Geology Word of the Week: W is for Wadi (وادي‎ )

A Wadi, Oman, January 2009.

def. Wadi ( وادي): ‎
1. An Arabic word meaning "valley."
2. A valley or canyon-- usually in an arid part of the world such as the Middle East-- that contains an ephemeral streambed, which generally fills with water only after heavy rainfall.

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.

Jebel Misht: Accretionary Wedge #32

I am participating in my first Accretionary Wedge- yay! For those of you who don't know, the Accretionary Wedge is a monthly "geology blog carnival" where geobloggers of all kinds are invited to blog on a theme.

I contemplated participating in the past two Accretionary Wedges, but I'm very busy with my thesis this winter. Therefore, I didn't quite have enough time and energy to bake something for Accretionary Wedge #30 or to write about something I was surprised to learn for Accretionary Wedge #31.  This month's Accretionary Wedge is easy, though! For Accretionary Wedge #32, I just have to post my favorite geology picture.

One of my favorite geology pictures (I have several- so difficult to chose!) is a picture of my favorite campsite ever. The picture below shows a makeshift campsite just off a road in northern Oman. The beautiful mountain in the background is Jebel Misht, one of several exotic limestones in the middle of the Samail Ophiolite. I was lucky enough to spend a few nights at this campsite in 2009 and 2010 as part of my PhD thesis fieldwork. One of my field sites, located near the small village of Al-Bana and close to the Misht campsite, has been named "Jebel Misht Travertine" by my research group.

Jebel Misht is a popular climbing destination. Making your way up the tall southeast cliff is not an easy task.  When a French team of climbers accomplished the first successful ascent of Jebel Misht in 1979, the Sultan of Oman arranged to have the climbers picked up by helicopter from the top of the mountain and whisked off to the palace for a celebration. Jebel Misht means "Comb Mountain" in Arabic. Indeed, the mountain's majestic cliff resembles a gigantic comb resting peacefully amidst the seafloor rocks of the ophiolite.

Jebel Misht campsite, Oman, January 2009.

Geology Word of the Week: O is for Ophiolite

Shadows over Oman mantle peridotite, January 2009.

def. Ophiolite:
An ophiolite is a segment of ocean crust and mantle tectonically exposed on land by obduction (overthrust), usually when an ocean basin closes. An ophiolite sequence consists of variably altered oceanic rocks, including marine sediments, ocean crust, and part of the mantle. The name ophiolite means "snakestone" from "ophio" (snake) and "lithos" (stone) in Greek. The rock sequence is named for the brilliant green, snake-like serpentine minerals which form in altered ocean crust and mantle. Ophiolites are rare but nonetheless found throughout the world. Notable ophiolites are found in Cyprus, the northwestern US, the Alps, Papua New Guinea, and Oman.

A Birthday Rock: Peridotite

Today is my birthday, so I am going to post some pictures of my favorite rock, which is peridotite. One of my committee members often refers to peridotite as "prettytite." I agree that peridotite-- which is comprised primarily of the minerals pyroxene and olivine-- is very, very pretty.

Image taken from here.

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.

A Year of Travel & New Year's Resolutions

I am relatively new to the geoblogging scene, but several geobloggers-- such as Callan Bentley over at Mountain Beltway and Jessica Ball over at Magma Cum Laude-- have posted a summary of their year of travel. I love travel, so I think I will continue their year-end tradition here at Georneys. Thanks to other geobloggers for the idea!

I am very fortunate to have the ability and opportunity to travel often, both for my work and for my personal life. Below is a summary of my 2010 travels. I've blogged about a few of these most recent travels. Perhaps I will blog about some of the others in the coming year, particularly since I plan to spend most of my time in lab and then writing up my thesis so that I can graduate!

December 2009 - January 2010: South Africa & Oman
My fiance Jackie lives in his native South Africa, so we commute between Cape Cod and Cape Town to see each other. My advisors are fortunately wonderful about letting me periodically work on my thesis from South Africa. I traveled to South Africa in December 2009 to spend the holidays with Jackie and his family. At the end of December, Jackie and I flew to Oman for a month of fieldwork for my thesis research. Jackie came along as my field assistant. We then flew back to South Africa, where I spent another week before returning to Cape Cod.

Jackie, an elephant, and I, Knysna, South Africa, December 2009.

Audio Slideshow on My Thesis Research in Oman

Sitting on some travertine, Samail Ophiolite, Oman, January 2009.

A little over a year ago, Woods Hole Oceanographic Institution's Oceanus Magazine put together a wonderful audio slideshow on my thesis research in Oman. Since I just presented some of the results of this research at AGU, I thought this would be a good time to post a link to the slideshow. Be sure to check out the other Oceanus audio slideshows here. There is so much great research happening at Woods Hole Oceanographic Institution! These slideshows are designed for a general audience, so I explain my research in fairly simple terms. One of the challenges of recording the audio for this slideshow was avoiding technical language. They made me keep re-recording the audio until I was able to explain my research with as little jargon as possible! Also, I apologize for my overuse of the word "fascinating." I just find my research so- well- fascinating!

Click on the link below to watch the slideshow:
Oceanus Audio Slideshow

Field Animal Favorites

If I were not a geologist, I think I would be a zoologist or would go to graduate school to study animal behavior. I really like animals. I limit myself to two housecats because I like to travel and animals require you to stay home and take care of them. However, a part of me wants a whole zoo... in my one bedroom apartment. I think this runs in the family. My grandmother has six cats, three dogs, fifteen horses, several cows, peacocks, and some goats. She used to have a three-legged goat that lived in her house with her. My sister has two ferrets, many lizards, and fish. My sister also breeds (yes, breeds) tarantulas. Yes, my sister is cool and bad-ass. My parents currently only have two cats and a dog, but when I was growing up we also had nine guinea pigs and myriad hermit crabs and fish.

Fortunately, in my geological wanderings I often come across field animals... so I will probably continue to limit myself to the two cats. This weekend I am mired in histograms and models and putting together my AGU (American Geophysical Union, a big annual geology conference) poster. I like analyzing data, but it can be a bit tiring sometimes. So, to take a quick break from data analysis and poster-making, here are some of my favorite field animals I've run across on geology trips. From camels to coatis to streetcats, they all make me happy.

Bison, Sheep, Goats, and Camels... Oh My!

Bison Jam, Yellowstone, Fall 2005.