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.

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).

Geology Word of the Week: S is for Speleothem

Before I started a geology blog, I used to sporadically blog about geology over at Skepchick. These days, I blog here at Georneys about geology, and I blog over at Skepchick about other skeptical and scientific things, such as how to spend your final days before an apocalypse. Occasionally, I will re-post some of my old geology posts from Skepchick. I will also sometimes cross-post on both blogs. The post below originally appeared on Skepchick in 2009 here. I have modified and added to the original Skepchick post.

Posing with a pseudostalagmite, Oman, January 2009.

def. Speleothem:
An encompassing term used to describe all types of chemical precipitates that form in caves.

A New Year's Day Rock: Travertine Icings and Scums

Happy New Year!

To celebrate the new year, here are some photos of some very new rocks. These travertines in Oman are some of the youngest rocks I've encountered in my geological wanderings.

These "icings" and "scums"  are travertines (mostly the mineral calcite) that are precipitating from highly alkaline (pH ~11-12) springs that form when rainwater circulates through mantle peridotite. Thin layers of newly-formed travertine (icings) often float on the surfaces of the alkaline pools. The first year I was in Oman (2009), there was a rare desert rainstorm that pushed the travertine icings to the bottom of the pools. The icings grew back with a few days, so we know that these travertines are very young indeed! Travertine scums often coat the bottoms of the pools, giving the pools a stunning bright turquoise color. 

I am studying the formation of these young travertines- and other types of carbonates- in the Samail Ophiolite in Oman. You can learn more about my thesis research here, and I'll surely blog more about this research in the future. For now, enjoy these pictures of beautiful, newly-formed, desert travertine icings and scums.

Travertine ice 1, Oman, January 2010.