stefan Hergarten and Thomas Kenkmann, geophysicists at the University of Freiburg in Germany have built their analysis on a previous study done by Johnson, who found that for craters 85 kilometers in diameter and larger, the geologic record is probably complete. But Hergarten and Kenkmann searched for craters that were “only” 6 kilometers across or more, and they came up with the same conclusion: we’ve simply found them all.

The result, as surprising as it seems, is somewhat satisfying.

“It tells us that it’s not just others being too stupid to find new craters,” he says.

Also, on the other hand, it means that geologists should somewhat change their focus, and start looking for small craters. Jay Melosh, an impact crater expert at Purdue University in West Lafayette, Indiana says the results are consistent with his recent observations: diminishing returns of crater hunting.

“What the new paper does is give the crater hunters a lot of hope for smaller craters,” Melosh says.

However, there is an important mention to be made; on a geological scale, the Earth’s surface is no immobile – it moves both horizontally and vertically, and therefore things that were once on the surface (such as craters) may now be buried. This study focused only on craters on the surface, but there may be some big ones out there – they just may be buried.

The most famous one is actually the most famous crater of them all: Chicxulub, in Mexico, the remnant of the asteroid that wiped off the dinosaurs. So if you want to find craters, Johnson has a good tip for you:

“Don’t stop searching,” he says, “just search deeper.”

Mysterious Siberian craters attributed to methane. Permafrost methane release might have begun

Remember the “mysterious” craters in Siberia? You know, the ones which “no one could explain”? Well, geologists had a pretty good idea what was happening, and the studies they recently conducted confirmed their theories. The craters are caused by methane seeping from the melting permafrost.

The crater in Siberia is 30 meters wide, and probably over 100 meters deep. It was caused by methane.

Air near the bottom of the crater contained very high concentrations of methane – about 9.6%. In case you’re wondering, the normal concentration of methane in air is somewhere at 0.000179%. So, sorry to burst your bubble guys, but there was never any serious talk about meteorite crashes, missile explosions or aliens. If you’ve read that somewhere, you can just cross it off your list of serious science journalism.

The Russian researchers from the  Scientific Centre of Arctic Studies in Salekhard working in the area attribute the hole formation to the abnormally hot Yamal summers of 2012 and 2013, which were warmer than usual by an average of about 5°C.  What does global warming have to do with this? Well, the permafrost has huge quantities of methane and carbon dioxide trapped in it. If it starts to melts, it starts to release those gases and dramatically exacerbates global warming. The only questions is if this warming was caused by the two abnormally hot winters, or, as Hans-Wolfgang Hubberten, a geochemist at the Alfred Wegener Institute in Potsdam, Germany believes, by a slow and steady thaw in the region.

The depths of the craters (there are quite many) are not known, but when Russian scientists lowered a 50 meter cable with a camera to it, they couldn’t even see the bottom – so it’s much deeper than that. They believe there is a pool of water somewhere between 70 and 80 meters, but its impossible at the moment to say how deep that pool really is.

 “Its rims are slowly melting and falling into the crater,” says Andrei Plekhanov, one of the scientists working in the area. “You can hear the ground falling, you can hear the water running, it’s rather spooky.”

There are several risks associated with this phenomenon. The most obvious would be of someone actually falling in such a crater, but in the remote areas of Siberia, the risk is fairly small. Much more concerning is the risk of trapped methane threatening local communities and industries.

 “If [a release] happens at the Bovanenkovskoye gas field that is only 30 km away, it could lead to an accident, and the same if it happens in a village,” says Plekhanov.

crater siberia

However, in the long run, the risk remains global warming. If you look at a satellite picture of the area, you see countless rather similar holes, and though there’s not yet an official explanation as to how they came to be, it seems safe to say that permafrost methane leakage is also responsible. The accelerated effect this phenomenon will lead has not yet been studied.


Alien debris found in lunar craters

Well the title may be a little flashy, but here’s what it’s about: some highly unusual minerals have been found at the centers of impact craters on the moon. Geologists working on the case believe that they may be the shattered remains of the space rocks that made the craters, but didn’t exhume any material from the Moon’s crust.


The foreign matter is probably asteroid debris, but some of it can even be from Earth – which is known to throw up its fair share of material as it gets hit by asteroids.

Interestingly enough, the discovery of this material didn’t come from analyzing the craters themselves, but rather by looking at a computer model of how meteorite impacts affect the Moon. To be more specific, researchers simulated a high-angle, exceptionally slow impacts — at least slow compared to possible impact speeds. What they found took them completely by surprise.

“Nobody has done it at such high resolution,” said planetary scientist Jay Melosh of Purdue University. Melosh and his colleagues published a paper on the discovery in the May 26 online issue of the journal Nature Geoscience.

They found that when the impact is slow enough (that means speeds of under 43,000 kph), the rocks which are hit don’t really vaporize, as was previously believed. Instead, the mass gets shattered into a rain of debris that is then swept back down the crater sides and piles up in the crater’s central peak.

In the case of the Copernic crater, depicted above, which is estimated to be about 800 million years old, the foreign material stands out because it contains minerals called spinels. Spinel is a magnezium/aluminum mineral that only forms at great pressures, like in the Earth’s mantle, for example (or even in the Moon’s mantle). But spinels are also relatively common in some asteroids which are fragments of broken or failed planets from earlier days of our solar system.

Via Wikipedia

Spinel.Via Wikipedia

Judging by these results, scientists now believe that the unusual minerals observed in the central peaks of many lunar impact craters are not lunar natives, but imports.

“An origin from within the Moon does not readily explain why the observed spinel deposits are associated with craters like Tycho and Copernicus instead of the largest impact basins,” writes Arizona State University researcher Erik Asphaug in a commentary on the paper. “Excavation of deep-seated materials should favor the largest cratering events.”

If true, this also means that pockets of material from the early Earth might be in cold storage on the moon, says Asphaug.

“Even more provocative,” explains Asphaug, “is the suggestion that we might someday find Earth’s protobiological materials, no longer available on our geologically active and repeatedly recycled planet, in dry storage up in the lunar ‘attic’.”

Via Discovery

Asteroid that wiped out the dinosaurs may have been a set of binary asteroids

The (still debated) asteroid that slammed into the Earth 65 million years ago and played a crucial role in wiping dinosaurs out, may have actually been a binary system- 2 asteroids engaged in an orbit around each other.

Double trouble

binary asteroid

The surprising claim comes from analyzing the proportion of asteroid craters on Earth that were formed from binary impacts; the results also add to the concern of those who fear catastrophic collisions in future. Here’s the deal: our planet bears the scars of twin-asteroid impacts just like single impact craters; a good example is the Clearwater Lakes near Hudson Bay in Canada, formed 290 million years ago. However, examples like this are pretty rare: 98% of all craters are single impact, with only 2 in 100 coming from a binary system.

“It’s been known for 15 years that about 15 per cent of near-Earth asteroids are binary,” says Katarina Miljković at the Institute of Earth Physics in Paris, France.

So, all things being equal, if 15 percent of all asteroids are binary, why aren’t 15 percent of craters binary ? Miljković and her colleagues believe they have found the answer: they ran computer simulations and found that even binary systems often form a single crater, mimicking a single asteroid impact.

Considering that the crater is typically 10 times bigger than the asteroid, this seems intuitive. The team found that only unusual cases involving two small, widely separated asteroids are guaranteed to form a pair of distinct craters. Their simulations confirmed that such situations are just rare enough to explain why paired craters account for only 2 per cent of all Earth’s craters.

Symmetry and non-symmetry


The next step was, of course, seeing if single craters caused by single asteroids could be differentiated by single craters caused by binary asteroids. What they found is that it is possible to identify which of Earth’s single craters had binary origins – these craters should be subtly asymmetrical – a feature displayed by the crater near Chicxulub in Mexico – thought to lead to the extinction of the dinosaurs.

“The Chicxulub crater shows some important asymmetries,” says Miljković. “It is worth considering that it was formed by a binary asteroid.”

Geophysical research is key to studying such impact craters – gravity measurements are a great indication for this, especially for asteroids which are still buried. Studying the gravity anomalies supported this theory, as Petr Pravec at the Academy of Sciences of the Czech Republic in Ondrejov explained.

“The signatures also suggested that the Chicxulub crater might have been formed by a binary asteroid impact,” he says.

So what did Chicxulub looked like? Most likely, if it was indeed a binary, the 180 km radius of the crater suggests the combined diameter of the two asteroids being somewhere around 7 to 10 km – the same diameter as the single rock previously imagined to be the culprit.

Twice the asteroid – twice the problem?

If this is true, what does it mean for future impact mitigation and preparation? Even with today’s technology, we have what it takes to totally avoid the dangers posed by an asteroid, but what happens with a binary?

“I am not sure if any of the proposed asteroid deflection techniques could deflect both binary components with a single weapon,” says Katarina Miljković at the Institute of Earth Physics in Paris, France, who led the new study.

However, researchers seem prepared for this possibility as well. Don Yeomans of NASA’s Near Earth Object Program thinks that won’t be a problem for a future asteroid-deflecting spacecraft.

“There is a slim chance that the autonomous navigation camera might be confused with two images in its field of view, but I should think these issues would be easily overcome,” he says.


Volcanic eruption in Hawaii

Hawaii isn’t all warm breezes, mojitos and surfing; it’s what geologists call a hot spot, one of the most active volcanic regions on the face of the planet, so it was little surprise when Kilauea erupted; after all, it is one of the most potent volcanoes in the world, being in a constant eruption since the 3rd of January, 1983 (yes, you read that right)

This time, lava came out to the surface through a fissue, after the Pu’u ‘Ō’ō crater collapsed, event which led to the dramatic and destructive display we can see now; the magnificent volcano threw lava at heights of 65 feet, which then began to flow. As USGS reports, it is still erupting powerfully at two locations, and no less than 18 earthquakes were detected inside the volcano (I haven’t been able to find out their magnitude, but they shouldn’t be too great – still, the seismic tremor levels remain significantly elevated).

You can get maps, photos, videos, and even webcam views at Kilauea status, and we will also keep you posted with what happens.

Despite the fact that this eruption doesn’t come as a surprise to anybody, the 370 feet collapse of one of the volcano’s floors (Pu’u ‘O’o) was pretty unexpected. Janet Babb of the U.S. Geological Survey said this weekend’s activity indicates “new episodes in eruptions and further unknowns”.