Making the Moon: The Practice Crater Fields of Flagstaff, Arizona

Between the years of 1969 and 1972 the astronauts of the Apollo missions personally explored the alien landscape of the lunar surface, shuffling, bounding, digging, and roving across six sites on the Moon. In order to prepare for their off-world adventures though, they needed to practice extensively here on Earth so they would be ready to execute the long laundry lists of activities they were required to accomplish during their lunar EVAs. But where on Earth could they find the type of landscape that resembles the Moon’s rugged, dusty, and — most importantly — cratered terrain?

Enter the Cinder Lakes Crater Fields of Flagstaff, Arizona.

The Cinder Lakes Crater Fields northeast of Flagstaff, near the famous San Francisco peaks and just south of the Sunset Crater volcano, were used for Apollo-era training because of the inherently lunar-like volcanic landscape. LRV practice as well as hand tool geology and lunar morphology training were performed there, as well as ALSEP – Apollo Lunar Surface Experiment Package – placement and setup practice.

The photo above shows Apollo 15 astronauts Dave Scott and Jim Irwin driving a test LRV nicknamed Grover along the rim of a small “lunar crater.” (This particular exercise was performed on Nov. 2, 1970… 44 years ago today!)

Detonation of a "lunar crater" in 1967 (USGS)
Detonation of a “lunar crater” in 1967 (USGS)

Although the craters might look similar to the ones found on the Moon, they were actually created by the USGS in 1967 by digging holes and filling them with various amounts of explosives, which were detonated to simulate different-sized lunar impact craters. The human-made craters ranged in size from 5-40 feet (1.5-12 meters) in diameter.

The two crater field sites at Cinder Lakes were chosen because of the specific surface geology: a layer of basaltic cinders covering clay beds, left over from an eruption of the Sunset Crater volcano 950 years ago. After the explosions the excavated lighter clay material spread out from the blast craters and across the fields, like ejecta from actual meteorite impacts. A total of 497 craters were made within two sites comprising 2,000 square feet.

Detonations were done in series to simulate ejected debris from cratering events of different ages. And one of the areas of Cinder Lakes was designed to specifically replicate craters found within a particular region of the Apollo 11 Mare Tranquillitatis landing site.

Watch a contemporary educational film from the USGS showing the crater field detonations here. (HT to spaceflight archivist David S. F. Portree for the link.)

The completed Cinder Lakes Crater Field #1 in October 1967 (USGS)
The completed Cinder Lakes Crater Field #1 in October 1967 (USGS)

Today only the largest craters can be distinguished at all in the publicly-accessible Cinder Lakes field, which has become popular with ATV enthusiasts. But a smaller field, fenced off to vehicles, still contains many of the original craters used by Apollo astronauts, softened by time and weather but still visible.

A couple of other areas were used as lunar analogue training fields as well, such as the nearby Merriam Crater and Black Canyon fields — the latter of which is now covered by a housing development. Geology field training exercises by Apollo astronauts were also performed at locations in Texas, New Mexico, Nevada, Oregon, Alaska, Idaho, Iceland, Mexico, the Grand Canyon, and the lava fields of Hawaii. But only in Arizona were actual craters made to specifically simulate the Moon!

Read more about the Cinder Lakes Crater Field in a presentation document (my main article source) by LPI’s Dr. David Kring, and you can find more recent photos of the Crater Lakes sites on this page by LPI’s Jim Scotti.

Top photo research: J.L. Pickering. Source: The Project Apollo Image Archive. 

Apollo 12 astronauts Pete Conrad and Alan Bean during geology training at Cinder Lakes on October 10, 1969 (NASA)
Apollo 12 astronauts Pete Conrad and Alan Bean during geology training at Cinder Lakes on October 10, 1969 (NASA)

Selling Rocks from Outer Space: an Interview with ‘Meteorite Man’ Geoff Notkin

What’s the oldest thing you’ve ever held in your hand? A piece of petrified wood? A fossilized trilobite? A chunk of glacier-carved granite? Those are some pretty old things, sure, but there are even older objects to be found across the world… that came from out of this world. And thanks to “Meteorite Men” co-host, author, and educator Geoff Notkin and his company Aerolite Meteorites, you can own a truly ancient piece of the Solar System that can date back over 4.5 billion years.

Founded in 2005, Aerolite (which is an archaic term for meteorite) offers many different varieties of meteorites for sale, from gorgeous specimens worthy of a world-class museum to smaller fragments that you could proudly — and economically — display on your desk. Recently I had the opportunity to talk in depth with Geoff about Aerolite and his life’s work as a meteorite collector and dealer. Here are some of the fascinating things he had to say…

Geoff holds one of his found meteorites (© Geoff Notkin)
“I promised myself as a kid that one day I would have an actual meteorite.” (© Geoffrey Notkin)

So Geoff, what initially got you interested in meteorites and finding them for yourself?

“It’s been a lifelong passion for me, but I’m lucky in that I can really put my finger on a specific event when I was a kid and that was my mother taking me to the Geological Museum in London when I was six or seven… I was already a rock hound, I loved collecting fossils, and my dad was a very keen amateur astronomer. And so I had this love of astronomy and this fascination with other worlds for as long as I can remember. I’m a very tactile person; I’m very hands-on. I like to know how things work… I want to know all the bits and pieces. I was frustrated a bit, because I wanted to know more about astronomy. I could see all these planets and places through the ‘scope, but I couldn’t touch them. But I could touch rocks and fossils.

“So I’m six or seven years old, and I’m on the second floor of the Museum in the Hall of Rocks and Minerals. And at the back was this small display area that’s very dark. And you walked through an arch, it’s almost like walking into a cave. And it was very low light back there, and that was the meteorite collection.

“There were a couple of large meteorites on stands, and in those days — it was the late 60s — security wasn’t the issue that it is today. So you could touch the big specimens, and so I put my hands on these giant meteorites and I was absolutely enthralled.  And I had this sort of epiphany: meteorites were the locus between my two interests, astronomy and rock-hounding. Because they’re rocks… they’re rock samples from outer space. I promised myself as a kid that one day I would have an actual meteorite.

“By finding or owning meteorites, you are forging a solid and tangible connection with astronomy.”

“Of course at the time there was no meteorite business, no meteorite magazines, there was no network of collectors like there is today. Back in the late 60s when I gave myself this challenge it was like saying I was going to start my own space program! But not only did it come true, it’s become my career.”

One of the meteorites offered at (© Geoff Notkin)
One of the meteorites offered at (© Geoffrey Notkin)

What makes Aerolite such a great place to buy meteorites?

“I think the caring for the subject matter really shows on the website. We have the best photography in the entire meteorite industry. I think we have the largest selection… we certainly spend a great deal of time discussing the history and importance of pieces… every single meteorite on our website has a detailed description and in most cases multiple photographs. My view is if you’re going to do something, you should really do it to the best of your ability. We don’t cut any corners, we don’t sell anything unless we’re one hundred percent sure of what it is and where it came from.

“I want buyers and visitors to look at the website and share my sense of wonder about meteorites. I think meteorites are the most wonderful things in existence, they’re actual visitors from outer space — they’re inanimate aliens that have landed on our planet.”

“We do this because we want to share our passion. We stand by every piece that we sell.”

How can people be sure they are getting actual meteorites (and not just funny-looking rocks?)

“This is something that’s more important to pay attention to now than ever. Are there fakes, are there shady people? Yes and yes. If you go on eBay at any given time you will find numerous pieces that are being offered for sale that are either not meteorites at all or are one thing being passed off as another thing. Sometimes this is malicious, sometimes people just don’t know any better. So the best way to buy a meteorite and know that it’s real is to buy from a respected dealer who has a solid history in the field.

“I’m by no means the only person who does this. There are a number of very well-established dealers around the world, and a good place to start is the International Meteorite Collectors Association (of which Geoff is a member) which is an international group with hundreds of members — collectors and dealers… it’s sort of a watchdog group that tries to maintain high standards of integrity in the field.

“My company has a very strict policy of never offering anything that’s questionable.”

“I see fakes all the time,” Geoff added. “On eBay, on websites, in newspaper ads… you do have to be careful. My company has a very strict policy of never offering anything that’s questionable. And we do get offered questionable things. There are some countries that have strict policies about exporting meteorites — Australia and Canada being two of them — and we work very closely with academia in both countries, and we have legally exported meteorites from those countries. Not only do we abide by international regulations, we actively support them.”

Geoff and some of his 'alien'-hunting gadgets in the  Chilean desert. (© Geoff Notkin)
Geoff and some of his ‘alien’-hunting gadgets in the Chilean desert. (© Geoffrey Notkin)

So you not only offer meteorites for sale to the general public, but you also donate to schools and museums.

“We work very closely with most of the world’s major meteorite institutions. I have provided specimens to the American Museum of Natural History in New York, the British Museum of Natural History in London, the Vienna Museum of Natural  History, the Center for Meteorite Studies… we work with almost everyone. When we find something that is new or different or exciting, we always donate a piece or pieces to our colleagues in academia. It’s just the right thing, it’s the right thing to do if you discover something important to make it available to science.

A sample of a beautiful, partially-translucent pallasite meteorite (© Geoff Notkin)
A sample of a beautiful, partially-translucent pallasite meteorite (© Geoffrey Notkin)

“Most universities and museums don’t have acquisitions budgets and can’t afford to buy things that they might like to have. In return they classify the meteorites that we found, and they go into the permanent literature and become more valuable as a result. A meteorite with a history and a name and classification is worth more than a random meteorite that somebody just found in a desert. So everybody benefits, it’s a really good match.”

In other words, you really are making a contribution to science as opposed to just “looting.”

“Exactly. And I have, a very few times, gotten emails from disgruntled viewers who didn’t understand what we were doing, saying ‘what makes you think it’s okay to come to Australia and take our meteorites,’ for example. So I wrote a very courteous email back saying that we were in Australia with the express permission and cooperation of the Australian park services and one of the senior park rangers was there with us. And not only did we follow the proper procedure in having those specimens exported from Australia, I donated rare meteorites to collections just as a ‘thank you’ for working with us. It wasn’t a trade, it was a thank you. So everywhere we go, whatever we do, we try and leave a good impression.”

Geoff added, “I do this out of love… this isn’t the best way to make a living! Being a meteorite hunter is probably not the best capital return on your time but it’s a very exciting and rewarding life in every other way.”

Geoff Notkin is also the host of STEM Journals, an educational show on COX 7 soon entering its third season (© Geoff Notkin)
Geoff Notkin is also the host of STEM Journals, an educational show on COX 7 soon entering its third season (© Geoffrey Notkin)

And thus, by buying meteorites from Aerolite, customers aren’t just helping pay for your expeditions and your work but also supporting research and education too.

“People who purchase from us are really participating in the growth of this science. Also, something very near and dear to my heart is science education for kids. You know that I am the host of an educational series called STEM Journals, which is a very — I think — amusing, entertaining, funny, fast-paced look at science, technology, engineering, and math topics. But you can’t make a living doing television shows like that. This is a labor of love… we do it because we think it’s important. If I didn’t have a commercial meteorite company to help underwrite the costs of educational programming and educational books, we just couldn’t do it. It’s as simple as that.

“So we always try to give back. That’s why I speak at schools and universities and give away meteorites to deserving kids at gem shows… because it was done to me when I was seven years old. The look of wonder you see on a kid’s face when you connect with them and they start to grasp the wonder of science… that’s something they’ll never forget.”

That’s great. And it sounds like you haven’t forgotten it yet either!

“I must say after all these years, I’ve been doing this close to full time for nearly twenty years and you never lose the amazement and the wonder of when a meteorite’s found or uncovered. I never go ‘oh, jeez, it’s just another billion-year-old space rock that fell to Earth!’ So it is a privilege to be in a work field where almost daily something wondrous happens.”

As we here at Universe Today know, when it concerns space that’s a common occurrence!


One last thing Geoff… do you think we’ll ever run out of meteorites?

“The meteorite collecting field has grown tremendously in the past ten years, and Meteorite Men is part of that. There is a finite supply of meteorites. Of course there are more landing all the time, but not enough to replenish the demand. Periodically there is a new very large discovery made, such as the Gebil Kamil iron in Egypt a couple of years ago. But what is happening is a significant increase in price and a decrease in selection, so some of the real staples we used to see… you can’t get them anymore.

“Still, people who want a meteorite collection, now is a great time for them to be buying because there are more meteorites available than in the past — but it’s not going to stay that way for very long. It’s like any other collectible that has a finite supply.”

Makes sense… I’ll take that as ‘inside advice’ to place an order soon!


My thanks to Geoff for the chance to talk with him a little bit about his fascinating past, his passion, and his company. And as an added bonus to Universe Today readers, Geoff is extending a special 15% off on orders from Aerolite Meteorites — simply mention the code UNIVERSETODAY when you place an order!* (Trust me — once you browse through the site you’ll find something you want.) Also, if you’re in the Tucson area, Geoff Notkin and Aerolite Meteorites will have a table at the Tucson Gem and Mineral Show starting Jan. 31.

One of several meteorite-hunting books by Geoff, featuring an introduction by Neil Gaiman.
One of several meteorite-hunting books by Geoff, featuring an introduction by Neil Gaiman.

Be sure to check out Geoff’s television show STEM Journals on COX7 — the full first two seasons can be found online here and here, and shooting for the third season will be underway soon.

Want to know how to find “inanimate aliens” for yourself? You can find Geoff’s books on meteorite hunting here, as well as some of the right equipment for the job.

And don’t forget to follow Aerolite Meteorites and Geoff Notkin on Twitter!


*Sorry, the code isn’t valid for items already on sale or for select consignment items.

What Craters on the Moon Teach Us About Earth

When the Moon was receiving its highest number of impacts, so was Earth. Credit: Dan Durda

Some questions about our own planet are best answered by looking someplace else entirely… in the case of impact craters and when, how and how often they were formed, that someplace can be found shining down on us nearly every night: our own companion in space, the Moon.

By studying lunar impact craters both young and old scientists can piece together the physical processes that took place during the violent moments of their creation, as well as determine how often Earth — a considerably bigger target — was experiencing similar events (and likely in much larger numbers as well.)

With no substantial atmosphere, no weather and no tectonic activity, the surface of the Moon is a veritable time capsule for events taking place in our region of the Solar System. While our constantly-evolving Earth tends to hide its past, the Moon gives up its secrets much more readily… which is why present and future lunar missions are so important to science.

linne_shade_scalebTake the crater Linné, for example. A young, pristine lunar crater, the 2.2-km-wide Linné was formed less than 10 million years ago… much longer than humans have walked the Earth, yes, but very recently on lunar geologic terms.

It was once thought that the circular Linné (as well as other craters) is bowl-shaped, thus setting a precedent for the morphology of craters on the Moon and on Earth. But laser-mapping observations by NASA’s Lunar Reconnaissance Orbiter (at right) determined in early 2012 that that’s not the case; Linné is actually more of a truncated inverted cone, with a flattened interior floor surrounded by sloping walls that rise up over half a kilometer to its rim.

On our planet the erosive processes of wind, water, and earth soon distort the shapes of craters like Linné, wearing them down, filling them in and eventually hiding them from plain sight completely. But in the Moon’s airless environment where the only weathering comes from more impacts they retain their shape for much longer lengths of time, looking brand-new for many millions of years. By studying young craters in greater detail scientists are now able to better figure out just what happens when large objects strike the surface of worlds — events that can and do occur quite regularly in the Solar System, and which may have even allowed life to gain a foothold on Earth.

Most of the craters visible on the Moon today — Linné excluded, of course — are thought to have formed within a narrow period of time between 3.8 and 3.9 billion years ago. This period, called the Late Heavy Bombardment, saw a high rate of impact events throughout the inner Solar System, not only on the Moon but also on Mars, Mercury, presumably Venus and Earth as well. In fact, since at 4 times its diameter the Earth is a much larger target than the Moon, it stands to reason that Earth was impacted many more times than the Moon as well. Such large amounts of impacts introduced material from the outer Solar System to the early Earth as well as melted areas of the surface, releasing compounds like water that had been locked up in the crust… and even creating the sorts of environments where life could have begun to develop and thrive.

(It’s been suggested that there was even a longer period of heavy impact rates nicknamed the “late late heavy bombardment” that lingered up until about 2.5 billion years ago. Read more here.)

In the video below lunar geologist David Kring discusses the importance of impacts on the evolution of the Moon, Earth and eventually life as we know it today:

“Impact cratering in Earth’s past has affected not only the geologic but the biologic evolution of our planet, and we were able to deduce that in part by the lessons we learned by studying the Moon… and you just have to wonder what other things we can learn by going back to the Moon and studying that planetary body further.”

– David Kring

David is a senior staff scientist at the Lunar and Planetary Institute in Houston, TX.

It’s these sorts of connections that make lunar exploration so valuable. Keys to our planet’s past are literally sitting on the surface of the Moon, a mere 385,000 km away, waiting for us to just scoop them up and bring them back. While the hunt for a biological history on Mars or resource-mining an asteroid are definitely important goals in their own right, only the Moon holds such direct references to Earth. It’s like an orbiting index to the ongoing story of our planet — all we have to do is make the connections.


Learn more about lunar research at the LPI site here, and see the latest news and images from LRO here.

Scientists Suggest Evidence of Recent Lunar Volcanism


A team of researchers at India’s Physical Research Laboratory (PRL) claims it has found evidence of relatively recent volcanic activity on the Moon, using data from NASA’s Lunar Reconnaissance Orbiter and the Chadrayaan-1 spacecraft. According to the findings the central peak of Tycho crater contains features that are volcanic in origin, indicating that the Moon was geologically active during the crater’s formation 110 million years ago.

In an article by the Deccan Herald, a Bangalore-based  publication, the PRL researchers claim that vents, lava channels and solidified flows of inner crustal material found within Tycho were made as recently as 100 million years ago — after the creation of the crater.

This could indicate that there was pre-existing volcanic activity within the Moon at the site of the Tycho impact, lending credence to the idea that the Moon was recently geologically active.

In addition, large boulders ranging in size from 33 meters to hundreds of yards across have been spotted on Tycho’s central peaks by LRO, including one 400-foot (120-meter) -wide specimen nestled atop the highest summit. How did such large boulders get there and what are they made of?

A 400-foot-wide boulder within the central peak of Tycho. (NASA/GSFC/LROC)

The researchers hint that they may also be volcanic in origin.

“A surprise findings revealed the  presence of large boulders–about 100 meter in size –on top of the peak. Nobody knew how did they reach the top,” said Prakash Chauhan, a PRL scientist.

Without further studies it’s difficult to determine the exact origin and ages of these lunar formations. The team awaits future research by Chandrayaan-II, which will examine the Moon from orbit as well as land a rover onto the lunar surface. Chandrayaan-II is expected to launch in early 2014.

The PRL team’s findings were published in the April 10 issue of Current Science.

Read the article in the Deccan Herald here.

A Peek at a Pitch-Black Pit


MESSENGER captured this high-resolution image of an elongated pit crater within the floor of the 355-km (220-mile) -wide crater Tolstoj on Mercury on Jan. 11, 2012. The low angle of sun illumination puts the interior of the pit crater into deep shadow, making it appear bottomless.

Pit craters are not caused by impacts, but rather by the collapse of the roof of an underground magma chamber. They are characterized by the lack of a rim or surrounding ejecta blankets, and are often not circular in shape.

Since the floor of Tolstoj crater is thought to have once been flooded by lava, a pit crater is not out of place here.

The presence of such craters on Mercury indicates past volcanic activity on Mercury contributing to the planet’s evolution.

Read more on the MESSENGER mission website here.

Image credit: : NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Tranquillityite – Moon Mineral Found In Western Australia


When it comes to our natural human curiosity, we want to know if there’s something new out there… something we haven’t discovered yet. That’s why when lunar rock samples were returned, geologists were thrilled to find very specific minerals – armalcolite, pyroxferroite and tranquillityite – which belonged only to our Moon. However, over the years the first two were found here on Earth and tranquillityite was disclosed in specific meteorites. Named for Tranquility Base, site of the first Moon landing, tranquillityite was supposed to be the final hold-out… the last lunar unique mineral… until now.

Birger Rasmussen, paleontologist with Curtin University in Perth, and colleagues report in their Geology paper that they’ve uncovered tranquillityite in several remote locations in Western Australia. While the samples are incredibly small, about the width of a human hair and merely microns in length, their composition is undeniable. What’s more, tranquillityite may be a lot more common here on Earth than previously thought.

Rasmussen told the Sydney Morning Herald, “This was essentially the last mineral which was sort of uniquely lunar that had been found in the 70s from these samples returned from the Apollo mission.The mineral has since been found exclusively in returned lunar samples and lunar meteorites, with no terrestrial counterpart. We have now identified tranquillityite in six sites from Western Australia.”

Why has this remote mineral stayed hidden for so long? One major reason is its delicate structure. Composed of iron, silicon, oxygen, zirconium, titanium and a tiny bit of yttrium, a rare earth element, tranquillityite erodes at a rapid pace when exposed to natural environmental conditions. Another explanation is that tranquillityite can only form through a unique set of circumstance – through uranium decay. Rasmussen explains it’s evidence these minerals were ‘always’ located here on Earth and we share the same chemical processes as our satellite.

“This means that basically we have the same chemical phenomena on the Moon and on Earth.” says Rasmussen. And one of the reasons it has taken so long to be found is, “No one was looking hard enough.”

Image Credit: Birger Rasmussen
And exactly what does it take to locate it? More than a billion years old, the only sure way to identify tranquillityite is to subject it to a series of electron blasts. By exposing it to a high-energy accelerating electron beam, it produces spectra. From there “an elemental composition in combination with back-scattered electron (BSE) brightness and x-ray count rate information is converted into mineral phases.” According to Rasmussen’s paper, “Terrestrial tranquillityite commonly occurs as clusters of fox-red laths closely associated with baddeleyite and zirconolite in quartz and K-feldspar intergrowths in late-stage interstices between plagioclase and pyroxene.”

While it has no real economic value, terrestrial tranquillityite is another good reason mankind should try to preserve pristine regions such as the northeast Pilbara Region and the Eel Creek formation. Who knows what else we might find?

Original Story Source:

What are Earthquake Fault Lines?

False-color composite image of the Port-au-Prince, Haiti region, taken Jan. 27, 2010 by NASA’s UAVSAR airborne radar. The city is denoted by the yellow arrow; the black arrow points to the fault responsible for the Jan. 12 earthquake. Image credit: NASA

Every so often, in different regions of the world, the Earth feels the need to release energy in the form of seismic waves. These waves cause a great deal of hazards as the energy is transferred through the tectonic plates and into the Earth’s crust. For those living in an area directly above where two tectonic plates meet, the experience can be quite harrowing!

This area is known as a fault, or a fracture or discontinuity in a volume of rock, across which there is significant displacement. Along the line where the Earth and the fault plane meet, is what is known as a fault line. Understanding where they lie is crucial to our understanding of Earth’s geology, not to mention earthquake preparedness programs.


In geology, a fault is a fracture or discontinuity in the planet’s surface, along which movement and displacement takes place. On Earth, they are the result of activity with plate tectonics, the largest of which takes place at the plate boundaries. Energy released by the rapid movement on active faults is what causes most earthquakes in the world today.

The Earth's Tectonic Plates. Credit:
The Earth’s Tectonic Plates. Credit:

Since faults do not usually consist of a single, clean fracture, geologists use the term “fault zone” when referring to the area where complex deformation is associated with the fault plane. The two sides of a non-vertical fault are known as the “hanging wall” and “footwall”.

By definition, the hanging wall occurs above the fault and the footwall occurs below the fault. This terminology comes from mining. Basically, when working a tabular ore body, the miner stood with the footwall under his feet and with the hanging wall hanging above him. This terminology has endured for geological engineers and surveyors.


The composition of Earth’s tectonic plates means that they cannot glide past each other easily along fault lines, and instead produce incredible amounts of friction. On occasion, the movement stops, causing stress to build up in rocks until it reaches a threshold. At this point, the accumulated stress is released along the fault line in the form of an earthquake.

When it comes to fault lines and the role they have in earthquakes, three important factors come into play. These are known as the “slip”, “heave” and “throw”. Slip refers to the relative movement of geological features present on either side of the fault plane; in other words, the relative motion of the rock on each side of the fault with respect to the other side.

Transform Plate Boundary
Tectonic Plate Boundaries. Credit:

Heave refers to the measurement of the horizontal/vertical separation, while throw is used to measure the horizontal separation. Slip is the most important characteristic, in that it helps geologists to classify faults.

Types of Faults:

There are three categories or fault types. The first is what is known as a “dip-slip fault”, where the relative movement (or slip) is almost vertical. A perfect example of this is the San Andreas fault, which was responsible for the massive 1906 San Francisco Earthquake.

Second, there are “strike-slip faults”, in which case the slip is approximately horizontal. These are generally found in mid-ocean ridges, such as the Mid-Atlantic Ridge – a 16,000 km long submerged mountain chain occupying the center of the Atlantic Ocean.

Lastly, there are oblique-slip faults which are a combination of the previous two, where both vertical and horizontal slips occur. Nearly all faults will have some component of both dip-slip and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant.

Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit:
Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit:

Impacts of Fault Lines:

For people living in active fault zones, earthquakes are a regular hazard and can play havoc with infrastructure, and can lead to injuries and death. As such, structural engineers must ensure that safeguards are taken when building along fault zones, and factor in the level of fault activity in the region.

This is especially true when building crucial infrastructure, such as pipelines, power plants, damns, hospitals and schools. In coastal regions, engineers must also address whether tectonic activity can lead to tsunami hazards.

For example, in California, new construction is prohibited on or near faults that have been active since the Holocene epoch (the last 11,700 years) or even the Pleistocene epoch (in the past 2.6 million years). Similar safeguards play a role in new construction projects in locations along the Pacific Rim of fire, where many urban centers exist (particularly in Japan).

Various techniques are used to gauge when the last time fault activity took place, such as studying soil and mineral samples, organic and radiocarbon dating.

We have written many articles about the earthquake for Universe Today. Here’s What Causes Earthquakes?, What is an Earthquake?, Plate Boundaries, Famous Earthquakes, and What is the Pacific Ring of Fire?

If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.


Earth Formation

One of the oldest questions for mankind is how the Earth was formed. However, no one has an exact answer. First by the best estimates it occurred over 4 billion years ago before any life appeared. So there are no eyewitness accounts and other pieces of evidence. The best we can do is look at the geologic record and the stars to get our answers. While we may not have the entire picture we have a good idea and it all starts with how stars are born.

Just like the formation of the Earth and other planets stars take a long time to be be born. Stars are essentially formed from clouds of gas in space. We know these as nebulas. You can basically consider them to be star forges. Over time gravity causes the atoms of gases and space dust to start coming together and gathering. Over time this gather of gases gains more mass and with it stronger gravity. This is a process that can take millions of years. In time the gravity causes the gases, mainly hydrogen to fuse in a nuclear reaction and a star is formed.

The formation of the Earth occurred after this intial phase happened for our Sun. After the Sun was formed we know from observations and other indirect evidence that there were left over gases and heavier elements. The gravity of the Sun helped to flatten these left overs into a disk and start to fuse them together. This created the planetesimals and planetoids which would later make up the planets. Over time these planetesimals would collide creating even bigger masses. It was in this method that the Earth was eventually formed.

Now we need to know that fusion eventually creates heavier elements such as carbon and iron. These elements were to compose a significant part of young Earth. The pressure and heat from radioactive decay of elements and the aftershocks of massive collisions caused the Earth to be molten. Over time the surface of the Earth cooled and became the Crust. However the molten layers that remained became our mantle and the core. The currents of this massive underground ocean of magma cause volcanic activity that released gases. These would lead to the creation of the atmosphere and the oceans starting the water cycle.

The formation of the Earth was only the beginning and we still see the Earth changing year by years through erosion and plate tectonics. However in learning more about the formation of the Earth we are able to better understand what makes life possible on our planet.

If you enjoyed this article there are several others on Universe Today that you will enjoy. There is a great article on plate boundaries and an interesting piece on early Earth.

You can also find some great resources online. There is a great web page on the University of Oregon web site that goes into detail about the formation of the Earth. You can also look at the Hadean page on the Smithsonian website. It talks about the Hadean period the period of geologic time when the Earth was formed.

You can also listen to Astronomy Cast. Episode 108 is about the life of the Sun.


Tallest Mountains


There are many tall mountains around the world as well as on other worlds. Mount Everest is the highest mountain in the world at 8,848 meters. Mauna Kea is the tallest mountain in the world. The tallest mountain is measured from base to top while the highest mountain is measured from sea level to the top.  Everest is located in the Himalayan mountain range in Nepal and near Tibet. Mauna Kea is located in Hawaii and is 10,200 meters from base to tip. From sea level though, it is only about 4,205 meters tall.  Mauna Kea is an extinct shield volcano.

These are not the only tall mountains though. K2 is in the Karakoram mountain range on the border of Pakistan and China. It is 8,612 meters tall and is generally considered the second tallest mountain in the world. The Himalayans are home to many tall mountains besides Mount Everest. This includes Mount Kangchenjunga at 8,586 meters and Mount Lhotse I at 8,501 meters.

Most of the world’s tallest mountains are located in Asia; however, there are a number of tall mountains that are located on other continents. The seven tallest mountains in different continents are known as the Seven Summits. Climbing all seven mountains is a mountaineering challenge that was started in the 1980’s.The first of these is Mount Everest. Another summit is Aconcagua, which is a mountain in Argentina in South America. At approximately 6,962 meters, it is the tallest mountain in the Americas. North America’s tallest mountain is Mount McKinley at 6,194 meters. Mount Kilimanjaro can be found in Tanzania in the continent of Africa and is 5,895 meters tall. The large summit of Mount Kilimanjaro is covered with an ice cap that is receding and according to scientists will eventually be gone. Mount Elbrus, the tallest mountain in Europe at 5,642 meters, can be found in Russia. Vinson Massif is Antarctica’s tallest mountain at 4,897 meters. It is also very large being 21 kilometers long and 13 kilometers wide.  Australia-Oceania’s largest mountain can be found in Indonesia. At 4,884 meters, it is Puncak Jaya, which is also known as the Carstensz Pyramid.

The tallest mountain that we know of is not even on Earth. It is located on Mars and is known as Olympus Mon.  A shield volcano, Olympus Mon is 27,000 meters tall. Mars is not the only other planet with tall mountains though. Venus’ Maxwell Montes is 11,000 meters tall. Satellites also have tall mountains including our Moon, which has Mons Huygens at 4,700 meters tall. The moon Io has a mountain, Boösaule Montes, which is approximately 17,000 meters tall.

Universe Today has articles on tallest mountain and tallest mountain in the Solar System.

For more information, you should take a look at what are the world’s tallest mountains and highest mountains.

Astronomy Cast has an episode on Earth you will find interesting.


How Are Rocks Formed?

As a terrestrial planet, Earth is divided into layers based on their chemical and rheological properties. And whereas its interior region – the inner and outer core – are mostly made up of iron and nickel, the mantle and crust are largely composed of silicate rock. The crust and upper mantle are collectively known as the lithosphere, from which the tectonic plates are composed.

It in the lithosphere that rocks are formed and reformed. And depending on the type of rock, the process through which they are created varies. In all, there are three types of rocks: igneous, sedimentary, and metamorphic. Each type of rock has a different origin. Therefore, the question, “How are rocks formed?” begs three distinct answers.

Continue reading “How Are Rocks Formed?”