Category: Geography Notes PPT

Every year almost 20,000 earthquakes occur in the world and do you know it is one of the most unpredictable natural disasters that causes a lot of damage wherever it occurs. You must be thinking that it should be studied properly to know why and how it occurs and how we can save ourselves from this. Well, there is a separate branch of study that deals with this part comprehensively and deals with every aspect related to it. This is an interdisciplinary field of study which has a long history and that got contributions from various Mathematicians, Physicists, Geologists, Engineers, inventors, etc. Let’s study it in this article. It will help you in understanding one of the major disciplines and getting a basic knowledge about it.

Study of Earthquake – An Introduction

If we dig into a particular concept deeply then it becomes a separate study field, for example, if we study climate it will be called climatology, when we study land, it becomes geomorphology, etc. Have you ever wondered what it will be called when we study earthquakes? 

If we talk about earthquakes first then the sudden movement or shaking of the earth’s crust whose early warning is difficult and also can occur at any time and any place mostly due to natural reasons but sometimes also occurs due to man-made activities, then this is known as earthquakes and when we study the earthquakes, it is called as seismology and the one who studies it will be called a seismologist. 

Seismology Meaning

It is a separate branch of Geology or Science that deals with earthquakes. It is a scientific and interdisciplinary subject that studies earthquakes and their related concepts. This term is made up of two words ie. Seismos means earthquake and logy mean study. Thus, this term refers to the study of earthquakes. Robert Mallet who was a geophysicist, inventor, and engineer is considered the father of seismology because of his great research in this field.

The energy flows under the Earth in the forms of some waves which are known as seismic waves and seismology studies these waves. These waves not only help in understanding and predicting earthquakes but also helps in understanding the composition and internal structure of the Earth which is complex but has become much easier to understand its structure because of the distinct nature of the passing of these waves through different surfaces. The two major types of these waves are P waves and S waves. The former can be passed through solid, liquid, and gaseous material whereas the latter can only pass through the solid surface.

Definitions

• The basic definitions are ” study of earthquakes ” or  ” study of seismic waves “.

• According to the Cambridge dictionary, ” it is the scientific study of the sudden, violent movements of the earth connected with earthquakes.”

History of Seismology

Its history can be traced back to 4,000 years ago whereas the quest to learn the natural causes of earthquakes by man actually started only 26 centuries ago. This concept gained a global look in the year 1889 when the first time teleseismic record was done and a seismograph was developed. It was the time when seismology was seen as a separate global science. Its birth happened in 1889 but its origin actually began on Nov 1, 1775, with the Lisbon Earthquake, which was considered as the major event that entirely changed our outlook towards this naturally occurring event. Various mathematicians, physicists, engineers played a great role in this. Thus, it is an interdisciplinary science that can not be separated entirely from the history of continuum mechanism, applied mathematics, and general wave theory. The event of 1889 was considered as the first revolution in this field whereas the second revolution occurred when initial computers were introduced in 1950 – 1955 in this field. 

Series of Contribution

Some of the earliest major contributions in this field are mentioned below:

• Aristotle ( ca. 340 B.C.E ) was considered as the first person who tried to give an explanation of earthquakes and classified them into 6 types.

• Seismoscope was invented by a Chinese scholar namely Chang Heng. It is considered the earliest known instrument in this regard.

• The earliest work in this field was from England of Robert Hooke’s ” Discourse on Earthquakes ” ( 1667 to 1697 ).

• John Mitchell who was a Geology professor at Cambridge University was the first who declared the fact that ” earthquakes originate within the Earth “.

• The first-ever seismometer was designed by James David Forbes in the year 1841.

• The first-ever recording was done in Japan by John Milne in 1880 but it could record only local earthquakes and the first ever recording that got a global sense was done by Ernst von Rebeur Paschwitz in 1889.

• The first-ever electromagnetic seismograph along with photographic recording was designed in 1906 by Boris Borisovich Golitzin.

Famous Seismologists

The person who studies and works in the discipline of seismology is known as Seismologists. Basically, he is the one who studies earthquakes and seismic waves. Some of the notable seismologists are John Michell, Charles F. Richter, Clarence Edward Dutton, John Milne, Harry Fielding Reid, Richard Dixon Oldham, and Beno Gutenberg, etc.

Seismic Instruments 

Some of the major seismic tools and instruments are used by the seismologist while studying this discipline such as seismometers, seismographs, and seismograms. Among these, the motion of the ground on the Earth can be recorded by a seismograph during the occurrence of an earthquake. They are installed basically at different locations of the Earth to record the movements that cause earthquakes and works as a seismic network. If we talk about a seismometer, it is a part of the seismograph only whereas the ground movement and shaking of a specific location are recorded with a seismogram. Besides these, seismologists also use various scales such as the Richer scale, the Mercalli scale, and the Moment Magnitude scale. Here, the first one the earthquakes on a scale of 1 to 10 and the second one on a scale of 1 to 12 whereas the third one is nothing but a successor of the first one.

Did you know?

Around 80% of the total number of earthquakes occurred in the region which is generally known as the ” Ring of Fire ” and this region is a home of almost 452 volcanoes which is also more than 75% of the world whereas if we talk about the largest earthquake ever recorded in the world, then it was occurred on May 22, 1960, with a magnitude of 9.5 in Chile.

Conclusion

Thus, here we have covered and learned about a separate branch of science that deals with one of the most important concepts related to the Earth. It has extreme importance because of the occurrence of several numbers of earthquakes on the Earth every year and it is very important to understand this concept more clearly so that we can deal with it. We have comprehensively covered the seismology meaning, history, and origin of the seismology here. We believe that with this article you have got basic knowledge of this subject and you will get more knowledge about its related concepts like earthquakes and seismic waves, etc. 

We have seen seismology meaning, definitions, history or origin, etc. Let’s have a look at few questions:

When Water logs, Soil Flows, and this mechanism is what we call Solifluction. That said, Solifluction is a term used for the slow downhill flow of soil in regions of the Arctic Ocean. It takes place slowly and is computed in millimeters or centimeters per year. It approximately uniformly affects the entire thickness of the soil instead of amassing in certain areas. It totally results from the waterlogging of sediment instead of short-lived events of saturation from storm runoff.

When Does Solifluction Take Place?

Solifluction occurs during the summer season thaw when the water in the soil is trapped by frozen permafrost underneath it. This waterlogged alluvium moves down slope by gravity, supported along by freeze-and-defrost cycles that thrust the top of the soil outward from the slope (a process of frost heave).

How to Determine Solifluction?

The major indication considered by geologists for solifluction in the landscape is hillsides that possess lobe-shaped slumps, same as small, thin earthflows. Other signs of identifying solifluction include patterned ground, signs of order in the stones and soils of alpine landscapes.

How Does a Landscape Affected By Solifluction Looks?

What is solifluction must now be clear to you. But do you know how a landscape affected by solifluction looks? It looks the same as the bumpy ground yielded by substantial landsliding but appears more like fluid, like melted ice cream or molten/diluted cake frosting. The indications may subsist long after arctic atmospheric circumstances have changed, as in subarctic regions that were once glaciated in the Pleistocene ice ages. Solifluction is regarded as a periglacial process, as it only needs chronic freezing conditions instead of the permanent presence of ice bodies.

Is there a Difference Between Solifluction and Soil Creep?

Solifluction in geology is one of the forms of creep that happens either in high altitudes or in cold climates where the mass of the saturated rock waste comes down the slope.

Soil creep means the movement of the slow downslope of the superficial rocks. It is an ongoing process and also a surface phenomenon taking place on the slopes.

Changes in Solifluction Movement Rates

Various Research activities carried out at the site depleted substantially in recent years, because of the personnel changes. Besides this site, little is known about recent solifluction movement rates in other regions of the Austrian Alps. In addition, nothing is familiar about regional similarities or differences with respect to solifluction rates and respective drivers in Austria, since solifluction measurements have not been conducted earlier on at several sites distributed over a massive area at the same time.

Studied Landforms

All studied solifluction lobes were situated in the central part of the Hohe Tauern mountain, central Austria, in a 38 km (west–east) by 11 km (north–south) large-scale region.

Solifluction monitoring was carried out at five sites namely: Elisabeth Felsen (ELF), Fallbichl (FAB), north-east facing slope at the Hinteres Langtal cirque (HNE), See Schartl (SES), a south-west facing slope at the Hinteres Langtal cirque (HSW) and the selection of the 5 solifluction lobes was based on the following parameter:

• Area-wise distribution of the studied solifluction landforms and thus, to a certain degree, a region-wide reflection of the central part of the Hohe Tauern mountain range.

• the morphological proof that solifluction acted upon these slopes a minimum few times in the past

• the plausibility during fieldwork to apply synergies with the permafrost and periglacial monitoring network set up at nine sites in the Niedere Tauern and Hohe Tauern mountain ranges

Steak is a colour of a mineral when powdered and observed against unglazed porcelain (white ceramic plate). Streak plates that have been used rigorously will be laminated with streaks and powdered minerals. However, they can easily be cleaned with water and damp or dry 220 grit sandpaper. In addition, Aluminum oxide or silicon carbide sandpaper works best to clean streaks since the granules are hard enough to smoothen out the surface of the streak plate. The sanding should be carried out wet to control dust.

    

                           

How to Determine the Colour of the Streak?

A “streak test” is conducted to identify the colour of a mineral in its powdered form. The colour of a mineral’s powder is commonly a very crucial property for determining the mineral.

How is a Streak Test Conducted?

The streak test is carried out scraping a specimen of the mineral covering the piece of unglazed porcelain termed as a “streak plate.” The streak test should be undertaken on clean, unworn, or freshly broken specimens of the mineral. This is conducted in order to minimize the possibility that a foreign matter, pollutant, weathered coating, or corrosion will influence the outcome of the test.

This can yield a little amount of powdered mineral on the surface of the plate. The powder colour of that mineral is what we call a “streak.”

Streak Colours of Common Minerals

Uses of Streak Plates

Additionally to their usage in conducting the streak test, streak plates can be used any time you require a little amount of powdered mineral. In performing the acid test to differentiate calcite from dolomite, dolomite might need powdering in order to exhibit effervescence with dilute hydrochloric acid. Simply use the streak plate in order to create some powder of your specimen and add a small amount of acid to it right on the streak plate. For this test, a black streak plate makes monitoring easier since powdered dolomite is white.

A few minerals will yield a stench (odour) upon being powdered or fragmented. For example, sphalerite releases an odour of sulfur when it is powdered or broken. Scraping it across a streak plate is the easiest way to undertake this test.

Traces to other mineral properties can be acquired while conducting the streak test. Minerals harder than the streak plate are rapidly determined. Experienced testers can approximate the hardness of a specimen by how complicated it is to mark the streak plate. augite often displays its splintery cleavage, olivine most commonly exhibits its granular characteristic, and black tourmaline displays its brittleness. Having said that When you conduct a streak test, look for just beyond the colour of a specimen’s powder.

Fun Facts

• Rubbing the mineral across an unglazed porcelain white plate determines and describes the colour of the powder left on the plate, i.e. the streak.

• Mineral pyrite is gold-coloured, however, its streak is greenish-black.

• Most transparent and pale coloured or translucent minerals have a non-identifying white streak.

• Minerals having a hardness of above 6.5 will not display a streak since they are harder than a piece of unglazed porcelain.

The tertiary period ( also referred to as the Paleogene period and Neogene period) represents the first geological period in the Cenozoic era. The tertiary geological period lasted from approximately 66 million to 2.6 million years ago.  The tertiary geological period began with the death of non-avian dinosaurs (any dinosaurs that are not birds) in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to Quaternary glaciation at the end of the Pliocene Epoch. The dates have been further adjusted as Science advances when new evidence is found. 

Tertiary Time Period

The tertiary time period began about 66 million years ago with a mass extinction that noticed the dinosaur and ended when the ice ages of the Quaternary Period began, about 2.6 million years ago.

Tertiary Period Epochs

Following are the Five Tertiary Period Epochs:

1. The Paleocene Epoch (first epoch of the tertiary period) lasted from 65 to 55.8 million years ago. This epoch marks the beginning of the Cenozoic era and the tertiary period.

2. The Eocene Epoch (second epoch of the tertiary period) lasted from about 55.8 to 33.9 million years ago

3. The. Oligocene Epoch (third epoch of the tertiary period) lasted from about 33.9 to 23 million years ago.

4. The Miocene Epoch (fourth epoch of the tertiary period) lasted from about 23 to 5.3 million years ago.

5. The Pliocene Epoch (fifth epoch of the tertiary period) lasted from about 5.3 to 2.6 million years ago.

Tertiary Plants

The tertiary plants closely resemble the plants that we have at present. The warmer climate of the tertiary period, in the beginning, favored dense forests. As the climate cooled, it opened woodland and grassland became abundant. The grasses played an important role during the tertiary period as they supported a large herd of grazing animals. 

Tertiary Period Climate

The tertiary period climate during the beginning was very warm and moist compared to today’s climate. Much of the Earth was tropical or subtropical. Plant trees grew as far North as Grasslands. The climate began to cool by the middle of the tertiary i.e. during the Oligocene epoch. The cooling trend of the climate continues and by the Pliocene epoch, ice had begun. 

Tertiary Period Animals 

During the start of the tertiary era, the first large mammals and primitive primates were largely seen. Soon, at the start of the second epoch of the tertiary period i.e. Eocene epoch, the first modern mammals began to appear, and within a short span, most modern mammals were observed. Reptiles during the tertiary era were replaced as the dominant vertebrates by mammals. Fossils reveal that during the early tertiary era, birds, reptiles, fish, and amphibians were also seen. The earliest observed hominid relatives of humans, Proconsul and Australopithecus, also appeared during the Tertiary era. Modern families of flowering plants were also developed whereas marine invertebrates and non-mammal marine vertebrates experienced only moderate evolution.

Tertiary Period Major Events

In terms of tertiary period major events, the tertiary era covers the major demise of dinosaurs and the beginning of the most recent ice age. At the start of the tertiary period, reptiles were replaced by mammals as dominant vertebrates. Furthermore, all the non-avian dinosaurs also became extinct. Modern types of birds, reptiles, fish, amphibians, were numerous at the beginning of this period, but also continued to appear early on, and also the new age families of flowering plants evolved. At last, but not least the earliest recognizable hominid relatives of humans also appeared. 

With respect to the geology, there was a plethora of tectonic activity that continued from the previous eras, culminating in the division of Gondwana and the clashing of the Indian landmass with Eurasian plates. This caused the formation of the Himalayas, the gradual establishment of the continent of Australia, the separation of South America from West Africa and its connection with North America, and Anatatrica taking its present position below the South pole.  

With respect to the climate, the period was marked by extensive cooling at the beginning of the Paleocene with tropical – to – moderate global temperature and ending before the first massive glaciers at the start of the Quaternary.

 Did You Know?

• The tertiary period is the period that belongs to the Cenozoic era.

• The Cenozoic era was further divided into Palaeogene, Neogene, and Quaternary periods. The Palaeogene and Neogene periods are togetherly known as the tertiary period.

• The Paleogene period is further subdivided into the Oligocene epoch and the second epoch of the tertiary period i.e. Eocene epoch and the Pliocene epoch. Each of these epochs contributed to the life forms, species, and other different factors of the tertiary period.

• The second epoch of the tertiary period starred 65 million years ago with a span of 17 million years. It was one of the dominant parts of the Paleogene period and contributed immensely in the life of the development of the Paleogene period.

• The tertiary period includes the present-day configuration of the continents, the cooling of global temperatures, and the rise of mammals as the planet’s dominant vertebrates.

• The tertiary era falls between the Mesozoic and the Quaternary, although no longer recognized as any formal unit by the International Commission on Stratigraphy. 

• Italian geologist Giovanni Arduino in 1760 introduced the name “ Tertiary’

• The present Geological time scale uses the terms Paleigen and Neogene rather than the Tertiary. It observed the three periods of geological time including the Quaternary, in the Cenozoic era.

The Triassic period emerged in the Earth’s history at the time when Triassic dinosaurs were evolved. The period was followed by the Jurassic period and the Cretaceous period. At the end of the Cretaceous period, the dinosaurs were wiped out in a mass extinction event along with the majority of all other life. 

As a period of geological time, the boundaries of the Triassic are defined based on the rocks found and fossil records. It was the German geologist Friedrich August von Alberti who first introduced the Triassic period. It got its name because this period of geologic time is represented by a three-part division of rock type in Germany. These three different rock layers are (from the bottom to the earliest) the Bunter ( which is a red bead and brown sandstone), the Muschelkalk, and the Keuper. These types of rock are found in local areas, but not globally.

When did Triassic Era Begin?

The Triassic era began 250 million years ago and ended 201 million years ago. The period before the Triassic era is known as the Permian. This was the time when the different varieties of animals lived, including a group of animals known as synapsids which later evolve into mammals. One member of this group was a large, sail-backed animal known as the dimetrodon, which looks like a dinosaur but was not.

Further, the  Permian-Triassic extinction event occurred 250 million years ago. This was the largest extinction event our planet has ever observed. During this period, 70% of the species on the land disappeared along with 95% of those in the oceans. This was not only the beginning of the Triassic era and the ending of the Permian period, but it was such a serious catastrophe that it is used as a marker of the end of the geological era, the Paleozoic era.

Triassic Period Animals 

Some scientists believe mammals evolved from a group of extinct mammals- like reptiles, Theriodontia, which were Therapsids.. These mammals were tiny and considered to have been nocturnal. The earliest – known turtle Proganochelys, also appeared during the Late Triassic. 

The Triassic animals like turtles, frogs, salamanders, lizards (including sphenodontia & snakes), and pterosaurs first appeared during the Triassic. Insects during the Triassic period begin to undergo complete metamorphosis from larva through pupa to adult.

Triassic Jurassic Extinction

Triassic Jurrasic extinction also, known as the end Jurassic extinction is a glocal extinction event that occurred at the end of the Triassic period (about 252 million to 201 million years ago) that resulted in the expiration of some 76% of all marine and terrestrial species and about 20% of all taxonomic families. It is observed that the end of the Jurassic extinction was the significant moment that enabled dinosaurs to become the dominant land animal on Earth. 

The end-Triassic extinction specifically affected the ammonoids and conodonts. These are the two groups that serve as important index fossils for assigning relative ages to different strata in the Triassic System of rocks. Only the phylloceratid ammonites were able to survive during the Triassic extinction, and they gave rise to the explosive radiation of cephalopods later in the Jurassic Period. Furthermore, varied families of bivalves, gastropods, brachiopods, and marine reptiles also became extinct.

A large part of the vertebrate fauna on land disappeared, although the dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes were minimally affected by the transition. In fact, most of the authorities maintain that the end-Triassic mass extinction on land opened ecological niches that were filled relatively quickly by dinosaurs. Plant fossils and palynomorphs (a microscopic fossil composed of especially pollen or grains) exhibit no significant changes in diversity across the Triassic-Jurassic boundary.

Triassic Extinction

The end of the Triassic period initiates with a massive extinction followed by massive volcanic eruptions about 208-213 million years ago. The supercontinent Pangea began to break apart. 35% of all the family’s animals die out, including labyrinthodont amphibians, conodonts, and all marine reptiles except ichthyosaurs.

Most of the synapsid reptiles, which had governed the Permian and early Triassic period, were dead (excluding mammals). Most of the early, primitive dinosaurs were also dead, but other, more adaptive dinosaurs developed in the Jurassic. 

Nobody is sure what causes the late Triassic extinction. The possibilities are global cooling or an asteroid impact. A 210 million-year-old meteor crater surrounding Manicouagan Reservoir, Quebec, Canada, maybe the remains of the culprit.

This extinction enables many dinosaurs to expand into different fields that were unoccupied. Dinosaurs would become increasingly commanding, plentiful, diverse, and lived the same way for the next 150 million years. The Jurrasic and Cretaceous was the true “ Age of Dinosaurs” rather than the Triassic.

Did You Know?

• The triassic period had 3 epochs, the Early triassic, the middle triassic, and the Late triassic.

• The Triassic period observed a rise in the dinosaurs, and they would rule the planet for the next 185 million years.

• The Triassic period started with the Permian Triassic extinction event and ended with the Triassic Jurassic extinction event.

• The dinosaurs that lived during the Triassic period were Melanorosaurus, Plateosaurus, Thecodontosaurus, and the Staurikosaurus.

• The Triassic period lasted about 50.6 million years.

• The shortest period of the Mesozoic era was the Triassic period. 

• The Triassic period is the first of the three geological periods of the Mesozoic era.

There are two terms commonly and widely used in meteorology with respect to air currents. They are updraft/vertical draft and downdraft. An updraft is a small-scale rising air current usually within a cloud. Similarly, a downdraft is a downward moving current of air within a cloud. Both these phenomena can be caused due to several factors. A very simple example of the updraft is the upward movement of the warm air from the surface towards the sky. Similarly, the example of downdraft is the downward movement of the cool air from the skies to the surface of the earth. 

Causes of an Updraft

During the daytime because of the radiation being reflected by the ground, the air above the surface gets heated. Local daytime heating makes the surface warmer and since the air gets warmer it gets less dense than the cool air above it. Because of this relative difference in the density, the warmer air begins to ascend upwards from the surface and is replaced by the cooler air which descends towards the surface. This movement of the warm air is known as thermal updraft because there is an updraft of warm air. The updraft is also created because of the turbulence that occurs when an air current passes over the barriers of topography such as the mountains. There are also common cases of updrafts occurring in thunderstorms as well. Such a type of updraft is known as thunderstorm updraft.

The updrafts are especially important as they play a significant role in the development of a storm. Especially during the early stages of a storm the warm air rising because of thermal updraft reaches the level when the condensation starts which supports the starting of the precipitation. With the cooling and falling of the precipitation in a mature storm, both the updrafts and downdrafts are caused. These drafts are also caused by the low pressure and high-pressure regions. Low-pressure regions attract large volumes of air which as it rises upward causes an updraft. Sometimes there is a rotation of the air current while moving upwards towards a low-pressure region or until the warm air of a thermal updraft encounters an air current with lower density, which comes to be known as rotating updraft.

Effects of Updrafts

Whenever there is a huge amount of moist and wet air that forms an updraft, it can lead to phenomena such as cyclones or tornadoes. For example, a supercell updraft is a thunderstorm that is caused by the presence of a deep and persistent rotating updraft. Whenever a thermal updraft which consists of warm air goes up away from the surface it cools down and later precipitates which mostly leads to rainfall because of a phenomenon known as convection. Thus, a convective updraft is a phenomenon causing rainfall in most cases. Not only, updrafts but such natural phenomena are also caused because of the downdrafts as well. Whenever there is a downdraft in huge amounts and vigorous speed it is known as downburst or microburst which has the capability to cause a tornado. 

Many times there are plenty of accidents as well caused because of thermal updraft/convective updraft, thunderstorm updraft, or a rotating updraft. These updrafts and downdrafts are a huge problem for flight travel and are major contributors to airplane crashes even during take-offs and landing. An example of such an incident is the crash of Delta Airlines Flight 191 during its final landing at the Dallas International Airport in 1985. 

Conclusion

As is clear from the article, an updraft or a downdraft is a natural phenomenon occurring because of the movement of air currents upward or downward respectively. These phenomena are responsible for a lot of natural activities such as rainfall, thunderstorms, tornadoes, or a supercell. Because of the turbulence that is created in the atmosphere because of such phenomena they are known for bad weather conditions and are grave risks to flight travels and also can cause severe natural calamities as well. An image of an updraft is shown below: