Video games can change your brain

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Video games can change your brain

Scientists have collected and summarized studies looking at how video games can shape our brains and behavior. Research to date suggests that playing video games can change the brain regions responsible for attention and visuospatial skills and make them more efficient. The researchers also looked at studies exploring brain regions associated with the reward system, and how these are related to video game addiction.

Do you play video games? If so, you aren’t alone. Video games are becoming more common and are increasingly enjoyed by adults. The average age of gamers has been increasing, and was estimated to be 35 in 2016. Changing technology also means that more people are exposed to video games. Many committed gamers play on desktop computers or consoles, but a new breed of casual gamers has emerged, who play on smartphones and tablets at spare moments throughout the day, like their morning commute. So, we know that video games are an increasingly common form of entertainment, but do they have any effect on our brains and behavior? Over the years, the media have made various sensationalist claims about video games and their effect on our health and happiness. “Games have sometimes been praised or demonized, often without real data backing up those claims. Moreover, gaming is a popular activity, so everyone seems to have strong opinions on the topic,” says Marc Palaus, first author on the review, recently published in Frontiers in Human Neuroscience. Palaus and his colleagues wanted to see if any trends had emerged from the research to date concerning how video games affect the structure and activity of our brains. They collected the results from 116 scientific studies, 22 of which looked at structural changes in the brain and 100 of which looked at changes in brain functionality and/or behavior. The studies show that playing video games can change how our brains perform, and even their structure. For example, playing video games affects our attention, and some studies found that gamers show improvements in several types of attention, such as sustained attention or selective attention. The brain regions involved in attention are also more efficient in gamers and require less activation to sustain attention on demanding tasks. There is also evidence that video games can increase the size and efficiency of brain regions related to visuospatial skills. For example, the right hippocampus was enlarged in both long-term gamers and volunteers following a video game training program. Video games can also be addictive, and this kind of addiction is called “Internet gaming disorder.” Researchers have found functional and structural changes in the neural reward system in gaming addicts, in part by exposing them to gaming cues that cause cravings and monitoring their neural responses. These neural changes are basically the same as those seen in other addictive disorders. So, what do all these brain changes mean? “We focused on how the brain reacts to video game exposure, but these effects do not always translate to real-life changes,” says Palaus. As video games are still quite new, the research into their effects is still in its infancy. For example, we are still working out what aspects of games affect which brain regions and how. “It’s likely that video games have both positive (on attention, visual and motor skills) and negative aspects (risk of addiction), and it is essential we embrace this complexity,” explains Palaus.

Fungal toxins easily become airborne, creating potential indoor health risk

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Fungal toxins easily become airborne, creating potential indoor health risk

Toxins produced by three different species of fungus growing indoors on wallpaper may become aerosolized, and easily inhaled. The findings, which likely have implications for “sick building syndrome,” were published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.

“We demonstrated that mycotoxins could be transferred from a moldy material to air, under conditions that may be encountered in buildings,” said corresponding author Jean-Denis Bailly, DVM, PhD, Professor of Food Hygiene, National Veterinary School of Toulouse, France. “Thus, mycotoxins can be inhaled and should be investigated as parameters of indoor air quality, especially in homes with visible fungal contamination.” The impetus for the study was the dearth of data on the health risk from mycotoxins produced by fungi growing indoors. (image: microscopic view of a sporulating Aspergillus, showing numerous light spores that can be easily aerosolized and inhaled together with mycotoxins. credit: Sylviane Bailly.) In the study, the investigators built an experimental bench that can simulate an airflow over a piece of contaminated wall paper, controlling speed and direction of the air. Then they analyzed the resulting bioaerosol. “Most of the airborne toxins are likely to be located on fungal spores, but we also demonstrated that part of the toxic load was found on very small particles — dust or tiny fragments of wallpaper, that could be easily inhaled,” said Bailly.. The researchers used three fungal species in their study: Penicillium brevicompactum, Aspergillus versicolor, and Stachybotrys chartarum. These species, long studied as sources of food contaminants, also “are frequent indoor contaminants,” said Bailly. He noted that they produce different mycotoxins, and their mycelia are different from one another, likely leading to differences in the quantity of mycotoxins they loft into the air. (Mycelia are the thread-like projections of fungi that seek nutrition and water from the environment.) The findings raised two new scientific questions, said Bailly. First, “There is almost no data on toxicity of mycotoxins following inhalation,” he said, noting that most research has focused on such toxins as food contaminants. Second, the different fungal species put different quantities of mycotoxins in the air, “probably related to mycelium organization,” but also possibly related to the mechanisms by which mycotoxins from different fungi become airborne — for example via droplets of exudate versus accumulation in spores. Such knowledge could help in prioritizing those species that may be of real importance in wafting mycotoxins, he said. Bailly noted that the push for increasingly energy efficient homes may aggravate the problem of mycotoxins indoors. Such homes “are strongly isolated from the outside to save energy,” but various water-using appliances such as coffee makers “could lead to favorable conditions for fungal growth,” he said. “The presence of mycotoxins in indoors should be taken into consideration as an important parameter of air quality,” Bailly concluded.

The mere presence of your smartphone reduces brain power, study shows

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The mere presence of your smartphone reduces brain power, study shows

Your cognitive capacity is significantly reduced when your smartphone is within reach — even if it’s off. That’s the takeaway finding from a new study from the McCombs School of Business at The University of Texas at Austin.

McCombs Assistant Professor Adrian Ward and co-authors conducted experiments with nearly 800 smartphone users in an attempt to measure, for the first time, how well people can complete tasks when they have their smartphones nearby even when they’re not using them. In one experiment, the researchers asked study participants to sit at a computer and take a series of tests that required full concentration in order to score well. The tests were geared to measure participants’ available cognitive capacity — that is, the brain’s ability to hold and process data at any given time. Before beginning, participants were randomly instructed to place their smartphones either on the desk face down, in their pocket or personal bag, or in another room. All participants were instructed to turn their phones to silent. The researchers found that participants with their phones in another room significantly outperformed those with their phones on the desk, and they also slightly outperformed those participants who had kept their phones in a pocket or bag. The findings suggest that the mere presence of one’s smartphone reduces available cognitive capacity and impairs cognitive functioning, even though people feel they’re giving their full attention and focus to the task at hand. “We see a linear trend that suggests that as the smartphone becomes more noticeable, participants’ available cognitive capacity decreases,” Ward said. “Your conscious mind isn’t thinking about your smartphone, but that process — the process of requiring yourself to not think about something — uses up some of your limited cognitive resources. It’s a brain drain.” In another experiment, researchers looked at how a person’s self-reported smartphone dependence — or how strongly a person feels he or she needs to have a smartphone in order to get through a typical day — affected cognitive capacity. Participants performed the same series of computer-based tests as the first group and were randomly assigned to keep their smartphones either in sight on the desk face up, in a pocket or bag, or in another room. In this experiment, some participants were also instructed to turn off their phones. The researchers found that participants who were the most dependent on their smartphones performed worse compared with their less-dependent peers, but only when they kept their smartphones on the desk or in their pocket or bag. Ward and his colleagues also found that it didn’t matter whether a person’s smartphone was turned on or off, or whether it was lying face up or face down on a desk. Having a smartphone within sight or within easy reach reduces a person’s ability to focus and perform tasks because part of their brain is actively working to not pick up or use the phone. “It’s not that participants were distracted because they were getting notifications on their phones,” said Ward. “The mere presence of their smartphone was enough to reduce their cognitive capacity.”

Frequent sexual activity can boost brain power in older adults, according to new study

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Frequent sexual activity can boost brain power in older adults, according to new study
Research from the Stowers Institute provides evidence suggesting that cancer cells might streamline their genomes in order to proliferate more easily. The study, conducted in both human and mouse cells, shows that cancer genomes lose copies of repetitive sequences known as ribosomal DNA. While downsizing might enable these cells to replicate faster, it also seems to render them less able to withstand DNA damage.

More frequent sexual activity has been linked to improved brain function in older adults, according to a study by the universities of Coventry and Oxford.

Researchers found that people who engaged in more regular sexual activity scored higher on tests that measured their verbal fluency and their ability to visually perceive objects and the spaces between them. The study, published today in The Journals of Gerontology, Series B: Psychological and Social Sciences, involved 73 people aged between 50 and 83. Participants filled in a questionnaire on how often, on average, they had engaged in sexual activity over the past 12 months — whether that was never, monthly or weekly — as well as answering questions about their general health and lifestyle. The 28 men and 45 women also took part in a standardized test, which is typically used to measure different patterns of brain function in older adults, focusing on attention, memory, fluency, language and visuospatial ability. This included verbal fluency tests in which participants had 60 seconds to name as many animals as possible, and then to say as many words beginning with F as they could — tests which reflect higher cognitive abilities. They also took part in tests to determine their visuospatial ability which included copying a complex design and drawing a clock face from memory. It was these two sets of tests where participants who engaged in weekly sexual activity scored the most highly, with the verbal fluency tests showing the strongest effect. The results suggested that frequency of sexual activity was not linked to attention, memory or language. In these tests, the participants performed just as well regardless of whether they reported weekly, monthly or no sexual activity. This study expanded on previous research from 2016, which found that older adults who were sexually active scored higher on cognitive tests than those who were not sexually active. But this time the research looked more specifically at the impact of the frequency of sexual activity (i.e. does it make a difference how often you engage in sexual activity) and also used a broader range of tests to investigate different areas of cognitive function. The academics say further research could look at how biological elements, such as dopamine and oxytocin, could influence the relationship between sexual activity and brain function to give a fuller explanation of their findings. Lead researcher Dr Hayley Wright, from Coventry University’s Centre for Research in Psychology, Behaviour and Achievement, said: “We can only speculate whether this is driven by social or physical elements — but an area we would like to research further is the biological mechanisms that may influence this. “Every time we do another piece of research we are getting a little bit closer to understanding why this association exists at all, what the underlying mechanisms are, and whether there is a ’cause and effect’ relationship between sexual activity and cognitive function in older people. “People don’t like to think that older people have sex — but we need to challenge this conception at a societal level and look at what impact sexual activity can have on those aged 50 and over, beyond the known effects on sexual health and general wellbeing.”

Cancer cells may streamline their genomes in order to proliferate more easily

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Cancer cells may streamline their genomes in order to proliferate more easily
Research from the Stowers Institute provides evidence suggesting that cancer cells might streamline their genomes in order to proliferate more easily. The study, conducted in both human and mouse cells, shows that cancer genomes lose copies of repetitive sequences known as ribosomal DNA. While downsizing might enable these cells to replicate faster, it also seems to render them less able to withstand DNA damage The findings, published June 22, 2017, in PLoS Genetics, suggest that ribosomal DNA copy number could be used to predict which cancers will be sensitive to DNA-damaging chemotherapeutics. “Drugs that damage DNA are often used to treat cancer, but it’s not clear why they would selectively kill cancer cells,” says Jennifer L. Gerton, Ph.D., an investigator at the Stowers Institute who led the study. “Our results suggest that off-loading copies of ribosomal DNA could create instability in the genome that makes cells particularly susceptible to chemotherapy with DNA-damaging drugs.” Ribosomal DNA plays a critical role in healthy cells and cancer cells alike. It encodes structural components of ribosomes, the miniature factories responsible for producing the proteins that carry out many functions of the cell. Despite their importance, these repetitive sequences are often skipped over and not analyzed in genome studies. The few studies that have included analysis of ribosomal DNA thus far have shown that the number of copies of the repetitive sequences expand and contract all the time. Gerton hypothesized that cancer cells, which are highly proliferative and might need more than the usual amount of ribosomes, would select for expansion of copy number. What she and her colleagues found was exactly the opposite. The team combed through data from eight different human cancer genome projects. First author Baoshan Xu, Ph.D., a former postdoctoral research associate in the Gerton Lab now starting his own lab at Sun Yat-sen University in China, worked with Hua Li, Ph.D., to use computational methods to count the number of copies of ribosomal DNA in normal and cancer cells of 162 patients from the eight projects. For five of the projects, Xu and Li saw no change in copy number. For three, he saw a loss of ribosomal DNA copies in the cancer cells relative to the normal cells. To confirm their results, the researchers turned to John Perry, Ph.D., a Stowers senior research associate, and Linheng Li, Ph.D., a Stowers investigator who had generated a mouse model of leukemia. This time, Xu used a sophisticated technique called droplet digital PCR to count the ribosomal DNA copies in normal and cancer cells from the mice. He witnessed the same phenomenon that he had seen in the human cancer genome databases. The cells somehow managed to be highly proliferative, made more ribosomal RNA, and synthesized more protein, all with fewer copies of ribosomal DNA. “Cancer is exerting the same kind of pressure on the genome that we thought it would, but it’s working in a counterintuitive way,” said Gerton. “We thought pressure to proliferate would lead to expansion of copy number, so there would be more DNA transcribed into RNA. Instead, it led to contraction of copy number. We speculate less DNA to copy promotes proliferation. We are testing this idea now.” Gerton suspected that this streamlined genome would come at a cost. Previous studies on budding yeast showed that whittling down the number of copies of ribosomal DNA created a genome that was very sensitive to DNA damage. To see if this same result held true in higher organisms, Gerton’s team treated cancer cells from Li’s mice with four different DNA damaging drugs. They found that the cancer cells were more sensitive to DNA damage than normal cells. “If what we found in mice held true for human cancer, it could be very useful in the clinic,” she said. Gerton thinks that ribosomal DNA breaks regularly and then undergoes either expansion or contraction, and is currently investigating the mechanisms that underlie that instability.

Yale Chemistry Professor Has the Key for More Sustainable Agro-Chemicals

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Yale Chemistry Professor Has the Key for More Sustainable Agro-Chemicals

Key for More Sustainable Agro-Chemicals

Nilay Hazari, Professor of Chemistry at Yale, did not anticipate that his work around catalysts would one day lead to real commercial opportunity. “Our goal was to develop something as an academic endeavor,” Hazari says. But when Hazari presented his technology to the Office of Cooperative Research (OCR), they saw potential. What Hazari and an enterprising graduate student named Patrick Melvin have developed is a novel method of catalysis using palladium—a technology that will make it easier to synthesize insecticides, pesticides and pharmaceuticals in a more sustainable way. “The technology has been known for 50 years,” Hazari says. In fact, three researchers were awarded the Nobel Prize for their work on palladium-derived catalysis in 2010. “But ours is more efficient,” Hazari adds, “and that should save companies money because they will need less starting material.” Melvin, who has worked on this pre-catalyst for the past five years in Hazari’s lab says: “A previous graduate student had been working on a very specific type of palladium pre-catalyst and his studies showed limitations. My goal was to create a system which avoided these limitations. It was a truly collaborative effort.” Yale has just partnered with a global leader in the provision of industrial scale catalytic agents to make the Hazari catalytic system widely available to manufacturers worldwide. “I like to think that it’s possible to scale,” says Hazari, who adds that with the high price of palladium it’s impossible for his lab to test more than 25 grams. Industry needs amounts in kilograms—or even tons. David Lewin, Senior Associate Director of Business Development at OCR, has been working with Hazari since he first disclosed the new technology in 2013. He says “This is a great example of theory becoming practice—it’s not easy to partner catalysts, it has to be something pretty special.” Hazari, who received tenure in 2016, is eager to see his catalyst put to the test—and to see the culmination of years of work from his graduate students. “It’s eye-opening to see all the commercial aspects that go into licensing,” Hazari says. “I really relied on OCR to drive the process.” Melvin, who is headed to a post-doctoral fellowship at the University of Michigan, says the experience of bringing this technology forward to license has been immensely rewarding. “Never in my wildest dreams would I have thought that this project would result in this type of deal,” says Melvin. “It brought a unique dimension to my graduate work and I truly enjoyed the experience of seeing this go from a purely research project to something with a potentially large industry impact.”

Ultra-Thin Camera Creates Images Without Lenses

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Ultra-Thin Camera Creates Images Without Lenses
Traditional cameras—even those on the thinnest of cell phones—cannot be truly flat due to their optics: lenses that require a certain shape and size in order to function. At Caltech, engineers have developed a new camera design that replaces the lenses with an ultra-thin optical phased array (OPA). The OPA does computationally what lenses do using large pieces of glass: it manipulates incoming light to capture an image. Lenses have a curve that bends the path of incoming light and focuses it onto a piece of film or, in the case of digital cameras, an image sensor. The OPA has a large array of light receivers, each of which can individually add a tightly controlled time delay (or phase shift) to the light it receives, enabling the camera to selectively look in different directions and focus on different things. “Here, like most other things in life, timing is everything. With our new system, you can selectively look in a desired direction and at a very small part of the picture in front of you at any given time, by controlling the timing with femto-second—quadrillionth of a second—precision,” says Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering in the Division of Engineering and Applied Science at Caltech, and the principal investigator of a paper describing the new camera. The paper was presented at the Optical Society of America’s (OSA) Conference on Lasers and Electro-Optics (CLEO) and published online by the OSA in the OSA Technical Digest in March 2017.
  “We’ve created a single thin layer of integrated silicon photonics that emulates the lens and sensor of a digital camera, reducing the thickness and cost of digital cameras. It can mimic a regular lens, but can switch from a fish-eye to a telephoto lens instantaneously—with just a simple adjustment in the way the array receives light,” Hajimiri says. Phased arrays, which are used in wireless communication and radar, are collections of individual transmitters, all sending out the same signal as waves. These waves interfere with each other constructively and destructively, amplifying the signal in one direction while canceling it out elsewhere. Thus, an array can create a tightly focused beam of signal, which can be steered in different directions by staggering the timing of transmissions made at various points across the array. A similar principle is used in reverse in an optical phased array receiver, which is the basis for the new camera. Light waves that are received by each element across the array cancel each other from all directions, except for one. In that direction, the waves amplify each other to create a focused “gaze” that can be electronically controlled. “What the camera does is similar to looking through a thin straw and scanning it across the field of view. We can form an image at an incredibly fast speed by manipulating the light instead of moving a mechanical object,” says graduate student Reza Fatemi (MS ’16), lead author of the OSA paper. Last year, Hajimiri’s team rolled out a one-dimensional version of the camera that was capable of detecting images in a line, such that it acted like a lensless barcode reader but with no mechanically moving parts. This year’s advance was to build the first two-dimensional array capable of creating a full image. This first 2D lensless camera has an array composed of just 64 light receivers in an 8 by 8 grid. The resulting image has low resolution. But this system represents a proof of concept for a fundamental rethinking of camera technology, Hajimiri and his colleagues say. “The applications are endless,” says graduate student Behrooz Abiri (MS ’12), coauthor of the OSA paper. “Even in today’s smartphones, the camera is the component that limits how thin your phone can get. Once scaled up, this technology can make lenses and thick cameras obsolete. It may even have implications for astronomy by enabling ultra-light, ultra-thin enormous flat telescopes on the ground or in space.” “The ability to control all the optical properties of a camera electronically using a paper-thin layer of low-cost silicon photonics without any mechanical movement, lenses, or mirrors, opens a new world of imagers that could look like wallpaper, blinds, or even wearable fabric,” says Hajimiri. Next, the team will work on scaling up the camera by designing chips that enable much larger receivers with higher resolution and sensitivity.

Volcano (بركان)

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Volcano (بركان)

What is Volcano? or Definition of volcanoes

Volcanoes (بركان) are conical or dome-shaped structures built by the emission of lava and it contained gases from a restricted vent in the earth’s surface. The volcanoes are having truncated tops representing the crater, that acts as the avenues for the magma to rise Volcanoes take many forms, and the activity that is associated with their eruption is highly varied. The activity of volcanoes differs in the amount and type of material ejected. The size, temperature and composition of the material ejected determine the shape of the volcano or the form of extrusion volcanoes also differ in the violence and the timing of successive eruptions

Types of Volcanoes

  1. A volcano is ‘Active’ when it is erupting intermittently or continuously. A volcano which has not erupted for a long time is known as ‘Dormant’, whereas an ‘Extinct’ volcano is one, which has stopped eruption over a long time.
  2. On the basis of mode of eruption as well as on the basis of nature of eruption, different types of volcanoes have been recognized.

Basing on the mode of eruption volcanoes are classified as:

  1. Central types: Where the products escape through a single pipe (or vent).
  2. Fissure types: Where the ejection of lava takes place from a long fissure or a group of parallel or closed fissures.

Based on the nature of eruption,

  1. Explosive Type:- In which case the lava is of acidic (felsic) in nature and because of their high degree of viscosity, they produce explosive eruptions.
  2. Quiet types: In this case the lava is of basaltic compostion (mafic lava), which is highly fluid and holds little gas, with the result that the eruptions are quiet and the lava can travel long distances to spread out in this layers.
Besides the above, a number of other types of volcanoes have been identified according to their degree of explosive activity and nature of eruption. They are as follows
  1. Hawaiian type:- Silent effusion of lava without any explosive activity.
  2. Strombolian type: periodic eruption, with a little explosive activity
  3. Vulcanian type: Eruption takes place at longer intervals and the viscous lava quickly solidifies and gives rise to explosions of volcanic ash.
  4. Vesuvian type: Highly explosive volcanic activity and eruptions occur after a long interval (measured in tens of years).
  5. Plinian type: – The most violent type of Vesuvian eruption is sometimes described as Plinian. Here huge quantities of fragmental products are given out with little or no discharge of lava
  6. Palean type: This is the most violent type of all the eruption. They are characterized by eruption of ‘nuees ardentes’

Volcanic topography:-

It includes both positive as well as negative relief features. The High or elevated relief features comprising of hills, mountains, cones, plateaus or upland plains are some of the examples of positive relief feature, while the low lying relief features like craters, calderas, tectonic depression etc. represent the negative relief features.
  1. Positive relief features: – These features are formed due to both quiet as well as explosive volcanic activity, and some of which are as follows:
  2. Hornitos: These are very small lava flows
  3. Driblet Cones: The most acid lava often gives rise to quite small conelets and are known as driblet cones.
  4. Cinder cones: – These are volcanoes of central type of eruption, steep-sided with uniform slopes of 30 to 40 degrees.
  5. Lava cone. These are built up of lava flows, due to heaping of lava during quiet type of eruption. It is also known as lava or ‘Plug-dome’.
  6. Composite cone:- These are made up alternatively of pyroclastic material and lava. Due to rude stratification, they are also known as ‘Strato-volcanoes’.
  7. Shield-volcanoes:- These are made up of lava alone and due to quiet type of eruptions, whereby piling up of flow after flow of fluid lava, a rounded dome like mass is produced
  8. Spatter-cone. Small cones formed on lava flows where breaks occur in the cooled surface of the flow allowing hot gases and lava to be blown out.

  • Volcanic plateau:- These are formed because of fissure type of eruption.

  1. Negative relief features:
  2. Crater:- This is a depression located at the summit of the volcanic cone.
  3. Calders:- Sometimes because of violent volcanic explosion the entire central portion of the volcano is destroyed and only a great central depression, named a ‘caldera’ remains. The calderas may also be formed due to erosion and enlargement of the crater.
  • Lava-tunnels: the more mobile lavas of basic composition, when erupted onteh surface in the form of flows quickly consolidate and form a solid crust while the interior may still remain fluid. Under such conditions the enclosed fluid lava drain out through some weak spots lying at the periphery of the flow, forming what is known as ‘lava tunnel’.
  1. Cone in cone topography:- After an explosion destroys an existing crater, a new built smaller cone with its own crater is built up. This is known as cone in cone topography
Explosion-pits are also negative relief features of volcanoes

Volcanic products:

A volcanic eruption comprises solid, liquid and gaseous materials. Fragments of rocks ejected during an explosive eruption are called ‘pyroclastic materials’. The pyroclastic materials of various size grades are known differently as follows
  1. Volcanic blocks (or bombs):- Diameter of the fragments is always above 32 milimeters
  2. Cinder or lapilli:- Here the diameter is between 4mm to 32 mm
  • Ash:- These particles range in size between 0.25mm to 4 mm
  1. Fine-ash: Minute particles of diameter less than 0.25 mm constitute the fine ash.
  2. Tuff:- Rocks made up of ash and fine ash are known as tuffs and the welded ruffs are known as ‘Ignimbrite’.
  3. Agglomerates: Pyroclastic rocks consisting mainly of fragments larger than 20 mm in diameter, are known as agglomerates.
Other products of Volcanism
  1. Porus or spongy: Masses of solidified frothy lava is known as Pumice or Scoria. But scoria is having a little dark colour and course texture than that of pumice.
  2. Spilitic lava: These are albitic (soda-rich) lava and it produce pillow structure.
  3. Gaseous product:- Steam forms the most important constituent of volcanic gases and contributes nearly 90% of the total content of volcanic gases. Gases like carbon-dioxide, nitrogen Sulphur-dioxide, hydrogen-sulphite, boric acid vapours, phosphorous arsenic-vapour etc. forms a part of the volcanic gases.
  4. Nuee ardente:- An incandescent cloud of gas and volcanic ash, violently emitted during the eruption of pelean types of volcanoes.

Features Associated with the Decaying phases of Volcanism

  1. Fumaroles: – These are fissures or vents through which volcanic gases are ejected
Fumaroles emitting sulfurous vapor are called ‘Salfataras’ and those which emit carbon-dioxide and boric-acid vapor are known as Mofettes and Safoni respectively
  1. Hot Springs: These are fissures through which host water escapes. The water usually gets heated with increased temperature below, may be magnetic or radioactive heat.
Calcareous deposits formed from hot springs are known as Travertine tufa and similarly, siliceous deposits are called Siliceous sinters
  1. Geyser: – Hot springs ejecting boiling water and steam at regular intervals are geysers. Siliceous deposits formed around geysers are known as ‘geyserite’

What are Pseudo Volcanic features?

Pseudo-volcanic features:- Mud-volcanoes, meteor-craters are of non-volcanic origin and are exampes of pseudo-volcanic features.

Cause of Volcanism

  1. The release of high pressures, which build up within magma chambers below the ground surface.
  2. Accumulation of radio-active heat produces magma; of course, other factors like frictional heat and the increase of heat with depth causes the formation of magma. Their eruption on the earth’s surface causes volcanism.

Distribution of Volano

  1. They are concentrated in a narrow-belt called Circumpacific Ring of Fire. Where the volcanoes are located on the high young folded mountains.
Other volcanic areas include the scattered areas in the Pacific, particularly the Hawaiian Islands, a belt that includes Arabia, Madagascar and the rift valley of Africa, the Mediterranean belt, the volcanoes of West-indies and those of Iceland.

Stratigraphic Classification, nomenclature and descriptions

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Stratigraphic Classification, nomenclature and descriptions

Stratigraphic Classification and nomenclature

Of the many possible kinds of stratigraphic units, three have been particularly useful. They are
  1. Lithographic (or Rock-stratigraphic) Units:
  2. Biostratigraphic units
  3. Chronostratigraphic (or Time-rock or Time-stratigraphic) units.
The above three types units are interrelated in many ways. However, a separate scheme of classification and terminology has developed for each type of unit. Considerable controversy exists about the relative importance of these three separate classification. However, each is important for particular purposes and relative importance varies with the circumstances. Lithostratigraphic studies constitute the first step in establishing the stratigraphy of any area/region and though lithostratigraphic and biostratigraphic studies should generally precede chronostratigraphic classification.

Some basic Definitions of Stratigraphic

  1. Stratum: A geologic stratum is a layer of rock with some unifying characters, properties or attributes, distinguishing it from adjacent layers. Adjacent strata may be separated by visible planes of bedding or parting or by less perceptible boundaries of changes in lithology, mineralogy, fossil content, chemical constitutions, physical properties, age or other properties of rocks.
  2. Stratigraphic units: A stratigraphic unit is a stratum or assemblage of adjacent strata, recognized as an unit (or distinct entity) in the classification of the Earth’s rock sequence, with respect to any of the many characters, properties or attributes which the rock may possess.
  3. Formal vs. Informal Stratigraphical terminology: Stratigraphic units and their names are classified as informal if they are not formally proposed and are used in a broad or a free sense without the precise connotation as required by the code of stratigraphic nomenclature. A formal unit is a name representative of an established or conventionally agreed scheme of classification.
Earlier established stratigraphic units and their nomenclature, if they do not conform to the code and satisfy the rules are considered as “informal”. They are placed in inverted comma or parentheses if they are used. The initial letter of a named formal unit/term should be in capital. Correlation: To correlate in a stratigraphic sense is to show correspondence in character of the strata and their stratigraphic positions. Lithological correlation is a demonstration of correspondence in lithologic character and stratigraphic position. A correlation of two fossil beds is a demonstration of correspondence in their content and in their stratigraphic position. A chronostratigraphic correlation is a demonstration of correspondence in age and stratigraphic position.

Lithostratigraphic units:

The lithostratigraphic units are the subdivision of rocks in the Earth’s crust distinguished and delimited on the basis of lithologic characteristics. The units are recognized and defined by observable physical features rather than by inferred geological history; boundaries may be placed at sharp contacts or drawn arbitrarily within a zone of gradation. Both vertical and lateral lithostratigraphic boundaries are placed where the lithology changes. Rock-stratigraphic units are the practical units of general geological work that serve as a foundation for describing, mapping and studying lithology, local and regional structures, stratigraphy, economic resources and geologic history. The units are independent of any time concept. Their boundaries may coincide with or transgress time horizons. The ‘Formation’ is the fundamental unit in rock stratigraphic classifications. A formation is a body of rock characterized by lithologic homogeneity; it is mappable at the Earth’s surface or traceable in the subsurface.

Ranks of Lithostratigraphic Units

The following hierarchy of formal lithostratigraphic units is recognized Supergroup Group Subgroup Formation Member Bed A member is next in rank below a formation it is not defined by specified shape, extent or thickness. A bed is the lowest rank in formal lithostratigraphic unit. A group consists of two or more successive and naturally related or associated formation and is higher in rank than a “Formation”. In certain areas stratigraphers have named and defined assemblages of formations, within already established useful groups of formations; these constitute supergroups eg., Vindhyan Supergroups
  1. Biostratigraphic Units: A biostratigraphic unit is a body of rock strata characterized by its content of fossils contemporaneous with the deposition of strata. All fossils contained in a biostratigraphic unit are remains of organisms that lived when the sediment surrounding them was deposited. The organisms might have been buried in situ or transported to their place of burial, but in either case, they belong to the deposit as contemporaneous original constituents. Some sedimentary rocks contain reworked fossils derived from other rocks; they can be distinguished from the fauna and flora indigenous to the deposits and are to be ignored in defining a biostratigraphic unit. Biostratigraphic units are fundamentally different from rock stratigraphic units. The boundaries of these two types of units may or may not coincide. The biostratigraphic evidence is the most useful means of determining time-stratigraphic boundaries. Fossils reflect irreversible evolutionary change and adoption to the environment and all biostratigraphic units are records of time and biofacies

Types of Biostratigraphic Zones:

Two types of formal biostratigraphic zones are recognized viz.,
  1. The assemblage zone
  2. The range zone
An assemblage zone is body of strata characterized by a certain natural assemblage or association of fossils, with regard to their ranges, eg. Meeker as assemblage zone of Spiti. Thus, it is a body of strata whose content of fossils of a certain kind taken in its entirety constitutes a natural assemblage or association from adjacent strata. An assemblage zone should have a specifically designated and decimated type section or reference section, eg., the otoceras – Ophiceras assemblage zone, Lilang, and Spiti, characteristics fossils of an assemblage zone are called guide fossils. A range zone is a body of strata representing the total horizontal and vertical range of occurrence of one particular species or genus, e.g., Miscellanes miscella range zone. The principal reference of a range zone is the type specimen or reference specimen. An epibole (acme zone/peak zone) is the body of strata representing the maximum development of a species/genus. It is a special type of range zone. Eg., Glossopteris acme zone in the flora of Raniganj Formation. The fossil names are to be italicized. The initial letter of formal zone terms, except the name of species should be capitalized. Biostratigraphic boundaries may be directly or indirectly applicable to establishing both rock stratigraphic and time-stratigraphic units. They contribute to a better understanding of the correlation, depositional and faunal history of strata sequence.

Chronostratigraphic units and Geological Time units:-

A chronostratigraphic unit is a body of rock strata unified by representing the rocks formed during a specific interval of geological time. The geologic time units are abstract units and are defined after the chronostratigraphic unit. A chronostratigraphic unit is defined after a specifically designate and delimited type section or reference section. Each unit is the record of an interval of time that extended from the part to the end of its deposition. These units are used for
  1. Correlation of rocks of different areas on the basis of age equivalence or contemporaneity of origin
  2. Establishing the systematic geologic time sequence of rocks for indicating their relative position and age with respect to Earth’s history.
Both the upper and lower limit of a chronostratigraphic unit should be defined in the type section for providing a standard for the unit. In the type area, the boundary should preferably be based on stratigraphically useful objective criteria representing some significant geological episodes. In the type area, the boundaries are usually made to coincide with one of the observable stratigraphic units (either biostratigraphic or lithostratigraphic). Paleontological parameters provide the most successful way of local and worldwide correlation of all rank of Phanerozoic chronostratigraphic units. Relationship to adjacent strata, unconformities, and intrusions, lithologic similarity, radioactive ages, et., are also useful in local time correlation. The isotopic age determination technique can be applied to sedimentary rock by dating authigenic minerals and to igneous rocks by dating suitable primary minerals. Radiometric age determination is of great importance for interregional and intraregional chronostratigraphic correlation of Precambrian rocks. Ranks of Chronostratigraphic and Geologic Time Units: The hierarchy of these units is as under:     A system is chronostratigraphic unit of major representing a major division or grouping of rock strata corresponding to a specific major interval of geological time
The Phanerozoic rocks are formerly classified into the following system:
Cambrian, Ordovirian, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary and Quartrary. Most of the formal systems have their region in Europe. Subdivisions of some of the standard systems may be used locally, eg., Paleogene and Neogene subsystems of the Tertiary system. A series is a chronostratigraphic unit next in rank, below a system. The rocks of a series represent the specific interval of geological time of the type section of strata for the series. Both the boundaries of the types section or reference section should be defined with precise stratigraphic boundaries. Upper, Middle, and Lower may be used for series divisions of a system. A stage is a chronostratigraphic unit next in rank below a series. It is defined after a type section or reference section. It is an important unit for chronostratigraphic classification and correlation. Generally, it is based on a succession of zone of biostratigraphy. A stage can be subdivided into sub-stages, if necessary, ‘Chronozone’ may be used in informally to cover a body of strata formed during any minor interval of geological time. The time span is represented after a lithostratigraphic or biostratigraphic unit. ‘Age’ and ‘Time’ may be used informally to cover any geological time. A formal chronostratigraphic unit is usually given a binomial name. The initial letters should be capitalized e.g. Lower Cretaceous series: Devonian System. It should be named after a geographic feature in the type area. When fossil name is used, the fossil name (genus and species) should be capitalized and printed in Roman type to distinguish it from a biostratigraphic unit. Standard name approved by the International Subcommission on Stratigraphic Classification should be followed for the systems. The term for the geologic time corresponding to a system is a period and bears the same name as the system. Eg. Cambrian period, Triassic Period. A period can be subdivided and referred to as Late, Middle, and Early. An era is geological time unit of higher rank, than the period and consists of several periods, eg., Paleozoic Era. A series is named after its position within a system qualified by capitalized adjective – Upper, Middle, and Lower, eg., Upper Triassic Series. A stage should preferably be named after the type area, eg., Camic Stage. The term for the geologic time corresponding to a stage is ‘age’ and bears the same name as the ‘stage’. The name of a sub stage should be derived from its type area.

Geologic-Climatic units:

A geologic Climatic unit is an inferred widespread climatic episode from a subdivision of Quaternary rocks. It is an abstract unit. A geologic-climatic unit is defined from the records which include rock bodies, soil and organic material. Such units can be extended geographically as far as the geologic climate record can be recognized. These units are used for correlating episodes of Quaternary deposition in different areas and in establishing the historical sequence of climatic events in the Quaternary period. Glaciation and interglaciation are the two units of geologic-climatic classification. These are named after a lithostratigraphic and soil stratigraphic units. South Africa and the erstwhile USSR differed from stratigraphers of the other parts of the world and did not approve of the three tier, Litho, Bio and Chronostratigraphic classification. South African geologists use only one set of stratigraphic terms- Group system, Series, stage., and consider the use of these terms, prefixed where necessary, by the qualifications Litho- or Chronostratigraphic, is to be preferred to separate series of terms for such system of classification. Soviet geologists believe that the system of stratigraphic subdivisions should represent natural stages of geological change of Earth as a whole or of individual large regions, and correspondingly should be based on the combination of all manifestations of deposition which objectively indicate these stages, namely by overall analysis of the complex data of evolution of the organic and non-organic world. They are of the view that each of the subdivisions of the Earth and in the evolution of the organic world. Thus, the Soviet geologist feels that in stratigraphy, there can only be one scale which unifies the stratigraphic subdivisions. They do not believe in the concept of differentiation into several stratigraphic divisions (litho-, bio- and chrono-) with non-coinciding boundaries. The Soviet stratigraphic commission uses, in brief, the following criteria
  1. Correlation on the basis of a single geochronological scale based on “natural” stages and evolution organic life;
  2. Stratigraphic scale should be evolved taking into account all the evidence together
  3. Irreversibility of geological phenomena, alternation of large transgressions and regression of the sea and corresponding changes in the course of organic evolution
  4. The presently recognized system are natural divisions their boundaries are characterized by unconformities and/or stratigraphic breaks, abrupt changes of species and evidence of igneous activity. The system is paleontology distinct and is successively marked by the development of new life groups.
A few Russian Stratigraphers have pleaded for the modification of Russian Code to fall in line with the International Code of stratigraphic nomenclature. The important points touch upon this text, are tabulated below
Categories of Classification Basis of Classification Units
Formal Informal
Lithostratigraphic (rock stratigraphic) Lithology Lithological characters of attributes of the rocks Hierarchy of Terms Supergroup, Group, Subgroup, Formation, Member beds Beds, zone  
Biostratigraphic Paleontology contemporaneous fossil content of rock types 1)      Assemblage of all or specific kinds of fossil 2)      Range of specified taxon 3)      Overlapping range of specified taxon 4)      Peak of development of a specified taxon 1)      Assemblage Zone 2)      Range zone 3)      Concurrent-range zone Epibole (acme/peak zone)
Chronostratigraphic (time-stratigraphic) Geochronology: Geologic age of the rocks System Series Stages Substage
Geologic time units. These are defined after chronostratigraphic units Geologic time: These are not stratigraphic but abstract units. Era Period Epoch Age Age, time

Principle of Stratigraphy | Geology Notes

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Principle of Stratigraphy | Geology Notes

Principle of Stratigraphy

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History of Principle of Stratigraphy

In his book published in 1913 entitle ‘Principle of stratigraphy’ Amadeus William Grabau defined stratigraphy as “ it is inorganic side of historical geology, or the development through the successive geological ages of the earth in rocky framework or lithosphere”, Krumbein and Sloss (1951) stated that stratigraphy may now be considered as the integrating science which combines data from almost all other branches of earth science, resulting in historical geology. Waller (1960) defines stratigraphy as the branch of geology that deals with the study of an interpretation of stratified and sedimentary rocks and with the identification, description, sequences (both horizontal and vertical), mapping and correlation of stratigraphic rock units. The word ‘Stratified” include layered metamorphic as well as volcanic rocks. In the past over six decades, a large volume of data pertaining to subsurface geology, mainly from the exploration and exploitation of petroleum, coal, and water and oceanographic survey, contributed significantly to the understanding of the stratigraphy of many inland and offshore regions of the world.

Present day Study of Stratigraphy

Sedimentary rocks and the fossils they containing the fundamental materials for understanding stratigraphic concepts. The study of the present-day sediments, their formation and distribution is essential for understanding the principle of stratigraphy, the interpretation of ancient sedimentary rocks and for establishing the stratigraphic record.

Components of Stratigraphy:

The subject of stratigraphy can be divided into two major parts viz.,
  1. Physical stratigraphy and
2. Biostratigraphy, the components of which are shown in Table 1.
Physical Stratigraphy Biostratigraphy
Stratigraphy Column Biostratigraphic column
Sedimentary Petrology Palacontology
Classification of Sediments Classification of Organisms
Sedimentary process Biological processes
Lithologic correlation Biostratigraphic correlation
Sedimentary tectonics Organic evolution
Most stratigraphic studies help in solving problems in palaeogeography, historical geology, and economic geology. All the data collected are organized, analyzed, interpreted or synthesized to give the required results.

Principles

The stratigraphic column for the Earth was built up over a few hundred years, mainly since the 18th century and was based on many principles
  1. Earlier catastrophic theories of Earth history
  2. The principle of superposition of strata
  3. Principle of uniformitarianism
  4. Walther’s law concerning sedimentary facies
  5. Principle of faunal succession
The catastrophic concept: In the earlier part of the 19th century, the opinions or the explanations of time distribution of organisms were greatly influenced by Cuvier, a French vertebrate paleontologist, and his followers. According to Cuvier, each major period of geologic time was terminated by a world-wide catastrophe which wiped out all life. He believed that animals and plants were then reestablished in modified form by an act of Creation at the beginning of the succeeding period, that within each period of time, the various animals and plants were unchanged, that new forms were introduced at widely separate times. Herodotus, a Greek philosopher, deduced correctly in the 4th century BC that fossils were remains of ancient sea creatures and that the rocks containing them were formed beneath the sea. His ideas became lost for over 2000 years, suppressed by religious beliefs. As late as in the 17th century, some scientists in Britain believed that Earth was 6000 years old, that fossils are relics on Noah’s flood or the work of the devil and that geological history in a series of deluges which killed all life, and followed by the special creation of new fauna.

The principle of Superposition of strata:

Nicolas Steno (1638-87) recognized a sequence of lithologic events in the mountains of western Italy. He recognized that older rocks were overlain by younger rocks, he drew up stratigraphic laws to explain the organic origin of fossils and tried to explain unconformities, folding and faulting. His principle of superposition of strata states that “If one series of rock lies above another then the upper series was formed after the lower series, unless it can be shown that the beds were inverted as a result of the tectonic action.”

The Principle of Uniformitarianism:

This principle, established by James Hutton (1726-97), is the fundamental concept in geology. It propounds that process which operates at present also operated in the past and produced similar results. Put in a simpler way it states that, “ the present is the key to the past”, the various process need not have operated at the same rate nor with the same intensity. It is possible that a process which operated in the past is not seen today or all the process now operating did not operate in an exactly similar way in the past. Organic materials may have changed progressively in form and character through the influence of organic evolution, with advancing geological time. The degree of correlation between ancient and present-day process decreases as the time interval increases. There is a very close relationship between sedimentation and stratigraphy. The study of recent sediments their process of formation and distribution helps in establishing the principles of the interpretations of ancient sedimentary rocks. The stratigraphic record is the result of the continuity of sedimentary processes through geological time. Walther’s Law concerning Sedimentary Facies Johannes Walter (1894) stated that- “the various deposits of the same facies, area and similarity the sum of rocks different facies area were formed beside each other in space, but in crustal profile, we see them on top of other. It is a basic statement of far-reaching significance that only those facies and facies areas can be superimposed, primarily, that can be observed beside each other at the present time. Middleton (1973) summoned up this concept as follows: “A comfortable vertical sequence of facies was generated by a lateral sequence of environment”. This law is one of the basic assumptions of facies analysis and was demonstrated in many modern sedimentary environments in which sub-environments prograde across one another.

The Principle of Faunal Succession:

In the last years of the 18th century, William Smith, an English engineer, recognized distinctive leads within rocks like the chalk and the coal-bearing strata in widely separated areas. He observed that each group contained a particular assemblage of fossils quite distinctive from above of the strata above and below. Smith was able correlate apparently the similar sedimentary rocks on the basis of the similarity of the fossils. He also noticed that there was the same succession of fossil assemblages from older to younger beds in all parts of Englands. He scrutinized that each of the succession of fossils belonged to a specific spin of geological history. That rocks formed during that time are likely a contain the same fossils. This is called The principle of faunal succession and has proved very useful in the correlation of rocks occurring in widely separated by the fossils they contain. The above principles combined with the mapping of the rocks in the field, head to an understanding of the gradually evolving Earth and its history. Attempts to work out the actual geological dates with the help of radioactive isotopes of certain elements led to the calculation of the ages of rocks. These methods are referred as radiometric dating methods and have proved specifically useful in fixing the stratigraphic positions of unfossiliferous rocks. By a detailed study of the lithological characteristics, the palaeontological characteristics (fossil contents), order of superposition and the structural characteristics of strata, supported by absolute dating of rocks and it is possible to establish the local stratigraphy and the regional stratigraphy of an area and correlate the stratigraphic sequences even between widely separated areas. In the Comment section please provide your views and share you Lecture notes with us
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