Field of Science

The Alvarez and the Crater of Doom

"It was nothing of this earth, but a piece of the great outside; and as such dowered with outside properties and obedient to outside laws."
"The Colour Out of Space", by H.P. Lovecraft (1927)

Until 50 years ago, it seemed that a characteristic peculiarity of the Cretaceous-Palaeogene (or K–Pg) ) transition, famous for the mass extinction event that "killed" off the dinosaurs, was the apparent lack of a complete stratigraphic record. However, in the decade 1960-1970 the American geologist Walter Alvarez discovered a homogeneous and complete succession of bedded limestone- and marl-layers in the gorge of Gubbio (also Gola del Bottaccione, located in the far north-eastern part of the Italian province of Perugia, Umbria), called the "Scaglia rossa"-formation.

Alvarez attempted to calculate the rate of deposition of this formation by analyzing the concentration of rare earth metals found in the sediments. A constant rain of micrometeorites, enriched in such metals, coming from outer space causes a constant concentration of rare earth metals in the sediments. A sudden change, therefore, can indicate that the rate of sediment deposition also suddenly changed.

It was during this research that Alvarez discovered the today well-known Iridium anomaly. At first, the origin of this anomalous concentration remained unclear. In 1980, Walter Alvarez and his father, the nobel-prize physicist Luis W. Alvarez (1911-1988), proposed two possible explanations - a very slow sedimentation rate of the Scaglia Rossa, resulting in an apparent concentration of micrometeorites, or the impact of a large mass of extraterrestrial material at once.

But Alvarez could not provide further evidence to confirm or disprove both hypotheses.


In 1981, geologists Antonio Camargo-Zanoguera and Glen Penfield presented during a geophysical conference their research on a geological mystery discovered 30 years earlier, during surveys on the Yucatan peninsula (south-eastern Mexico). The two researchers proposed a new interpretation of a circular structure revealed by seismic investigations and buried under 300 to 1.000 m of sediments, considered until then of volcanic origin. They suggested that the circular structure was a weathered and buried crater, formed by the impact of a large meteorite.

Only ten years later, some researchers from the University of Arizona started to study the crater and obtained the first absolute age - 65-million-years. Research in 1993 revealed that the structure was in fact an impact crater with a total diameter of 180 km. The crater was named after the nearby town of Chicxulub - meaning "the devil's tail".

Alvarez, meanwhile, continued his research on the impact hypothesis and noted the temporal coincidence of the Iridium anomaly, the Chicxulub-impact and the mass extinction at the end of the Cretaceous. The impact could explain the observed rare earth elements anomaly, was an important time marker, and also appeared to be the main culprit to blame for the extinction of the dinosaurs. In 1995 the limit between the Cretaceous and the Palaeogene was therefore defined at the stratotype (the GSSP) of El Kef (Tunisia), coinciding with the peak of Iridium and the mass extinction of foraminifera at the base of a clay layer (also referred as K-Pg boundary clay) deposited after the impact.

Today more than 350 sites worldwide are known to record the Cretaceous-Palaeogene sedimentary transition. Within a radius of 500 km the debris layer of the impact is very thick; around the crater it reaches a thickness of 100 to 80 m. In a radius of 500 to 1.000 km the sediments are typical tsunami deposits - layers containing debris and spherules (molten rocks that subsequently cooled to form droplets) transported by the waves from the impact site. With increasing distance, the layer thins out to form the known Iridium rich clay overlying a layer with small spherules. In a distance over 5.000 km the impact is represented by a single layer of red clay that still contains traces of the material ejected from the crater.

The geological evidence supports the hypothesis that a large extraterrestrial mass collided with earth.

According to the most popular scenario, the mass extinction event at the end of the Cretaceous marking the end of dinosaurs, large marine reptiles and ammonites, was caused by the consequences of the impact. Shock wave and fire storms were soon followed by the release of large quantities of gas from the vaporized rocks, rich in carbonates and sulphates. The gases reacted with the water vapor to form acid rain, and the dust in the atmosphere blocked the sun causing a many years-long nuclear winter. Depending on the locality and the ecological niche that a species occupied - and a good dose of luck - these changes decided a species' fate - to survive or to be doomed.

De La Beche's Awful Changes

Caricatures are exaggerated sketches of a person or human behavior. However, such cartoons appear only at a superficial glance as simple drawings, as they contain deep and complex insight in our culture and society. This consideration is also true for scientific caricatures, dealing with subjects or persons involved in science and research.

For a long time, the caricature by British geologist Henry De la Beche (1796-1855) "Awful Changes. Man Found only in a Fossil State - Reappearance of Ichthyosauri" was considered a caricature of fellow geologist and paleontologist William Buckland (1784-1856). The sketch was widely publicized in Francis Buckland's (1826 - 1880, son of William) book-series "Curiosities of Natural History" (1857-72), including a biography of his father.

"A lecture, - 'You will at once perceive,' continued Professor Ichthyosaurus, 'that the skull before us belonged to some of the lower order of animals; the teeth are very insignificant, the power of the jaws trifling, and altogether it seems wonderful how the creature could have procured food."

However, geologist and earth-science historian Martin J.S. Rudwick realized the connection of this scene with some drawings produced before 1831 by De la Beche in his diary, where he ridiculed the approach adopted by Charles Lyell. In the unpublished drawings, a lawyer (the reference to Lyell, who actually was a lawyer, seems obvious) is carrying a bag with "his" theory around the world, or he is shown wearing particular glasses (like Professor Ichthyosaurus), and offering his "view" and the resulting "theoretical approach" to a geologist carrying a hammer and collecting bag, a reference to the geologist actually working in the field. De la Beche never completed the sketch, because he abandoned this design in order to try out others, including the now famous "Awful Changes."

De la Beche believed that Lyell injected too much of his lawyer profession into the emerging field of geology, focusing too much on theories than real research. "Awful Changes" does lampoon one crucial part of Lyell's uniformitarianism - theory, the concept of time repeating itself, as prehistoric animals are behaving much like Victorian scholars. In a second cartoon De la Beche is mocking another idea of Lyell, the effects of present causes operating at the same slow magnitude throughout geologic history. The cartoon shows a vast U-shaped valley, in the foreground a nurse with a child, presumably the son of William Buckland, can be spotted. The child is peeing into the huge valley and in the caption De la Beche has his nurse exclaiming, "Bless the baby! What a valley he have made!!!"

The caricature was inspired by the ongoing debate of river-erosion at the time. The glacial theory wasn't still accepted to explain the formation of large valleys and the shape of many valleys in Europe was hard to explain only based on, as proposed by Lyell's uniformitarianism, slow fluvial erosion.

Carl Friedrich Christian Mohs's Mineralogical Legacy

Carl Friedrich Christian Mohs, lithography by Joseph Kriehuber (1832).

Talc – Gypsum – Calcite – Fluorite – Apatite – Feldspar – Quartz – Topaz – Corundum – Diamond - the Mohs Scale of Mineral Hardness is familiar to rock-hounds and earth-science students alike. The ten-point hardness scales lists common minerals in the order of the relative hardness, with talc being the softest and diamond the hardest mineral found in nature.

The Mohs scale is named after German mineralogist Carl Friedrich Christian Mohs, born January 29, 1773, in the town of Genrode, at the time part of the principality of Anhalt-Bernburgs. After attending school, he worked in his father's business as a merchant, but in 1796 he went to the University of Halle to study there mathematics, physics and chemistry. He continued his studies at the famous Royal Saxon Mining Academy of Freiberg, where he studied under the renowned geognost Abraham Gottlob Werner. Werner published in 1787 a »Kurze Klassifikation und Beschreibung der verschiedenen Gesteinsarten« - Short classification and description of the various rock types - as a guide for identifying and classifying rocks and minerals. Unlike other mineralogists at the time, mostly using chemical analysis, Werner uses easily recognizable features, like color or crystal shape, to classify minerals and rocks. Mohs is impressed by Werner's approach. In 1804, he publishes himself a “student-friendly” classification chart for minerals, based on his experience in the mining district of the Harz mountain and as a consultant for wealthy mineral-collectors. In his book »Über die oryktognostische Classification nebst Versuchen eines auf blossen äußeren Kennzeichen gegründeten Mineraliensystems« - The genetic-geological classification and an attempt to introduce a mineral-system based on outer properties - Mohs combines various physical properties of minerals, like color, hardness and density, with six classes of crystal shapes, to identify 183 different minerals.

Mohs scale of hardness sets from the 19th century, Mohs's geological hammer, and a letter to his wife.

Mohs continues to travel, collect material and improve his mineral classification system. He visits Štiavnica in Slovakia, famous for the local Mining Academy, and the mining district of Bleiberg in Carinthia. He visits and studies mines in Hungary, Transylvania and Scotland, and quarries in Germany and Austria.

In 1812, now a professor in the Austrian city of Graz, he creates a preliminary hardness scale and continues to publish guidelines for mineral identification. In 1818 he returns to Freiberg and between 1822-1824 Mohs publishes his final version of the hardness scale in the book »Grund-Riß der Mineralogie« - Essentials of Mineralogy.

The Mohs scale of mineral hardness is based on the ability of one natural sample to scratch another sample visibly. The samples of matter used by Mohs are readily available to a student or miner. Minerals with a hardness of 1 or 2 can be scratched with a fingernail. A coin will scratch minerals with a hardness of 3, the blade of a pocket knife scratches minerals of the hardness 5 and 6. Glass will scratch minerals with a hardness of 7, and harder minerals scratch each other.

Calcite crystals, example of a common mineral with hardness 3.

Artist M.C. Escher and his Crystal-inspired Artwork

There is something breathtaking about the basic laws of crystals. They are in no sense a discovery of the human mind; they just “are” – they exist quite independently of us. The most that man can do is become aware, in a moment of clarity, that they are there, and take them into account. Long before there were people on the earth, crystals were already growing in the earth's crust. On one day or another, a human being first came across such a sparkling morsel of regularity lying on the ground or hit one with his stone tool and it broke off and fell at his feet, and he picked it up and regarded it in his open hand, and he was amazed.” 
- M. C. Escher (1898-1972)

Dutch artist Maurits Cornelis Escher was fascinated, or maybe even obsessed by "the systematic compartimentalization of space." Many of his illustrations show symmetrical shapes repeated into infinity, completely occupying all the available space. It is not a coincidence that Escher's work reseambles the molecular lattice structure and resulting crystal structure of minerals. Some of his surreal illustrations are even clearly based on crystals.

Spessartine-Garnet on Feldspar, Shigar Valley, Pakistan, and artwork by Escher.

Escher's half brother Berend Escher (1885-1967) was a professor of geology at Leiden University in the Netherlands, whose specialization was crystallography, mineralogy and vulcanology. It is likely that the artist Escher was introduced into the world of crystals by the mineralogist Escher.

Atomic Bomb Dropped Over Japan Created A New Kind Of Minerals - Hiroshimaites

The nuclear fire above Hiroshima in the early morning of August 6, 1945, not only vaporized parts of the city but also created new minerals. In 2015 geologist Mario Wannier discovered small particles of metal and glass in the sand collected along the shores of Miyajima Island and Motoujina Peninsula, located south of the hypocenter of the explosion.

Hiroshima city and bay area with location of the A-bomb hypocenter and sampling sites at Motoujina Peninsula and Miyajima Island. Optical microscopy image with a collection of glass spherules, cemented fragments and metallic spherules. From WANNIER et al. 2019.

Chemical analysis showed a layered structure of unknown minerals, mostly combinations of aluminum, silica, iron and calcium. The researchers argue that the particles formed by condensation from the mushroom cloud after the nuclear blast. As the mushroom cloud, containing traces of vaporized materials like stone, steel, concrete and rubber, cooled along its borders, small particles of glass-like material formed and rained down. Currents and the movement of the waves later accumulated the particles in the sand along the shores around the hypocenter of the explosion. Based on the unique chemical composition and the site of the discovery, the researcher named the new minerals Hiroshimaites, as they are artificial "tectites" (droplets of molten material formed by the heat of a meteorite impact). The studied sand samples contained up to 2% of particles, so along the shores of Hiroshima estimated 2,000 to 3,000 tons of Hiroshimaites may still lay in the ground.

Maria Matilda Ogilvie Gordon - A Women Geoscientist In The Dolomites

The 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, but already in the first year her interests into the natural world prevailed 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 the famous geologist Baron Ferdinand Freiherr von Richthofen (pioneer geologist of 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 eminent 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 the Triassic sediments, convinced her to become rather a geologist.
The pastures of Stuores in the Gader-Valley with outcrops of Triassic marl.

Richthofen was over sixty years old and therefore he couldn't provide much support in the field. Maria Ogilvie remembers later the challenge and danger of field work, 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.
The published paper, a summary of her thesis "The geology of the Wengen and Saint Cassian Strata in southern Tyrol", finally earned her 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.

Fossil corals from the pastures of Stuores, plate from LAUBE (1865).

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 the 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 many times the Dolomites.

Landscape profile of the Langkofel-massif after GORDON & PIA (1939): Zur Geologie der Langkofelgruppe in den Südtiroler Dolomiten. Maria Matilda included hand-drawn sketches in her research.

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

Interested in reading more? Try:

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

The Earth-shattering Monster of Loch Ness

The first purported photo of Nessie was published in The Daily Mail" on April 21, 1934.  The image, taken by a London surgeon named Kenneth Wilson, was touted for decades as the best evidence for Nessie — until it was admitted as a hoax decades later.

In 2001 Italian geologist Luigi Piccardi presented at the Earth Systems Processes meeting in Edinburgh a hypothesis, explaining the supposed appearance of the lake monster in Loch Ness as a result of the local geology. According to Piccardi, the historical description of the monster - appearing on the surface with great (earth)shakes and waves - could be based on seismic activity along the Great Glen fault. The Great Glen fault is a transcurrent fault where two bits of Earth - the Grampian Highlands, composed of early Paleozoic plutonic rocks, and the Northern Highlands, composed mostly of Neoproterozoic rocks with Palozoic sedimentary covers - are sliding sideways against each other.


Loch Ness is a 36 km long lake, located just above the fault zone. As the fault moves, earthquakes happen and cause bubbles and waves on the lake's surface. In an interview published in the Italian newspaper "La Repubblica" Piccardi explains:

"There are various effects on the surface of the water that can be related to the activity of the fault ...[]... the beast appears and disappears with great shakes. I think it's an obvious description of what really happened…[] We know that there was a period [1920-1930, a period characterized by many reported sightings of Nessie] with increased activity of the fault, in reality, people have seen the effects of the earthquakes on the water."

According to the biography of St. Columba, the scene described by Piccardi happened in the year 565. Trying to cross the river Ness the missionary is attacked by a beast. However, Columba implores the protection of god and the monster promptly disappears. The original text, however, is very vague and gives no detailed description of the event, stating only that it was an "unknown beast" and it approached with the mouth wide open and a loud roar. In the myth, the supposed lake monster is of much less importance than the ability of St. Columba to tame beasts and demons and doing so
to impress the local pagans. It is quite possible that the supposed encounter with the monster was added to make Colomba´s legend bigger than real life. The vague description presented doesn't really support any proposed scenario, neither seismic activity nor a presumed surviving plesiosaur, living in a lake formed by glaciers during the last ice age some 18,000 years ago. Modern sightings in Loch Ness can more reasonably be explained by a combination of hoaxes, misidentification of common animals or waves and the local tourist industry, keeping the myth alive to attract tourists. Research done in the lake has never produced any clue for the possible existence of a population of larger animals in the Loch.

Also, historic seismicity doesn't seem to support the existence of an earth-shaking monster in the Loch. Earthquakes along the Great Glen fault range between a magnitude of 3 to 4, too weak to cause any observable effects on the lake. Stronger events are exceptionally rare and were recorded only in 1816, 1888, 1890 and 1901. These earthquakes don't coincide with the years of supposed increased activity of Nessie, like in the decade around 1933.