Category: Geography Notes PPT

Lapies, also termed as Lapiaz, is a weathered limestone surface. When water flows over a surface having limestone along with other hard rocks, lapies are formed. Limestone being a soft rock, erodes the limestone forming several narrow and deep trenches like structures, clints, and grikes dispersed by sharp pin-like vertical pinnacles roughly parallel to each other. Such topography is known as lapies. Their grooves vary in depth from a few millimeters to meters. Their base is extremely hard as they commonly form on tilted rocks. Lapies are peculiar to karst, being related to various karst surfaces but especially those constituted by pure limestone beds of considerable thickness.

Karst Topography

A topography is formed from the process of dissolving or breaking apart soluble rocks such as limestone. It is set apart by underground drainage systems with caves and cenotes. A distinctive topography indicates the breaking apart of underlying rocks by surface or groundwater. Large drainage systems are likely to have both surface and underground or karst drainage components. It generally forms in areas of plentiful rainfall where bedrock comprises carbonate-rich rocks. Some karst topography regions are dominated by several caves. The underground drainage system is one of the remarkable features of the karst regions. The chemical process of solution and precipitation results in the formation of the landforms either through erosion or deposition. The development of such landforms changes from region to region.

Karst topography is known as after the standard topography developed in limestone rocks of the Karst region within the Balkans adjacent to the Adriatic Sea. It includes classic landforms in any dolomitic region, produced by groundwater action through the solution and deposition processes. Limestone is an organically formed sedimentary rock. In its pure state, limestone is formed from calcite or carbonate but where magnesium is additionally present it’s termed dolomite. Limestone is soluble in rainwater.

Limestone Pavement

 A natural karst landform resembling an artificial pavement consisting of a flat, incised surface of exposed limestone, in which the joints have been enlarged. They are made up of a series of clints and are bedrock exposures typically horizontal or gently inclined. The surface has been diffused in water over billions of years into clints or paving blocks with a complex reticulate pattern of crevices between them. The vegetation of limestone pavements is unusual because of the combination of floristic elements including woodland and its edge species. The crevices provide a humid environment favoring woodland plants.

Solved Examples

1. What are the Suitable Conditions For Karst Formation?

Answer:

The conditions are:

• Karst topography is generally found in regions where there is a stretch of water-soluble rocks.

• These rocks may be limestone at the surface or subsurface level. But, the limestone should not be porous.

• These rocks found there should be dense and well-jointed. They should not be thickly bedded. As the rocks found in the karst regions are permeable, the surface water drains underground and erodes the rocks with its horizontal and downward movement.

• An enduring source of water and a low water table to allow the formation of conspicuous features.

• Moderate to abundant rainfall to cause the solvent action of water that is the solution of rocks.

2. What are the Features of Karst’s Topography?

Answer:

• Uvalas-They are long trenches, also termed as valley sinks. Several sinkholes and dolines may combine as a result of subsidence to form a large depression called an Uvalas.

• Lapies-These ridges form due to distinctive solution activity along parallel to sub-parallel joints.

• Limestone Pavements- These structures cause progressive widening and enlargement of joints and cracks in the trenches. It is formed by the solvent action of underground water in the limestones.

• Polije- It is a very large depression in the karst region. These structures are formed by the merging of several uvalas or partly due to faulting.

• Ponor-  This is a natural opening or a portal where a lake or stream flows either completely or partially underground into a karst groundwater system.

• Caves- Limestone dissolves along the bedding planes which is formed due to water percolating down either through materials or through cracks and joints and moves horizontally along with them, resulting in the formation of long and narrow gaps called caves.

Around the earth, there is a dominant magnetic field which is called the magnetic field of the Earth. Around that magnetic field, there is a region of space, that space is known as the magnetosphere. All the planets in the solar system have their Magnetosphere just like we have Jupiter magnetosphere and Uranus magnetosphere, but the earth has the strongest Magnetosphere. The geospace magnetosphere covers the planet and acts as a shield to our planet. Magnetosphere is also the reason why Life on Earth became possible.

What is Earth’s Magnetosphere?

On the other hand, the Magnetosphere is the region of space that surrounds an astronomical object where charged particles are affected by the object’s magnetic field. This is created by the planet or star with an active interior dynamo. The earth’s magnetosphere is formed by the interaction of the solar wind with the earth’s magnetic field. Thousands of years ago, the Chinese discovered that the Lodestones, which were basically magnetic minerals, would align in roughly the north-south direction. But the main thing is that no one could understand the reason for this effect and afterwards when William Gilbert published De Magnate and demonstrated that our earth behaved like the giant magnet and loadstones were aligning with Earth’s magnetic field.

Importance of Magnetosphere

Many harmful radiations come from the sun. The atmosphere of the magnetosphere protects the homes from these harmful radiations. It also protects the atmosphere from the solar winds.

Composition of Magnetosphere

The magnetosphere has large amounts of plasma, electrically charged ions which are anions and cations. They are positive and negatively charged.

Under Mars’ magnetosphere, the surface of Mars is not that magnetic as earth. Electric currents are shown through detailed maps which shape the magnetic field.

Magnetosphere Structure

The basic structure of the Magnetosphere is known as atmospheric structure. Internally the structure of the Magnetosphere is very complex. The structure is very complicated as it has often overlapped. The overlap is dependent on the region whether it’s high energy charged particle or low energy charged particle or it is an uncharged particle. So the structure depends on these factors.

1. Magnetopause

Magnetopause is the area where the pressure is balanced between the planetary magnetic field and the pressure from the solar wind in the Magnetosphere. The structure of the Magnetopause depends on the magnetic field. The structure also depends upon the Mach number as well as on the beta of plasma.

2. Bow Shock

The bow shock is the outermost layer of the Magnetosphere.

3. Magnetosheath

The magnetosheath is the area between the Bow shock and the magnetosphere. It has some amount of plasma. It is formed from the solar wind.

4. Magnetotail

The magnetotail is the region that is opposite to the magnetic field which is compressed. The Magnetotail has two lobes. The names of the two lobes are northern and southern lobes respectively.

Earth’s Magnetosphere

The Earth’s Magnetosphere is also known as the geomagnetic field. The region between the earth magnetic field and the solar wind is known as the Earth’s Magnetosphere. The region is always in motion because Earth is affected by the changing solar wind. The interplay between the wind and the magnetic field of the earth is the reason for the creation of electric fields, plasmas and current inside of earth’s Magnetosphere.

The Earth’s Magnetosphere is made up of three charged particles that are found in the magnetic field of the earth. The Earth’s Magnetosphere is very important to us because in the absence of the Magnetosphere the solar particles can damage the Earth’s protective layers which protect us from the ultraviolet rays of the sun. The ultraviolet rays can cause skin cancer, skin disease etc. which are very harmful to us. The size of the Earth’s Magnetosphere is about 65,000 kilometres.

Some Facts about Magnetosphere

The magnetosphere is defined as the region of space above the earth’s Ionosphere in which the charged particle motion is dominated by the geomagnetic field. So, here on this page, we will discuss some of the facts about the Ionosphere and Magnetosphere and those are like-

• Earth’s internal magnetism creates the region around the planet known as the Magnetosphere. 

• Where the various planets in our solar system consist of magnetospheres, earth contains the most powerful one of all the rocky planets. This magnetosphere is very vast which has played a crucial role in our planet’s habitability.

•  In the absence of this Magnetosphere, the agitating action of these solar activities could strip the protective layers from the earth that protects us from the sun’s ultraviolet radiation. This is also the main importance of the Magnetosphere.

Minerals are naturally occurring inorganic solids found in the earth’s crust and they are either made up of one element or they are a combination of elements. Most minerals are highly valuable and their study, classification, and excavation all fall under the subject of geology. In this article, we will discuss the occurrence and formation of minerals. Several factors affect the formation of a mineral. Since minerals occur in a wide variety of environments, we have a wide array of these resources forming under various chemical and physical conditions. If we classify minerals based on their process of forming, we will have four types, namely: igneous, sedimentary, metamorphic, and hydrothermal. 

Minerals Found in Igneous Rocks

Igneous rocks form due to the cooling and solidification of lava. The minerals occurring in these rocks are igneous. Partial melts of previously formed rocks exist in the earth’s crust and mantle and at times due to tectonic tensions, the molten mass travels towards the surface and starts cooling. If they solidify below the earth’s surface, they form intrusive rocks and otherwise they form extrusive rocks. The mineral compounds which exist in the earth’s mantle travel to the surface with the lava and then solidify as part of an igneous rock. This process leads to the formation of igneous minerals. Some igneous minerals are olivines, pyroxenes, and micas. 

Minerals Found in Sedimentary Rocks

Minerals found in sedimentary rocks are a result of the process of sedimentation. In this process, rocks and soil undergo erosion by the various forces of nature, including wind and water. These eroded particles travel to different regions and settle layer by layer in certain places. In these regions, structures formed of sedimentary rocks come to life. Sedimentary rocks contain many valuable minerals such as quartz, feldspar, calcite, dolomite, etc. 

Minerals Found in Metamorphic Rocks 

Metamorphic rocks form due to the complete metamorphosis of existing rocks. Metamorphosis means transformation and this change occurs due to certain physical phenomena. Environmental changes such as an increase or decrease in temperature or pressure lead to chemical changes in the mineral compounds of rocks to give rise to new minerals. This process is the basis of the occurrence of metamorphic minerals. Some examples of such minerals are garnet, corundum, and kyanite. 

Minerals Found in Hydrothermal Rocks 

Hydrothermal minerals occur in the fissures of rocks and form as a result of the chemical precipitation of hot solutions erupting from the earth’s core. In the previous three types, we observe that minerals are closely intergrown within the rocks in an interlocking pattern. However, hydrothermal solutions tend to flow into the fractures in a rock structure to gain a suitable space for chemical precipitation of the minerals in the solution. Geologists collect their samples from these very fissures. When a mineral undergoing precipitation grows without any external disturbance, beautifully shaped crystals come to life. This crystalline form gives an aesthetic appeal to the minerals. 

Petroleum: Formation and Occurrence 

This section is a short discussion on petroleum formation and occurrence. Petroleum is a very crucial industrial mineral. Petroleum is a result of the slow decomposition of organic matter due to chemical biochemical factors. This mineral naturally occurs in layers between sedimentary rocks. The trapped organic matter undergoes decomposition by bacterial action and changes in the chemical environment. This process turns the organic waste into globules of oil and gas. 

Questions and Answers

Q1. Explain the term Minerals and State their Importance. 

Answer: Minerals are solid inorganic compounds naturally occurring in rocks in the earth’s crust. Minerals are highly valuable commercially and industrially. Coal, natural gas, and petroleum act as fuels. Several other minerals find application in medicines, fertilizers, etc. 

Q2. Name the Softest and Hardest Minerals. 

Answer: Talc is the softest naturally occurring mineral and diamond is the hardest one. 

Q3. Explain the reason behind the Wide Variety in the Colour, Texture, Lustre and Hardness of Minerals. 

Answer: The physical properties of minerals are widely spread when it comes to colour, density, hardness, lustre, etc. This variety yields from the fact that each mineral is formed from a particular set of elements under particular environmental conditions, making them unique.

For anyone who has ever been in a desert, you know how secluded, aloof and lonely the landscape can be. An oasis is a place in a desert where water comes up to the surface from deep underground. Trees and other plants grow around an oasis and animals come to eat the plants, drink and find shelter. Oases are quite intriguing to both humans and animals and simultaneously are crucial parts of an ecosystem that can be found all around the world.

What are Oasis Geological Features?

Following are the oasis geographical features that you must know to have an improved understanding of what oasis is exactly.

• Oases are created and conserved by nature as well as by men.

• Some man-made wells in neighbourhood oases have been maintained for generations to achieve keeping the oasis as a viable water source for travellers, livestock and locales nearby that bank on the water for survival.

• The natural environment of the oasis also imparts itself to water conservation and preservation; the trees, shrubs and other flora that mushroom in the environment of the oasis help retain water in the ground and shade the oasis from the component around it.

• In absence of oases, trade and travel routes would have been made almost impossible

• Without oases, the watering and feeding of people and livestock would have been constrained.

• Oases situated in the desert (as most are) are constantly threatened by moving sands and other weather-associated elements and are safeguarded by the shelter of trees around them.

• Palm trees, tubers, and other plants are particularly good at securing an oasis from dangerous elements and contribute greatly to the ecosystem with their deep roots and outstanding water retention abilities.

• We as humans are unable to live directly by a body of freshwater, but oases enable us to maintain and sustain life in the strident interior of continents around the world.

Natural Oasis

Oases that are fed by above-ground rivers, such as the Nile River, can be formed by underground aquifers and rock layers hundreds of miles away. This vital association between oases and rivers implies that water sources can be created and conserved even with no water sources visible nearby. Other oasis geological features like oceans, lakes, ponds and streams can also be sources of water in an oasis relying on the location.

What is a Desert?

The driest place present on the planet is a desert. Deserts undergo less than 250mm of rain in a year. A Desert is commonly hot in the daytime and colder at nights. There are different types of desert that range from tropical hot desert like the Sahara in North America to cold deserts such as the Gobi in Central Asia. Only animals and plants that require very less water for survival can live in a desert.

What is a Sand Dune?

Sand dune is basically the hill of sand which is created by winds as they blow across the desert. The more vigorous the wind is, the farther it will carry sand particles before they eventually fall to the ground.

Did You Know

• Along with being a distinctive geographical feature, oases provide food, water, shelter and shade for people passing through as well to plants and animals that live in the area of the oasis.

• Life deprived of reliable water sources together with the constant desire to travel many days between the next water sources has been a theme of trade, travel and nomadic lifestyles for ages that made oasis infamous.

• Life in harsh climates is difficult for sustenance for many creatures on Earth, including humans, and yet numerous species of plants and animals have managed to maintain these harsh environments quite well.

Ozone layer depletion is one of the most alarming environmental issues of the present time. The chloro- and Bromo- chemical compounds released into the atmosphere from industries and domestic buildings deplete the ozone layer. The most common compounds that cause ozone layer depletion are halocarbons like Chlorofluorocarbons. Chlorine reacts with atmospheric ozone, breaking an oxygen atom from the ozone ring and leads to a chain of reactions, in which the ozone gas is decomposed into oxygen and chlorine monoxide. Also, counteracting the ozone depletion in the stratosphere, ozone layer recovery has also been observed by scientists. 

The ozone layer depletion increased exponentially and the thinning of stratospheric ozone was observed more significantly in the polar regions, ever since researchers discovered the ozone hole. The gradual thinning of the ozone layer had led to the formation of an ozone hole over the Antarctic regions. Due to the depletion of the ozone layer, a greater amount of ultraviolet rays reaches the earth’s surface. There are several adverse effects of UV rays on humans as well as on the environment. Exposure to UV rays makes humans prone to cataracts, skin cancer, immune system damage, etc. However, recent climate surveys and research establish the fact that the ozone layer is recovering.

Ozone Cycle

The symbol of ozone gas is O3. It is formed when oxygen absorbs photons from the ultraviolet rays and photodissociation of oxygen molecules occurs. Here, the ozone cycle refers to the continuous process of dissociation and regeneration of ozone molecules due to the effect of ultraviolet radiations. On photodissociation, a diatomic oxygen molecule (O2) dissociates into two free radicals of atomic oxygen [O]. Each of these two atomic oxygen molecules reacts with diatomic oxygen molecules forming ozone gas. Therefore, every free radical of atomic oxygen forms one molecule of ozone gas, in reaction with diatomic oxygen.   

The chemical reactions involved in the formation of ozone are as follows.

O2 → [O] + [O]

[O] + O2 → O3

Ozone molecules split into diatomic oxygen and free radicals of atomic oxygen on the absorption of UV light. The resulting atomic oxygen radical again reacts with another diatomic oxygen molecule and forms an ozone molecule. This continuous process formation of ozone gas terminates when a free radical of atomic oxygen reacts with ozone and dissociates it into two molecules of diatomic oxygen. 

The chemical reactions involved in the splitting of ozone into two molecules of diatomic oxygen are as follows.

O3 + UV radiations → O2 + [O]

[O] + O3 → 2O2

The ozone layer depletion has occurred due to the reaction of ozone with highly reactive free radical catalysts like Bromine (Br ), Chlorine (Cl ), Nitrous oxide (NO ), and (OH ). Each of the above free radicals has an unpaired electron, that renders them highly reactive. The hydroxyl and nitric oxide free radicals occur naturally in the atmosphere whereas the free radicals of Chlorine and Bromine have human-made sources. The most common sources of the free radicals of chlorine and bromine are Chlorofluorocarbons (CFCs). These are mostly released from cooling appliances and certain industrial equipment. The CFCs are chemical compounds that travel as high as the stratosphere without decomposing or dissociating in the troposphere, as they exhibit low reactivity. 

On reaching the stratosphere, these chlorofluorocarbons absorb ultraviolet radiations and release the highly reactive free radicals of chlorine and bromine in the atmosphere.

The chemical reaction involved in the splitting of CFCs into free radicals of Chlorine and Bromine is as follows.

CFBr3 + Ultraviolet radiations → CFBr2 + Br

CFCl3 + Ultraviolet radiations → CFCl2 + Cl

These free radicals eventually react with the stratospheric ozone and degenerate it into diatomic oxygen through several types of catalytic reactions. For example, when the free radical of chlorine gas reacts with ozone, chlorine monoxide and diatomic oxygen are formed. The chlorine monoxide formed in the above step reacts with an ozone molecule and forms two molecules of diatomic oxygen. Now, another product of this reaction is a free radical of chlorine. Hence, a chain of reactions is initiated when a free radical of chlorine reacts with ozone. 

The chemical reactions involved in this chain reaction are as follows.

O3 + Cl → O2  + ClO 

O3 + ClO → 2O2 + Cl 

The free radical of chlorine produced in the above reaction will react with another ozone molecule forming diatomic oxygen and chlorine monoxide.

Ozone Hole Over the Antarctic 

The ozone column over the Antarctic regions had depleted by about 60 percent with respect to the average global ozone layer depletion. This phenomenon was recorded in 1985 by Joseph C. Farman, Jonathan D. Shanklin, and Brian G. Gardiner, in the British Antarctic Survey. In comparison with the previous records, this decrease in the ozone layer was found to be even greater than 50 percent. Ozone layer depletion is categorised into two phenomena, one is the depletion of ozone in the troposphere and the other is the formation of the ozone hole in the stratosphere at the polar regions.

Why is the Hole in the Ozone Layer Recovering?

The ozone hole recovery began in the late 1990s and the size of the hole has been decreasing ever since. In 1982, the size of the ozone hole was recorded to be 16.3 million km2. There are several international treaties such as NASA ozone layer recovery that are being religiously followed by various countries across the globe, to control the production and consumption of ozone-depleting substances. The recorded reductions are quite promising to anticipate that the ozone hole will be mostly recovered in the near future.

Ozone Layer Recovery

The ozone layer recovery has been one of the most significant agendas for the conservation of the environment. As per the recent records, the ozone layer is recovering and it is expected that the concentration of ozone in the atmosphere is likely to be restored like that of the 1970s by 2060s. The objective of the Montreal Protocol on Substances That Deplete The Ozone Layer was to control the production and use of CFCs and similar halocarbons that are potent threats to the ozone layer. Ideally, by 1998, the levels of global consumption of CFCs and similar halocarbons were to be reduced by 50 percent from the levels of 1986. By 2005, after several amendments, the consumption of CFCs and other ozone layer depleting substances was reduced by about 95 percent.

When is the Ozone Layer Expected to Recover?

It had been anticipated that the ozone holes over Antarctica will be of smaller sizes, if the consumption of CFCs and halocarbons is controlled, after 2040. Also, scientists have recorded that the stratospheric ozone levels will be restored to that of 1980, by 2060s. The concentration of ozone in the stratosphere and troposphere are affected by the levels of gases like carbon dioxide, nitrous oxide, methane, in the atmosphere. These gases can release reactive free radicals that deplete the ozone layer. The ozone level is expected to go up steadily but slowly since the halocarbons like CFCs stay longer in the atmosphere. 

An increase in stratospheric ozone levels was discovered in 2014 as a result of the phase-out of CFCs and other ozone-depleting substances across the globe. The practices as per the international treaties were to be accredited for this hike in the stratospheric ozone levels. Researchers observed that the ozone concentration in the upper stratosphere has been increasing since 2000, while the ozone hole over Antarctica has been reducing in size. The smallest ozone hole was recorded in 2019, this was a milestone in the ozone hole recovery and bolsters the fact that reduced consumption of substances that deplete ozone has the ozone recovered. This evidently shows how much has the ozone layer recovered with the international treaties to control the consumption of substances potent to deplete the ozone layer.

Ozone is one of the greenhouse gases and any changes in its concentration in the troposphere and stratosphere, have an impact on the earth’s temperature. The ozone hole over Antarctica is an opening for the harmful UV rays to be incident directly on its inhabitants. Also, the decrease in the concentration of stratospheric ozone has a cooling effect on the climate of our planet. Nevertheless, the increasing carbon dioxide levels in the atmosphere produces a counteractive heating effect as well. As the ozone layer is recovering gradually, researchers are anticipating that the ozone concentration in the stratosphere will be restored within a few decades. Hence, the earth ozone layer recovering will also reduce the cooling effect at the poles due to ozone depletion.

Plate tectonics is a scientific theory that describes the large-scale movement and the distribution of the plates that make up the earth’s lithosphere. The plate tectonic theory is built from the concept of the sliding and movement of the continents. The geoscientific community has accepted the plate tectonic theory after obtaining significant proof on the seafloor spreading concept. The theory provides a uniform understanding of mountain-building processes, volcanoes and earthquakes. Also, it has provided an in-depth understanding of the evolution of Earth’s surface and reconstruction of the past of the continents and oceans. Moving further the plate tectonic theory and the tectonic plates definition are explained below.

What are Tectonic Plates?

The outermost layers of the Earth are divided into two – the lithosphere and asthenosphere. This difference is based on the differences in the mechanical properties and the transfer of heat in-between the two layers. These two provide the basis 

Now, thinking about the topic the first two questions that arise are – what is tectonic and what is plate. The tectonic meaning includes all the large-scale activities such as the volcanic activity that takes place on the lithospheric mantle of the earth. And a plate here means the fragments of the lithospheric surface of the earth which are different from each other in various properties. Thus, in order to define tectonic plates or also known as the lithospheric plates, one says that the tectonic plates are the separate and distinct plates made up of lithosphere which ride upon the fluid-like asthenosphere.

The tectonic plates are made up of lithospheric mantle consisting of two types of crustal material: either the oceanic crust which is found below the water of oceans (made up of silicon and magnesium) or the continental crust (made up of silicon and aluminium) which floats on the water or both. An example of a tectonic plate containing both the oceanic crust and the continental crust is the African plate which consists of the continent and the parts of the floor of the Atlantic and the Indian Ocean.

When asked how many tectonic plates are there, one can easily name several of them such as the seven continents – Asia, Africa, Europe, North America, South America, Australia and Antarctica which are the continental plates, and the ones beneath the oceans forming the base of the Pacific, Atlantic and the Indian Oceans are the oceanic plates.

The tectonic plates are known to move and the existence of the current map of the world has come into existence because of the movement of tectonic plates. These lithospheric plates move by a typical range from 10 mm – 40 mm per year (the rate of growth of fingernails) to 160 mm per year (the growth rate of hair). Examples of the slow-moving plate include the Mid-Atlantic ridge while the fast-moving plate includes the Nazca plate. As these earth plates move over the limited space on earth sometimes they separate while sometimes they come into contact with each other. The location where two earth plates meet is called the tectonic plate boundaries. 

The reason for the movement of earth plates and different types of plate boundaries is explained further.

Why Do Plates Move?

Given that there are differences between the physical characteristics of the lithosphere and the asthenosphere, it is widely accepted that the reason for the question, why do plates move, is the relative density of the oceanic lithospheric plate and the relative weakness of the asthenosphere. This difference leads to the creation of specific zones at which the oceanic plate starts submerging into the asthenosphere because of higher density. These are known as subduction zones and it is considered to be one of the driving forces of plate motion. Including this there are other factors that contribute to the movement of the earth plates which are mentioned below:

• One of the driving forces considered for the movement of the lithospheric plates is the mantle dynamics where it is thought that large-scale convection currents in the upper mantle are being passed through the asthenosphere. These convection currents reach the plates which show varying density distribution and affect them differently causing them to move. 

• Another one of the reasons for tectonic plates is the action of gravity. It is thought that there is a slab pull at the subduction zones i.e. the lithospheric plates being pulled into the asthenosphere because of gravity. Hence, in most cases, gravity acts as a secondary driving force for plate movement.

• The third important driving force for plate movement is the rotation of the Earth. Tidal forces and centrifugal forces have been considered to be also the reason for continental drift. These forces, the result of the gravitational pull of the Moon and the Sun, are thought to provide aid or a small push over long periods of time for the movement of the continents.

Although there is proof of the tectonic movement by the seafloor spreading i.e. the creation of new oceanic crusts due to the volcanic eruptions inside the oceans indicating recycling of the oceanic lithospheric plate, there has not been conclusive evidence on the major driving force of the lateral movement of the lithospheric plates. The current movement is still undergoing active research and the movement is said to be a sum of all the above mentioned driving forces, with some forces playing an active role while the other a more passive one. 

Tectonic Plate Boundaries and Its Types

The locations at which the tectonic plates meet or the locations from which they separate are called the tectonic plate boundaries. Depending on the movement of the tectonic plates relative to each other, there are four different types of plate boundaries. These different types of plate boundaries are stated below:

1. Divergent Boundaries: These types of tectonic plate boundaries are formed when two tectonic plates are moving away from one another. This leads to the creation of more rivers or huge water bodies. It is a constructive plate boundary of the four boundaries. 

2. Convergent Boundaries: These ones are formed when two plates collide with each other. In this case, mostly a subduction zone is created and the oceanic plate (heavier in weight) moves below the continental plate (lighter in weight). Sometimes, there is a continental collision when the subduction zone is completely destroyed and its a simple collision. This kind of plate boundary of the four different types of plate boundaries is the most destructive one. At the junction of such a boundary, mountain ranges appear. 

3. Transform Boundaries: In this type of tectonic plate boundaries, the earth plates slide past each other or grind past each other in a lateral movement. It can move to the left or right depending on the point of observation. 

4. Unclear Boundaries: There are plate boundary zones where the interaction between the tectonic plates is unclear and the phenomenon occurring at the belt of such a boundary is not well defined.

Conclusion of the Tectonic Plate Theory

As mentioned at the beginning, if one is to define plate tectonics, it can be said that the Plate tectonics theory or the Tectonic plate theory is a scientific theory describing the movement of the segments of the earth’s lithosphere. It covers a wide range of concepts relating to what are tectonic plates and what are types of tectonic plates, why do they move, and how are they formed. It has been developed by geologists and is an ongoing research field.