Geological Star Trek Review – “Amok Time”

In September 2018 astronomers announced the discovery of an exoplanet with 8.47 times Earth’s mass and twice Earth’s radius in the 40-Eridani star system, distant 17 light-years from our Sun. In the Star Trek universe, the Eridani constellation is mentioned as the star system where the planet Vulcan is located, homeworld of Commander Spock. In the episode “Amok Time”, first aired on September 15, 1967, the Enterprise visits the planet. As it orbits its sun on a very narrow orbit, surface temperatures are higher as on Earth. Also, the atmosphere is very thin, barely breathable, and non-Vulcans have a hard time adapting to the harsh environment. According to Star Trek lore, the desert-planet Vulcan orbits its sun together with the planet T´Khut, a geologically very active lava-planet.

In the movie Star Trek 2, released in 1982, the star 40-Eridani-A is mentioned as Vulcan’s sun. In 1991, Gene Roddenberry, creator of Star Trek, published a short article together with astrophysicists Baliunas, Donahue and Nassiopoulos, arguing that the constellation of Eridani would be the most fitting place for Spock’s homeworld.

The 40-Eridani system is a triple star system, with Eridani-A as primary star accompanied by a red and a white dwarf star, named respectively Eridani-B and Eridiani-C. Only Eridani-A is stable enough to host a hypothetical habitable planet. Eridani-B emits too much dangerous radiation and Eridani-C is prone to flares, sudden eruptions of energy and matter. As Eridani-A is smaller than our Sun, also the habitable zone, where a planet could exist with liquid water, is narrower. Unlike the fictional planet Vulcan, the real exoplanet seems to be a Super-Earth or a small gas giant. According to the published preliminary results, the planet orbits its star in just 39 to 40 Earth days, along the inner limit of the habitable zone.

Famously Commander Spock is the science officer aboard the Enterprise, including some notions on geology.

“Obsession” (1967).

In the episode “The Apple”, Spock immediately notes the lush vegetation of the planet Gamma Trianguli VI. He correctly deduces that soil-nutrients (and therefore geology) plays a role in supporting this peculiar paradise-like world. With his sharp geological eye Spock identifies also hornblende and quartz in a collected rock.

Hornblende, Moos in Passeier, South Tyrol.

Geological Star Trek Review – “The Enemy Within”

During a minerals-gathering mission on planet Alpha 177 by the crew of the Enterprise, a transporter accident creates an evil duplicate of Captain Kirk.

In the episode the malfunction is explained by the interference of a yellow ore, collected on the alien planet’s surface, with the transporter’s circuits. The ore is not identified in the episode, but seems to consist of some alien mineral.

In many episodes of Star Trek the crew of the Enterprise visits mining colonies or is on a mission to search for valuable minerals and crystals. There exists even a geological tricorder, designed for analyzing rock samples and comparing them to the records memorized in the mineralogical database of the federation. By convention, the names of terrestrial minerals end with the suffix “-ite”, the denominations of elements with the suffix “- ium”, “-um”, “-on”, “-gen” or “-ine”. Unfortunately it seems that this nomenclature is not always applied with the necessary scientific scrutiny in the 23th century.

There are around 5,000 to 7,000 minerals known on Earth, but we still know little about the mineralogy of other worlds. Over 300 minerals have been identified in meteorites so far. Meteorites display a mineral composition different to most rocks found on Earth. The most common type are stony meteorites, consisting of silicate minerals like olivine, pyroxene and traces of iron-nickel alloys. Just 1% of meteorites are pure silicate rocks. The smell of some fragments resembles asphalt or solvents, evidence for 4.6 billion years old carbon-compounds preserved inside the rock. 4 to 5% of all space debris is represented by iron meteorites, consisting of an almost pure iron-nickel alloy with eventually embedded small crystals of silicate minerals.

Around 130 minerals were discovered on Mars and 80 to 100 on the Earth’s Moon. Most are also found on Earth, however, as some of those minerals were formed under conditions that don’t exist on Earth, such as low gravity or the complete absence of liquid water, some are indeed unknown, alien minerals.

There are about 15,300 possible ways to combine all known elements, so there may be even more alien minerals out there.

The mineralogy of an exoplanet depends on its chemical composition. By analyzing the light of a star, it is possible to identify the chemical composition of distant star systems. As the star and the planets form from the same accretion disk, knowing the chemical composition of the star can provide also some information on the chemical composition of the planets orbiting the star.

The exoplanet 55 Cancri -e is roughly twice Earth’s radius, but has just eight times its mass. Its specific density is too low if compared to Earth. Earth is composed mostly of iron, oxygen, magnesium and silicon, with some sulfur, nickel, calcium and aluminum added to the mix. Observing the composition of the 55 Cancri-e’s host star, astronomers discovered a high concentration of carbon and oxygen. It’s likely that most minerals on 55 Cancri-e are based on a combination of the two elements, forming minerals with a low specific density. Surprisingly enough, carbon minerals are quite rare on Earth. Just fifty have been identified on Earth, and most are associated with life, forming from decaying organic biomass. It seems that on Earth, life “hijacked” carbon and carbon-minerals formed by pure inorganic processes (like diamonds) are uncommon.

Maria Matilda Ogilvie Gordon and her research in the Dolomites

Maria Matilda Ogilvie Gordon
Maria Matilda Ogilvie Gordon

Scottish Maria Matilda Ogilvie Gordon (1864-1939), or May as she was called, was the oldest daughter of a pastoral family composed of eight children, five boys and three girls. Maria Ogilvie entered Merchant Company Schools’ Ladies College in Edinburgh at the age of nine. Already in these early years, she showed a profound interest in nature. During holidays she enjoyed exploring the landscape of the Scottish Highlands accompanied by her elder brother, the later geologist Sir Francis Ogilvie. Maria Ogilvie aspired to become a musician and at age of eighteen she went to London to study music, becoming a promising pianist. Already in the first year her interests shifted towards the natural world and she went for a career in science.

Studying both in London and Edinburgh she obtained her degree in geology, botany and zoology in 1890. Maria Ogilvie hoped to follow-up their studies in Germany, but in 1891, despite a recommendation even by famous geologist Baron Ferdinand Freiherr von Richthofen (famous for describing the fossil reefs in the Dolomites), she was rejected at the University of Berlin – women were still not permitted to enroll for higher education in England and Germany. She went to Munich, where she was welcomed friendly by paleontologist Karl von Zittel (1839-1904) and zoologist Richard von Hertwig (1850-1927). However, she was not allowed to join male students. Sitting in a separate room she listened through the half-open doors to the lectures.

In July 1891, Richthofen invited her to join a five-week trip to the nearby Dolomites Mountains, visiting the Gröden-Valley. From the very first day, Maria Ogilvie was immensely impressed by the landscape and learned rock climbing to better explore the mountains. Richthofen introduced Maria Ogilvie to alpine geology and they visited the pastures of Stuores in the Gader-Valley. At the time Maria Ogilvie was studying modern corals to become a zoologist, but Richthofen, showing her the beautifully preserved fossil corals found here in outcrops of Triassic sediments, convinced her to try a geological career.

The Stuores pastures with fossil-rich marls.

Richthofen was over sixty years old and therefore he couldn’t provide much support in the field. In later years Maria Ogilvie remembers the challenge and danger of fieldwork, sometimes accompanied by a local rock climber named Josef Kostner:

» When I began my fieldwork, I was not under the eye of any Professor. There was no one to include me in his official round of visits among the young geologists in the field, and to subject my maps and sections to tough criticism on the ground. The lack of supervision at the outset was undoubtedly a serious handicap. «

For two summers she hiked, climbed and studied various areas in the Dolomites and instructed local collectors to carefully record and describe their fossil sites. In 1893 she published “Contributions to the geology of the Wengen and St. Cassian Strata in southern Tyrol”. In the paper she included detailed figures of the landscape, geological maps and stratigraphic charts of the Dolomites, establishing fossil marker horizons and describing the ecology of various fossil corals associations. She described 345 species from the today 1.400 known species of mollusks and corals of the local Wengen- and St. Cassian-Formations. This paper, a summary of her thesis “The geology of the Wengen and Saint Cassian Strata in southern Tyrol”, finally earned her some respect by the scientific community. In 1893 she became the first female doctor of science in the United Kingdom. The same year she returned into the Dolomites to continue with her geological and paleontological research. In 1894 she published the important “Coral in the Dolomites of South Tyrol.” Maria Ogilvie argued that the systematic classification of corals must be based on microscopic examination and characteristics, not as usually done at the time, on superficial similarities.

In 1895 she returned to Aberdeen, where she married a longstanding admirer. Dr. John Gordon respected and encouraged her passion for the Dolomites. He and their four children accompanied Maria Ogilvie on various excursions into the Dolomites. In 1900 she returned to Munich, becoming the first woman to obtain a Ph.D. She helped her old mentor, paleontologist von Zittel, to translate his extensive German research on the “Geschichte der Geologie und Palaeontologie” – “The History of Geology and Palaeontology.”

Maria Ogilvie continued her studies and continued to publish. In 1913 she was preparing another important work about the geology and geomorphology of the Dolomites, to be published in Germany, but in 1914 with the onset of World War I. and the death of her publisher, the finished maps, plates and manuscripts were lost in the general chaos. In 1922 she returned into the Dolomites, where she encountered the young paleontologist Julius Pia, who, during the war, had carried out research in the Dolomites. Together they explored the mountains, searching for fossils.

Geological map of Cortina d’Ampezzo, published by Maria Matilda Ogilvie Gordon in 1934.

Apart from scientific papers, Maria Matilda published also one of the first examples of geological guide books for the Dolomites. To honor her contributions in 2000 a new fossil fern genus, discovered in Triassic sediments, was named Gordonopteris lorigae.


  • WACHTLER, M. & BUREK, C.V. (2007): Maria Matilda Ogilvie Gordon (1864-1939): a Scottish researcher in the Alps. In BUREK, C. V. & HIGGS, B. (eds): The Role of Women in the History of Geology. Geological Society: 305-317

Geological Star Trek Review – “The Devil in the Dark”

The 1967 Star Trek episode “The Devil in the Dark” was written in just three days by screenwriter Gene L. Coon. Despite the rushed production, this first season episode is almost always included in every “best of” list. Trekkies value the story and message, as Kirk finds a peaceful solution to a conflict with an unknown life-form, but also love some remarkable classic scenes and lines, including “Pain! Pain! Pain!” and “I’m a doctor, not a bricklayer!” This episode holds also a special place in many geologist’s hearts as it features a lot of geo-babble.

It is one of the rare episodes starting not on board of the Enterprise, but in the mines of Janus VI. According to federation classification Janus VI is a type-E rocky planet with an iron core, similar in size to Earth but just 1.3 billion years old and apparently without atmosphere or life on the surface. It’s rich in minerals and elements, like gold, uranium, platinum, cerium and the fictional pergium. Mining an extraterrestrial world is still fiction, but science shows that it may be profitable. Asteroids are rich in platinum, iridium, palladium and gold. One hundred tons of rock from an asteroid might today be worth more than 9,000 dollars, compared to just 60 dollars worth the same amount of terrestrial rocks. Estimated 5,000 to ten millions of asteroids can be found near Earth and companies are already dreaming of future prospecting and mining spaceflights. Mining asteroids would not necessarily benefit Earth, as bringing the ore to Earth would be costly, but might benefit nearby colonies, outposts or industrial complexes. In “Devil in the Dark” it is mentioned that “dozen planets depend on you for pergium.” Pergium is somehow needed for common power generators (but apparently outdated, as Chief Engineer Scotty hasn’t seen such a thing in over twenty years), providing energy not only for the colony on Janus VI but other worlds.

The mining colony in the episode was successfully operating for over fifty years but after the miners opened up a new level deep within the planet suddenly a monster started to attack and kill people. The Enterprise sends Kirk, Spock and McCoy for help. Spock during a meeting with the chief engineer Vanderberg, the administrative head of the mine, notes a strange sample in the office:

“It’s a silicon nodule. There are a millions of them are down there. No commercial value.”

“But a geological oddity, to say the least. Pure silicon?”

“A few trace elements. Look, we didn’t call you here so you could collect rocks.”

Later Spock and Kirk are able to injure the supposed monster and recover what seems to be living tissue, however, a close inspection reveals the tissue to be “fibrous asbestos, a mineral.” Asbestos is indeed a silicate mineral, which is found as aggregates of thin fibrous crystals on Earth.

Byssolithe, a type of silicate, forms fibrous crystals.

After this discovery Spock speculates that the supposed monster is an alien life-form, not based on carbon compounds as on Earth, but on silicon. The strange silicon nodules destroyed by the clueless miners are eggs and the creature was just defending her children. After Spock joins with the mind of the creature a peaceful agreement is found between the miners and the alien. The miners will not hurt or kill the creatures and the creatures will allow the miners to use their tunnels to mine the deeper pergium-rich layers of the planet (and so become rich). The Horta, as this alien is named in the series, use a sort of hot acid to melt their tunnels in the solid rocks.

The silicon-based life-form as depicted in Star Trek is surprisingly scientifically accurate. In life as we know it only ten elements play a mayor role. Carbon is one of the most important elements, followed by oxygen, nitrogen, hydrogen, potassium, calcium, magnesium, iron, phosphorus and sulfur. Carbon is common in the universe but relatively rare on Earth. Strangely silicon is quite common in Earth’s rock, but plays only an insignificant role in biological processes. Some microorganisms, like radiolarians and diatoms, use silaffins and silica-hydrogels to build their tiny shells. Siliceous sponges use silicon to support their body by constructing a framework composed of tiny needles of silicon dioxide. However, all those organisms use silicon only to build their skeleton, not in their living tissue or metabolism.

Carbon, despite its relative rarity on Earth, has some important advantages for life on Earth. It can form stable and complex macromolecules within the range of terrestrial temperatures. Living bacteria are found on Earth in 240°F hot springs and on frozen rocks of Antarctica, thriving at -60°F . Atomic bounds between carbon-carbon, carbon-oxygen and carbon-hydrogen atoms are strong and the formed molecules are soluble and stable in water. Water is so important for carbon-based life as it´s a perfect environment for molecules to react with each other, resulting in a life-sustaining metabolism. Silicon, like carbon, can form stable bounds with itself and other elements like carbon, nitrogen, phosphorus, oxygen, sulfur and many metals. Such silanes can form sheets, chains, tubes and even complex three-dimensional frameworks. In theory silanes could be combined to form organelles of a living cell and even reactive molecules sustaining an alternative metabolism.

That said, silicon shows a very strong affinity to oxygen and hydrogen. On Earth the tissue of a silicon-based life-form would slowly react with the oxygen of the air and the hydrogen in the water, corroding and killing the creature. Doctor McCoy even mentions this fact in the episode. However, Spock notes that the creature comes from within the planet, where suitable conditions for silicon-based life might exist.

Silicon-life would need an oxygen-free atmosphere, an environment with no water and an alternative liquid for its metabolism. Possible alternative solvents that may work include liquid methane and ethane, but also sulfuric and hydrocyanic acid.  The acid could explain the (fictional) ability of the Horta to “digest rock” and to “tunnel” so quickly “for nourishment” through the planet. As such compounds are unstable at higher temperatures, the silicon-based life-form would best thrive in a very cold environment.

Could such life really exist? Unfortunately we don’t know for sure and the Horta is never again mentioned in the original series. Maybe this question will be answered by future generations, when humanity encounters life, but not as we know it. How will we react? In “The Devil in the Dark,” the first response was fear and hate, in the end overcome by knowledge and emphaty – a message in the best tradition of Star Trek.

Geology and Alpine-Type Fissures

Swiss professor of philosophy Horace-Bénédict de Saussure (1740-1799) was one of the first naturalists to collect observations and measurements in the field. He did so by traveling the Alps and climbing various mountains, among others the Mont Blanc, with 4.810 meter the highest peak of the Alps. During his ascent, he recorded the physiological reactions of his body to the increased elevation, measured air temperature and described the rocks which compose the mountain. One of De Saussure’s guides onto the peak of Mont Blanc was Jacques Balmat, a local chamois hunter and Strahler. A strahler is a crystal seeker, so named after the Strahlen, the shining quartz crystals. The granite of Mont Blanc is famous for its Alpine-type fissures, hosting sometimes spectacular crystals.

The crystal seeker Jacques Balmat, painting by Henry Lévèque.
Reconstruction of an Alpine fissure in Mont Blanc granite, with quartz, flourite and chlorite crystals.

Most common are gash fractures formed during the Alpine orogenesis some 25 to 15 million years ago. Below 500°C rocks like gneiss, schist and amphibolite tend to react brittle to tectonic deformation. Permeable to circulating fluids, in the open fissures and at temperatures of 600 to 100°C crystals will start to grow.

Kluft – an Alpine-type fissure in the field. from “Mineralklüfte und Strahler der Surselva” by Flurin Maissen (1950). A stiff layer will tend to deform, flattened and stretched to the point that it “necked”, opening a gash fracture between boudins. Thin layers will wrap around this point, partially forming quartz veins. More deformed, the layers will tend to weather more easily.

Almost 80% of the Alpine-type minerals comprise feldspar, chlorite, calcite, and quartz. Typical Alpine-type minerals are actinolite, apatite, dolomite, epidote, flourite, hematite, titanite, rutile and zeolithe – more than 140 minerals are known from Alpine-type fissures found in the Eastern Alps.

Alpine-type fissure in greenschist with a typical mineral paragenesis of adularia , quartz and chlorite.

De Saussure’s son – Nicolas Théodore de Saussure – will in 1792 name the mineral dolomite, giving the Dolomites their modern name.

Lake Alleghe

The lake of Alleghe in the Cordévole Valley formed at 7:02 in the morning of January 11, 1771. That day a river flowing through the valley became dammed by a landslide coming from the mountain Piz.

The valley of Cordévole with the village and lake of Alleghe, on the left of the mountain Piz the scar of the landslide is barely visible in the forest, in the background the Civetta (3.220m).

The Alps-traveler and naturalist Belsazar Hacquet (1739-1815) remembers a visit to the lake in 1780:

The river Cordévole became my guide, by following him I would find the valley of Cadore. However, just after some hundred steps the river was flowing in a large lake, existing here only for the last nine years. I walked around in eastern direction, leaving the villages of Sternade and Saviner behind me, until I arrived at the base of the mountain of Piz. First the lake was narrow, only near Saviner it became more than 100 Venetian fathom [an old length unit used in the mining industry of these times, one fathom ca. 1,8 meter] wide and more than thirty deep.

The last mentioned village once was situated on a hill, and in the valley there were four smaller villages …[]… flooded by the lake, …[]… [the village] Marin, was buried with the village of Riete beneath the collapsing mountain of Piz, the last described village located previously on the top of the mountain.

Standing on the top of the mountain, I immediately noted that the mountain has a volcano on top of it, and it was possible to see how deep [its volcanic dikes] went. After the mountain collapsed, it could be seen that its base was composed of limestone, build up by mighty layers, dipping from west to east with a 45 degrees angle. The [slip] surface of the landslide is so smooth, that a man has difficulties to climb on it to the top of the mountain.

The strange notion by Hacquet of an active volcano in the Dolomites is based maybe on his discovery of volcanic rocks in the area, however – as we today know – these volcanic deposits are more than 235-million-years-old. At the time of Hacquet’s geologic investigation, volcanic forces were believed to cause strong and sudden movements of Earth, explaining sudden disasters like a landslide.

The landslide of Alleghe killed 48 people and destroyed parts of the village of Riete and some farms. Water levels in the landslide-lake continued to rise over the next weeks, inundating the village of Peron. Only in February 1771, a new outflow formed, stabilizing water levels and creating the modern lake.

Historic depiction of the landslide-lake in the “Atlas Tyrolensis” of 1774 by Peter Anich and Blasius Hueber. Note the boulders on the southern shore of the lake. Anich and Hueber were the first cartographers to use signatures to display geomorphologic features -like landslides – in their maps.

Geology and the 1963 Landslide of the Vajont Dam

The valley of Vajont (or Vaiont) in the Italian Dolomites is characterized in the upper part by a broad catchment area, eroded by ancient glaciers, and a narrow gorge carved into limestone formations by the river Vajont in the lower part. This peculiar shape made this valley a perfect site for a dam and a hydroelectric power station.

View of Mount Toc with the landslide of Vajont. The small lake on the left is what remains of the reservoir.

Construction of the Vajont dam started in 1956 and was completed in 1960. At the time, it was the highest double-curvature arch dam in the world, rising 261,6 meters above the valley floor and with a capacity of 150 to 168 million cubic meters. The filling of the reservoir began in February 1960; eight months later the lake was already 170 meters deep. Soon afterward, first fissures were noted on the slopes of Mount Toc and November 4, with the lake 180 meters deep, a first landslide with 700.000 cubic meters fell into the lake. Alarmed, technicians decided to reduce the filling rate of the reservoir. This strategy was successful until mid-1963 when, between April and May, the depth of the reservoir was rapidly increased from 195 to 230 meters. By mid-July, the depth was 240 meters, another slight increase in movements of the unstable slope was noted. In early September, the depth of the lake was 245 meters, the movements accelerated to 3,5 centimeters per day. In late September, the water level was lowered in an attempt to slow down the entire slope. October 9, the reservoir’s depth had finally been lowered to 235 meters. Even so, the slope continued to move at a rate of 20 centimeters per day, enough to open large fissures along the entire flank of Mount Toc.

Summary of events observed during the filling of the Vajont reservoir. Geological investigations, precipitation, water levels in the reservoir and groundwater levels and rate of movements. The last rise of the reservoir level was accompanied by strong earthquakes coming from the slopes of Mount Toc. Note also how the groundwater level became synchronous with the reservoir level in 1961, suggesting that the previously isolated aquifers in the mountain became connected to the lake.

October 9, 1963, at 10:39 p.m. local time, the entire flank of Mount Toc collapsed. Within 30 to 40 seconds estimated 240 to 270 million cubic meters of fossil landslide deposits and bedrock plunged into the reservoir, containing 115 million cubic meters of water, filling the 400 meters deep gorge behind the dam. The landslide pushed part of the water out of the lake, generating a wave with a maximal height of 230-240 meters. In the villages surrounding the reservoir, Erto, Casso, San Martino, Pineda, Spesse, Patata, Cristo and Frasein, the wave claimed 160 victims. A 100 to 150 meters high wave rushed into the gorge of the Vajont, in direction of the densely populated Piave valley. There the wave destroyed the villages of Longarone, Pirago, Villanova, Rivalta and Fae, in less than 15 minutes more than 2.000 people were killed.

Aerial photo of the Vajont site before and after the landslide (SEMENZA 1964).

If the landslide of Vajont was a preventable disaster is still debated to this day.

The valley of Vajont is characterized by a succession of Jurassic/Cretaceous to Eocene marl and limestone-formations, forming a large fold, with the valley following the axis of the fold. Sedimentary layers found along the slopes of the mountains, especially on Mount Toc, plunge into the valley, forming possible sliding planes for a mass movement.

Calcare del Vajont – limestone from the Vajont site. In similar geological formations thin layers of clay can be found. If wet, such layers form perfect sliding planes.

After the disaster, geologists discovered thin layers of green claystone (5-10 centimeters thick) in the limestone of the Vajont site. The clay layers acted as sliding planes for a prehistoric landslide and were reactivated by the rising water in the reservoir.

Two N-S geological sections from Monte Toc to Monte Salta before 9 October 1963 and after. 1a Quaternary; b stratified alluvial gravels; 2 Scaglia Rossa (Upper Cretaceous–
Lower Paleocene); 3 Cretaceous-Jurassic Formations (Socchér Formation sensu lato and coeval): b Socchér Formation sensu stricto; c Ammonitico Rosso and Fonzaso Formation; 4 Calcare del Vaiont (Dogger); 5 Igne Formation (Upper Liassic); 6
Soverzene Formation (Lower and Middle Liassic); 7 Dolomia Principale (Upper Triassic); 8 faults and overthrusts; 9 failure surfaces of landslides; 10 direction of water flow into aquifers (from SEMENZA et al. 2000).

For more than three years, the movements were monitored and various geologists studied the creeping slope. Shear zones with crushed rocks were discovered during the construction of a tunnel deep inside the mountain. Some geologists warned of a deep-seated landslide, like Austrian engineer Leopold Müller in 1960 and later Italian geologist Eduardo Semenza and Franco Giudici. Other geologists proposed superficial sliding planes, able to cause only small landslides. Small landslides, as happened in 1960, were always expected during the filling of the reservoir. In 1961 the construction of a by-pass tunnel was started, just in case the reservoir would become partially obstructed by a landslide. In the same year, calculations, based on a small model of the entire reservoir, suggested that a (small) landslide into the lake could generate a 30 meters high wave. Technicians recommended to not exceed a water level of 700 meters a.s.l., surpassed, however, in 1963 by 10 meters.

Eduardo Semenza in July 1964, the geologist, son of the engineer who planned the dam, was one of the first to recognize that prehistoric landslide deposits and gravel of landslide-dammed lakes filled the Vajont valley. In the background shattered bedrock of the 1963 event.

The continuous rejection of the worst-case scenario by authorities and the electric power company, running the dam, was, in part, based on a lack of understanding of large mass movements at the time. Only few geologists and engineers imagined that an entire flank of a mountain could collapse. The Vajont reservoir was an important economic investment, providing energy to nearby large cities and industries, and many politicians supported its construction. Nobody dared to abandon the entire project.
When in the last days of October 1963 it was realized that over 200 million cubic meters of rock were ready to slip into the reservoir, the disaster was inevitable.


  • SEMENZA E. (1965): Sintesi degli studi geologici sulla frana del Vajont dal 1959 al 1964. Museo tridentino di scienze naturali, Trento Vol. 16(1): 51
  • SEMENZA, E. & GHIROTTI, M. (2000): History of the 1963 Vaiont slide: the importance of geological factors. Bull Eng Geol Env 59: 87–97

How to Identify Feldspar in the Field

Feldspars are by far the most common minerals, constituting nearly 60% of all terrestrial rocks. They are important in both magmatic (formed by crystallization from molten magma) and metamorphic rocks (formed by alteration of older rocks by heat and pressure over time). It’s only in sedimentary rocks that feldspars are relatively rare, as the crystals easily break (having a perfect cleavage) and tend to decay and erode in contact with water.

Feldspar is a name that comprises a series of aluminosilicate minerals with three end members: orthoclase (potassium feldspar K[AlSi3O8]), albite (sodium feldspar Na[AlSi3O8]) and anorthite (calcium feldspar CaAl2Si2O8). Albite and anorthite form a completely miscible series called plagioclase. Albite and orthoclase can form a complete miscible series at higher temperatures.

As there is miscibility between the various members of the feldspar group, exact feldspar identification in the field, without chemical analysis, can be difficult (to impossible).

Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite. Euhedral crystals are commonly elongate with a tabular appearance, colorless to white in appearance; however, traces of iron-oxides can cause greenish, greyish-yellow or reddish-pink coloration. Orthoclase often displays Carlsbad twinning and light is reflected differently by the crystal faces of the two intergrown crystals. Luster is vitreous to pearly.

1-6 cm large orthoclase (K-feldspar) in the Terlaner ryhodacitic porphyry (a subvolcanic rock). The crystal displays characteristic Carlsbad twinning and secondary reddish coloration by iron-oxides.

Plagioclase is the most important feldspar in basaltic magmatic rocks. On fresh surfaces colorless to whitish, on eroded surfaces often colored greenish-yellowish by traces of decomposing sericite, chlorite and epidote (however, reddish coloration by iron-oxides also possible). Virtually identical to orthoclase when fresh, shows less well developed twinning (polysynthetic twinning with lamellar crystals intergrowth, visibile only on microscopic scale) and generally forms smaller crystals. In granitoid rocks, plagioclase is composed mostly of albite (70 to 50%), in basaltic rocks (like diorite, gabbros and basalt), with an abundance of calcium, anorthite prevails with 60 to 90%.

Auer Formation, former pyroclastic flows deposits, with a matrix of sanidine (potassium feldspar) crystals, reddish-pink plagioclase crystals and quartz.

Feldspar has a relatively high mineral hardness of 6 after Mohs and can barely be scratched with the blade of a pocket knife or geological hammer. In metamorphic rocks, like orthogneiss (metamorphic granitoid rocks), it can form characteristic porphyroclasts, harder mineral grains surrounded by a groundmass of finer grained crystals, referred to colloquially as “Augen” (=eyes).

Reiner Orthogneis, Altkristallin, Rein in Taufers.

Weathered alkali-feldspar (orthoclase-albite series) will decay to white, crumbly argillaceous minerals, like kaolinite. Plagioclase decays to argillaceous minerals or fine-grained aggregates of colourless to grey sericite (mica variety).


  • AVANZINI et al. (2007): Erläuterungen zur Geologischen Karte von Italien Im Maßstab 1:50.000 Blatt 026 Eppan. APAT/Autonome Provinz Bozen Amt für Geologie und Baustoffprüfung
  • MARETSCH, W.; SCHERTL, H.-P. & MEDENBACH, O. (2016): Gesteine – Systematik, Bestimmung, Entstehung. Schweizerbart Verlag: 368
  • MEYER, J. (2017): Gesteine der Schweiz – Der Feldführer. Haupt Verlag: 444
  • MEYER, J. (2017): Gesteine einfach bestimmen – Der Bestimmungsschlüssel. Haupt Verlag: 140

The Origin of ‘Geology’

Curiously enough the first time the word geology appears in written form, is in the last will of an Italian naturalist in 1603.

“La giologia”, the first use of the word geology in Ulisse Aldrovandi’s last will.

In the 17th century, noblemen began collecting natural objects in their cabinets and private museums. The displayed natural oddities and specimens were mostly acquired by chance from lucky discoverers. It was only later that naturalists started to go in the field, even if such an activity was considered more a necessity to gather more specimens than a means to explore the natural world.

Swiss professor of philosophy Horace-Bénédict de Saussure (1740-1799) was one of the first to propose that naturalists should not only collect specimens, but also take observations and exact measurements in the field. Naturalists or natural philosophers were names given to well-educated people interested and dedicated to the slowly emerging fields of “natural history” and “natural philosophy.” Natural philosophy was interested in all observable phenomena in nature, from the physiological reaction of the body on the summit of Mount Blanc (climbed by de Saussure in 1787) to the rocks composing the mountain. Natural philosophy itself later became divided into three sub-disciplines: zoology (the collection of animals), botany (the collection of plants) and mineralogy (the collection of minerals and rocks, including fossils). The collection of rocks, minerals and fossils only slowly evolved in a science studying rocks, minerals and fossils.

In Germany, leading in mining technologies at the time, “geognosie” (translated maybe as knowledge about the earth) evolved from geography. Mapping the distribution of rocks on the surface, geognosts projected the rock formations also into the underground. This science was referred to as “mineralogical geography” or “géographie souterraine.” May the Italian name “anatomia della terra” – anatomy of the earth – best describe the goals of this new science. Geognosie was a practical science, less interested in formulating theories. You may say geognosie would describe of which rocks a mountain is made of, but it couldn’t explain how a mountain formed.

In 1778, French naturalist Georges-Louis Leclerc de Buffon argued in his Nature’s Epochs the need to create a geotheory to understand the evolution and structure of earth. In that same year, the term geology was introduced (hesitantly) in the literature by Swiss naturalist Jean-Andre de Luc in his Letters on Mountains:

“I mean here by cosmology only the knowledge of the earth, and not that of the universe. In this sense, “geology” would have been the correct word, but I dare not adopt it, because it is not in common use.”

Despite de Luc’s concerns, geology became synonymous with the proposed theory of earth, as a part of cosmology dedicated to the description and explanation of earth and its relationship with animals, plants and humans.

“In now addressing my brother -geologists – and under this term I would comprehend all who take an interest in the progress of a science whose problems are inseparably interwoven with the whole study of nature – I have been influenced by the conviction that it is good for us, as workers in the same field, occasionally to pause and question ourselves as to the ultimate bearing of our investigations.”

David Page (1863): The Philosophy of Geology.

However, the word geology itself has much older roots. In his last will written in 1603, the Italian Renaissance naturalist Ulisse Aldrovandi (1522-1605) introduced the term “giologia” to refer to the study of “fossilia” – the unearthed things. The new science “giologia,” so Aldrovandi’s hope, would study the origin of rocks, minerals, petrified organisms (Aldrovandi recognized some fossils as once living things) and the layers of earth.

The Fossils Of The Dolomites – From Myth To Science

The first scientific mention of fossils from the Dolomites dates back to August 18, 1741. In a lecture with the title Dissertatio de Fossilibus universalis Diluvii by Franz Ferdinand von Giuliani, physician in the city of Innsbruck, he describes petrified shells from the Puster-Valley as evidence for the biblical flood (a popular explanation at the time). Since the Puster-Valley is cut into metamorphic rocks like schist and gneiss, rocks that contain no fossils, Giuliani probably was describing fossiliferous formations from the nearby Dolomites.

Fragment of an ammonite, an extinct group of marine mollusc animals.

In the Dolomites, the remains of ancient reefs and marine basins, it is easy to spot and find fossils. Since ancient times shepherds and farmers have found fossils in the pastures and on their fields. People wondered about the origins of the strange rocks, and for a long time myths and stories provided some explanations. For example, cloven hoof-like impressions found on rocks were explained as the devil’s footprints.

Section of Megalodus sp. or the devil’s hoof shell.
The fossil casts of Bellerophon, an extinct genus of marine snail, were also referred to as the devil’s curled horns.

Between December and January and during the Walpurgis Night (April 30th to May 1st) the devil will join the witches’ sabbath on the 2.563 metres high Schlern. Dancing all night long, at dawn the devil will return to hell, leaving behind only the imprints of his hooves on the bare rocks of the Dolomites.

In the Puster-Valley the devil is called “Tuifl” or “Krampus” and has the appearance of a half human–half goat demon, including cloven hooves.

It wasn’t until 1781, after naturalists compared the strange imprints with shells of modern mollusks, that they recognized that the devil’s hooves, in reality, are the cross-sections of bivalves. Some 216 to 203 million years ago large bivalves of the family Megalodontesidae lived on the muddy bottom of the Tethys Ocean. After their death, the shells were buried and partially filled with fine carbonate mud. The sediments of the Tethys Ocean were pushed upwards by tectonic movements some 65 to 40 million years ago. Today erosion slowly removes the surrounding sediment revealing the heart- of hoof-like sections of the cockle-like animals.

Megalodus sp. fossil casts.

And it wasn’t until the 19th century that the fossils of ancient sea creatures were seen as evidence that the Dolomites like Venus, the ancient goddess of beauty, were born out from the sea in the geological past.