Category: Geography Notes PPT

Earth is the planet in our solar system that has the capability to provide life. The surface of the earth is a zone where three main components of the environment meet, overlap as well as interact. 

There are four major domains of the Earth as follows-  lithosphere, atmosphere, hydrosphere, and the biosphere. The atmosphere is further divided into four layers based on composition, temperature, and other properties that are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. 

There are Two Main Divisions of the Surface of the Earth

1. Continents: Continents are large landmasses.

The Highest Mountain Peak on this planet is Mount Everest. 

2. Ocean Basins: Oceans are huge water bodies.

Mariana Trench is the deepest Oceanic trench on this Earth which derives its name from the nearby Mariana Islands.

The Four Major Domains of the Earth

The four major domains of the earth interact with each other as well as affect each other in some way or the other.

Lithosphere: The solid portion of this planet is called the Lithosphere. 

Atmosphere: The gaseous layers that surround the earth are called the atmosphere.

Hydrosphere: Water covers a very big area of the earth’s surface that is called the Hydrosphere.

Biosphere: Biosphere is the zone where land, water, and air together are found.

1. Lithosphere – The Domain of Land

The very outermost portion of the Earth which consists of the Upper Mantle and also the Crust of the Earth is known as the Lithosphere.

Lithosphere has very rigid mechanical properties. The uppermost part of the lithosphere is called the pedosphere. The tectonic plates are a subdivision of the Lithosphere. The major changes in these tectonic plates had created a total of seven continents on the planet earth. These continents are – Asia, America, Europe, Africa, Antarctica and Australia. Asia is the largest continent and the smallest continent is Australia.

2. Hydrosphere – The Domain of Water

The domain of water is called the hydrosphere. It comprises different sources of water and also various types of water bodies like rivers, lakes, seas, oceans, etc. Water is very essential for all living organisms in the world. 

The hydrosphere comprises water on earth in Oceans, Seas, Rivers, Lakes, and even in frozen forms where 2.5% is freshwater and in this 2.5%; approximately 69% is in snow and ice form. The other 97.5% of Earth’s water is salt water and 71% of the surface of the Earth is covered by oceans. Earth got a total of seven oceans namely – the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian, and Southern oceans

3. Atmosphere – The Domain of Air

The atmosphere is divided into five layers and they are:

1. Troposphere (0 – 12 km): It is the lowermost layer of the earth’s atmosphere, and extends to an average of 12 km from the surface of the earth. Nearly all the water vapour and moisture found in the atmosphere lie in this section – the “troposphere”.

2. Stratosphere (12 – 50 km): It is the second-lowest section of the atmosphere, just after the troposphere, and is separated by the troposphere via the tropopause. The ozone layer of the earth is also included in this layer, the Ozone layer is filled with a high concentration of Ozone gas.

3. Mesosphere (50 – 85 km): Mesosphere is in the middle of the other atmospheric layers. In the mesosphere, the temperature dropped down by the increase in the altitude, this trend will then be followed by all the layers above it. It can be said to be one of the coldest places on the planet earth, with a temperature of – 85 °C (- 120 °F; 190 K). 

4. Thermosphere (80 km to 500 – 1000 km): This layer is the second-highest in the five atmospheric layers. It expands from the mesopause (which separates it from the mesosphere) all the way above to the thermopause (which cuts it from the exosphere). This is sometimes referred to as the exobase, as it lies just under the exosphere.

5. Exosphere (700 km to ~10,000 km): It is the outermost layer of the earth. It extends to 10,000 km outside the earth’s surface, after that it disappears in the solar wind. The main composition of this layer consists of extremely low densities of hydrogen and helium, some other molecules like traces of Nitrogen gas are also present in this layer.

About 99 per cent of the atmosphere is composed of nitrogen and oxygen where Nitrogen is 78 percent, oxygen is 21 per cent, and other gases comprise 1 per cent.

4. Biosphere – The Domain of Life

The biosphere is the zone of contact between land, water, and air. It is the zone where life exists and that is what makes this planet unique.

The organisms in the biosphere are divided into:

1. Plant kingdom

2. Animal kingdom

Before we discuss “What is Absolute Humidity?”, let’s learn about water vapour and Humidity. Water vapour is a highly variable element of the atmosphere that plays an important role in the hydrologic cycle. High rates of evaporation of water from the earth’s surface keeps the lower atmosphere almost constantly saturated in wet, humid tropical rain forests. In dry, hot deserts, there is typically no water to evaporate, and the amount of water vapour in the atmosphere is almost non-existent. Water vapour in the atmosphere is described by several parameters, including vapour pressure, relative humidity, dew point temperature, water vapour density, and Absolute Humidity. The most familiar is possibly relative humidity.

Humidity

The Earth’s atmosphere is made up of gases kept together by gravity. It protects the Earth and all living things from the sun’s rays. It is made up of different layers with various pressure, thickness, density, and mass. Changes in the atmosphere can cause variations in the atmosphere’s conditions, which can have a significant impact on the Earth and its inhabitants. Humidity is one of the factors that can affect these changes in the air.

The concentration of water vapour in the air is referred to as humidity. Water vapour, or water in its gaseous state, is normally transparent to the naked eye. Humidity suggests the possibility of snow, dew, or fog. Humidity is affected by the temperature and pressure of the device under consideration. Cold air has more humidity than warm air because it contains the same amount of water vapour. The dew point is a related parameter. When the temperature rises, the amount of water vapour needed to achieve saturation rises as well. As a parcel of air’s temperature falls, it will gradually achieve saturation without adding or losing water mass. The amount of water vapour within a parcel of air can vary significantly. 

Humidity is commonly measured using three methods: absolute, relative, and specific.

Absolute Humidity Definition

Let’s define absolute humidity, it is the mass of water vapour divided by the mass of dry air in a certain volume of air at a specific temperature. The warmer the air is, the more water it can absorb. Absolute humidity is the measure of water vapour or moisture in the air, regardless of temperature. It is expressed as grams of moisture per cubic meter of air (g/m3).

Absolute and Relative Humidity

The water vapour (in grams) present in 1 m3 of air is weighed to determine absolute humidity. This isn’t a very useful parameter in meteorology, even then, it’s more important to know how much water can be obtained in the form of rain from a given volume of air. Another metric, relative humidity, is used for this. Air may contain a fixed amount of water vapour at a given temperature and pressure, if this amount is reached, the air becomes saturated with vapour, and any slight change in pressure or temperature, or any addition of vapour, causes the air to become oversaturated, the excess water vapour condenses as small drops of liquid water. The temperature at which condensation occurs for a given amount of water vapour present in the air at a given pressure is known as condensation temperature or dew point temperature. The percentage ratio between the amount of water vapour present in the air and the amount of vapour needed to make the air saturated with moisture at the same temperature is known as relative humidity.  Relative humidity of 100% means that the air is saturated with vapour and on the verge of condensing the water vapour into drops of water, from a meteorological perspective, this is a state that is theoretically conducive to precipitation. Low relative humidity, on the other hand, means dry air that is not conducive to precipitation.

Specific Humidity

The ratio of the mass of water vapour to the total mass of the air parcel is known as specific humidity (or moisture content). The mixing ratio, which is defined as the ratio of the mass of water vapour in an air parcel to the mass of dry air in the same parcel, is roughly equal to specific humidity. As the temperature drops, so does the amount of water vapour needed to reach saturation. As the temperature of a parcel of airdrops below a certain level, it will gradually reach saturation without adding or losing water mass.

How to Measure Absolute Humidity

The density of water vapour in the air (kg/m3) is known as absolute humidity. To measure absolute humidity, first, calculate vapour pressure in millibars using the dewpoint temperature and formula number. Then multiply the vapour pressure in millibars by 100 to get Pa. Once you have the vapour pressure in Pa, you can use the gas law to measure water vapour density (i.e. absolute humidity) by substituting Rw for R in the gas law formula and using the vapour pressure instead of the total atmospheric pressure used to calculate air density.

Air Density and Volume

Humidity is determined by water vaporization and condensation, all of which are primarily influenced by temperature. As a result, when more pressure is applied to a gas saturated with water, the volume of all components decreases at first, roughly in accordance with the ideal gas law. However, some of the water can condense until it reaches nearly the same humidity as before, resulting in a total volume that differs from that expected by the ideal gas law. Conversely, as the temperature drops, some water condenses, causing the final volume to deviate from what the ideal gas law predicts. As a result, gas volume can also be expressed as dry volume, which excludes the humidity content. This fraction adheres to the ideal gas law more closely. The saturated number, on the other hand, is the volume that a gas mixture would have if the humidity was applied before it reached saturation (or 100 percent relative humidity).

The number of molecules present in a given volume of any gas is constant at a given temperature and pressure (see ideal gas law). So, if the temperature and pressure remain constant, as water molecules (vapour) are added into the volume of dry air, the number of air molecules in the volume must decrease by the same number.  (Adding water molecules to a gas without removing an equivalent number of other molecules would inevitably result in a shift in temperature, pressure, or total volume; that is, a change in at least one of these three parameters.) If the temperature and pressure remain constant, the volume increases, and the displaced dry air molecules move out into the extra volume at first, until the mixture gradually becomes uniform by diffusion.)

Global Climate

Humidity has two main effects on the energy budget and, as a result, on temperature. Water vapour in the atmosphere, for example, contains “latent” energy. This latent heat is absorbed from the surface liquid during transpiration or evaporation, cooling the earth’s surface. At the surface, this is the largest non-radiative cooling effect. It accounts for around 70% of the average net radiative warming at the surface.

Second, of all greenhouse gases, water vapour is the most concentrated. Water vapour is a “selective absorber,” similar to a green lens that allows green light to pass through but absorbs red light. Water vapour, like other greenhouse gases, is invisible to most solar radiation, as can be seen. However, it absorbs the infrared radiation released (radiated) upward by the earth’s surface, which is why humid areas have no nocturnal cooling while desert regions cool significantly. The greenhouse effect is caused by this selective absorption. It increases the surface temperature well above its potential radiative equilibrium temperature with the sun, and water vapour is the primary cause of this warming.

Water, unlike most other greenhouse gases, is not only below its boiling point anywhere on the planet but also below its freezing point at certain altitudes. It precipitates as a condensable greenhouse gas, with a far lower scale height and a far shorter atmospheric lifetime — weeks rather than decades. The Earth’s blackbody temperature, which is below the freezing point of water, would allow water vapour to be removed from the atmosphere if no other greenhouse gases were present.

Conclusion

Water vapour is a highly variable element of the Earth’s atmosphere. It plays an important role in the hydrologic cycle. Humidity suggests the possibility of snow, dew, or fog. Cold air has more humidity than warm air because it contains the same amount of water vapour. Absolute and relative humidity. The water vapour (in grams) present in 1 m3 of air is weighed to determine absolute humidity. Relative humidity of 100% means that the air is saturated with vapour. This is theoretically conducive to precipitation. Low relative humidity, on the other hand, means dry air that is not conducive to rain.

Ashfall is a volcanic reaction. It is made of the tiny fragments of the jagged rocks and with the rest of the things like volcanic glass and minerals. The ash is the outcome of a huge volcanic explosion. The volcano ejects a sequence of volcanic ash falls in the scenario, and due to inaction, the gas mixes with the atmosphere.

Definition of Volcano 

Based on the details of volcano definition, the coarse particles of the volcano ash appear like fine grains of sand. The particles are highly powdery, and they are known as tephra. These are solid materials referring to the solid portions created due to volcanic ejections. Ash is an outcome of explosive volcanic outpours. The gas inside the volcano includes magmas, and the chamber expands gradually on heating, and this will violently push up the molten rock or the magma out of the volcanic passage. With the right volcano definition, it is easy to know in detail about the hottest ejection and the outcome so naturally aggressive. 

Definition of Volcano in Geography

Based on the definition of Volcano In Geography, the volcano is described as the opening on earth’s crust through which the volcanic ash or lava passes. The gas escapes violently, and underneath there is the volcano with the liquid magma and the dissolved gases. The gas is made to rise through the cracks through the earth’s crust, and this can be highly explosive, making the gas spread in the atmosphere. The force and the intensity of the explosion can shatter the propels and help crash the liquid rock into the air. In time the magma cools down and solidifies the gas fragments and the volcanic rock particles. 

After the eruption, the rock fragments get mixed in the air, and it helps create the ash cloud. Now, the wind acts as the carrier and holds on to the smaller volcanic ash particles to far-off distances. The ash is found quite far off from the site of the eruption. The particles which are small would be carried by the wind, and at the end, the whole picture is violent and devastating. The molten rocks are in all places, and when going through the volcano description, one is sure to have an idea regarding this aggressive natural phenomenon. 

In time the volcanic ash deposition turns thicker, and the larger particles are found closer to the site of eruption. Based on the intensity of this natural occurrence, one can understand what is meant by the volcano and the effects of the same on nature. In time the deposition gets thinner and then disappears gradually. Apart from shooting the volcanic ash in the air, the explosion can even create a heap of ash along with rock and volcanic ashes. This is generally called the pyroclastic flow. The faster avalanches of the volcanic heap cannot be easily handled by humans. The pyroclastic flow can help raze the buildings and can even uproot the trees.  

The Impact of Volcanic Ash 

The plumes of the volcano eruption can spread over a longer distance in the sky and can turn the daylight into absolute darkness. This can change and reduce the visibility to a great extent. Even after the eruption is over, one can see the menacing clouds, and these are accompanied by lightning and thunder. Volcanic lightning is the most uncommon occurrence, and scientists will often debate on the working and evoking of the volcano. A great many scientists think about the sheer energy of the massive volcanic explosion, and the particles are charged with high electric intensity. 

Nature of the Dormant Volcanic State 

There is even the dormant volcano, and one does not come to know about it till the time of the explosion. In consequence, there is an interaction between positive and negative charged particles, and at one time, you can see the explosion and get ready for the devastation. Things are thrown into the cooler atmosphere, and one finds the shattered pieces of the volcanic debris. Lightning bolts occur, and there is a minimum balance between the charged distributions. 

Conclusion

The volcanic ash is hard in composition, and it is highly abrasive. This kind of ash will never dissolve in water. The particles of the volcanic ash are mostly two millimeters, and some particles are even smaller in shape and composition.

Biogeography is the scientific investigation of the distribution of species and ecosystems in geographic setting and across geological time. Biological communities and living Organisms often differ in a regular fashion through geographic gradients of elevation, isolation, latitude, and habitat area.

The biogeographic regions are basically “those predominant divisions of the earth’s surface of estimated continental extent, which are attributed by distinct assemblages of animal types”. That said, a Biogeographic region is basically an area of plant and animal distribution consisting of similar or shared properties throughout.

Introduction and Identification of Biogeographic Zones

• Zone 1 – Trans-Himalayan

In the immediate north of the Great Himalayan range are the Trans-Himalayas which encapsulates three biogeographic provinces i.e. — Himalayan Sikkim, Ladakh mountains, and Tibetan plateau. It constitutes about 5.6% of the country’s landmass. This area mostly lies between 14,800 to 19,700 feet and is very cold and dry. The extensive region of Trans-Himalayan comprises bare rock and glaciers. The only vegetation is the scanty alpine steppe. With its scanty vegetation, it has a superfluous wild sheep and goat community in the world. The snow leopard, black bears, marbled cat, marmots, wolf and kiang can be spotted here, as are the migratory Black-necked Cranes.

This representation of the Himalayas has the youngest and loftiest mountain sequences in the world. The 2,400 kilometres long Himalayan mountain arc contains distinctive biodiversity in wake of its high altitude, rich flora, soothing temperature and steep gradient. Biogeographically, they create a part of the Palearctic realm. The Himalayas contain three biogeographical provinces i.e. — Central Himalayas, East Himalayas, West Himalayas, and Northwest Himalayas, which together comprise about 6.4% of the country’s area.

• Zone 3 – The Indian Desert

This area comprises two biogeographical provinces i.e. The Thar desert and The Rann of Kutch. The larger is the Thar or Great Indian Desert, consisting of Rajasthan and parts of Haryana and Punjab, moreover adjoining Pakistan. The Indian part of the Thar Desert occupies 170,000 km. The climate reflects very hot and dry summers while cold and arid winters. The area experiences rainfall less than 70 cm. A highly endangered bird—The Indian Bustard is found here, in addition to foxes, snakes, camels, gazelles, foxes, and spiny-tailed lizards.

The second biogeographical province— The Rann of Kutch that lies in Gujarat is a vast area of salt marsh spread across the border between India and Pakistan. This larger area has desert on one side and the sea on the other allowing several ecosystems and desert vegetation. Its deserts and grasslands are home to various wildlife that have adapted to its harsh conditions. These account for endangered and endemic animal and plant species, like the Indian wild ass. The Rann is home to many domestic and migratory birds such as the greater flamingo, lesser flamingo and the Houbara bustard. The Little Rann is an accommodation to the world’s largest population of Indian wild ass with other mammals including the Indian wolf, desert fox, blackbuck, chinkara and others.

A transitional zone between the desert and the denser forests of the Western Ghats are the semi-arid areas. The area is characterized by discontinuous vegetation blanketed with bare soil and soil water that remains in deficit throughout the year.

The mountains running through the west coast of peninsular India comprising one of the unique biological regions of the world are the Western Ghats.

The diverse topography and different climate develop a wide range of habitats that support distinctive sets of plant and animal species. The Western Ghats hills are amongst the 25 biodiversity hot-spots identified globally, known for their high levels of endemism and association with evergreen forests.

On the farther side of Ghats is the Deccan Plateau, the largest unit of the Peninsular Plateau of India. The highlands of Deccan are blanketed with unique types of forests that offer a wide variety of forest products.

The biggest unit of the Great Plain of India is the Gangetic Plain. River Ganga is the main water stream after whose name this plain is named. The thickness of the plain is characterized by the alluvial sediments that vary significantly with their maximum in the Ganga plains.

Some of the highest population densities and Topographic uniformity from the trees belonging to these forests are teak, shisham, sal, khair etc.

• Zone 8 – North-East India

One of the poorest regions in the country consists of several species of bamboos, orchids, ferns and other plants. Here the wild relatives of plants such as mango, banana, citrus and pepper can be grown and found.

Comprising two groups of islands, i.e., the Arabian Sea and Bay Islands vary considerably in origin and physical features.

The Indian coasts differ in their structures and features with the Indian coastline extending over 7,516. 4 km. Extensive deltas of Krishna, Kaveri and Godavari, are the prominent features of this coast. Mangrove vegetation along the tracts of the coast at Ratnagiri in Maharashtra is a reflection of coastal plains. Different crops are grown with Rice being the main crop of cultivation. Coconut trees grow on the coastal plains. 

Chert is a fine-grained and hard sedimentary rock that is composed of micro-crystals of quartz (SiO2). It commonly occurs in the form of nodules, layered deposits and concretionary masses. Chert rock is composed of remains of siliceous ooze, the sediment which covers the major portion of the deep ocean floor. Chert often breaks up into pieces with sharp edges and this was used by people to make weapons and tools out of chert.

           

Properties and Characteristics of Chert

Chert is just as hard as crystalline quartz and a tough rock also which makes it quite hard to penetrate. It stands above the landscape and prevents soil erosion. It has a waxy lustre and is never transparent.

Formation of Chert

Do you know how the chert stone forms? Chert usually occurs in the form of carbonate rocks to irregular nodules in limestone, chalk and dolomite formations. In the sediments, microcrystals of silicon dioxide grow up to form irregular nodules when the silica is moved over to the site of formation by the groundwater. If these nodules are large in number, they grow to form layers of chert rock within the sediment mass. In some parts of oceans, many diatoms and radios live which have a silica skeleton. When they die, they fall to the floor, dissolve and recrystallize. Thus, chert is also considered a biological sedimentary rock.

Composition of Chert

Chert rock is usually a biogenic rock which is made up of extracts of diatoms, radios and sponge spicules. It is a microcrystalline silicon dioxide. It may also move like a liquid rich in silica and forms nodules in rocks. This is done by replacing the original chert mineral usually carbonates. For this reason, it is also termed to be of chemogenic origin.

Colours of Chert Rock

Chert stone can be seen in many colours. The range exists between white and black or cream and brown. Other chert stones such as green chert or red chert are also very common. It gets its darker colour from the addition of higher organic and mineral matters. Higher organic content can lead to grey or black chert rocks and higher amounts of iron oxides lead to red colour.

Types of Chert Rock

There exists a large variety in the types of chert, which depends on the chert minerals, their visibility and physical properties.

Let us know about some of the chert rock types and their properties.

1. Jasper

It is primarily formed as primary deposits found in connection with magmatic formations. This provides its characteristic red colour. It also occurs in yellow, black or green colours.

2. Flint

It is microcrystalline quartz which is formed by the replacement of calcium carbonate with silica. It is usually found as nodules and was historically used to make tools.

3. Opal

It is a form of hydrated silicon dioxide and is often of Neogenic origin.

4. Common Chert

It is the most abundant form of chert which forms in limestone formations by replacing calcium carbonate with silica. It is less used to make gemstones and tools while flint is much more preferable.

5. Radiolarite

It is another form of chert rock that is formed as primary deposits and contains radiolarian microfossils.

6. Magadi

It is a chert rock that is formed from a sodium silicate precursor in alkaline lake environments.

7. Tripolitic Chert

A light-coloured porous siliceous sedimentary rock, Tripolitic Chert is formed by the weathering of chert or siliceous limestone.

Uses of Chert Stone

In today’s life, Chert has minimal uses but in the historic periods, it was often used for construction purposes and makings of tools.

A. Tools

In historic times, chert was frequently used as a material for the preparation of stone tools. Like other stone tools, chert also fractures in a Hertzian cone when it is struck with some force. When a chert stone is beaten against iron or steel, it results in sparks making it ideal for starting fires. Both common chert and flint were frequently used for making fire igniting tools.

B.   Construction Purposes

It is ubiquitous in some regions as stream gravel and fieldstone. Chert is used as a construction material and for road surfacing. The primary reason why chert is used for it is that it tends to get more firm and compact during rain while others get wet and muddy.

The continental crust is the outermost layer of the earth’s lithosphere. It forms the landmasses, that is, the continental shelves and the continents on Earth. The continental crust is developed near the subduction zones at the boundaries between the oceanic and continental tectonic plates. The crust forms almost all the land surface of the Earth. 

Oceanic and Continental Crust

The composition of the continental crust is mostly granitic in nature, and it is slightly lighter than the oceanic crust. The continental crust thickness comes to about 40 kilometers, that is, 25 miles roughly. However, the oceanic crust has a thickness of 6 kilometers approximately. There is a difference in the composition of continental crust and oceanic crust. Unlike the basaltic oceanic crust, it is rich in granite. The oceanic crust is rich in magnesium and iron. The density of Earth’s continental crust is 2.7 grams per cubic centimeter, whereas, the density of the oceanic crust is roughly 2.9 -3 grams per cubic centimeters. 

The variations in the density of lithospheric rock have an evident impact on the elevations of oceanic and continental crust. Those parts of the continental crust that have a lower density floats quite high in the mantle due to their greater buoyancy. The average depth of the oceanic crust is 3790 meters and the average elevation of the continental crust above the sea level is 840 meters. The difference between the elevation and densities of oceanic crust vs continental crust has led to the formation of two main levels of Earth’s surface. 

Continental Crust: Formation

After understanding the continental crust definition, let us now go through the formation of continental crust.  The continental crust is mainly formed near the subduction zones. The oceanic lithosphere is converted into the mantle of the earth, at the sites of convergent boundaries between the oceanic and continental crust. The top layers of the oceanic plates are subducted under the margins of the continental crust. These scraped-off rocks from the oceanic crust add to the lateral growth of the continental crust. The continental margins are mostly outlined as volcanic arcs, and these volcanoes make an addition to the continental crust. 

Island Arc: There are volcanoes aligned along the subduction zones located at the ocean basins. At these sites, the oceanic plates are piled up one above the other. These volcanic arcs along the oceanic subduction zones are known as island arcs. The composition of these island arcs comprises rocky materials ranging from the continental crust and oceanic crust. The density and thickness of the materials constituting the island arcs are likely to vary between that of the continental and oceanic crust. Apparently, the collection of the island arcs led to the formation of the first continent. 

The age of continental crust, rather than the age of the oldest continental crust is about 260 million years. Also, the most ancient continental rock found on this planet happens to be 4 billion years old. The youngest of all ocean crusts is most likely to be found at the mid-ocean ridges, that is, at the sea floors at the sea centers. When the oceanic tectonic plates split apart, the molten magma from beneath oozes out to fill in the void created by the movement of the tectonic plates. 

The continental crust is said to have been formed by re-elimination. It is a kind of accretionary process. Mostly, accretion is a process, in which small solid rock materials agglomerate to constitute large objects, such as the planets. Initially, the solid particles coming together are microscopic in nature and there is a disc of gas, as well. The total mass of the microscopic particles happens to be around 1 percent of the mass of the gas disc. This process of accretion is quite fast and efficacious. 

When the oceanic tectonic plate begins to subduct under the continental tectonic plate, it starts to pull along magma, sediments from the ocean floor, and bigger rocky materials. There is a steady increase in the pressure and temperature with an increase in the oceanic depth. This subsequently leads to the melting of the rocky materials. As the rocks melt, the denser particles sink towards the center and move downward within the descending plates. The less-dense material, that is rich in silica, makes up the granulites and sticks to the continental plates’ bottom. These silica-rich granulites add to the mass of the continental crust.

Continental crust and oceanic crust are two of the most basic areas that are to be understood for the study of the movement of tectonic plates and the consequent phenomena. The continental crust supports the existence of life on the land. The continental crust lies just above the sea level with certain convergent sites with the oceanic crust. The definition, formation of continental crust, and comparison between oceanic vs continental crust are discussed above. Hence, a detailed study of the continental crust facilitates the research on the formation of various landmasses and phenomena like earthquakes and tsunamis.