TS
Tectonics and Structural Geology

Structural Geology

Features from the Field: Sheath Folds

Features from the Field: Sheath Folds

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]

Features from the Field: Stretching Lineations

Features from the Field: Stretching Lineations

Deep beneath our feet, deformation of rocks at high temperature produces impressive structures such as shear zones, that localize the movement of two volumes of rock with respect to one another. Shear zones are strongly deformed bands with strongly foliated structures (i.e., with rocks that look like a pile of leaves) and kinematic indicators, such as S-C fabrics, that tell us geologists which way ...[Read More]

Features from the Field: Shear Zones and Mylonites

Features from the Field: Shear Zones and Mylonites

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]

TS Must-Read – Ramsay (1980) Shear zone geometry: a review

TS Must-Read – Ramsay (1980) Shear zone geometry: a review

Ramsay’s 1980 important contribution is a practical and theoretical handbook about shear zones, where the reader can find a detailed classification of shear zones, their description, and mathematical explanation. A definition of the concept of shear zones opens the article, followed by the shear zones classification into three types, namely brittle (e.g., Fig. 1a), brittle-ductile (e.g., Fig ...[Read More]

#OnTheRocks – Because Earth is just beautiful!

#OnTheRocks – Because Earth is just beautiful!

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]

Franciszka Szymakowska (05/02/1927 – 2007): the woman whose drawings unraveled the geological history of the Carpathians

Franciszka Szymakowska (05/02/1927 – 2007): the woman whose drawings unraveled the geological history of the Carpathians

  Franciszka Szymakowska was born on the 5th of February in 1927 in Krakow. She was lovingly known as “Niusia” (Antoni 2007). About her early life, not much is known. Franciszka did her studies at the Faculty of Mathematics and Natural Sciences of the Jagiellonian University and graduated in 1952. During her studies, she started to work at the Polish Geological Institute. She remained affilia ...[Read More]

Features from the Field: Angular Unconformities

Features from the Field: Angular Unconformities

An angular unconformity is an erosional surface that truncates older, tilted sedimentary layers and that is overlain by younger layers, oriented parallel to the unconformity. The discovery and interpretation of angular unconformities, like the famous Hutton’s unconformity at Siccar Point, Scotland, marked a paradigm shift in the geological theories of the 18th century. At that time, the theo ...[Read More]

TS Must-Read – Hubbert and Rubey (1959)

TS Must-Read – Hubbert and Rubey (1959)

“The Role of Fluid Pressure in Mechanics of Overthrust Faulting” by Hubbert and Rubey is a “groundbreaking” article from the end of the 1950s. It’s a remarkable piece of research, written in an old-fashioned way, for modern standards. Many ECS that may not have read the original paper yet are certainly familiar with its textbook content. Let’s go quickly through it!   The article, as a key po ...[Read More]

100 years of Marie Tharp – The woman who mapped the ocean floor and laid the foundations of modern geology

100 years of Marie Tharp – The woman who mapped the ocean floor and laid the foundations of modern geology

Marie Tharp (July 30, 1920 – August 23, 2006) would have turned 100 on this very day and she continues to live through her legacy of having mapped the world’s oceans. Similar to famous painters, some of whom only gain appreciation after their death, Marie Tharp is one of the most underappreciated scientists in the history of the earth sciences. Marie was born in Ypsilanti, Michigan. Due to h ...[Read More]

Features from the Field: Chevron Folds

Features from the Field: Chevron Folds

Folds are among the most strikingly beautiful structures we can observe in rocks. There are several ways folds may form in rocks. For instance, folds in sedimentary rocks may develop by liquefaction of soft sediments, but the most common way to produce folds – and also my favorite – is by deformation. When rocks are compressed by tectonic forces, layers (or foliations) bend and warp, p ...[Read More]