Monday Geology Picture: A Stripe of Sunlight on Table Mountain, South Africa

A sunlight stripe falls on Table Mountain one morning in Cape Town.
A stripe of sunlight falls on Table Mountain one morning in Cape Town.

A few weeks ago my husband and I were driving to work one morning in Cape Town, South Africa. As always, we had a stunning view of Table Mountain. However, that morning the mountain looked particularly stunning since it was illuminated by a thick strip of sunlight, which was streaming through some clouds on the overcast day.

The Geology of Star Trek: The Next Generation Episode “Chain of Command, Part I”

Spelunking Starfleet officers!

Like my fellow geoblogger Jessica Ball, I wish that I could be a geologist on Star Trek. I can think of no better, more exciting job than traveling the universe as a geological researcher for the United Federation of Planets. Sign me up, Starfleet!

Maybe one day in my life– or in my children’s or grandchildren’s lives– there will be opportunities for Earth geologists to travel to other planets and planetary bodies. Already, there are hundreds (thousands?) of geologists who work in the exciting field of Planetary Geology. However, today planetary geologists primarily rely upon remote sensing, rovers (on Mars and Earth’s moon), and little bits of space rock that fall to Earth to understand the geology of other planets and planetary bodies. While several humans have walked on the moon, only one geologist (Harrison Schmidt) has walked on the moon.

A few years ago I became interested in Star Trek after watching a few episodes of The Next Generation with some friends in graduate school. Now my husband and I are hooked on Star Trek. We’re currently watching Season 6 of The Next Generation, and I’m also watching Season 2 of Deep Space Nine (so that I have something to watch when my husband is away. He’s forbidden me from watching TNG without him). I’m contemplating buying a Star Trek uniform costume and visiting a Star Trek convention. Any suggestions, for either the uniform or a convention? Are there ever Star Trek conventions in Africa? Also, my husband and I (and also our friend Mo, a fellow Star Trek fan) have already penciled in a visit in 2014/2015 to the Star Trek theme park currently being built in Jordan.

I like Star Trek for many reasons, one of which is the favorable light in which science is portrayed on the show and also the rational way in which science (even if it’s fake “Star Trek science”) is used an explanation for mysterious phenomena which occur on the show. However, the science on Star Trek is often not real science. That is, the scientific explanations on the show are sometimes inaccurate– or at least apply a bit of poetic license to a scientific fact or theory. Also, much of the show’s technology, such as teleportation and warp drive, is not currently scientifically feasible. I recently learned about a book written by Lawrence Krauss called The Physics of Star Trek (next in the queue on my Kindle reading list!) that goes into some of the physics shown on the show.

After I heard about Krauss’s book, I thought to myself: why not write about the geology of Star Trek? This is the first post in what may become a series of posts about the geology of Star Trek. In this post I am going to point out some of the geological inaccuracies of a particular episode, but I hope that these posts will not always be about nit-picking the scientific details. I hope that the geology of Star Trek, even if sometimes scientifically inaccurate, can inspire some young people (myself included, perhaps?) to learn more about planetary geology and geology in general.

I can imagine several topics of interest regarding the geology of Star Trek:

-Types of planets encountered on Star Trek

-Geology of non-Earth-like planets

-Terraforming planets for settlement

-Geoengineering of environment (atmosphere, climate, weather, soil, etc.) and of plate tectonics

-Diversion of meteoroids / comets / asteroids from impact with inhabited planets and planetary bodies

-Volcanic activity of Star Trek planets

-Best geologic lairs for Vulcans, Klingons, Romulans, Cardassians, and other Star Trek species

-Building stones seen/used on Star Trek

-Magnetic fields of Star Trek planets

-Atmospheres of Star Trek planets

-Geochemistry of Star Trek. If it hasn’t been done already, someone should really come up with a Star Trek periodic table. Which element names mentioned on the show are real and which are made up?

-Tools of Star Trek geologists (Do they just need tricorders? What geologic measurements can be made with a tricorder? Why didn’t I have a tricorder for my PhD thesis research?)

-Various mining operations shown in Star Trek

-What are those dilithium crystals made of, anyway?

Perhaps my blog readers can suggest additional topics?

Now that I’ve introduced “The Geology of Star Trek” series, let me move on to my first topic of discussion. In this post, I’d like to talk a little about the geology of a cave shown in the Star Trek: The Next Generation episode “Chain of Command, Part I.” In this episode, Captain Jean-Luc Picard,  Chief Medical Officer Beverly Crusher, and Lieutenant Worf are sent on a covert mission to the Cardassian planet Celtris III to destroy a biological weapons facility. The facility is supposedly located in a deep underground cave.  Decked out in black with various spy gear, Picard, Crusher, and Worf make their way through the cave to the supposed location of the weapons facility. When they arrive, they discover that there is no biological weapons facility. Rather, the intelligence about the supposed facility was leaked by the Cardassians as a trap to capture Picard. The episode ends with Picard being taken away by the Cardassians as Crusher and Worf escape.

Sneaking through the cave on Celtris III.

The overall plot of this particular Star Trek episode is excellent, but the geology of the cave on Celtris III is somewhat implausible. I suspect that many of the walls of the “cave” are artificial and part of a Hollywood sound stage set-up. Some views of the cave interior also seem to feature painted backgrounds or special effects. Fake and painted rocks aside, however, there are still some fundamental problems and inconsistences with the geology of the cave.

For example, after reaching a steep drop in the cave, Picard says, “We’ll have to rappel from here. This is sheer granite. We’ll have to use fusing pitons.”

"This is sheer granite. We'll have to use fusing pitons."

Granite caves are not unheard of, but they are somewhat unusual. Caves are most commonly formed as solutional caves in soft, easily dissolved and re-precipitated rocks such as limestone, dolomite, and halite. The re-precipitation of minerals such calcite forms speleothems, including stalagtites and stalagmites, that are commonly found in solutional caves. Granite is a very hard rock that is not easily dissolved and re-precipitated. Therefore, solutional caves are not going to form in granite, and granite caves are not going to contain significant speleothem precipitates. The most common type of cave that forms in granite is an erosional cave, a type of cave that forms when flowing water (a stream or possible seawater) erodes rock to form a cave.  Some granite caves also may form by seismic activity.

So far, I’m willing to buy that Picard, Crusher, and Worf are in a granite cave. A close-up shot of a fusing piton being inserted even makes the rock (or fake rock) look pretty similar to granite:

The rock looks granite-ish to me. Or maybe rhyolite-ish with phenocrysts.

However, the next few shots show that the “granite” cave has abundant speleothems, which would rarely (never?) occur in a granite cave! The big speleothems look much more similar to what would be seen in a classic limestone solutional cave:

Picard contemplates the cave, which now looks like a limestone cave!
Rapelling down a wall in the granite/limestone cave.

After Picard, Crusher, and Worf repel (500 meters, according to the dialogue) down the wall of the “granite” cave and continue walking along, they reach a solid wall and cannot progress any farther. Fortunately, Picard is able to tell with his tricorder that,  “There’s a lava tube beyond here [the wall] that runs for 75 meters, and it connects with another chamber. We need to get through here.”

Investigating the rock wall with tricorders.

Hang on a minute! Aren’t Picard, Crusher, and Worf supposed to be in a granite cave (that strangely resembles a limestone cave in some shots)? Lava tubes are a common type of cave, but they aren’t going to be found in a granite cave, and they are very unlikely to be found at 700 meters depth (in one of the early cave scenes Picard notes that the supposed weapons facility is located ~700 meters depth, and the lava tube seems to connect very close to the supposed weapons facility cavern).

For those of you who are not familair, let me explain a little bit about igneous rocks. Igneous rocks are rocks which form from molten material, which is called magma in the subsurface and lava on the Earth’s surface. There are two types of igneous rocks: plutonic rocks (which form in the subsurface from magma) and volcanic rocks (which form on Earth’s surface from lava). Granite is one type of plutonic igneous rock. A common volcanic rock is basalt.

Lava tubes are common primary caves, but they are found close to Earth’s surface, not at 700 meters depth! Furthermore, lava tubes may sometimes be connected to other lava tubes or types of volcanic primary caves, but they are rarely connected to extensive networks of caverns. Since granite is a plutonic rock and not a volcanic rock, it is impossible for a lava tube to form in granite.

To sum up, there are three geological issues with the cave featured in this Star Trek episode:

1. Granite caves are uncommon.

2. Granite caves do not generally contain speleothems such as stalagtites and stalagmites. These are generally a feature of solutional caves in rocks such as limestone.

3. Lave tubes are not found in granite caves and not found in caves at depth. This is because (a.) granite does not form from lava, and (b.) lava flows on Earth’s surface.

Bad geology aside, I do think that it’s pretty cool that Picard, Crusher, and Worf can map out the cave with their tricorders and that Worf can conveniently cut through a rock wall to the hidden lava (err… granite? limestone?) tube by using his phaser. Just check this out:

Phaser versus cave wall #1.
Phaser versus rock wall #2.
The "lava tube" revealed!
Crawling through the "lava tube."

If anyone has an extra tricorder and phaser lying around, could you please send them to me for my upcoming geologic fieldwork in Alaska? Thanks!

Cango Caves in Pictures

Miniature lake at Cango Cave.

I haven’t yet received a reply to my letter to Dr. Sheldon Cooper about why geology is a real and valuable science and why caves are interesting, but that’s okay. For those of you who agree that caves are interesting, I thought I’d share some pictures from my most recent spelunking trip.

Back in September, my husband and I took a weekend trip to Outdshoorn, South Africa, where I rode an Ostrich and also saw some weatherstones. We also visited the Cango Caves, a large, beautiful, and impressive network of limestone caves. We visited the excellent (though slightly worn-down) geology exhibit at the Interpretive Center (or Centre, to be properly South African) and then went on a guided tour of the caves. We decided to go on the “Adventure Tour.” We were pleasantly surprised to discover that the “Adventure Tour” is actually fairly adventurous, even for two adventurous geologists! My 6’3″ husband actually had some trouble making his way through some of the tight squeezes.

Below are some pictures (albeit not the best since they were taken with a waterproof point-and-shoot camera) from our adventure tour through Cango Caves. Enjoy! Click on any of the pictures in the gallery below for a larger version.

 

Geology Word of the Week: S is for Speleothem

Posing with a pseudostalagmite, Oman, January 2009.

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

If you’ve ever been in a cave, you’ve probably seen speleothems. Speleothems generally precipitate from groundwater which has percolated through the bedrock surrounding the cave and leached various elements and compounds. When the enriched water reaches the cave, changing conditions (a large open space has very different pressure and temperature than pore spaces in bedrock) allow gases, such as carbon dioxide, to escape from the water. Evaporation can also occur. The changing composition of the water encourages the (usually very, very slow) precipitation of speleothem minerals from cave waters.

Chemically, the speleothems which form in a particular cave are similar in composition. Most caves are formed in limestone, and so the speleothems will generally be formed of calcite, the dominant mineral in limestone. However, depending on how and where the speleothem is precipitated, it can take on a variety of shapes. Scientists and other cave explorers have given different names to these various morphologies. Examples of speleothems are stalactites, stalagmites, flowstones, cave coral, cave drapery, cave curtains, and cave crystals. There are dozens of names for various cave mineral formations, so speleothem is a nice catch-all phrase for geologists to use.

Here is a great picture (from Wikipedia) of some of the most common types of speleothems:

Photo by Dave Bunnell of some common speleothems. Taken from Wikipedia here. Click photo to enlarge.

Most speleothems form over thousands upon thousands of years. Thus, you shouldn’t touch or remove speleothems unless you’re doing so for legitimate science. Even when collecting speleothems for science, one should be conservative. Geologists should take small samples and obtain the necessary permissions. Fortunately, for my own research in Oman I am often able to collect speleothems which have fallen on the ground and are no longer growing.

At the top of this post is a picture of me with a stalagmite in Oman. I didn’t sample this one, but I did sample some of its neighbors. This particular stalagmite isn’t forming in a true cave but rather in an open hallow underneath a layer of rock. Water percolated through the layer of rock and formed speleothems in the hallow underneath. The speleothems I study in Oman are thus really pseudospeleothems– they are not in true caves but rather in little overhangs and hallows.

Now, for those of you who still confuse stalactite and stalagmite, here’s a reminder of something you probably learned in grammar school but may have forgotten by now:
StalaCtites hang tight (or tite) to the Ceiling while stalaGmites grow up from the Ground.

Finally, below are few more pictures of some Omani pseudospeleothems. These pseduospeleothems are forming in overhangs in travertines (carbonate precipitates) which are forming at the surface of the peridotite layer of the ophiolite. Be sure to click on the two panoramas to enlarge them. Note the location of the pseudospeleothem column in the two panoramas. Many pseudospeleothems are located in the overhang around this column. The last picture has my colleague Lisa standing next to this column for scale; this shows the enormous size of the travertine deposit.

Travertine pseudospeleothems, Oman, January 2009.
Water dripping from a pseduospeleothem straw, Oman, January 2009.
Panorama of Wadi Sudari Travertine I, Oman, January 2010.
Panorama of Wadi Sudari Travertine II, Oman, January 2010.
Lisa standing next to an enormous column of travertine, Oman, January 2009.