19 June 2025

Ischigualasto – The Valley of the Moon

The name is old – from the native Quechua tribe and it means the place where you put the moon. Ischigualasto is an extraordinary almost off world experience. Geologists have been visiting the valley in Argentina for more than one hundred years. It doesn’t take long to see what attracts them.

9 April 2023

Cerro de los Siete Colores - The Hill of Seven Colors

The colors could have come from the palette of a painter. Yet the Cerro de los Siete Colores (The Hill of Seven Colors) is quite real.

Millions of years of geological activity followed by erosion have created something magnificent on this Argentinian hillside.

Marine sediments combined with lake and river flows, elevated with the movement of the tectonic plates, combine to produce a dazzling array of color for the eyes to take in.

31 December 2018

The Bicheno Blowhole: Geology at its Most Playful


Nature may often be cruel but from time to time it can also be almost sublimely daft.  Close to the small town of Bicheno on the east coast of the Australian island of Tasmania, a rare geological feature known as a blowhole provides endless hours of fun for visitors. Each time the blowhole ‘erupts’ you never quite know what you are going to get in terms of the shape and size of the water.  One thing is for sure, though: you are going to get wet.
Image Credit Flickr User  ScottWeatherson

A blowhole is a sea cave which grows inwards and up, resulting in a perpendicular shaft open at the surface. They occur when there is a weak joint in the rock and as the waves pound and erode the rock just above the waterline a cave is slowly but surely formed.

This can get to quite a length but if, as it develops, it hits a vertical weakness in the rock then it will head upwards – until it breaks the surface and hits daylight.

25 November 2018

The Richat Structure – Earth’s Bull's-Eye

Imagine if you were an alien species intent on conquering the earth by force.  Now, you might just appear over the various capital cities of the world and wait for your countdown to get to zero or you might, being a little timid of the explosive force that you are about to unleash, wish to do it from a safe distance.  What you would need to look for, then, is a handy bull's-eye – on the bull's-eye that is the Earth itself.

Look no further, alien invader.  The Richat Structure in Mauritania provides the perfect target towards which you can aim your death ray, annihilation laser or whatever you call your extraterrestrial weapon of mass destruction.  It’s almost as if another species, in a previous visit, had chalked in a target already and then become bored and wandered back to Betelgeuse.

2 June 2016

Rock Islands: Palau’s Coral Reef Remnants

Have you ever wondered what would happen to a coral reef if they surfaced, quickly and with some violence?  This is what happened in Palau approximately 35 million years ago.  The geological name for this event is a subduction episode (more about that later) but the result was that millions of years of coral reef deposit were suddenly thrust above sea level. The result is Palau’s rock islands or Chelbacheb as the place is known to the inhabitants of this western Pacific Ocean nation.

Image Credit
The country of Palau is made up of eight large islands and over 200 islets created by a volcanic event over 100 million years ago. Yet at the southern tip of this archipelago things get even more islandy (if that word didn’t exist then it does now).  The Rock Islands lagoon consists of around 450 small islands which cover an area of 18 square miles.  They are now uninhabited and many of them are impossible to beach upon because of their shape. 35 million years of erosion has shaped many of them to appear as stone mushrooms.

19 May 2014

Tafoni – Nature's Rock Art

Tafoni – you may not have heard the term but the chance are, if you have visited an ocean shore, (or less likely a desert!) that you have seen them with your own eyes. Essentially they are caves (mostly in miniature) and their formation can often result in beautiful patterns. Yet why are they formed in the first place?

31 May 2013

Peña de Bernal: Now Officially the World’s Tallest Rock

About 8.7 million years ago in what is north central Mexico, a pair of tectonic plates converged.  One was forced under the other and sank in to the mantle of the Earth. The resulting volcanic activity formed a dacite rock which, after hardening, eventually forced itself through as a solid plug to the surface. This subduction zone activity created Peña de Bernal which has, you could say, weathered the passing time remarkably well. It has recently been declared the tallest monolith on Earth.

It has taken an age of argument for the monolith, in the Mexican state of Querétaro, to finally acquire this status.  For many years scientists have that the Rock of Gibralta and South Africa’s Sugarloaf Mountain were both larger than the Mexican monolith.  However, the journal Geosphere has finally settled the competition and declared that Peña de Bernal is indeed the world’s tallest free standing rock.

7 September 2011

Forget Aquarius - Is this the Dawning of the Age of the Anthropocene?

Human history on a geological scale is miniscule, tiny – a blip.  The geological time scale goes back four and a half billion years from the fiery birth of the earth to the present day.  Now, however, some scientists are calling for an end to the current epoch – the Holocene.  They are suggesting we have moved in to a new epoch altogether – the Anthropocene.  This translates literally to the Human Epoch.  So why the need for change?

The term Anthropocene was only coined ten years ago by Paul Crutzen.  The Nobel Prize winning atmospheric chemist, best known for his groundbreaking work on ozone depletion coined the term to satisfy his need to describe the age in which we are now living.  It is different from the Holocene, he argues (image of the Early Holocene left). The Anthropocene is the representation of the effect a single species has had on the planet.  That species is, of course, us.

His case is that by our actions we are going to leave a permanent signature in our earthly geology. These actions will be traceable back to us even millions of years in the future when scientists (possibly not us by that time) will be able to see the point at which we changed the earth’s oceans and biosphere irreversibly.

The geological time scale is vastly important in terms of understanding what has happened to the earth over hundreds of millions of years.  As rock is penetrated it delivers revelations about what life was like ten thousand, ten million or at its very beginnings billions of years ago.

The changes to the time scale have to this point always been natural.  The great big meteoric rock that killed off the dinosaurs for example was one point at which the time scale changed.

So indeed was the Ice Age which resulted due to a shift in the earth’s orbit.   There are many different epochs and their records are in the rocks.  Imagine them like pages in a book, each one making a chapter telling its own part of the planet’s lengthy and complex history.

Not just one book, though – think volumes.  It’s like one of those huge episodic Dickens novels but about stone instead.

Each epoch is only a small part of the scale.  They are subdivisions of a Period – the one in which we find ourselves currently is the Quaternary Period.  Each Period is a subdivision of an Era.

We are in the Cenozoic Era.  Still with us?

We are currently in the Holocene epoch, which has only been around since the last Ice Age twelve thousand years and is in terms of geological eras still pretty wet behind the ears itself.  Even its name translated from the Greek means entirely new.  So, why bother with the change at all – couldn’t we, shouldn’t we simply be included in the Holocene?

Well, that sets the scene for what will no doubt become the hottest of heated debates in geological circles.  Like Knights Templar of stones and rocks, there is a body which guards the integrity of the geological time scale.  They go under the marvellous title of the International Commission on Stratigraphy (image in the head of a certain Time Lord flashing his telepathic paper and saying I’m with the ICS – cool).

In May they will meet up to discuss the findings of their Anthropocene Working Group (no doubt referred to as the AWG).

The battleground is set – with it seems just under half of the ICS agreeing with the need to change and slightly over half of them in favour of giving the idea the old heave ho.  Most foresee, however, that we are living in an age which may well see a massive shift in the contents of the fossil record. However, it was only a few years ago that scientists were predicting a new Ice Age and look what came of that.

It is possible of course (and many geologists agree) that it is way too early to tell if this will truly be the case as – to put it simply – we just haven’t been around long enough to leave anything but a thin sliver on the fossil record.

Although they use the term informally they see no need to, ahem, set it in stone.

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Image Credits
Ammonite - Flickr User Kevin Zim
Fossil Frog Flickr User Kevinzim
Early Holocene
Meteor Collision
Ice Age House

15 August 2011

Baatara Gorge – the Waterfall that Drops into a Cave

Only discovered in 1952 the Baatara Waterfall in Lebanon is something more than a little unusual.  If waterfalls can be said to have a trick up their sleeve then this one has one of the best.  The waterfall drops a staggering 837 feet (255 meters) in to an enormous cave of Jurassic limestone.

Situated on the Lebanon Mountain Trail the abyss in to which the waterfall drops is also known as the Three Bridge Chasm. It gets this name because the journey in to the valley below takes in three naturally formed bridges, each rising above the one below.

The waterfall is at its peak when the winter snows begin to melt and the water cascades in to the chasm. Scientists in the eighties dyed the water and showed that it eventually came back in to daylight in the nearby village of Mgharet al-Ghaouaghir.

One of the most remarkable geological formations on the planet, the installation of safety equipment was considered to equip the site with a Tyrolienne or other such climbing facilities to cater for sports enthusiasts. Fortunately, this idea was discarded as the authorities decided that the installation of such equipment would degrade the outstanding beauty of the place.

It must have been a day to remember for Henri Coiffait, the French bio-speleologist who discovered the Pothole in 1952.  Strange that it took until the twentieth century to discover something that was within walking distance of the town of Tannourine and the little village of Balaa. Perhaps it was obscured from view - walking across the meadow towards it, one might not guess what was about to reveal itself. However, that very year the local potholing club explored the pothole, reaching the bottom. It was not, however, fully mapped until thirty years later.

The Jurassic limestone at the top sequence of the pothole is over 160 million years old.  The formation is vital to the locality as it is from here that mush of the fresh water in the area is sourced.  Water from the stream slowly infiltrated the limestone over the millennia.

The top bridge was revealed, then over a vast period of time vertical and circular erosion, combined with a series of collapses created the middle and bottom two bridges.  Even today the development of the pothole is not complete – neither will it ever be while water flows in to it.  Most destructive are the winter freezes which, when the ice melts, often cause large chunks of the side of the pothole to break away.

There is nothing to mark the waterfall and the chasm except a sign post which very strictly instructs visitors not to go too close to the edge as they are slippy and a fall would lead to almost certain death.  Likewise, walking on the middle bridge is prohibited as it would be in danger of collapse with the added weight of an unwary tourist.

The length of time that this remarkable geological site has left, before erosion does it work, is something that can only be guessed at.  However, in the interim this outstanding waterfall and pothole is something which can be enjoyed by visitors to Lebanon.

1 January 2011

Pamukkale – Turkey’s Cotton Castle

In Turkish the name literally means Cotton Castle and it is easy to see why it was given that.  Yet this geological wonder is also the site of the ancient city of Hierapolis and over the centuries the two have seemed to come together, merged almost, in to one. In fact some of the old tombs in the city's necropolis have beome part of landscape - literally.

The site itself is a series of travertines and hot springs.  The travertines here have a concentric appearance and are almost sheer white giving the area an ethereal, other worldly appearance.  The hot springs precipitate calcium carbonate at their mouths and produce the strange almost organic looking structures.

Before the area was declared a World Heritage Site it had its fair share of troubles.  Vehicles were allowed up and down the hills and hotels were built on top of the remains of Hierapolis.  Today the vehicles are prohibited and the hotels long since demolished, leaving the area to recover.  People are allowed to bathe in the travertine pools but are not allowed to wear shoes as these may damage the deposits.

The travertine pools are at the top of a cliff which looks like, from a distance, that it is made from chalk or has been whitewashed by some giant Turkish Tom Sawyer doing his chores.

The site is home to not one but seventeen hot water springs which have varied temperatures from lukewarm to boiling hot.  Transported over several hundred meters the water is then deposited in to the travertine terraces.  The calcium carbonate is first deposited as a soft jell which eventually hardens (hence the ban on footwear) and then becomes part of the structure of the travertine.

One of the more bizarre spectacles at Pamukkale is the site of ancient buildings which have been half buried by calcium carbonate deposits over the millennia. Hierapolis was a Greek speaking spa town, very popular with the wealthy of the ancient world for centuries.  In fact the city was not fully abandoned until late in the fourteenth century.

Although now abandoned as an inhabited city, Pamukkale receive many visitors each year to partake of the spring waters and for the almost blinding natural beauty of the place.  The travertines, formed as the water has cascaded over the cliff face of the site 12 miles north of Denizli, are really something special.

This place is extraordinary by virtue of its outstanding natural phenomena - balmy, profoundly mineralized water elegantly cascading from springs and creating pools and terraces which are visually spectacular. It is little wonder that Hierapolis, an extraordinary illustration of a Greco-Roman thermal installation, was founded.

There is a local legend which to our ears does not sound terribly politically correct.  A local girl was so ugly that no one wanted to marry her and she decided to commit suicide.  She threw herself in to one of the natural pools at Pamukkale and was transformed in to a ravishing beauty.  Naturally a passing noble man decided to marry her and they lived happily ever after.  No Shrek-like musings on the nature of beauty here.

People still come in numbers to experience the curing effects of the water, which is said to help with high blood pressure, eye and skin diseases and circulation problems among many others.  Yet for many it is simply the spectacle of the place which draws them to Pamukkale, the Cotton Castle.