TS
Tectonics and Structural Geology

Field Geology

Faults vs. Fractures — How to Tell Them Apart ?

October 16, 2025
A futuristic Black geologist wearing AR glasses stands in a glowing cave surrounded by four holographic screens labeled Geological Aspect, Geometry, Topology, and Kinematics & Mechanism, each displaying geological diagrams and fracture models, symbolizing modern geoscience visualization.
Observation. Measurement. Connection. Motion — the four pillars of the Holo-Geologist. Credit: Gemini 2.5.

Faults and fractures can sometimes be confusing, especially for students taking their first geology courses. When they go hiking in the mountains and see a crack in the rock, they often wonder — is this a fracture or a fault? Even scientists sometimes mix the two terms, so it’s good to understand the difference. Since faults and fractures are important in many fields such as tunnel engineering, hy ...[Read More]

Where earthquake faults reach the ground surface: insight from 2016 Kumamoto event

October 2, 2025
Where earthquake faults reach the ground surface: insight from 2016 Kumamoto event
Futagawa fault cutting across a road. Picture taken shortly after the earthquake in 2016 (Kumamoto Earthquake Memorial Museum KIOKU, 2025)

What does a seismogenic fault look like? We can sometimes observe surface earthquake faults, which propagate ruptures from the hypocenter to the ground surface. In 2016, intense seismicity was observed during the Kumamoto earthquake sequence in Japan. This sequence consisted of many shallow earthquakes, including a strong foreshock and the subsequent mainshock with numerous aftershocks. The earthq ...[Read More]

Throwback Summer – retracing student steps at the Pic Saint-Loup, France

September 18, 2025
picture pic Sant Loup
The Pic Saint-Loup, Occitania, France (Credit: Lauretta Kaerger)

The region around the Pic Saint-Loup is a popular destination for many European universities to teach mapping field courses – and there is a reason for it, even besides the great landscape, good food and nice weather. Let’s take a tour to discover why! The Pic Saint-Loup itself is indeed so impressive that some former students return at later stages in life “dragging” along other geologists ...[Read More]

Remembering Janos Urai – A master of all scales

September 18, 2023
Remembering Janos Urai – A master of all scales
Janos in the quarry on Naxos where marble slices were cut that allowed forming a 3D picture of amphibolite and pegmatite boudins at centimetre to decimetre scale. The picture is from a teaching lecture by Janos

As many will know, on Sunday, 28 May 2023, one of the most prominent, energetic and valued members of the Tectonics and Structural Geology community, Emeritus Professor Janos Urai, was lost in a tragic climbing accident in Belgium. Here we remember Janos for the amazing scientist that he was and for the huge legacy that he has left, in the form of his own transformative contributions and the inspi ...[Read More]

Features from the Field: Sheath Folds

and October 4, 2021
Features from the Field: Sheath Folds
Spectacular sheath folds in Cap de Creus (Spain), produced by deformation in a Variscan shear zone. Photo by Dr. Melanie Finch.

Shear zones are areas of intense deformation that localize the movement of one block of the crust with respect to another. In previous posts, we have seen that shear zones contain some very deformed rocks called mylonites, lineations that tell us the direction of movement, and useful kinematic indicators, such as S-C fabrics, that allow geologists to understand which way the rocks moved. However, ...[Read More]

TS Must-Read – Armijo et al. (1986) Quaternary extension in southern Tibet: field observations and tectonic implications

April 13, 2021
TS Must-Read – Armijo et al. (1986) Quaternary extension in southern Tibet: field observations and tectonic implications

This contribution is a very detailed field report of the Sino-French expedition in eastern Tibet that took place in 1980-1982. Armijo and coauthors accurately analyse the different tectonic styles present in the north and south of the Yarlung-Zangbo Suture Zone, frequently defined as the “chord” joining the eastern and western syntaxes of the Himalayan orogen (Fig. 1). North of the chord, strike-s ...[Read More]

Josefa Cuevas de Sansores (24-02-1920 – 2010) – Mexico’s first woman geological engineer

March 26, 2021
Josefa Cuevas de Sansores (24-02-1920 – 2010) – Mexico’s first woman geological engineer
An artists illustration of Josefa Cuevas de Sansores (credit: Annique van der Boon)

Josefa Cuevas Sansores was born on the 24th of March, 1920 to Andrea Aguilar Argüello. Andrea was a professor herself and graduated in 1929 specializing in ‘Instrucción Primaria Inferior y Superior’. She used the knowledge she had gained during her studies to found several kindergartens in Yucatán, one still carrying her name). Josefa had three older sisters, two of which became school teachers, w ...[Read More]

Janet Vida Watson (1 September 1923 – 29 March 1985): The woman who could translate the story of Precambrian rocks into a crystal-clear message

January 29, 2021
Janet Vida Watson (1 September 1923 – 29 March 1985): The woman who could translate the story of Precambrian rocks into a crystal-clear message
An artists illustration of Janet Watson (credit: Annique van der Boon)

On a late summer day in September 1923, Janet Vida Watson was born. With a father working in palaeontology and a mother who did research in embryology until her marriage, Janet grew up with science all around her. She went to South Hampstead High School, known for its science teaching and continued her education in General Science at Reading University. She graduated in biology and geology in 1943 ...[Read More]

Features from the Field: Shear Zones and Mylonites

, and January 25, 2021
Features from the Field: Shear Zones and Mylonites
Dextral, ductile shear zones crosscut foliated schist at Cap de Creus (Catalona, Spain). Photo © Jordi Carreras

The San Andreas Fault in California, the Alpine Fault in New Zealand, or the Main Frontal Thrust in the Himalayas are some of the most famous and largest fault zones that accommodate the relative displacement between two adjacent crustal blocks. Such faults, however, represent only the shallower expression of something much bigger: a crustal shear zone. In the first 10 kilometers or so of the crus ...[Read More]

#OnTheRocks – Because Earth is just beautiful!

January 15, 2021
#OnTheRocks – Because Earth is just beautiful!
The El Gordo Megabed from the Tabernas basin in Almeria, Spain. El Gordo which directly translates to the Fat Megabed is a fitting name for this huge sedimentary structure. The photo was taken on the morning after St.Patricks day on a field camp for Irish students. The photographer's previously thought to be incurable hangover was most certainly cured by the site. Credits: Grace Fitzgerald

From the time the first Kodak camera in 1888 went on sale we can say with confidence a geologist somewhere was trying to capture field photographs. We love to capture the beauty of the field and every geologist has a story to tell. The EGU would like to connect these stories globally in our new #OnTheRocks series. #OnTheRocks will produce a compilation of geological photographs on different scales ...[Read More]