Category: Geography Notes PPT

Mortality is defined as being mortal or being susceptible to death. The opposite of mortality is immortality. Mortality definition is the frequency of death in a given population. Out of the many other components of demography such as demographic size, geographical distribution and composition, etc. Mortality definition is used as a factor of change in demographic. Mortality as one of the components of demography is measured as mortality rate. In simple terms, the rate of mortality definition states the death rate in a particularly given region which brings changes in the demographics of that particular region. Hence, it is an important concept in the study of population. 

What is the Meaning of Mortality Rate?

Mortality meaning provides the basis for mortality rate and its estimation. Mortality is the possibility of and susceptibility to death, and hence, the rate of mortality or the death rate is the measurement of the number of deaths that occur in a particular population, scaled to the size of that population per unit of time. Globally, this rate is taken as the measurement of the number of deaths per 1000 people per year. So, when the mortality rate is described as 11.5, it means that in total 11.5 people have died per 1000 people in a given area for a given population. In percentage, it is expressed as 1.15% of the total population. 

This concept is not to be confused with morbidity. Morbidity is either the prevalence or incidence of a disease. Hence, the morbidity rate is the rate of disease in a population. Morbidity and mortality meaning is thus different in the sense that morbidity is the condition of the prevalence of disease and mortality is the condition of death. For example, during the COVID-19 pandemic, the morbidity rate increases with the spread of the disease amongst the population. And the mortality rate is obtained with the increasing incidences of death whatever the cause may be. So, even though during the pandemic, the morbidity rate can be higher or lower or similar to the mortality rate but only in numbers. But they are both different. The morbidity rate is the prevalence of a specific disease and hence varies depending upon the disease but the mortality rate is the rate of death and is irrespective of the cause. Various causes can affect the rate of mortality. Some more specific mortality rates that affect population demographic over a period of time are Perinatal mortality rate, Maternal mortality rate, Infant mortality rate, child mortality rate, standardized mortality rate, age-specific mortality rate, infection fatality rate, etc. 

Statistics of Mortality

There are various causes of mortality. The causes of death influencing the components of demography differ greatly between the developed and less developed countries. According to Jean Ziegler, who was a United Nations Special Rapporteur on the Right to Food for 2000 to March 2008, stated that mortality is caused mainly due to malnutrition. The causes of death because of malnutrition accounted for 58% of the total mortality in the year 2006. Another cause of death is age-related death. Of approximately 1,50,000 people that die each day worldwide, almost two-thirds i.e. 1,00,000 per day die because of age-related issues. In industrialized nations, this proportion is much higher and reaches almost 90%. 

Relationship Between Mortality and Economics

A significant relationship between mortality and economics exists and is determined by scholars. When there is a low standard of living because of low incomes the mortality rate increases. This is because a low standard of living results in malnutrition which is already identified as one of the significant causes that give rise to conditions resulting in death as mentioned in the mortality meaning. There is a lack of hygiene and sanitation, an increase in exposure to and spread of disease, and a lack of proper medical care and facilities that comes with a low standard of living. This leads to a cycle as poor health leads to an increase in treatment cost that further aggravates the low living standards and becomes a strain on low-income households thus further leading to low living standards and decreased hygiene and health conditions. This is known as the health poverty trap. According to Indian economist and Nobel prize winner, Amartya Sen states that mortality rates are one of the possible indicators of economic success and failure. 

Another important factor that can influence the mortality rates adversely is the short term price increase. Scientific studies have shown that with an increase in food prices, there is an increase in the rate of mortality. Such effects are shown to have a high impact on vulnerable and low-income populations as compared to the population with higher income and living standards. With respect to the nations of the world, it is found that the national income of a country which is also an indicator of the standard of living of that country is one of the largest factors contributing to mortality rates. The mortality rates are found to be higher in countries with low national income as compared to countries with high national income. These factors in turn direct the demographic environment of a country. The demographic environment meaning, the population factors such as age distributions, births deaths, sex, education, etc. which determine the standard of living of a country are thus greatly influenced by mortality. 

These economic factors affect gravely the living conditions of children below the age of five years. It is found that in low-income countries, there is a higher risk of children dying from malaria, diarrhoea, respiratory infections, etc. which are easily preventable in high-income countries. Hence, this in turn affects the overall demographics of the nation. Hence, there is a visible and factual correlation between mortality and economic growth. 

Conclusion

Mortality which is defined as the condition of being dead is an important parameter to assess the growth and development of a given society and a nation. The causes that affect mortality rate are best indicators of prevailing conditions of human health and life from poor countries to the rich. Thus, mortality is an important concept to understand a given country and its demographic environment.

Ooze is a type of pelagic which means deep-sea sediment that is composed of a minimum 30 percent of the skeletal remains of the microscopic organisms that remain floated. Oozes are generally deposits of soft mud which is situated on the ocean floor. Oozes form on the areas of the seafloor which is quite far away from the land. This slow yet steady deposition of the dead microorganisms from the overlying waters is not concealed by the sediments that washed from the land. 

We will Learn More about Oozes Further in this Section. 

Radiolarian Ooze 

Radiolarian Ooze is a deep-sea ooze. In this type of ooze minimum of about 30 percent of the sediment constitutes the siliceous radiolarian tests. This Radiolarian-rich ooze mainly occurs in the equatorial regions of the Indian and Pacific Ocean. In this ocean, the ooze exceeds the carbonate-compensation depth as the depth increases, which is around 4500m in the central Pacific Ocean. 

Ooze

In this study we will also know about the subdivisions of Ooze. 

Calcareous Oozes is the first sub divisional ooze. This contains skeletons which are made of calcium carbonate and the second subdivision is siliceous ooze which contains skeletons that are made up of silica and then they are again subdivided according to the predominant skeleton type. Primordial and Primeval Ooze are somewhat similar as they existed at the beginning of their stage of development. The oozes have their own characteristic feature and ooze charm. 

More about Oozes

• Another type of ooze known as the globigerina ooze, comes under the calcareous oozes. This type of ooze contains the shells of the planktonic foraminifera and pteropod ooze which is made up chiefly of the shells of the pelagic molluscs. 

• The siliceous oozes also include the radiolarian ooze that comprises mostly the brown clay that is more than 30 percent of the skeletons of the warm-water protozoa, another is the diatom ooze which contains the frustules or the tiny shells of the diatoms. The siliceous oozes exist only where the rate of its deposition of the diatoms or the radiolarians is greater than the rate at which the silica content of the species are dissolved in the deep waters, thus the diatom oozes are quite confined to the belts in the North Pacific and the Antarctic, the radiolarian oozes are found precisely in the North Pacific under the eastern part.

• This Globigerina ooze is the most densely spread of the oozes which occur both in the Atlantic and in the Indian oceans. While, Pteropod ooze is found in the middle of the Atlantic.

• Biogenic ooze is also known as biogenic sediment. It is to be known that any pelagic sediment which contains more than 30 percent of the skeletal material. These biogenic sediments can be made up of either carbonate also known as a calcareous ooze or siliceous ooze. The skeletal material which is present in the carbonate oozes is a calcium carbonate that is generally in the form of the mineral calcite but at times it is also in the form of aragonite. 

• Foraminifera and Coccoliths are the main constituents of microorganisms which form skeletal debris. 

• Siliceous oozes are constituted with opal which is amorphous hydrated silica, this forms the skeletons of many microorganisms. Such organisms include diatoms, radiolarians, siliceous sponges and silicoflagellates. The biogenic oozes are distributed, and its distribution depends mainly on the supply of the skeletal material, dissolution of its, and dilution by other sediment types, like turbidites or clay.

• Most amazing fact is that the carbonate oozes cover roughly half of the world’s seafloor. Carbonate oozes are present above a depth of 4,500 metres, while below this they dissolve quickly. Calcite Compensation Depth (or CCD) thus represents the level at which the rate of carbonate accumulation merges with the rate of the carbonate dissolution. 

Photogrammetry is a simple technique that uses photographs for surveying and mapmaking. It is the science that helps in obtaining important information about the physical objects and environment through the process of recording, interpreting, and measuring the photographic images. It is a simple science of making measurements from photographs. 

In the year 1851, a French inventor by the name of Aimé Laussedat had a theoretical idea of the camera that could help in mapping but he wasn’t able to invent it. Fifty years later, in the middle of the nineteenth century, photogrammetry was invented and appeared simultaneously with the appearance of photography. A french surveyor by the name of Dominique F. Arago proposed the use of photographs to create a topographic map in the year 1840. The Prussian architect by the name of Albrecht Meydenbauer first coined the term photogrammetry in his 1867 article “Die Photometrographie.”

For many centuries photogrammetry has helped us in understanding the faraway objects and the surfaces of the earth. Due to its application, its uses have been expanded over the years and have led to the birth of powerful techniques that help many industries such as engineering, medicine, construction, and many more. Imagine you want to analyze an object, photogrammetry helps in gathering the data and the measurements of the object by only analyzing the changes in the position of that object by viewing two different images. Photo is analyzed and advanced processing software is used to do the photogrammetric job. In this article, the method of photogrammetry, the science involved behind the technique, the different types of photogrammetry will be explained.

Basics of Photogrammetry 

If we break down the word photogrammetry, we can clearly understand what the word means. Photo means light, ‘gram’ means drawing and ‘metry’ means measurement. Photogrammetry could be described as the 3-dimensional coordinate measuring technique that uses the photographs as the fundamental object for measurements. Photogrammetry generally revolves around the idea of gathering information from the photos which are collections of the object. 

The fundamental concept of photogrammetry is triangulation in which multiple photos are taken(At least two) to create a line of sight that will point on the object. The photos are taken from different angles and locations which helps in making accurate calculations that will help gather the data a person is looking for. The line of sight that was created because of the data that was collected can now be mathematically inserted to produce the 3-dimensional coordinates of the points of interest. Photogrammetry helps in creating 3 d models and maps of the real world. During World War II, the use of photogrammetry increased. During World War II, special aircraft were built that were designed to carry powerful cameras which were designed for aerial photography and better camera positioning. Photogrammetry during that time was extensively used to monitor the enemy countries territory. During the Apollo mission,  photogrammetry also helped in mapping the surface of the moon.

 

Types of Photogrammetry

Photogramteert can be classified into two types based on the splitting the field on which the camera is located during photography. On the basis of this approach, we have Aerial photogrammetry and Close range or terrestrial photogrammetry. 

What is Aerial Photogrammetry? 

For mapping, a particular area, the most commonly used photogrammetric method is aerial photogrammetry. In aerial photogrammetry, the camera is mounted in an aircraft and is pointed vertically towards the ground. When the plan follows a flight path and by mounting the camera vertically towards the ground the camera then takes multiple overlapping photos of the ground. The multiple photos which were taken were traditionally monitored by a stereo plotter. A stereo plotter is an instrument that helps the operator or the user see two photos at once in a stereo view. The stereo plotter also helps in determining the elevation by comparing the two different photos and also helps in conducting the necessary calculations. Stereo plotters were extensively used a decade ago but now all the photos taken during aerial photogrammetry are processed by automated desktop systems. 

What is Terrestrial Photogrammetry?

In terrestrial photogrammetry or close range photogrammetry, the camera is located on the ground which is either handheld or fixed and images are taken from the fixed position on the ground in the axis of the camera is parallel to the Earth surface. The coordinates and other data of the camera are collected at the time in which the photo is taken.  Theodolites are the instruments that are used for terrestrial photogrammetry or close range photogrammetry. Terrestrial photogrammetry is non-topographic which means it is not related to the arrangement of the physical features of the area. The output of the terrestrial photogrammetry are drawings, 3D models, and measurements. cameras can also be used to measure and model buildings,  help in engineering structures, stock-piles, film sets, etc. terrestrial photogrammetry is also called as Image-Based Modeling in the computer-based community. 

What is Stereo Photogrammetry? 

Stereo photogrammetry is a technique that involves the estimation of 3D coordinates of points on an object by considering the measurements made of two or more images taken from different positions. By collecting the points obtained from the x,y, and z coordinate the image is calculated. The principles on which Stereo photogrammetry is based is stereoscopic principles which allow the user to create or enhance the illusions of the image by the means of stereopsis for binocular vision. The binocular vision follows a simple principle that says that a user can present two different images separately by the right and the left eye and then the images are combined by the viewer’s brain to give a perception of 3D vision. There are many ways such as polarization, chroma depth, stereoscopic technique, etc that help in presenting the stereoscopic pictures. Stereophotogrammetry is turning out to be one of the emerging non-contacting techniques that helps in determining the characteristics and mode shapes of both rotating and nonrotating structures.

Applications of Photogrammetry 

Photogrammetry has been used in various fields such as medicine, engineering, mapping, architecture, manufacturing, police investigation, cultural heritage, and geology.

One of the most common uses of photogrammetry is creating maps out of aerial photos. It has proven to be accurate and cost-effective. Photogrammetry allows many government construction workers and architects to take clear pictures that help them to make clear and informed decisions about the projects without spending months working on the landscape. The photogrammetry technique is very detailed as a result of which it provides an exceptional level of information about the area. 

Many archaeologists use photogrammetry to quickly make plans of large sites which are very large and complex whereas meteorologists use photogrammetry to determine the wind speed of the tornadoes when they don’t have access to the weather data. 

Due to its precision, photogrammetry has made a mark in many industries such as engineering, film industries, etc. Here is the list of few places where photogrammetry has been used. 

  As photogrammetry is nothing but accurate measurements of images. The first industry to adapt or use this technology in engineering. While building a complex structure it is very important to have accurate measurements of everything. The planning and the execution should be perfect and because of this reason, photogrammetry is used. By using the images from drones, engineers can evaluate the sites of construction properly which ensures that everything runs smoothly without any hurdle. If a client needs to see the progress of the work, Photogrammetry is used to create perspective images and 3D renderings which helps in analyzing the current work. 

Photogrammetry plays an important role in film and entertainment. Throughout many years the filmmakers have started to heavily rely on photogrammetry for 3D modelling and accurate measurements that are required for world-building for games and movies. photogrammetry has started to play a big role in various CGI movies. The 3D modelling of photogrammetry can help in bringing the planned virtual worlds like cities and other historical places with accurate measurements.  Movies such as fight club, the matrix, and games such as the battlefield have utilized the technique of photogrammetry. 

Knowing all the details while solving a case is very important and photogrammetry plates an important role in the crime investigation. photogrammetry helps in documenting the precise measurements of the scenes of crime when presenting the case in front of the court. Photogrammetric lawyers are experts who are also present that are skilled at intre[retting the photo models and can also help in solving the case both inside and outside the courtroom. 

Land surveying is a method that uses science, measurements, and technologies to determine the surface of the earth. Land surveying uses photogrammetry to take accurate images of things such as landmasses. Land surveying also uses photogrammetry to get accurate measurements of a particular object. 

We live in a society where we can get everything online. From renting a book to renting or owning a house everything is dealt with online. As a result of this many buyers are depending on an online listing to find new homes and many real estates have to create a striking visual about the various properties which they want to sell. Instead of spending thousands of rupees on an advertisement, Modern drones and the technique of photogrammetry have been used by many real estate agents to create an accurate image of the house that they want to sell or rent. The viewers or the buyers can see the 3D image of the house from all the angles and can get a clear idea of what they are looking at. 

We have learned what is photogrammetry and the applications of it. Let’s see some of the related questions as well: 

The precession of the earth is a type of slow gyration, that rotates in its rotational axis like a spinning type body about another line that intersects it so as to describe a cone structure.

The Precession of the Earth’s Axis:

• The Earth’s axis rotates similar to a spinning top. The period taken by the precession is approximately 26,000 years.

• Hence, the North Celestial Pole will not always be pointing towards the same starfield.

• The precession of the earth is for the gravitational pull of the Sun and the Moon on the Earth.

Hipparchus was the first scientist to discover the precession of the earth, and he estimated that the precession of the earth’s axis is around 130 BC. While the period of precession being 26,000 years. 

The Pole Star located in the northern hemisphere is called the Polaris this is of 3000 B.C. The north celestial pole coincides with the star called the Thuban star, this star is of the constellation of Draco. In 14,000 A.D. the Vega, in Lyra, will be the northern pole star.

Precession of the Equinoxes 

Precession of the equinoxes means the motion caused by the equinoxes along the ecliptic, that is on the plane of the earth’s orbit. This is caused by the cyclic precession of the earth’s axis in its rotation.  

While compiling his star catalogue which completed in 129 BCE, the Greek astronomer, named Hipparchus noticed that the positions of the stars get shifted in a systematic way from the Babylonian (Chaldean) measures. This indicated that it was not the stars that were moving but it was the observing platform that is the earth that was moving. This motion of the body is called the precession and this consists of a cyclic type wobbling which happens in the orientation of Earth’s axis of rotation with a period of approximately 25,772 years. The motion of precession is the third-discovered motion of Earth, the other two preceding it are the daily rotation and the annual revolution. The precession of the earth is caused by the gravitational influence of the sun and by the moon which acts on the Earth’s equatorial bulge. While, to a lesser extent, the planets exert an influence on each other as well.

The projection of the sky in the Earth’s axis of rotation results in two points that are in the opposite directions, they are – the north and south celestial poles. This is for the precession the points trace out as circles on the sky. The north celestial pole generally points to within 1° of the arcs of the Polaris region. This will point closest to the Polaris of about 2100 CE. In the next 12,000 years, the north celestial pole will face about 5° from Vega. At present, the south celestial pole does not point towards the vicinity of any bright star.

This projection is of the sky of the Earth’s Equator. This projection is a great circle, which is called the celestial equator. Further, the celestial equator intersects another useful great circle, called the ecliptic. As the Earth orbits or revolves around the Sun, this constantly changes its own direction at an angle, from which the Sun is viewed to trace out to the ecliptic. The celestial equator is inclined at a 23.44° angle towards the ecliptic. The celestial equator and the ecliptic intersect at two points which are called the equinoxes (they are vernal and autumnal equinoxes). During the year, the earth orbits the Sun, and later it is seen crossing the Equator twice, in the month of March it moves from the Southern Hemisphere towards the Northern Hemisphere, and in the month of September, it moves in the opposite direction. The equinoxes move along the west, which is the ecliptic at the rate of 50.3 arcseconds in terms of annually as the celestial equator moves with the Earth’s precession.

Axial Precession 

In astronomical science, the axial precession occurs because of the gravitational, slow, and continuous change in the orientation of an astronomical body’s rotational axis. In particular, this is to be referred to as the gradual shift in the orientation of the Earth’s axis of rotation in a cycle which is about 26,000 years. This is quite similar to the precession of a spinning top, with its axis tracing out the structure of cones which are joined at their apices. The term is known as “precession” generally refers majorly to the largest part of the motion. While other changes in the alignment of Earth’s axis is called nutation and polar motion which are quite smaller in magnitude.

Define Rotation in Astronomy

A rotation is a type of circular movement of an object which is around the center (or at a point) of a rotation. While the geometric plane along which the rotation takes place is called the rotational plane, the imaginary line that extends from the centre and which is perpendicular to the rotation plane surface is defined as the rotation axis. 

In the field of astronomy, rotation is a commonly observed phenomenon. The stars, planets and all other similar bodies rotate around their own axis.  

This rotation is named the centrifugal acceleration which is in the reference frame of the earth that counteracts the effect of gravity and which is closer to the equator.  

Another result of the rotation of a planet is the phenomenon of precession. 

When the river meanders its way to the lake or the sea, the water slows down gradually, and the river flow loses the power in carrying the sediment along the way. The sediment gets dropped at the river mouth, and this is the first step of forming a River Delta. There are some rivers to drop a greater amount of sediment, which the tides and the waves cannot carry all through the way. In consequence, layers are built in forming the River Delta. Some deltas are extremely large that you can find human existence on them. In Egypt Nile delta is the most vital farming region or agricultural zone. 

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Understanding River Delta Diagram

If you look at the River Delta Diagram, you can well understand the structure and the shape of the delta in real life. There is the flat part of the delta, and the same is referred to as the delta plain, and it remains above the level of the water. From here, the river gets divided into many small channels, and these are known as distributaries. You also have the portion of the delta under the water. There is also the steep and the sloping delta, and it is the front that can easily face the ocean or the lake. There is the prodelta portion, and it rests away from the deeper mouth, and it is extremely under the water. 

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Not all deltas have similar shapes. Much depends on the amount of sediment that gets deposited by the actual river. This can be compared to the amount of sediment that faces erosion, and it is redeposited by the waves and also by the tides. Things are understandable from the River Delta Diagram, and once you follow the map, it is easy to have the best understanding of the delta influenced by the river. There are many river deltas present. For example, the Danube delta, Fly delta, Indus river delta, Amazon delta etc. 

Types of River Delta

Arcuate Delta – Here is the delta with the curve and the bow shape and it has the convex margin which faces the water body. The same is also called the fan-shaped delta with examples of the River Nile Delta in Egypt and the Ganges Delta in India. 

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Estuarine Delta – This delta is formed at the mouth of the submerging river. It forms due to continuous deposition at the sides of the estuary and the examples of the same are the Seine River Delta of France. 

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Birds foot Delta – The delta forms because of the deposition of the finer materials carried by the river water. The alluvial material that is being deposited is divided into smaller and finer distributaries. It is also called the finger delta and the example of the same is the Mississippi river delta, in the USA.

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Lacustrine Delta – The delta is formed when the river is flowing into the lake. The example of the same is Lough Leanne river delta in Ireland. 

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Truncated Delta – The Ocean and the sea wave currents can help in modifying and can even cause destruction of the deltas that are being deposited and delivered by the river by means of the continuous erosion action. The dissected and the eroded delta is called the truncated deltas.  

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Abandoned Delta – When the river is standing at the mouth and you have the formation of the delta at the left side. The accumulation of the abandoned material helps in forming the delta. This is the Abandoned Delta and the examples are Yellow River Delta, The China Delta and the Western part of the Ganges Delta formed due to the deposition of the Hooghly River. 

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Cuspate Delta – It is a tooth shaped delta and it is formed due to the flowing of the single distributary which flows and deposits the silt on either side forming the delta bed. An example of this is the Tiber River Delta in Italy.  

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How is the River Delta formed & It’s Delta Diagram Specification ?

By means of the delta formation diagram, it is understandable that in the uncommon sense, delta at times can even open into the land. So how is the delta formed? Once the river reaches the mouth, it becomes slow in motion. It slows down at the end when it is time for it to empty itself. In motion, the solid material and the sediment are carried downwards by means of the current, and it is made to fall at the bottom of the river. The velocity of the river becomes slow, and the sediment build-up of the same will make it possible for the river to break down into a single channel, and it is made to happen once the river reaches the mouth. 

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To define the delta in geography, there is the long and the narrow sediment mounding, and it is called the sleeve. The sleeve is there on the sides of the narrow and the thin distributary channels. A delta can be described as a wetland, and it is formed when the river empties the water and the sediment into one more water body like the lake or the ocean, and it can even empty the same into another river.

Owing to the river delta formation, when the conditions are right, the river is sure to form the deltaic lobe. There is the matured deltaic lobe to include the network of the distributaries, the range of the shallower and the smaller channels. These are called the distributaries, and they can easily depart from the river mainstream. At the deltaic lobe, the coarser and heavier components are made to settle down at first. However, the finer and the smaller sediments are carried far along with the downstream. This ultimately forms into the delta.

Based on the details of the delta geology, the finest material that is carried down to the mouth of the river is known as silt or alluvium. Silt is made of rich and fertile nutrients that are sure to help the plants and the microbes in the production and the growth of the food web. With the building up of the silt, there is the formation of new land. The specific land is called the delta.

Conclusion 

There are various river delta examples, and these are the Danube Delta, Amazon Delta, Euphrates Delta, Ebro Delta, Ganges–Brahmaputra Delta, Fly Delta, Indus River Delta and the Godavari Delta. These are classic delta formations giving the earth its distinct shapes.

If the axis of the earth would be straight then there will be a day at half of the Earth and night at another half of the Earth and there will be no point of seasons.  But we know that it’s not true because the Earth is tilted and we have seasons on our planet. In this article, we will talk about seasons, seasonal variation, how seasons occur, reasons, etc.

Why Do Seasons Change? 

The part of the Earth which got sunlight faces day and other parts of the faces night. It happens because of the rotation around the Earth. Seasons occur because of the apparent movement of the sun also. When the sun is directly overhead at one point of the earth, it increases the temperature of that region and leads to summer in that region and winter in another region where the sun is not overhead.

Reasons 

The cycle of seasons is caused due to the following reasons:

• The apparent movement of the sun also plays a vital role in forming seasons. We have the sun at 23.5°N in June, at 0° in September, 23.5°S in December and again up to March it’ll move to 23.5°N. The process continues which is called the apparent movement of the sun. 

How Do Seasons Change

We experience different seasons on earth because of the revolution of the earth around the sun. With the help of the above two diagrams, we will learn about how seasons occur. For learning about seasons we have to keep in mind the following points:

• The Earth has a tilted axis 

• It revolved around the sun in 365 days approximately

• It is divided into three lines ie. the equator at 0°, the tropic of cancer at 23.5°N,2, and the tropic of Capricorn at 23.5°S.

We’ll be explaining the occurrence of the four seasons of the Earth with respect to the Northern Hemisphere and what will happen in the Southern Hemisphere will also be mentioned along with that.

Summer Solstice

If we talk about the Northern Hemisphere, It is the time when the sun is directly overhead on the tropic of cancer and thus this part of the earth experiences the summer season and at the same time, due to the tilted axis of the Earth and the angle of incidence of the sun rays the southern hemisphere does not receive the same sunlight and thus temperature reduces and leads to winter. June 21 is considered as the hottest day. 

• Here, the Northern Hemisphere has summers and Southern Hemisphere winters.

• Days and nights are not equal because days are longer than nights.

• For example, due to this, India experiences ( which is in the northern hemisphere ) summers, and Australia experiences winters ( which is in Southern Hemisphere )

Autumnal Equinox

It is the time during September when the earth experiences the sun directly at the Equator. Due to this, the days and nights are equal. It is the time of the beginning of the autumn season in the Northern Hemisphere which ends with the winter solstice.

During this time, the southern hemisphere experiences the spring season or we can say the vernal equinox.

Winter Solstice

It is the time when the earth is facing the sun rays directly on the Tropic of Capricorn and we know that the region which faces direct rays experiences summers. Thus, the Northern Hemisphere has winters during this time, and summers are there in the Southern Hemisphere. 

• 22 December is considered as the coldest day of the year.

• The Northern Hemisphere has winters and the Southern Hemisphere has summers.

• Days and nights are not equal and Nights are longer than days.

• For example, India has winters during December and Australia has summers during this time.

Vernal Equinox

It is the time when the Earth faces sunlight directly on the Equator and it has equal days and nights. It is the time of March and spring season in the Northern Hemisphere and the season of autumn in the southern hemisphere. 

Did You Know

When the Earth is closest to the Sun i.e on Jan 5,  it is known as Perihelion and when it is away from the Earth i.e on July 5,  it is known as Aphelion and there is no relation of the distance of the Earth from the Sun in forming seasons which is generally presumed to be.