Category: travertine

Monday Geology Picture: Travertine Wall

A decorative travertine stone on a the front of a building in Brisbane, Australia.

Wow, the past couple of months have been busy! I spent most of May and June travelling for work. Life has calmed down now, so it’s time to resume my blogging… and try to stick with it a little better for the rest of the year!

To kick off some blogging, here’s a picture of a beautiful decorative travertine stone on the front of a building. I took this picture earlier today when I was walking around downtown Brisbane, Australia. There are quite a few beautiful decorative stones on various buildings in Brisbane… I’ll have to take some more pictures to share.

In this picture, you can see the various layers that were deposited from natural spring waters over time. The layers have been tilted 90 degrees — they would have originally been flat-lying.

Monday Geology Picture: Travertine Timeline

TravertineLayers
Travertine layers.

This week I’m featuring one of my all-time favorite geology pictures: a snapshot of layers of travertine, representing the build-up of carbonate crusts precipitated from springs over many years. This picture was taken several years ago during my Ph.D fieldwork in the Sultanate of Oman. The layers in this picture took several thousand years to accumulate.

Lost Wonder of the World: Pink and White Travertine Terraces

Pink terraces, near Rotorua, New Zealand. Painting of the terraces done prior to 1886. Image taken from here.

Last week’s geology word of the week was travertine. In response to the word of the week, a blog reader named Michael sent me a link to a wikipedia article about the spectacular– but lost– pink and white travertine terraces in New Zealand. I had never heard of these terraces before, but I clicked on the link to wikipedia and was immediately awestruck by paintings of these enormous travertine deposits. Intrigued, I began obsessively googling these travertines and found several more paintings and even a few grainy, late 1800s, black-and-white photographs. Often called the lost “Eighth Wonder of the World,” these travertines attracted many European tourists back in the 1800s, no easy feat in an age when reaching New Zealand required a long ship voyage.

As I googled, I became quite sad that these pink and white travertines are forever lost, buried underneath volcanic ash and mud when volcanic Mount Tarawera erupted in 1886. Somewhat ironically, the same volcano that created the travertine hotspring waters later buried them. This is probably not a unique or unusual occurrence; perhaps scientists can learn more about the formation and burial of volcano-associated travertines by studying the lost pink and white travertines in New Zealand.

I’ve decided that I need a time machine so that I can stand next to the enormous white travertine terraces and bathe in the warm waters next to the pink travertine terraces. As a travertine-studying geologist, I would also love to map and sample and learn about these impressively enormous travertines. Of course, there were no mass spectrometers back in the 1880s, so I’ll have to take my samples back to the present day so that I can analyze them properly. I’d also like to take fellow geobloggers Callan Bentley and Ron Schott with me in the time machine so that they can take some gigapan images of the beautiful travertines.

Yet, however impressive a gigapan image of the travertines might be, I have to admit that one of the reasons I find the white and pink travertines so intriguing is that they are lost forever. Regardless of the resolution or skill of the photographer, no modern photograph is likely to be as enchanting as the warm, almost glowing, paintings of the lost travertines. Furthermore, the grainy glimpses of the travertines in the old photographs tingle the senses, stirring up sensations of what the travertines must have been like in real life. Looking at the old photographs, I hear the trickling, bubbling, cascading travertine springwaters; smell the heavy, sultry steam; feel the soft carbonate between my toes; taste the faint sulfur in the air.

Pink terraces. Photograph by George Valentine, taken from here.

For many years, the pink and white terraces were thought to be completely lost, destroyed by the volcanic eruption. However, a team of scientists (including a geologist and some engineers from Woods Hole Oceanographic Institution, where I’m a student) recently re-discovered the lower portion of these travertine terraces hiding on the bottom of Lake Rotomahana. The scientists plan to carry out geophysical surveys to see if the rest of the terraces are destroyed or just buried underneath volcanic ash and mud.

Travertine hiding at the bottom of Lake Rotomahama. Photo by Dan Fornari, taken from WHOI website here.

Come to think of it, I’d still like to travel to Lake Rotomahama, even if the travertine terraces are no longer spectacularly displayed. The area looks beautiful, travertine terraces or not, and there’s bound to be some interesting volcanic rocks! If I ever travel to New Zealand, I’ll do my best to visit the region.

Here are a few more paintings and photographs of the pink and white travertines:

Another painting of the pink terraces. Image taken from here.
Late 1800s postage stamp. Image taken from here.
Painting of the white terraces. Image taken from here.
Another painting of the white terraces. Image taken from here.
 
Yet another painting of the white terraces. Image taken from here.
Hot water basins, white terraces. Picture taken from here.
Travertine pools & steam. Image taken from here.
More travertine pools & steam. Image taken from here.

You can view many more black and white photographs of the lost pink and white travertine terraces at the Auckland Art Gallery website.

Geology Word of the Week: T is for Travertine

Travertine terraces, Yellowstone, Western USA, Fall 2005.

After a month’s absence because of the Fukushima interviews, I am resuming the geology word of the week. For my new readers, every week I blog about a geology word. Over the past several months, I have been working my way through the alphabet, from A is for Alluvium to S is for Speleothem. I hope you enjoy this weekly feature!

def. Travertine:
1. Formal and specific: “A chemically-precipitated continental limestone formed around seepages, springs, and along streams and rivers, occasionally in lakes and consisting of calcite or aragonite, of low to moderate intercrystalline porosity and often high mouldic or framework porosity within a vadose or occasionally shallow phreatic environment. Precipitation results primarily through the transfer (evasion or invasion) of carbon dioxide from or to a groundwater source leading to calcium carbonate supersaturation, with nucleation/growth occurring upon a submerged surface (Pentecost, 2005).”

2. Translation of the above + a little more: A type of limestone (a calcium-rich rock composed primarily of the CaCO3 minerals calcite and aragonite) which forms by chemical precipitation (the stuff that makes the rock falls out of solution) from certain types of shallow or surface waters, such as springs and rivers. The trigger for the precipitation is usually gain or loss of carbon dioxide (CO2), which causes a pH change and changes the solution chemistry so that CaCO3 precipitates. This gain or loss of CO2 usually happens very close to the Earth’s surface as the CO2 is lost to or gained from the atmosphere. The waters that produce travertines are usually very acidic (low pH) or very alkaline (high pH). Often, travertines precipitate from acidic hotsprings, such as those at Yellowstone in the Western USA. However, contrary to many web sources (this wikipedia article, for instance), travertines do not always form at hotsprings; they can also form from cooler waters. Closely related to the word travertine is another T word: tufa. The difference between travertine and tufa is porosity– tufa is a type of highly porous travertine that generally forms from cooler waters (not hotsprings).

If you’re not a geologist– and even if you are– you might associate the word “travertine” more with fancy tiles and kitchen countertops than with geology. That’s okay– travertine tiles and countertops can be very beautiful. Personally, I’d love to have some gorgeous travertine in my kitchen or bathroom. Since I work on travertines as part of my PhD, such tiles and countertops would be part of my geology dreamhouse. However, perhaps it’s best that I don’t have any travertine in my kitchen. If I did, every time some poor houseguest complimented me on my beautiful kitchen I’d probably subject this poor person to a long lecture on just how amazing travertine is scientifically and what I’ve learned from studying travertines in Oman. I’d probably go on to excitedly point to a small layer or feature in a tile and bemoan how some of the textural characteristics were lost when the piece of travertine was polished to make it into a tile. Since my soon-to-be husband is also a geologist, he’d probably join in on the discussion and we’d scare away our poor houseguest.

Travertine bathroom. Image taken from here.

However, the value of travertine goes beyond the economic value of certain types of travertine as ornamental stones. There is also much scientific value that can be gleaned from studying travertine. Also, I’d argue that the beauty of seeing many travertines in their natural environment– no polishing– goes far beyond the beauty of any travertine tile or countertop. At least for me, anyway.

There are many good scientific reasons to study travertine. For example, study of carbon and oxygen isotopes in travertines (especially speleothem-type travertines that form in caves) can provide a chemical record about how the climate of a region has varied in the past. Study of travertines and the fluids from which they precipitate can also provide information about shallow groundwater. Since many travertines form from high-temperature springs (often heated by magma, such as at Yellowstone), study of these types of travertines can provide information on a volcanic system, such as water-magma interaction. As I mentioned in the definition above, travertines usually precipitate from either very high pH or very low pH waters. Study of the critters (bugs and fishy things and microbes) that hang out in these extreme pH environments provides interesting information about life in extreme environments, which might provide helpful information relevant to looking for life on other planets and figuring out the origin of life on our own planet. These are just a few of the ways that studying travertine is scientifically valuable.

Why do I study travertine, you might be wondering? Well, I study travertine because I am interested in learning more about how travertine interacts with atmospheric CO2. As many of you know, CO2 is a greenhouse gas that contributes to global warming. Humans release CO2 to the atmosphere through burning of fossil fuels. There is currently much effort being put forth around the world to investigate how we can reduce anthropogenic CO2 emissions and– maybe– even geoengineer our environment so that we can remove CO2 from the atmosphere and store it in another reservoir, such as underground in an abandoned oil well or a porous sedimentary layer.

Most travertines precipitate when water degasses CO2 to the atmosphere. This happens through the reverse of the following reaction:

(Opposite of) travertine formation through degassing of CO2. Reaction taken from Pentecost (2005).

However, a few travertines– such as the ones I study in Oman– actually precipitate when CO2 is “sucked up” into the water from the atmosphere. This happens through the following reaction:

Travertine formation through uptake of CO2. Reaction taken from Pentecost (2005).

If you think about it, this is really, really cool! Travertines that form in this manner are naturally sucking up CO2 from the atmosphere and storing this CO2 in solid rock– travertine. For my thesis research, I am studying the formation of such travertines from very high pH (highly alkaline) natural groundwaters (most are pH = 11-12) that occur in peridotite rocks in Oman. Very high pH groundwaters are rare, but they are found at several places around the world.

Below are some pictures of travertines I’ve encountered in my geology travels and research. The Omani travertines are my favorite. I think the newly-formed travertine looks like snow in the Omani desert. Click on any of the pictures below to view larger.

A final note: I really like the first definition above, which I took from a book called “Travertine” by Allan Pentecost. I like this definition because it is very specific, descriptive, and inclusive. However, this type of definition is probably daunting for the non-geologist. A common problem with definitions of scientific words is that they contain more scientific words. As a geologist who works on travertine, I am familair with the other sciencey words such as “aragonite”, “mouldic”, and “vadose.” However, I can see how a non-geologist might struggle with the first definition of the word travertine. In the second definition, I have tried to define travertine in plainer language.

Pictures of hot, low-pH (acidic), CO2-degassing travertines in Yellowstone:

Travertine terraces engulfing trees, Yellowstone, Western USA, Fall 2005.
Travertine precipitating around a tree, Yellowstone, Western USA, Fall 2005.

Travertine engulfing civilization, Yellowstone, Western USA, Fall 2005.

More travertine! Yellowstone, Western USA, Fall 2005.

Closer view of travertine terraces, Yellowstone, Western USA, Fall 2005.

Here’s a picture of me and a friend posing with some tufa (very porous travertine):

Geology students with tufa towers in the background, Mono Lake, California, Fall 2005.

Pictures of cold, high-pH, CO2-absorbing travertines in Oman:

Layers of travertine time, Oman, January 2009.

Sitting atop some travertine, Oman, January 2009.

Investigating some more travertine, Oman, January 2009.

Travertine coating an alkaline streambed, Oman, January 2009.

Travertine coating a soda bottle, Oman, January 2009.

Travertine precipitating from an alkaline pool (geologist for scale), Oman, January 2009.

Travertine tower, likely formed from an alkaline waterfall (geologist for scale), Oman, January 2009.

Very large travrtine deposit, note the tower (see above picture) to give you a sense of scale, Oman, January 2009.

Alkaline streambed, Oman, January 2009.

Older (brown) and newer (white and black) travertine, Oman, January 2009.
Standing around an alkaline pool, Oman, January 2010.

Little travertine terraces, Oman, January 2010.
Older, brown travertine deposit, Oman, January 2010.

Older travertine (brown) and newer travertine (white and black), Oman, January 2010.

Unusual travertine morphology, Oman, January 2010.

Mini travertine terraces (car keys for scale), Oman, January 2010.

Large travertine deposit (locals have controlled the alkaline stream in a cement pool), Oman, January 2010.

Travertine terraces outlined, Oman, January 2010.

A tower amidst the travertine, Oman, January 2010.

A tower amidst the travertine (with labels), Oman, January 2010.

For more pictures of Omani travertine, see here and here.

Useful Link:
More on how CO2 affects water pH

Reference:
-Pentecost, Allan. Travertine. Berlin: Springer-Verlag, 2005.