Friday, March 24, 2017

30+ Thin Section Photos That Will Develop Your Interest in Petrography

 “thin section” of rock is a sample that is mounted to a microscope slide and cut so thin that you can see light through it. The process of creating a thin section is a blend of artistry, technology and science.  
The art of preparing thin sections has been critical to understanding the core samples that scientists are observing. Thin section samples allow scientists to observe minerals in rocks, their crystal structure and texture at a microscopic level.

Want to revise how do geologists study rock? Follow this link to see our blog on "Studying Rock".

In this blog, we're taking you into the journey of thin section photos that were captured and given by students and young professionals from Finland, Ireland, Denmark, Czech Republic and Plymouth (UK). 

Again our purpose is to encourage students and professionals' research by promoting "learning and scope" of Geology through our blogs. Help us to help others in learning and understanding geology. See this link that how you can contribute to Learning Geology.

Note: We are using following thin section photos by having permission from their owners. If 
you like to use these photos, leave us a message or email us here.

1. A beautiful heart shaped hornblende in XPL (cross polarized light) view.It is a thin section of basalt with some secondary mineralization in the vesicles. Plagioclase is present in the form of black and white matrix and large phenocryst (with some zoning). Alignment of plagioclase grains is indicative of the "flow" of magma.

Photo Credits: Astaley

2. Thin Section of a Biotite and Muscovite, XPL view 

Photo Courtesy: Laura

3. Thin Section of a Plagioclase (orthoclase) and Pyroxene, XPL 

Photo Courtesy: Laura

4. Eclogite in Thin Section, XPL

Photo Courtesy: Laura

 5. Cummulate Rock with Pyroxene and plagioclase, XPL

Photo Courtesy: Laura

6. Blueschist, XPL

Photo Courtesy: Laura

7. Agglomerate in a Thin Section, XPL view

     Agglomerates are pyroclastic igneous rocks that consist almost wholly of angular or rounded lava fragments of varying size and shape. Fragments are usually poorly sorted in a tuffaceous matrix, or appear in lithified volcanic ash. (

Photo Courtesy: Laura
8. Thin Section of a Pigeonite and Olivine, XPL

Photo Courtesy: Laura

9. Olivine phenocryst in Basaltic Lapilli, XPL

Photo Courtesy: Laura

10. Thin Section of a Gabbro, XPL

Showing minerals; Pyroxene and Olivine, plagioclase and others. Learn more about Gabbro here.

Photo Courtesy: Laura

 11. Another beautiful thin section of a Gabbro, XPL

Photo Courtesy: Laura
12. Thin Section of a Greenschist, XPL

Photo Courtesy: Laura

13. Thin Section showing intrusion of rocks from magma chamber into country rocks, XPL

Photo Courtesy: Jack Lewis Donnelly

14. Thin Section of a Sillimanite - a mineral found in rocks formed by the metamorphism of a mudstone. (XPL view)

Photo Courtesy: Jack Lewis Donnelly
15. Microgeode in ultrabasic vulcanite (
a rare copper telluride mineral), 30 µm thin section, PPL and XPL 

Photo Courtesy: Petr Hyks

Photo Courtesy: Petr Hyks
                                                              See original photo here

16. Muscovite & biotite (30 µm thin section, PPL and XPL)

Photo Courtesy: Petr Hyks

Photo Courtesy: Petr Hyks
Same photo in XPL view. See original photo here

17. Quartz and epidote (30 µm thin section, PPL and XPL)

Photo Courtesy: Petr Hyks

Photo Courtesy: Petr Hyks
                                                        See original here.

18. Olivine (30 µm thin section, PPL and XPL)

Photo Courtesy: Petr Hyks
See this photo here on Petr Hyks' website

19. Zircons in biotite (30 µm thin section, PPL views, showing extinction)
                          Photo Courtesy: Petr Hyks
                              See this photo here on Petr's website

20. Zircon in biotite (30 µm thin section, XPL)

Photo Courtesy: Petr Hyks
See this photo here on Petr's website

21. Kyanite surrounded by muscovite (30 µm thin section, PPL and XPL)

Photo Courtesy: Petr Hyks
See these photos on Petr's page here and here

22. Zircon crystal in chloritized biotite (30 µm thin section, PPL and XPL)

Photo Courtesy: Petr Hyks
See these photos on Petr's page  here and here
Petr Hyks is 21 year old geology student from Masaryk University in Brno (Czech Republic). He has uploaded 5000+ photos about geology, astronomy and meteorology on his Flickr page. Follow this link to visit his website. Thank you Petr for contributing to Learning Geology and helping others to learn geology through your thin section photos. 🙂 Now following 10 thin section photos are from a geology student of University of Helsinki, Finland.

23. Thin Section of Olivine Diabase in XPL and PPL view.

Photo Courtesy: GeoAmethyst

24. Thin Section of Basalt in XPL view
        Having minerals: Olivine (in center) plagioclase, pyroxene and other accessory minerals
Photo Courtesy: GeoAmethyst

25. Thin Section of a Trachyte, XPL view

    Trachyte is an igneous volcanic rock with aphanitic to porphyritic texture. It is volcanic equivalent of Syenite. Major or essential minerals are alkali feldspar with less amount of plagioclase, quartz or feldspathiod. 

Photo Courtesy: GeoAmethyst

26. Thin Section of a Harzburgite, XPL view
      Harzburgite is an ultramafic igneous rock. It chiefly contains plagioclase (under 10%) , olivine, orthopyroxene (enstatite), clinopyroxene (diopside) and biotite. There could be a small amount of talc, carbonate, tremolite, cummingtonite, chlorite, serpentine and titanite.
Photo Courtesy: GeoAmethyst

27.  Another thin section of Harzburgite, XPL view

Photo Courtesy: GeoAmethyst

28.  Thin Section of Pyroxenite (an ultramafic igneous rock), XPL view

Photo Courtesy: GeoAmethyst

29. Thin Section of Trachyte showing Sandine mineral in center, XPL view

Photo Courtesy: GeoAmethyst
30.  Thin Section of Andesite, XPL view
       It is an extrusive igneous, of intermediate composition, with aphanitic to porphyritic texture.              Here this thin section is showing chiefly hornblende and plagioclase.
Photo Courtesy: GeoAmethyst

31. Thin Section of Alkali Basalt (silica undersaturated) in XPL view.

Photo Courtesy: GeoAmethyst

32. Thin Section showing small clinopyroxene grains within orthopyroxene

Photo Courtesy: GeoAmethyst

Like this article? Leave a comment down or send us your valuable suggestion or feedback here  to help us in improving this article.
Useful Websites: 

1. Polarized light Microscopy (Image Gallery)
2. How to make a thin section
3. Petrographic thin section preparation
4. Guide to Thin Section Microscopy
5. Index of Minerals in Thin Section
Optical Petrography website by an Italian Geologist

7. Carbonate Thin Section Images and 

Friday, March 3, 2017


What is anthropocene?

The anthropocene Epoch is atop of the table.
Almost everyone will ask, what is Anthropocene? What is the Anthropocene age or Anthropocene epoch or Anthropocene era? So, here let's start with the definition and learn the ages of man effects on Earth.
The Anthropocene definition, Earth's most recent geologic time period as being human-influenced, or anthropogenic, based on overwhelming global evidence that atmospheric, geologic, hydrologic, biospheric and other earth system processes are now altered by humans.
The word combines the root "anthropo", meaning "human" with the root "-cene", the standard suffix for "epoch" in geologic time.
The Anthropocene is distinguished as a new period either after or within the Holocene epoch, the current epoch, which began approximately 10,000 years ago (about 8000 BC) with the end of the last glacial period.

Epoch definition and Epoch meaning

  1. an event or a time marked by an event that begins a new period or developmentb
  2. memorable event or date
  3. an extended period of time usually characterized by a distinctive development or by a memorable series of eventsb 
  4. division of geologic time less than a period and greater than an age
  5. an instant of time or a date selected as a point of reference (as in astronomy)

From when Anthropocene Epoch Start?

The Anthropocene Epoch should begin about 1950, the experts said, and was likely to be defined by the radioactive elements dispersed across the planet by nuclear bomb tests, although an array of other signals, including plastic pollution, soot from power stations, concrete, and even the bones left by the global proliferation of the domestic chicken were now under consideration.
The current Holocene epoch, is the 12,000 years of stable climate since the last ice age during which all human civilisation developed. But the striking acceleration since Anthropocene timeline, the mid-20th century of carbon dioxide emissions and sea level rise, the global mass extinction of species, and the transformation of land by deforestation and development mark the end of that slice of geological time, the experts argue. The Earth is so profoundly changed that the Holocene must give way to the Anthropocene.

The Anthropocene Review or Anthropocene theory (Debate on current epoch)

The Anthropocene Review or Anthropocene theory, According to the International Union of Geological Sciences (IUGS), the professional organization in charge of defining Earth’s time scale, we are officially in the Holocene epoch (entirely recent), which began 11,700 years ago after the last major ice age.
Holocene and Anthropocene both are geological epoch however, Anthropocene era has become an environmental buzzword ever since the atmospheric chemist and Nobel laureate Paul Crutzen popularised it in 2000. This year, the word has picked up velocity in elite science circles: It appeared in nearly 200 peer-reviewed articles, the publisher Elsevier has launched a new aca­demic journal titled Anthropocene and the IUGS convened a group of scholars to decide by 2016 whether to officially declare that the Holocene is over and the Anthropocene age has begun.
Many stratigraphers (scientists who study rock layers) criticise the idea, saying clear-cut evidence for a new epoch simply isn’t there. “When you start naming geologic-time terms, you need to define what exactly the boundary is, where it appears in the rock strata,” says Whitney Autin, a stratigrapher at the SUNY College of Brockport, who suggests Anthropocene is more about pop culture than hard science. The crucial question, he says, is specifying exactly when human beings began to leave their mark on the planet: The atomic era, for instance, has left traces of radiation in soils around the globe, while deeper down in the rock strata, agriculture’s signature in Europe can be detected as far back as A.D. 900. The Anthropocene, Autin says, “provides eye-catching jargon, but from the geologic side, I need the bare bones facts that fit the code.”

Nature of human effects


The human impact on biodiversity forms one of the primary attributes of the Anthropoceno. Humankind has entered what is sometimes called the Earth's sixth major extinction. Most experts agree that human activities have accelerated the rate of species extinction. The exact rate remains controversial perhaps 100 to 1000 times the normal background rate of extinction. A 2010 study found that "marine phytoplankton the vast range of tiny algae species accounting for roughly half of Earth's total photosynthetic biomass – had declined substantially in the world's oceans over the past century. From 1950 alone, algal biomass decreased by around 40%, probably in response to ocean warming and that the decline had gathered pace in recent years. Some authors have postulated that without human impacts the biodiversity of the planet would continue to grow at an exponential rate. 
Increases in global rates of extinction have been elevated above background rates since at least 1500, and appear to have accelerated in the 19th century and further since. A 13 July 2012 New York Times op-ed by ecologist Roger Bradbury predicted the end of biodiversity for the oceans, labelling coral reefs doomed: "Coral reefs will be the first, but certainly not the last, major ecosystem to succumb to the Anthropocene." This op-ed quickly generated much discussion among conservationists; The Nature Conservancy rebutted Bradbury on its website, defending its position of protecting coral reefs despite continued human impacts causing reef declines.
In a pair of studies published in 2015, extrapolation from observed extinction of Hawaiian snails led to the conclusion that "the biodiversity crisis is real", and that 7% of all species on Earth may have disappeared already. Human predation was noted as being unique in the history of life on Earth as being a globally distributed 'superpredator', with predation of the adults of other apex predators and with widespread impacts on food webs worldwide.


Permanent changes in the distribution of organisms from human influence will be identifiable in the geologic record. Many species have been documented moving into regions that were once too cold for them, often at rates faster than initially expected. This has occurred in part as a result of evolving climate, but also in response to farming and fishing, and the accidental introduction of non-native species to new areas by global travel. The ecosystem of the entire Black Sea may have changed during the last 2000 years as a result of nutrient and silica input from eroding deforested lands along the Danube River.


One geological symptom resulting from human activity is increasing atmospheric carbon dioxide (CO2) content. During the glacial–interglacial cycles of the past million years, natural processes have varied CO2 by approximately 100 ppm (from 180 ppm to 280 ppm). As of 2013, anthropogenic net emissions of CO2 increased atmospheric concentration by a comparable amount from 280 ppm (Holocene or pre-industrial "equilibrium") to approximately 400 ppm, with 2015–16 monthly monitoring data of CO2 displaying a rising trend above 400 ppm. This signal in the Earth's climate system is especially significant because it is occurring much faster, and to a greater extent, than previous, similar changes. Most of this increase is due to the combustion of fossil fuels such as coal, oil, and gas, although smaller fractions are the result of cement production and land-use changes (e.g. deforestation).


Changes in drainage patterns traceable to human activity will persist over geologic time in large parts of the continents where the geologic regime is erosional. This includes the paths of roads and highways defined by their grading and drainage control. Direct changes to the form of the Earth's surface by human activities (e.g., quarrying, landscaping) also record human impacts.


Sedimentological record

Human activities like deforestation and road construction are believed to have elevated average total sediment fluxes across the Earth's surface. However, construction of dams on many rivers around the world means the rates of sediment deposition in any given place do not always appear to increase in the Anthropocene. For instance, many river deltas around the world are actually currently starved of sediment by such dams, and are subsiding and failing to keep up with sea level rise, rather than growing.

Fossil record

Increases in erosion due to farming and other operations will be reflected by changes in sediment composition and increases in deposition rates elsewhere. In land areas with a depositional regime, engineered structures will tend to be buried and preserved, along with litter and debris. Litter and debris thrown from boats or carried by rivers and creeks will accumulate in the marine environment, particularly in coastal areas. Such manmade artefacts preserved in stratigraphy are known as "techno-fossils".
Changes in biodiversity will also be reflected in the fossil record, as will species introductions. An example cited is the domestic chicken, originally the red junglefowl Gallus gallus, native to south-east Asia but has since become the world's most common bird through human breeding and consumption, with over 60 billion consumed a year and whose bones would become fossilised in landfill sites.

Trace elements

In terms of trace elements, there are distinct signatures left by modern societies. For example, in the Upper Fremont Glacier in Wyoming, there is a layer of chlorine present in ice cores from 1960s atomic weapon testing programs, as well as a layer of mercury associated with coal plants in the 1980s. From 1945 to 1951, nuclear fallout is found locally around atomic device test sites, whereas from 1952 to 1980, tests of thermonuclear devices have left a clear, global signal of excess 14C, 239Pu, and other artificial radionuclides. The highest concentration of radionuclides was in 1964, one of the dates which has been proposed as a possible benchmark for the start of the formally defined age of Anthropocene.
Human burning of fossil fuels has also left distinctly elevated concentrations of black carbon, inorganic ash, and spherical carbonaceous particles in recent sediments across the world. Concentrations of these components increases markedly and almost simultaneously around the world beginning around 1950.