Tag Archives: rock

This rock fragment is over 4 billion years old. It may formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

Earth’s oldest rock was actually found on the moon and brought home by Apollo 14

In 1971, Apollo 14 astronauts brought home various minerals and rock samples from their brief lunar voyage. For decades, these lunar rocks have stayed in storage, occasionally being revisited by researchers curious to try out a new technique in order to learn more about the moon’s geochemistry. Imagine the surprise when scientists found in 2019 that one such rock was terrestrial in origin — to top it all off, it may very well be Earth’s oldest rock found thus far.

This rock fragment is over 4 billion years old. It may formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

This rock fragment is over 4 billion years old. It may have formed on Earth but ended up on the moon due to a massive asteroid impact. Credit: USRA/LPI.

This adventurous moon rock has quite the backstory. According to an international team of researchers, the two-gram piece of quartz, feldspar, and zircon was found embedded in a larger rock called Big Bertha. This combination of minerals shouldn’t be found on the moon but they’re quite common here on Earth. Quartz and zircon form in oxidized systems such as Earth, in high temperature and pressure environments experienced deep below the planet’s crust.

Since zircon contains uranium, whose half-life is predictable, the international team of researchers were able to confidently date the rock to about 4 to 4.1 billion years ago, corresponding to the Hadean Eon of Earth’s geological history. They also determined — based on the sample’s geochemical properties — that it must have formed at a depth of about 20 kilometers (12.4 miles) beneath Earth’s surface.

The Moon rock “Big Bertha”, collected during the 1971 Apollo 14 mission, contains an Earth meteorite that is 4 billion years old. Credit: Wikimedia Commons.

So, how did it end up on the moon? The most plausible explanation is that a massive asteroid impact hurled this traveling mineral into space and eventually crashed into Earth’s natural satellite, which happened to look a lot different than we know it.

For starters, the moon was about three times closer to Earth than it is today. Around 4 billion years ago, the planet was regularly bombarded by cosmic objects of all shapes and sizes, some responsible for producing craters thousands of kilometers in diameter on Earth — so the impactor hypothesis isn’t that far-fetched of an explanation at all. Once on the moon, the rock was further sculpted by new impacts which melted and altered it into a new kind of rock about 3.9 billion years ago. These forces also buried it deep below the lunar surface.

The Moon was much closer to the Earth than it is today when the rock fragment was produced and ejected from the Earth. Credit: LPI/David A. Kring.

The Moon was much closer to the Earth than it is today when the rock fragment was produced and ejected from the Earth. Credit: LPI/David A. Kring.

The rock probably stayed buried for eons until around 26 million years ago when another asteroid impact, this time on the moon, produced the 340-meter wide Cone Crater. Finally, Apollo 14 astronauts found the rock and reunited it with mother Earth.

“It is an extraordinary find that helps paint a better picture of early Earth and the bombardment that modified our planet during the dawn of life,” said Dr. David Kring, co-author of the new study and a researcher at the Lunar and Planetary Institute (LPI).

This may all sound a bit ridiculous, but this is the most plausible explanation. For the minerals to have formed on the moon, Science Alert writes that they must have formed 30 to 70 kilometers below the surface, in an “unusually oxidizing magmatic environment with oxygen levels much higher than those in the lunar mantle 4 billion years ago.” Theoretically, the fragment may have formed in weirdly water-rich pockets of magma deep within the ancient moon but it seems much more likely that the rock formed within our planet’s crust and later got jettisoned to the moon by one of the many daily meteor impacts that bombarded early Earth. 

Of course, there’s a lot of speculation involved in this scenario and the geological community at large is not so easily convinced. Researchers will have to verify this assumption by studying other lunar samples collected thus far. Hopefully, more new samples will be retrieved in the future now that NASA plans on returning humans to the moon.

The other candidate for the oldest material of terrestrial origin is a piece of zircon mineral dated from 4.4 billion years ago enclosed in a sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia. However, the dating has been disputed. Furthermore, the fragment is debris left over from that disintegrated long ago. By contrast, the Apollo 14 fragment is much better preserved since it didn’t endure millions of years of weathering. 

The oldest material of extraterrestrial origin found thus far are silicon carbide particles of the Murchison meteorite, which have been determined to be 7 billion years old, billions of years older than the 4.54 billion years age of Earth itself.

The findings appeared in the journal Earth and Planetary Science Letters.

Stonehenge? It’s probably built from second-hand materials

You’re a prehistoric builder. You look at these magnificent rocks used to build Stonehenge and you think “You know what would be even cooler? If we moved them a few hundred miles away”. While we can’t say exactly what went through the mind of these ancient builders, but modern research has revealed convincing evidence that parts of Stonehenge were constructed using rocks dragged from a different monument in modern day Wales.

Researchers believe some stones used at Stonehenge, near Salisbury in southwest England, were used in an earlier monument 175 miles (280 kilometres) away in southwest Wales. Image credits: Parker Pearson.

Built some 4,600 years ago, Stonehenge has fascinated historians and artists alike for centuries. We know, from previous research, that it was a bustling spiritual center, and must have held a huge significance for the society that built it. But scientists are also learning more things about it every year, including where it originally came from.

The first clue about Stonehenge’s origin comes from geology. The monument is constructed from a type of bluestone — a specific type of rock that is only found in Wales, not where Stonehenge currently lies. This has been suggested by researchers several times but it was conclusively demonstrated by several recent studies. In 2015, one such study revealed that the bluestones were extracted from quarries in the Preseli hills, some 280 kilometres (180 miles) away in west Wales. In 2019, researchers zoomed in even more, finding two specific quarries where the bluestones would have been extracted from.

Now, researchers have found another tantalizing piece of evidence suggesting that not only were the 43 giant bluestones moved over a whopping 150 miles — but they were removed from another dismantled monument. In other words, what’s possibly the most iconic monument in the world may be a second-hand creation.

A needle in a bluestone haystack

The discovery came when researchers analyzed the remains of another stone circle called Waun Mawn. Waun Mawn is one of the oldest stone circles in Britain and the country’s third largest. It has a diameter of 360 feet (110 metres) — the same as the ditch that encloses Stonehenge — and, like Stonehenge, is aligned to the midsummer solstice sunrise. It’s also a stone’s throw away from the bluestone quarries.

The Waun Mawn stone circle in the Preseli Hills in north Pembrokeshire, west Wales, during excavation in 2018, viewed from the north. Image credits: Adam Stanford/Parker Pearson et al./Antiquity Publications Ltd.

Archaeologists had been looking for this type of sister site to Stonehenge for a few years, but they discarded Waun Mawn because the preliminary surveys didn’t really show anything of interest.

In modern archaeology, researchers deploy remote surveys to “see” beneath the ground. These geophysical methods aren’t perfect, but they usually offer a good indication of where archaeologists should dig to find the most interesting things. For some unclear reason, the geophysical surveys at Waun Mawn didn’t find anything. But after ruling out other possible candidate sites, the archaeologists decided to dig anyway.

It was a grueling task that involved many days spent in cold, wind, and rain — but it was worth it.

“It was hard work over eight years with a big team and we hit many dead ends,” said study author Parker Pearson for ABC. “We had to start by excavating the bluestone quarries, then doing geophysical surveys across rough terrain, excavating possible sites, finding out that none of these were what we were searching for, and finally going back to a site we had discounted.”

“So, going back to it and finding out we should have stuck with it from the very beginning was certainly a surprise,” he added. “But the years in between weren’t wasted because we really get to know the landscape and to cross off all the other likely possibilities.”

Although they haven’t found completely irrefutable evidence, everything about what archaeologists found at Waun Mawn seems to suggest a connection to Stonehenge. It’s not just the size and geometry of the site that fits, it’s also the time: Waun Mawn stone circle was created somewhere after 3600 BC, a few hundred years before the first stages of construction at Stonehenge. The type of rocks also fits — it’s the same type of bluestone in the two monuments. Furthermore, one of the rocks at the site has an unusual pentagonal shape, just like the rocks seen in Stonehenge, and the rock chippings are also similar.

This stone hole was uncovered at Waun Mawn, with the stone packing used to secure the missing monolith still present. Image credits: Parker Pearson.

Building (and moving) the first Stonehenge

So why did they do it? Why did they go through this gargantuan task of carrying dozens of giant megaliths across the country? We’re not exactly sure.

The area around Waun Mawn thrived until some 5,000 years, when activity in the area seems to have completely stopped.

This begs two questions: first, what happened to these people, why did they migrate to different areas — and perhaps more importantly, why did they take the huge stones with them?

“It’s as if they just vanished. Maybe most of the people migrated, taking their stones—their ancestral identities—with them,” archaeologist Mike Parker Pearson, from UCL, said.

Moving three-ton bluestones 180 miles to Salisbury Plain, where Stonehenge currently lies, must have been a mammoth task, so why did they do it? At this point in the research, it’s not clear why they did it, but the rocks themselves must have been extremely important, “considered as not just valuables, but the very essence of who they were,” notes Pearson.

Not all researchers are convinced by this theory, and it’s up to upcoming research to prove whether this proto-Stonehenge was indeed built and dismantled in Wales and then transported to Salisbury. Further excavations are already underway.

Myth meets reality

The study is also notable because it seems to be linked with a piece of myth. In a 12th century book, the Welsh cleric Geoffrey of Monmouth wrote the story that the mythical wizard Merlin was enlisted to lead an army to Ireland and transport a ring of giganting mystical stones to what is believed to be Salisbury Plain.

We now know this to be nothing more than pseudohistory or myth, but this new find seems to suggest a kernel of truth to this legend — it may have not been Ireland but Wales, and it wasn’t magic that transported the rocks but hard work and clever engineering, but it seems like a kernel of truth nonetheless, and one of the rare instances where myth and reality actually intertwine.

In addition to the monument itself, the large-scale migration also raises some intriguing questions. The people who were buried at Stonehenge also appear to have originated from West Wales, as genetic analyses have shown, so the signs of a mass migration are there — which means there may have been other megalith sites waiting to be discovered.

“My guess is that Waun Mawn was not the only stone circle that contributed to Stonehenge,” said Parker Pearson in a news statement.

Journal Reference: Mike Parker Pearson et al. The original Stonehenge? A dismantled stone circle in the Preseli Hills of west Wales, Antiquity (2021). DOI: 10.15184/aqy.2020.239 , doi.org/10.15184/aqy.2020.239

Researchers find Earth’s oldest rocks — and they were probably created by meteorites

Scientists have found 4.02 billion-year-old rocks, which they believe to be the oldest rocks on the planet’s surface. These rocks, they explain, were likely created by meteorites.

The year is 4 billion BC — and the Earth is a hellish place. The planet doesn’t really have an atmosphere to shield it from meteorite impacts, and the planetary surface is still in its nascent days. As far as we know, no living creatures can inhabit Earth under these conditions — but this doesn’t mean the Earth is inactive. Geologically, lots of things are happening, and researchers have found strong evidence of this.

Australian geologists investigated the Slave Craton formation in Northern Canada, north of Yellowknife and the Great Slave Lake. This is one of the oldest and most stable tectonic structures on our planet, which makes it an ideal place to search for rocks from that period. In particular, researchers have focused on some areas near the Acasta River, discovering 4.02 billion-year-old silica-rich felsic rocks.

[panel style=”panel-default” title=”Felsic and Mafic” footer=””]Igneous rocks, which formed through the slow cooling of magmatic rocks, are typically split into two main groups: felsic, and mafic.

Felsic rocks are relatively rich in elements that form feldspar and quartz, contrasting with the mafic rocks, which are relatively rich in magnesium and iron. The term “felsic” combines the words “feldspar” and “silica”, while the word “mafic” combines “magnesium” and “ferric.”

Generally speaking, felsic rocks tend to be whiter or lighter than mafic rocks, which are generally dark and black.[/panel]

Scientists have long known that the Acasta rocks are very different from the vast majority of felsic rocks, such as granites. Now, in a new study, researchers have shown how these rocks may have formed — and it involves meteorites.

“Our modelling shows that the Acasta River rocks derived from the melting of pre-existing iron-rich basaltic rock, which formed the uppermost layers of crust on the primitive Earth”, said team leader Tim Johnson, from Curtin University, Perth.

They found that the Acasta River rocks were produced by partial melting of previously mafic rocks. This process happened at very low pressures, indicating that they were close to the surface. But there’s not much reason why the 900°C temperatures needed to melt the rocks would have been reached near the surface. Researchers suspect there was a drastic event, most likely a meteorite bombardment, that caused this rise in temperature.

“We estimate that rocks within the uppermost 3km of mafic crust would have been melted in producing the rocks we see today. We think that these ancient felsic rocks would have been very common, but the passage of 4 billion years, and the development of plate tectonics, means that almost nothing remains,” Johnson continues.

“We believe that these rocks may be the only surviving remnants of a barrage of extraterrestial impacts which characterized the first 600 million years of Earth History”.

The study has been published in Nature Geoscience and will be presented at the Goldschmidt conference on the 14th of August.

Using rocks for farming could improve soil quality, reduce CO2 emissions

Adding minute rock pieces to soils can release important soil nutrients and also suck up significant quantities of carbon dioxide.

Destruction and rebirth

Fields of green: volcanic soils often host rich, lush vegetation, as can be seen in this photo of Oahu. Image credits: Jason Jacobs / Flickr.

Since the dawn of mankind, humans have tried to find ways to improve agricultural yield — a goal still sought after today. With the global population set to reach 9.7 billion by 2050, researchers are looking for better ways to safely feed the world. Now, an innovative study by University of Sheffield researchers reports an unexpected way through which we can improve production, while also helping reducing carbon dioxide emissions: using rocks as fertilizers.

The idea is that adding fast-reacting silicate rocks to croplands could capture CO2 and give increased protection from pests and diseases. In time, this process would also restore soil structure and fertility, protecting against erosion.

Professor David Beerling, lead author of the research, explains.

“Human societies have long known that volcanic plains are fertile, ideal places for growing crops without adverse human health effects, but until now there has been little consideration for how adding further rocks to soils might capture carbon.”

Volcanic eruptions can be devastating — they destroy everything in their wake, burying surroundings in a blanket of hot ash. But in the long term, volcanic deposits can develop into some of the richest agricultural lands on earth. Take the soils in Italy, for example. The southern parts of the country feature dry, limestone-rich soils. But if you move towards the north, particularly around Naples, the soils are much more fertile — largely due to the eruptions of Mount Vesuvius. Similarly, volcanic areas like New Zealand or Hawaii often feature rich, lush vegetation.

This isn’t anything new. What Beerling is proposing, however, is taking crushed, small carbon-rich rocks (such as basalt) and using them to fertilize agricultural soils. As these minute pieces dissolve in the soil, they would take in carbon dioxide and eliminate nutrients.

The destruction once caused by volcanoes could be used to inject new life into soils.

Two birds with one stone

“The magnitude of future climate change could be moderated by immediately reducing the amount of CO2 entering the atmosphere as a result of energy generation. Adopting strategies like this new research that actively remove CO2 from it can have a massive impact and be adapted very quickly,” Beerling adds.

Of course, this could be applied to all types of soils for the purpose of absorbing CO2, but to take full advantage of the process, it would be best applied over arable land. This would not only absorb CO2 but also improve soil quality and reduce the need for pesticides.

The good thing about this approach is that it would work with a wide variety of rocks — the more calcium-rich, the better. However, the fastest weathering volcanic rocks are not suitable, Beerling told ZME Science in an email.

“The approach work would work best with basic silicate rocks, richer in magnesium and calcium, that weather faster and therefore capture more CO2. But as we point out the paper, the fastest weathering basic rocks — called ultramafics – are typically enriched in metals that can be toxic so you wouldn’t want to use them on croplands.”

Even better, many areas already spread crushed limestone over arable land to reverse acidification of soils caused by farming practices, including the use of fertilizers. So the machinery and infrastructure for the practice already exists — all that needs to be done is change the rock type.

“Crushing technology is common in the mining industry,” Beerlong added in our correspondence. “The size is the particles is a crucial determinate of the rate of chemical reactions. Small particles with a high surface area react faster. Limestone — essentially calcium carbonate — reacts very fast but more often than not releases carbon dioxide rather than sequesters it.”

Professor Stephen Long at the University of Illinois Champaign-Urbana, and co-author of the study, commented:

“Our proposal is that changing the type of rock, and increasing the application rate, would do the same job as applying crushed limestone but help capture CO2 from the atmosphere, storing it in soils and eventually the oceans.”

Long also notes that people don’t understand the full extent of climate change, and scientists haven’t been truly effective in communicating these issues. He added:

“Global warming is a problem that affects everyone on the planet. Scientists generally have done a poor job of getting across the point that the world must reduce emissions of greenhouse gases from fossil fuels and combine this with strategies for extracting carbon dioxide from the atmosphere to avoid a climate catastrophe.”

The research focus now is to see how much carbon dioxide the approach would capture, how much rock is required, and how much energy is required to crush and distribute the rock, researchers say. They also want to assess the long-term impact the treatment has on soils and watercourses.


Comparison theory experiment.

The Pentagon is one huge pile of ancient bugs, but don’t start evacuating just yet

New research shows that several famous buildings including the Pentagon in the US or the British Museum in London are giant heaps of microbes. No, really.


Variations of size and sorting of ooids.
Image credits Batchelor et al., 2017, Scientific Reports.

The one thing these buildings have in common is that they were erected using a special kind of rock called oolithic limestone. It gets this name from the tiny carbonate (CaCO3) beads which make up the material — they resemble tiny eggs in shape, and the term ‘oolith‘ is drawn from the Greek word for egg. The rock resembles fish roe or tightly-packed styrofoam in texture and is a quality, highly appreciated building material. Its mineral composition lends the limestone hardiness, durability, and a pleasant color, while its oolithic texture makes it easy to cut and sculpt in any direction.

The traditional view is that these ooids form from grains rolling across ocean floors and collecting sediments as they go. When they grow too big for currents to move them along, these ooids stack and fuse together with carbonate material precipitated from the surrounding water. New research from the Australian National University (ANU), however, comes to propose a much buggier origin story for ooliths — using a mathematical model, scientists arrived at the conclusion that the ooids were made of mineralized microbes forming concentric layers.


Comparison theory experiment.

Comparison between the team’s simulated results and experimentally grown ooid.
Image credits Batchelor et al., 2017, Scientific Reports.

“Jurassic oolite in England has been used to construct much of the City of Bath, the British Museum and St Paul’s Cathedral,” said first author Bob Burne in a news release. “Mississippian oolite found in Indiana in the US has been used to build parts of the Pentagon in Virginia and parts of the Empire State Building in New York City.”

“We have proposed a radically different explanation for the origin of ooids that explains their definitive features. Our research has highlighted yet another vital role that microbes play on Earth and in our lives.”

The team used mathematical modeling to simulate how ooliths form and identify the most likely mechanism of their growth. The algorithms they used to simulate the process were based on systems designed to describe how brain tumors develop. The most likely process of oolith formation, the one that best explains their size and internal mineralization patterns, the team explains, is the mineralization or microbial biofilms — in short, the fossilization of microbes and bacteria.

This process would explain the strikingly ordered structures seen in ooids, with very cleanly-defined concentric layers around a central point. It would also explain why ooids have roughly consistent maximum sizes despite a plethora of different environmental condition across the world’s oceans — something which the previous hypothesis never really explained in a satisfactory manner. Burne thinks the results debunk the popular “snowball theory” that ooids were formed by grains rolling on the seafloor and accumulating layers of sediment.

The paper “A biofilm and organomineralisation model for the growth and limiting size of ooids” has been published in the journal Scientific Reports.

Earth’s mantle is much hotter than we thought, scientists learn

We knew the Earth’s insides are hot, but just how hot are they? A new study found that the Earth’s mantle could go up to a whopping 1410 degrees Celsius (2570 degrees Fahrenheit), significantly more than was previously estimated.

Age of oceanic crust: youngest (red) is along spreading centres, where parts of the mantle rise up to create new crust. Credits: NOAA.

For once, something’s hotter and it’s not connected to global warming. The Earth’s mantle, the thickest layer of the Earth makes up 84% of the planet’s volume, lying between the Earth’s crust and its core. Because of its inaccessibility, pretty much everything we know about it comes from indirect evidence. Indeed, it’s a testament to how much geology has progressed that we’re able to describe it in such detail, but as it so often happens with indirect evidence, it can be quite difficult to get the figures exactly right. Now, this new study found that beneath our planet’s oceans, the mantle might be significantly hotter than we thought: by almost 110 degrees F (60 degrees C). This change could help us better understand tectonic processes and help us develop better models of our planet.

“Having such a hot mantle could mean that the mantle is less viscous (flows more easily), which could explain how tectonic plates are able to move on top of the asthenosphere,” the upper layer of Earth’s mantle, said study lead researcher Emily Sarafian, a doctoral student in the Geology and Geophysics Department at a joint program run by the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution.

Technically, the mantle is solid, but for geological purposes, it usually behaves like a fluid. Sounds strange? Well, imagine a jar of honey, which is viscous. The hotter it gets, the more liquid it becomes — and the opposite stands too, cold honey is quite solid.

“If you put honey in the fridge for an hour, it will barely flow when you take it out,” Sarafian said in an email to Live Science. “If, instead, you put honey on the stovetop, it will flow very easily, because it’s hotter.”

So the mantle is so hot that in some regards, it acts like a fluid. This is important because according to our understanding, there are convection currents in the mantle that move the tectonic plates around (and contribute to numerous geological processes). In other words, some parts of the mantle get hotter and become less dense, rising towards the surface. As they move, they transfer some of the heat towards the surface, where plumes of less dense magma break apart the plates at the spreading centers, creating divergent plate boundaries. At the other end of the process, some other end of tectonic plates cools down and sinks — thus, new crust is sometimes formed, and sometimes recycled in the mantle, maintaining an equilibrium.

Simplistic depiction of convection currents. Image credits: Wiki Commons.

To continue the analogy, imagine that the tectonic plates are like pieces of biscuit laid on top of the honey. If the honey (I mean, mantle) is hotter than we thought, then it means that it acts more like a liquid, and “flows more,” so to speak. It means that the currents might be stronger than we thought and the biscuits (plates) might “float” with less resistance — it also means that our current models might need some tweaking.

Hotter than hell

We knew very well that the mantle is hot, there’s plenty of clues to indicate that. For instance, it generates the hot lava that flows out from underwater volcanoes. We also know of the gravitational heat, left over from when gravity first condensed our planet from the hot gases and particles, and perhaps most significantly, of the heat from radioactive decay. But because we can’t really probe it directly, we’ve relied on models and lab experiments to estimate its temperature. The one piece of direct evidence we have is from mantle xenoliths — rocks that were brought up from the mantle by convection currents and exposed by mid-oceanic ridge spreading, but because those rocks undergo processes that significantly change their structure and chemistry, researchers prefer to create synthetic rocks to model conditions.

After the synthetic rock is created in the lab, researchers subject it to pressures and temperatures ranging around those of the mantle and see at what temperature it melts. This is called the solidus temperature. The problem with estimating this temperature is water. Due to a chemical quirk, water greatly affects the solidus temperature of these rocks. Therefore, estimating the water content of the rocks is essential for determining the solidus temperature.

Other teams were aware of this issue, “but they were never able to quantify how much water was in their experiments because the mineral grains that grow during an experimental run at mantle pressures and temperatures are way too small to measure with current analytical techniques,” Sarafian said. She added that researchers were using some corrections, adding a bit of extra water to the synthetic rock — but this correction was unnecessary, as the rocks already accumulate the water from the atmosphere.

She found the missing puzzle piece in olivine, a magnesium iron silicate with larger grains, which can be better measured. So she added olivine to the mix, which allowed her to measure water content more accurately.

A beautiful olivine crystal, not from this study. Image credits:
Rob Lavinsky


“We performed melting experiments the same way that previous scientists did, putting a synthetic rock to high pressure and temperatures, but by adding these grains to our experiments, we were giving ourselves a target that was large enough to analyze for water content,” she said.

With the new water correction, a different solidus temperature emerged, and a different temperature of the mantle.

Paul Asimow, a professor of geology and geochemistry at the California Institute of Technology who was not involved with the study, complemented the research in an accompanying commentary in the journal Science, saying that it is “an appreciable correction.”

Journal Reference: Emily SarafianGlenn A. GaetaniErik H. HauriAdam R. Sarafian — Experimental constraints on the damp peridotite solidus and oceanic mantle potential temperature. Science 03 Mar 2017: Vol. 355, Issue 6328, pp. 942-945.
DOI: 10.1126/science.aaj2165


Pretty rock found in Croatia points at Neanderthals’ softer, artistic side

A rock found at the Krapina site in Croatia 100 years ago seems to have been taken there by Neanderthals only because it was pretty, with no intention of being used as a tool.

Pretty rock is pretty,
Image credits David Frayer / University of Kansas.

A huge part of science is collecting stuff — data, questioners, images, stuff from caves. Sadly, what often happens is that things get collected, taken to a place such as a lab or museum to be examined, and then simply forgotten.

Sometimes though, research teams go museum-diving, and they make some pretty fantastic finds. An international team of researchers has (re?)discovered a piece of split limestone retrieved from the Krapina site in Croatia and stored in the Croatian Natural History Museum in Zagreb. The site was excavated between 1899-1905 and found to contain Neanderthal bones.

The best part? This piece of limestone wasn’t worked over and would have probably made a horrible tool anyway. Neanderthals couldn’t eat it, or use it in any other way. It simply was a pretty rock.

“If we were walking and picked up this rock, we would have taken it home,” said David Frayer, a professor emeritus of anthropology and corresponding author of the study.

“It is an interesting rock.”

The finding adds to a growing body of evidence showing that Neanderthals weren’t simple brutes. They were able to see simbolic or aesthetic value in objects, not just the “rock big, good for smash” property. Frayer and lead author Davorka Radovčić, curator at the museum, also published a paper in PLOS ONE in 2015 describing a set of eagle talons found at the same site which were fashioned into jewelry.

“People have often defined Neanderthals as being devoid of any kind of aesthetic feelings, and yet we know that at this site they collected eagle talons and they collected this rock. At other sites, researchers have found they collected shells and used pigments on shells,” Frayer said.

“There’s a little bit of evidence out there to suggest that they weren’t the big, dumb creatures that everybody thinks they were.”

Similar to how they found the talons, Frayer credited Radovčić’s keen eye for finding the rock among the items recovered from the site. The cave, he said, was dug in sandstone so the rock obviously was brought from somewhere else. It stands out in over 1,000 stone items recovered from the cave, but the original archaeologists didn’t give it much attention beyond bagging and tagging it.

Clam-shell view of the rock with black dendrites. The flake, only shown on Side A, fractured after excavation.
Image credits David Frayer / University of Kansas.

The rock, which measures roughly 5x4x1,5 inches, doesn’t show any striking platforms or other preparation of an edge, so the team suspects it wasn’t meant to be used as a tool. A small flake seems to fit in with the rest of the rock, but the break likely happened after the specimen was recovered

“The fact that it wasn’t modified, to us, it meant that it was brought there for a purpose other than being used as a tool,” Frayer said.

What caught Radovčić’s eye were the inclusions (black lines) that stood out from the brown rock. Its look is probably what made the Neanderthal want to collect it. He or she either carried it a few kilometers to the cave from a local outcrop of biopelmicritic limestone, or found it closer to Krapina — likely transported by a stream.

And yea I get that as far as archaeological findings go, this one is not so dramatic — it’s a stone from the stone age. But personally, I think it’s awesome. I like collecting rocks. Always have. The fact that one Neanderthal a hundred-and-some thousand years ago had the same hobby as me makes them more relatable than a gazillion cave paintings in France ever could.

Pretty rocks rule, my Neanderthal brother. Or sister.

The full paper was published in the journal Human Palaeontology and Prehistory with what is probably the best scientific paper name I have seen in a long time: “An interesting rock from Krapina”.

The types of rock: igneous, metamorphic and sedimentary

The three types of rocks

It’s the first thing you learn in a geology class — very briefly the three types of rocks are:

  • Igneous — they form from the cooling of magma deep inside the earth. They often have large crystals (you can see them with the naked eye).
  • Metamorphic — they are formed through the change (metamorphosis) of igneous and sedimentary rocks. They can form both underground and at the surface.
  • Sedimentary — they are formed through the solidification of sediment. They can be formed from organic remains (such as limestone), or from the cementing of other rocks.
    Now the long story, which is much more interesting, is this:

Now, the long story, which is much more interesting, is this:

Igneous Rocks

Lava flow on Hawaii. Lava is the extrusive equivalent of magma. Image via Wiki Commons.

Magma is the heart of any igneous rock. Magma is composed of a mixture of molten or semi-molten rock, along with gases and other volatile elements. As you go deeper underground, the temperature rises; go further and you’ll eventually reach the Earth’s mantle — a huge layer of solid rock surrounding the Earth’s core (which, in geologic time, behaves as a viscous liquid).

As you probably know, when magma cools, it turns into rock; if it cools while still underground at high temperatures (but at temperatures still lower than that of the magma), the cooling process will be slow, giving crystals time to develop. That’s why you see rocks such as granite with big crystals — the magma had time to cool off. The crystals are also differentiated, as you can see below.

Note the white, almost rectangular feldspar crystals, the grey virtually shapeless quartz crystals, and the black crystals, which can be either black mica or amphibole. Image modified from Eastern Illinois University.

Note the white, almost rectangular feldspar crystals, the grey virtually shapeless quartz crystals, and the black crystals, which can be either black mica or amphibole. Image modified from Eastern Illinois University.

However, if the magma erupts or is cooled rapidly, you instead get a volcanic rock – not really igneous, but also originating from lava. The classical example here is basalt, which can have many small crystals or very few large ones. Volcanic rocks are also called extrusive igneous rocks, as opposed to intrusive igneous rocks. Some volcanic rocks (like obsidian) don’t have any crystals at all.

Basalt — note the almost complete lack of visible crystals. Now compare it to the granite. Image via Georgia State University.


Not all magma is made equally: different magmas can have different chemical compositions, different quantities of gases and different temperature — and different types of magma make different types of rocks. That’s why you get incredible variety. There are over 700 hundred types of igneous rocks, and they are generally the hardest and heaviest of all rocks. However, volcanic rocks can be incredibly lightweight – pumice, for example, can even float, and was called by ancient sailors “the foam of the sea”. Pumice is created when a volcano violently erupts, creating pockets of air in the rock. The most common types of igneous rocks are:

  • andesite
  • basalt
  • dacite
  • dolerite (also called diabase)
  • gabbro
  • diorite
  • peridotite
  • nepheline
  • obsidian
  • scoria
  • tuff
  • volcanic bomb

Metamorphic Rocks

Here, the name says it all. These are rocks that underwent a metamorphosis; they changed. They were either sedimentary or igneous (or even metamorphic), and they changed so much, that they are fundamentally different from the initial rock.

Different types of metamorphism. Image via Tankon Yvtar.

There are two types of metamorphism (change) that can cause this:

  • contact metamorphism (or thermal metamorphism) — rocks are so close to magma that they start to partially melt and change their properties. You can have recrystallization, fusing between crystals and a lot of other chemical reactions. Temperature is the main driver here.
  • regional metamorphism (or dynamic metamorphism) — this typically happens when rocks are deep underground and they are subjected to massive pressure — so much so that they often become elongated, destroying the original features. Pressure (often times with temperature) is the main driver here.

Folded foliation in a metamorphic rock from near Geirangerfjord, Norway. Image via Wiki Commons.

Metamorphic rocks can have crystals and minerals from the initial rocks as well as new minerals resulting from the metamorphosis process. However, some minerals are clear indicators of a metamorphic process. Among these, the most usual ones are garnet, chlorite, and kyanite.

Equally as significant are changes in the chemical environment that result in two metamorphic processes: mechanical dislocation (the rock or some minerals are physically altered) and chemical recrystallization (when the temperature and pressure changes, some crystals aren’t stable, causing them to change into other crystals).

Marble is a non-foliated metamorphic rock.

They can be divided into many categories, but they are typically split into:

  • Foliated metamorphic rocks — pressure squeezes or elongates the crystals, resulting in a clear preferential alignment.
  • Non-foliated metamorphic rocks — the crystals have no preferential alignment. Some rocks, such as marble (the metamorphized version of limestone), are made of minerals that simply don’t elongate, no matter how much stress you apply.

Metamorphic rocks can form in different conditions, in different temperatures (up to 200 °C) and pressures (up to 1500 bars). By being buried deep enough for a long enough time, a rock will become metamorphic. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion; they can also form when the rock is heated up by the intrusion of magma from the Earth’s interior.

The most common metamorphic rocks are:

  • amphibolite
  • schist (blueschist, greenschist, micaschist, etc)


    A micaschist. The dark brown rounded minerals are garnet, and everything you see with a whiteish tint is the mica. The reddish areas are rusty mica. Image modified from Willowleaf Minerals.

  • eclogite
  • gneiss
  • hornfels
  • marble
  • migmatite
  • phyllite
  • quartzite
  • serpentinite
  • slate

Sedimentary Rocks

Sedimentary rocks are named as such because they were once sediment. Sediment is a naturally occurring material that is broken down by the processes of weathering and erosion and is subsequently naturally transported (or not). Sedimentary rocks form through the deposition of material at the Earth’s surface and within bodies of water.

A conglomerate — a rock made from cemented gravel. Image via Earth Physics Teaching.

Sedimentary rocks are quite difficult to classify, as they have several different defining qualities (the chemical make-up, the sedimentation process, organic/inorganic material), but the most common classification is the following:

  • clastic sedimentary rocks — small rock fragments (many silicates) that were transported and deposited by fluids (water, bed flows). These rocks are further classified by the size and composition of the clastic crystals included in the sedimentary rocks (most often quartz, feldspar, mica and clay).
  • conglomerates (and breccias)  conglomerates are predominantly composed of rounded gravel, while breccias are composed of angular (sharper) gravel.
  • sandstones  as the name says, it’s a rock made from many-sand-sized minerals and rock grains. The most dominant mineral in sandstone is quartz because it is the most common mineral in the Earth’s surface crust.

    An old, red sandstone. Image via Ian Hopkinson.

  • mudrocks  again, the name says it all — they’re rocks made from solidified mud. They typically contain very fine particles and are transported as suspended particles by turbulent flow in water or air, depositing once the flow settles.
  • biochemical rocks — you’ll probably be surprised to find out that most limestone on the face of the Earth comes from biological sources. In other words, most limestone you see today comes from the skeletons of organisms such as corals, mollusks, and foraminifera. Coal is another example of biochemical rock.
  • chemical rocks — these rocks include gypsum and salt (halite) and are formed mostly through water evaporation

Yes, salt is a mineral — and it can be quite beautiful. In this context, it’s called halite and can be classified as a sedimentary rock.

There are also other types of specific sedimentary rocks for example, the ones formed in hot springs. Most of the solid surface of our planet (roughly 70%) is represented by sedimentary rocks, but if you go deep enough beneath the Earth’s surface, there are plenty of igneous and metamorphic rocks to be found.

As I mentioned with biochemical rocks, fossils can become rocks in time. You can actually have entire mountains made up from reefs like you can see below.

This entire mountain in Romania was formed based on a coral reef. Image via MP Interactiv

Some common sedimentary rocks are:

  • argillite
  • breccia
  • chalk
  • chert
  • claystone
  • coal
  • conglomerate
  • dolomite
  • limestone
  • gypsum
  • greywacke
  • mudstone
  • shale
  • siltstone
  • turbidite

This is just scratching the surface you could spend a lifetime studying rocks and still be surprised. But I hope that for your general knowledge or to impress some friends (or if you’re considering starting geology), the information here was useful and interesting to you. Feel free to send any questions and comments my way and I’ll do my best to answer them!

Archaeologists Discover The World’s Largest Ancient Stone Block

Look at this incredibly big rock. Take a moment, ponder its dimensions, and its weight. Oh, but if you’re looking at the one in the middle, that’s not it – look over to the right. The one to the right, not fully excavated yet, is the biggest ancient stone block, weighing an impressive 1,650 tons (that’s 3,300,000 pounds, or 1,496,850 kg).

Photo credit: Deutsches Archäologisches Institut.

The year is 27 BC – the Roman Empire is in its more developed stages, and Lebanon is one of the most thriving areas on the planet. The place is the Baalbek site in Lebanon – a well known and studied site. It’s not completely unexpected to find huge monoliths in the area, but German archaeologists weren’t expecting something quite as big – 19.6 meters (64 feet) in length, 6 meters (19.6 feet) wide, and is at least 5.5 meters (18 feet) high.

The aim of this year’s excavations was to find new data about the mining techniques and the transporting of the megaliths.  At the same site, archaeologists discovered an already famous monolith – “Hajjar al-Hibla”. Hajjar al-Hibla is called The Stone of the Pregnant Woman or Stone of the South. It’s a Roman monolith from granite. Its exact purpose is still a matter of debate.

A different perspective of the Stone of the Pregnant Woman. Image via Wiki Commons.

Judging by this stone’s level of smoothness and configuration, it seems likely that it was meant to be transported without being cut. While techniques have been described for transporting the huge rocks, it’s still not clear how ancient Romans used to carry them. The next goal is to figure out how they transported them and why the rock still remained in the quarry.

Story via Deutsches Archäologisches Institut.

Evidence of 3.5-Billion-Year-Old Bacterial Ecosystems Found

To say that finding evidence of how life on Earth was 3.5 billion years ago is hard would be an understatement. Reconstructing the rise of life in its early stages is a monumental challenge – the evidence is only preserved in Earth’s oldest sedimentary rocks, and sedimentary rocks of that age are very hard to come by. However, a new study revealed the well preserved remnants of a complex ecosystem in a nearly 3.5 billion-year-old sedimentary rock sequence in Australia.

life australia

A rock surface is displaying “polygonal oscillation cracks” in the 3.48 billion years old Dresser Formation, Pilbara region, Western Australia. Such and similar sedimentary structures are of biological origin.

The study was conducted by a team which included Carnegie’s Nora Noffke, a visiting investigator, and Robert Hazen, a research scientist at the Carnegie Institution of Washington’s Geophysical Laboratory.

The Pilbara district of Western Australia is geologically speaking one of the most spectacular areas in the world. Scientists have described in detail deposits created by ancient photosynthetic bacteria, called stromatolites, and microfossils of bacteria – a very rare insight into that ancient world. However, one piece of the puzzle lacked from the Pilbara district: a phenomenon called microbially induced sedimentary structures, or MISS, had not previously been seen in this region. These structures are formed from mats of microbial material, much like mats seen today on stagnant waters, be they mainland or oceanic coastal lines. In other words, microbially induced sedimentary structures are primary sedimentary structures formed by the interaction of microbes with sediment and physical agents of erosion, deposition, and transportation.

But now, the team of geologists managed to locate this phenomenon in the old rocks, confirming their initial results with advanced chemical tests. The MISS was found in a formation called the Dresser Formation, and it strongly resembles a similar structure, dated 2.9 billion years ago.

“This work extends the geological record of MISS by almost 300 million years,” said Noffke, who is also a professor at ODU. “Complex mat-forming microbial communities likely existed almost 3.5 billion years ago.”

The team suggests that the bacterial mats were formed as a result of the interaction between the interactions of bacterial films with shoreline sediments from the region.

“The structures give a very clear signal on what the ancient conditions were, and what the bacteria composing the biofilms were able to do,” Noffke said.

Studying MISS is very important, because they are among the main targets for the Mars rovers. Thus, these results could have significant implications for studying life on other places in our solar system.

Journal Reference:

  1. Nora Noffke, Daniel Christian, David Wacey, Robert M. Hazen. Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in theca.3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia.Astrobiology, 2013; 131108054848000 DOI:10.1089/ast.2013.1030

Russia believes Phobos mission will bring them in back in the spatial spotlight

In these past few decades, the US space program seemed to have significantly overcome the Russian one, with all sort of missions and studies, but more recently, the balance seems to have turned once again, as NASA is undergoing numerous problems, while the Russians are planning an ambitious mission which is aimed at the Mars moon Phobos. This will be their first interplanetary mission in over 15 years !

Artist depiction of an extracting mission

The Phobos-Grunt mission is set to blast off from Kazakhstan’s Baikonur cosmodrome at 3:16 p.m. EST today with the purpose of extracting and bringing back some samples from the red planet’s moon (‘grunt’ means ‘dirt’ in Russian). If successful, it would shed some new light on the early days of the planet, and give some indication about the mechanisms which take place on Phobos. Furthermore, it would be a great morale and image boost for the Russian space agency, which has surpassed the cone of shadow in which it lay for years.

“If Phobos-Grunt fully carries out its mission, then this will be a world-class achievement,” Igor Lisov, editor-in-chief of the journal Novosti Kosmonavtiki (Space News), told Agence France-Presse. “The problem with Russian space exploration has been that people have forgotten the taste of victory. The task of this mission is to restore confidence in our abilities and the importance of the task.”

If everything goes according to plan, the $163 million mission will arive near Phobos in Autumn 2012, and drop its lander on the moon in the following months. The moon is most likely a potato shaped asteroid that was trapped by Mars’ gravity. After this, the lander will then return to the probe which will start its journey back to our planet, where it should arrive sometime in 2014, depending on the conditions and encountered problems.

Scientists are just boiling to get their hands on some samples; if it is indeed an asteroid, then it would be even more interesting, because these asteroids are leftovers from the solar system’s early days, primeval pieces that didn’t get absorbed by any planets. Also, some dust from Phobos could actually originate on Mars, from where it was brought as a result of a meteorite impact.

“This is really a very difficult project, if not the most difficult interplanetary one to date,” Phobos-Grunt lead scientist Alexander Zakharov told Reuters. “We haven’t had a successful interplanetary expedition for over 15 years. In that time, the people, the technology, everything has changed. It’s all new for us; in many ways, we are working from scratch.”