TS
Tectonics and Structural Geology

Features from the field

Features From the Field: Pencil Cleavage

Features From the Field: Pencil Cleavage

This edition of ‘Features from the field’ is brought to you by Sandra McLaren, a senior lecturer at the University of Melbourne. She will be talking about type of rock formation called “Pencil Cleavage” so called because it looks like pencils. Sandra even has a small collection of pencil/crayon shale which is the cover image of this post. I have seen quite a range of differ ...[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]

Features from the field: Volcanic rocks and landscapes

Features from the field: Volcanic rocks and landscapes

This edition of ‘Features from the field’ is brought to you by Sandra McLaren, a senior lecturer at the University of Melbourne. She will be talking about the volcanic activity and rocks in the Tower hill complex in Australia.   Volcanic activity is one of the most spectacular manifestations of our tectonically active planet. Volcanic eruptions can be highly dangerous when they oc ...[Read More]

Features from the field: crenulation cleavage

Features from the field: crenulation cleavage

In one of the former episodes of the ‘Features from the field’ series we have talked about foliations, and how they develop when rocks are pushed together by the movement of tectonic plates. It is quite uncommon, however, that tectonic forces are active in the same direction for an unlimited period of time. The rule, rather than the exception, is that the orientation of tectonic forces ...[Read More]

Features from the field: Bedding/Stratification

Features from the field: Bedding/Stratification

Bedding (also called stratification) is one of the most prominent features of sedimentary rocks, which are usually made up of ‘piles’ of layers (called ‘strata‘) of sediments deposited one on top of another. Every stratum is characterized by its own lithology (composition), sedimentary structures, grain size and fossil content that make it unique and different from the stra ...[Read More]

Features from the field: Ripple Marks

Features from the field: Ripple Marks

Earlier this year, Ian Kane, geologist at the University of Manchester, captured the iconic snapshot shown above. The picture reveals ripples, developed due to waves and currents in the sand of White Strand (near Killard, county Clare, Ireland) right next to Carboniferous sandstone that contains ‘petrified’ ripple marks! The image is powerful, because it shows the basic principle of geological act ...[Read More]

Features from the field: Foliation

Features from the field: Foliation

Have you ever walked on a mountain trail, passing past outcrops of rocks and noticed that many rocks appear to be split along a well-defined orientation? If you have, you might have seen one of the most important structures in metamorphic rocks – called foliation. The term ‘foliation’ derives from the Latin folium, meaning ‘leaf’. A rock with a foliation looks like a pile of R ...[Read More]

Features from the field: Boudinage

Features from the field: Boudinage

The Features from the Field series is back! In our previous posts, we have shown how rocks can deform during ductile deformation, producing folds. Folds very commonly develop in rocks when rock layers are shortened by tectonic forces in a specific direction. On the other hand, when layers are extended, we develop boudins. Boudins – the term comes from the French word for ‘sausage’ – are frag ...[Read More]

Features from the field: Folding

Features from the field: Folding

Folding is one of the most common geologic phenomena in the world. I should start with defining the term ‘deformation’ in order to understand the folding process better. In geology, deformation is an alteration of the size or shape of rocks. Deformation is caused by stress, the scientific term for force applied to a certain area. Stresses on rocks can stem from various sources, such as ...[Read More]

Features from the field: Strike Slip Faults Classification

Features from the field: Strike Slip Faults Classification

A strike slip faults is a fault on which most of the movement is parallel to the fault strike (Bates and Jackson, 1987). The term ‘wrench fault’ is also popularized in some researchers. Sylvester (1988) suggest not using wrench fault term for defining strike slip fault as general term because wrench fault was defined by Anderson (1905) as deep seated, regional and vertical faults. Many major strik ...[Read More]