Category: Geography Notes PPT

The Archean Eon is one of the two formal divisions, and life started first in this period around 4.6 billion years ago. This Eon began about 4 billion years ago with the earth’s crust formation. After the archean eon, the Proterozoic Eon was extended about 2.5 billion years ago. After the Proterozoic Eon, you will see the Precambrian archaeon. Precambrian is the second formal division after the archaean eon. 

About 4.6 billion years ago, the earth’s first formation stage was seen in the Hadean Eon, which is the informal division. The Archean Eon comes after the Hadean Eon and gives great influence to the people in knowing everything about that time in brief and much more specificity. 

The approachable nature of the archean Eon proves that this time has influenced the creativity and standardization of people to an amazing extent and has not lasted in being tedious and tough for the people. 

Developments have Taken Place in the Archean Eon Period

Following are some developments that took place in the Archean period that are listed in brief and informative details-

Liquid Water Started Increasing

The amount of liquid water started increasing on the Earth in this period. There were formations of various small lakes and ponds that contained stable and enough quantities of water in them, and this water did not even get frozen in the winters in the first place. 

The influence of liquid water was so amazing that it started the creation of aquatic life. This aquatic life included small microorganisms such as algae, fungi, etc., and this life was the first living organism creation of the Earth for sure. 

Moderate Temperatures Facilitated the Production of Greenhouse Gases 

The archean period had a moderate temperature throughout itself, and this facilitated the production of greenhouse gases with a slow and steady effect. These greenhouse gases actively included carbon dioxide, methane, and some other easily producible gases that have spread for the betterment of human health in the first place, and that too undoubtedly. 

For the same reason, the atmosphere has developed a great sense of moderation in its presence, and that is why this era has always facilitated active support towards everything present and alive in this era. 

All the above developments have provided great historical pace to the world for the future to experience and enjoy. That is why this era is definitely to be considered as the most crucial and important one in history as well as the future of the world for sure. 

The archean meaning has been best explained with all the above specifications, and these have also proved the worthiness of this period in the first place. The occurrence of a lot of factors has spread their importance in this period, and that is why the existence of the same is well-appreciated in the whole of history and will also continue to do so in the future. 

Therefore, the people who want to know the occurrence and development of historical times should avail themselves of the amazing archean period and all the possible and achievable information about the same for sure. 

We will read about the Bhangar Plains which are part of the Indian Plains. We will also learn about the various classification of the Northern plains through a map & diagram and the various classifications of the Bhangar plains and their characteristics. These notes will help the students of Class 9 in understanding the plains of India.

Bhangar Plain

The Bhangar Plains are situated south of the Bhabar and Terai Plains. Unlike the Bhabar Plains which are not good for farming or cultivation because of the presence of the sediments, the Bhangar Plains are suitable for farming and cultivation activities because these are well-drained plains of Northern India.

Map of Bhangar

This map and the diagram shows the classification of the Northern Plains of India. The Bhabar plains are starting from the foothills of the Himalayas. It is clear from the picture, that the Bhabar plains are having sediments deposited by the rivers and thus, these areas are not fertile in nature. Then comes the Terai Plains which are situated between the Bhabar and the Bhangar. These areas are thick forest and marshy areas which are also good for agriculture. Various famous National parks are also situated here. Then comes the Bhangar Plains and the Khadar Plains. The Bhangar are old plains of alluvial soil and the Khadar are new plains of Alluvial soil which are more fertile than the Bhangar.

Features of the Bhangar Plains

The various features of the Bhangar Plains are as follows:

Soil  

Alluvial soil is found in the Indo-Gangetic Plains including the Bhangar Plains. New alluvial soil is found in the floodplains ie. The Khadar Plains of Indo-Gangetic. This new alluvial soil is having extreme fertility and is also uniform in texture. The old alluvial soil is found in the Bhangar Plains which are having little elevated terraces and patches of alkaline efflorescences which are also called as ” usar “, which leaves some areas as infertile.

If we talk about Indus basin soils, mostly thick alluvial soil is found there called as the Khadar Soils. Away from the rivers and in the middle of the doabs, older alluvial soil is also widely distributed in those plains which are called the Bhangar soil.

Bhangar soil has a texture of medium to fine levels and also has low organic content.

This soil is highly useful and productive for agricultural activities when good irrigation and fertilisation facilities are available.

Other Features

These plains are beyond the flood plains, thus are less fertile as compared to the Khadar because the content of sandy-loamy soil is higher.

The Barind Plains and the formations of the ‘Bhur’ are some of the regional features of the Bhangar Plains.

The Barind Plains are formed in the delta regions of Bengal and Bhur formations are dominated in Ganga and Yamuna Doab.

The Bhangar Plains also contains fossils of various animals like rhinoceros, elephants, etc.

Kankars are also found in the Bhangar Plains.

Classification of the Bhangar

The Bhangar Plains can be divided into the following categories as per the irrigation levels:

On the basis of the type of irrigation, Bhangar plains can be subdivided into different types, that is the Barani and the Nahri region.

Barani areas are traditionally rainfed areas. They are the lower rain areas where especially low rainfall is there and thus, rain-fed dry practices are performed in such areas. If we talk about Bagar Tract location in India, that is the dry sandy soil region on the border of Rajasthan, adjoining the area of Haryana or Punjab. These regions in India are the places where you can find the old alluvial soil, thus they are referred to as the Barani region. It is important to remember that not all the Barani lands are part of the Bagar tract. Nowadays some Barani areas are dependent on tube wells for irrigation as groundwater levels are not too low at those places. In the age-old land revenue system, legally they may be registered as Barani lands but due to this modern tube well system, it can be popularly known as the Chahi region.

The other type on the basis of irrigation type is the Nahri. Nahri refers to the canal irrigated land. Let us take the example of the Rangoi tract. This area is referred to as the Nahri area because it is being irrigated by the Rangoi canal that flows near it. This canal is used for the purpose of transferring the water from the Ghaggar River to the dry and barren Bangar lands. For irrigation purposes in Nahri lands, the landowners are required to take water from the Warabandi roaster, and water is drawn from this canal. Have you heard about chak? It was the land revenue system at the time of the Britishers. It is the land revenue settlement circle in which the contiguous block of land is marked.

The next type on the basis of irrigation is Chahi. Chahi is any kind of land that is irrigated with the help of wells or tube wells. Chahi Khalis is the land that is especially irrigated by using the wells, while if we talk about Chahi Nahri, it is the land that is partly irrigated using a well and partly irrigated by using tubewell. Chahi sailab is that area that is partly irrigated by wells and partly by floods. Chahi taal or taal is that land that is irrigated using ponds.

Did you Know?

Bhur means the elevated land piece which is created by the accumulation of the sand by the winds along the banks of the Ganga river. We have read about the Bhangar properly along with the map of Bhangar. 

Chernozem is a type of soil that is black in colour and is rich in nutrients. The chernozem soil is rich in humus ranging between 4% to 16% along with a higher concentration of nutrients like phosphoric acids, phosphorus and ammonia. This makes the chernozem soil very fertile and hence one of the most useful soils for agriculture and results in high agricultural yields. 

Also, chernozem has high moisture storage capacities. It is also included as a Reference Soil Group of the World Reference Base for Soil Resources. It is one of the 30 soil groups which are classified by the Food and Agriculture Organization (FAO).

History and Formation of Chernozem Soil

Chernozem is a humus-rich grassland soil that is used extensively for agricultural purposes like growing cereals and for the raising of livestock all over the world. The word itself comes from the Russian language which means black earth. From the 19th and 20th century there have been discussions on the process of soil formation of Chernozem. They originated from the discussions on the climatic conditions of the early Holocene to roughly 5500 BC.

However, there has been no single consensus on any paleoclimate reconstruction that was able to accurately explain the processes of geochemical variations that had been found in Chernozems throughout central Europe. Better explanations were offered by the theory involving the anthropomorphic origin of the Chernozem soil formation. 

The Chernozem soil is also known to have the highest magnetic susceptibility as well. This high magnetic susceptibility of Chernozem is explained by the process of vegetation burning by humans. The reasoning is that the initially deposited soil containing significant concentrations of goethite and ferrihydrite was converted to maghemite because of the exposure to temperatures of around 220℃ which are only reached because of the vegetation burning. These events of vegetation burning are a rare occurrence when only left to natural processes. Hence, most of the vegetation burning would have been carried out by the humans leading to the formation of a chernozem soil profile.

The chernozem soil profile is also obtained when there is an accumulation of black carbon. This is observed in some regions such as the regions spanning from North America to Lower Saxony. This accumulation of black carbon is thought to partially originate from some charred materials. Because of these wide variations in the chernozem soil profile, the term summarizes the different types of black soils that have the same appearance but the processes of different formation histories. An image of the chernozem soil is shown below:

Distribution of Chernozem Soil

To answer the question, chernozem soil is found in which region, we must understand the distribution of the soil geographically. They are distributed in the middle latitudes of both hemispheres especially in zones commonly known as prairie found in Argentina, pampa found in Afghanistan, and the steppes in Asia or eastern Europe. Also, it was originally found by the Russian geologist Vasily Dokuchaev in 1883, in the region of the tall grass steppe or the prairie of Eastern Russia. In total, they are present in almost 1.8% land area of the total continental landmass which is approximately 230 million hectares of land. 

There are two concentrated belts in the world that show that the chernozem soil is found in which region. One of the belts is the Eurasian belt and the other one is the one along the Canadian Prairies. The Eurasian belt extends from eastern Croatia along the Danube river, from southern and eastern Romania to northeast Ukraine across the Central Black Earth Region of central Russia and southern Russia to Siberia. The Canadian Prairies belt in Manitoba passes through the Great Plains of the United States reaching as far as south of Kansas. Other places where similar such soil types are found are Texas and Hungary. The map given below shows that the chernozem soil is found in which region.

The layer of the chernozem soil ranges from a few centimetres to a few metres. In Ukraine, a 1.5-metre layer of the chernozem is found. Similar thick layers of chernozem soil profile are found in the Red River Valley region in the northern US and Canada. In small quantities, chernozem is also found in Poland, Northwest China, near Harbin. In Australia as well, the soil is found around the region Nimmitabel which is some of the richest soils in the nation.

Primarily there are two classification systems of the chernozem soil that are the Canadian Soil Classification and United States Soil Classification. They are classified as chernozemic, brown chernozem, dark brown chernozem, black chernozem, and dark grey chernozem. 

A continent is generally defined as a vast landmass differentiated by oceans from other landmasses. The landmass of the Earth is made up of seven continents. Some, like a giant island, are totally surrounded by water, while others are connected and divided only by an arbitrary line. There are many countries on some continents, but just a few on others. The sizes of continents differ significantly; Asia is more than five times the size of Australia.

Formation of Continents

The forming of continents takes a long time, millions of years are needed. The lithosphere’s various plates shift at a rate of 3 to 20 cm (1 to 8 inches) each year relative to each other. The forces that trigger continents to travel around the Earth’s surface are still unidentified.

7 Continents of the World

There are 7 continents in total on earth. Here is the list of those 7 continents:

1. Asia

2. Africa 

3. North America

4. South America

5. Antarctica

6. Europe

7. Australia

Asia

Asia is the world’s largest continent, occupying one-third of the planet’s surface. Asia is not only the largest continent in terms of land area, but it also has the most inhabitants. This is where half of the world’s population exists. This continent includes the world’s two most populated nations, China and India. It is the birthplace of many faiths, including Hinduism, Islam, and Buddhism.

Africa

Africa is the world’s second most populated continent. It is the birthplace of the Nile, the world’s longest river. The Sahara, the world’s biggest desert, is also located in Africa. Since the equator runs across the centre of Africa, it gets direct sunshine all year. Ethiopia, the world’s hottest region, is located in Africa.

North America

North America is the only continent with any climate imaginable: tropical, desert, continental, moderate, and polar. In North America, there are a total of five time zones. The population of North America is about double that of Europe. One of the Great Lakes, Lake Superior, is the world’s largest freshwater lake. It is situated on the United States-Canada border.

South America

The Amazon River, the world’s largest river by size, is located in South America. The anaconda, one of the world’s largest snakes, is also present in South America. South America is home to two of the world’s tallest volcanoes. Brazil, a South American country, is the world’s largest coffee producer.

Antarctica

In the summer, Antarctica occupies nearly 14.2 million square kilometres. Owing to the vast volume of sea ice that develops around its periphery during the winter months, it almost doubles in size. Antarctica is the world’s driest, windiest, emptiest, and coldest continent. Antarctica is home to almost 75% of the world’s glaciers. The thickness of the ice is estimated to be up to 4 kilometres. 

Europe

There are no deserts in Europe, making it the only continent without it. Europe was the central focus of both World Wars. Europe is host to the Vatican City, the world’s tiniest country.  The Euro is a single currency used by the majority of European countries. There are 44 countries in Europe. The most populous country in Europe is Germany, while most populous cities are London and Paris.

Australia

The biggest island in Australia. It is referred to as the “Island Continent.” Australia is also the world’s smallest continent. In contrast to Asia, that’s a drop in the bucket. There is only one nation in Australia, and that is Australia! It is known as “The Land Down Under” because it is completely south of the equator.

Solved questions

1. Which is the Biggest Continent in the World?

Ans: Asia is the world’s largest continent in terms of area. It occupies an area of 44,614,000 square kilometres.

2. Which is the Smallest Continent in the World?

Ans: The continent of Australia is the world’s smallest in terms of land area. It occupies a total area of 7,686,884 square kilometres.

3. The Equator Moves Through How Many Continents?

Ans: South America, Africa, and Asia are all passed by the equator.

Fun Facts

• Africa is the second-largest continent.

• While Europe is regarded as the wealthiest and richest continent, there are poor regions, especially in the continent’s eastern regions as well.

• There are a total of five-time zones in North America

• Asia is the largest continent, it covers one-third of the earth’s surface.

Denudation refers to the procedure of leaching, erosion, reducting, and stripping of the mainland. This is because of the removal of material starting from areas that are higher to the areas that are lower, such as lakes, rivers, valleys, seas, and more that have an everlasting filling of the lowlands. 

 

Denudation in geography includes all the process which leads to the wearing away of the surface of Earth when ice, water, waves, and wind moves. This entire procedure results in reducing the elevation. It is often mixed with erosion, as erosion refers to the transportation of the soil and rock particles from one place to another. At the same time, denudation is the word that involves all the activities that take place and result in lowering the surface of the Earth, which also includes erosion as one part. 

Denudation Process

The process involves chemical, biological, and mechanical processes. It includes weathering, erosion, and mass wasting.

 

Difference Between Weathering and denudation

Weathering is a slow cycle, but denudation is a cycle that takes a very long time to occur, as it involves different processes. The weathering is responsible for the breakdown of the rocks, while denudation is the sum of the wearing processes of the pieces on the surface of the Earth. Weathering is only one part of the entire denudation process. 

Agents of Denudation

The main agents of denudation include:

1. Weathering: It is the process in which the rocks break down into small particles. This decomposition of rocks can happen due to different types of weathering, which are physical, biological, and chemical weathering. 

2. Mass Movement or wasting: It is the rock wastes in the form of fragments of disintegrated rocks that occur due to weathering. This involves the movement of these rocks from a slope to the land because of gravity or other accelerated forces like that of wind or water.  

3. Erosion: It refers to the rock displacing that happens due to different natural agents. It also refers to the disintegration, deterioration, and wearing aways of the soil and rock on the surface of the land.

4. Transportation: Due to erosion, the particles that are loosened due to the process are transported from one place to another due to agents like wind, running water, sea waves, etc.

5. Deposition: It is the collection or deposition of those materials that are eroded, weathered, or transported. 

Types of Denudation

There are no specific types of denudation, but still, there are three regional types that have various directedness towards relief-formation, which is controlled by the fluctuations that happen in climate.

What is Denudation Chronology?

Denudation Chronology includes the study of topographic evolution that has taken place for a long time. It basically involves all the episodes and activities that take place in an erosion of the entire landscape, along with all the processes involved in denudation. In other terms, it is the study in which all the geological succession of all the rocks are studied, which involves different phases of denudation, degradation, creation, and recreation that have happened for a specific geological time scale. 

The activities of the model of erosion are the general and the most common approach that is used for establishing chronologies of denudation. 

The Outcome of the Things Studied in this are as follows:

• The entire geological rock history begins from the Cambrian time period to the Holocene time period. The Cambrian time was the initial geological period from where the major landforms started to develop, and the Holocene time is today’s epoch time. 

• The geological rock history of India that starts from Archaean and ends in the Pleistocene period is also studied.

• The first-ever geological period of India is the Archaean period that formed the Aravali mountains, and the Pleistocene period is the one in which the Tapi and the Narmada Valley are formed.

To study more about it, you can easily find a good denudation chronology pdf for your assistance.

What is Forest Denudation?

Forest denudation refers to the stripping off of the forest from some of its parts. This can happen due to erosion or some other reasons as well. When forest denudation occurs, it makes the layer of rocks and soil so thin that they eventually erode even when there is slightly heavy wind. Forest denudation can be prevented by reducing the chances of forest fires. It can also be prevented by reducing deforestation, which will reduce the cutting of trees.  

Also termed as Escher, Eskers are sand and gravel ridges formed by glacial meltwater flowing through tunnels within and beneath glaciers or meltwater channels on top of glaciers. Sediments accumulate in the channel or tunnel over time. As the ice recedes, the sediments form a ridge in the landscape. It is a type of fluvioglacial landform.

Eskers are significant because they can provide information about how ice sheets and glaciers behaved in the past. They can tell us about meltwater and aid in the reconstruction of the glacier’s former ice surface and snout orientation.

Physical Features of Escher

Eskers are typically a few metres to tens of metres high and tens to hundreds of metres wide, for example, 2,3. Cross-sectionally, they can be sharp-crested (triangular), round-crested (semi-circular), flat-topped (trapezoid), or multi-crested (having two or more crests).

The size and shape of the subglacial tunnel are determined by plastic flow and melting of the basal ice. This, in turn, determines an esker’s shape, composition, and structure. Eskers can be a single channel or part of a branching system with tributary eskers. 

They are rarely found as continuous ridges, but rather with gaps between the winding segments. Esker ridge crests are typically knobby and do not remain level for long periods of time. Eskers can have broad or sharp crests and steep sides. 

Eskers can be hundreds of metres or hundreds of kilometres long. Individual esker ridges formed beneath the massive continental-scale ice sheet that covered North America, for example, can reach lengths of up to 100 km. Aligned ridge groups can form fragmented esker chains up to 300 km long. The Eurasian Ice Sheet created similarly long eskers in Scandinavia.

Significance of Esker

Eskers formed in subglacial tunnels are useful tools for learning about the nature and evolution of glaciers and ice sheets. They document the routes of basal meltwater drainage near the ice margin.

Because of the weight of the overlying ice, the subglacial meltwater is under high pressure. As a result, it can flow uphill! This means that eskers frequently go uphill and climb local topography on a local scale.

The path of pressurised meltwater in subglacial channels is primarily determined by the slope of the ice surface rather than the slope of the bed. As a result, eskers are typically oriented parallel to the ice flow and transverse to the ice terminus.

As a result, the path of an esker section can be used to reconstruct the ice surface slope and orientation at the time of formation.

The eskers produced by the last North American and Eurasian ice sheets most likely record the ice sheets’ final retreat as climate warming increased the rate of meltwater production towards the end of the Pleistocene. As a result, by studying eskers, we can gain a better understanding of how glaciers and ice sheets respond to climate change.

These palaeo glaciological insights are critical for forecasting the contemporary Antarctic and Greenland Ice Sheets’ responses to human-caused climate change, as well as their potential contribution.

Origin of Eskers

Eskers can be found all over the land that was once covered by the former North American (Laurentide) Ice Sheet, Eurasian Ice Sheet, and British-Irish Ice Sheet. 

The most common subglacial eskers preserved on palaeo-ice-sheet beds are those formed in subglacial meltwater channels (termed R-channels, which are incised upwards into the basal ice).

Breiamerkurjökull in Iceland and Hybyebreen in Svalbard are two excellent examples of recently formed eskers.

The zig-zagging eskers are mostly in the flow direction, whereas the moraines are parallel to the ice margin.

Eskers are more common on paleo-ice-sheet beds in areas of crystalline bedrock with thin surficial sediment coverings than in areas of thick deformable sediment. This is because meltwater flowing at the bed is more likely to incise upwards into the ice to form an R-channel where the bed is hard; meltwater is more likely to incise downwards where the bed is deformable.

Detailed Geology of Escher

The majority of eskers are thought to have formed within ice-walled tunnels by streams flowing within and beneath glaciers. They were most common during the glacial maximum when the glacier was slow and sluggish. Stream deposits remained as long winding ridges after the retaining ice walls melted. If water is under pressure in an enclosed pipe, such as a natural tunnel in ice, it can flow uphill.

Eskers can form above glaciers as a result of sediment accumulation in supraglacial channels, crevasses, linear zones between stagnant blocks, or narrow embayments at glacier margins. Eskers form near the terminal zone of glaciers, where the ice is slower moving and thinner.

Path:

The water pressure of an esker in relation to the overlying ice determines its path. In general, the ice pressure was high enough to allow eskers to run in the direction of glacial flow, but force them into the lowest possible points, such as valleys or river beds, which may deviate from the glacier’s direct path. This process is responsible for the formation of wide eskers on which roads and highways can be built. Less pressure, which occurs closer to the glacial maximum, can cause ice to melt over the streamflow, resulting in steep-walled, sharply-arched tunnels.

Examples of Esker

Glacial landforms like Escher are found in the following regions-

1. Europe:

Uppsala Sen is a 250-kilometre-long (160-mile-long) river in Sweden that runs through the city of Uppsala. The Badelundasen esker stretches over 300 kilometres (190 miles) from Nyköping to Lake Siljan. Pispala is located on an esker between two glacier-carved lakes in Tampere, Finland. Punkaharju in Finnish Lakeland is a similar location.

The Kemba Hills are a 5 km esker in Aberdeenshire, Scotland, near the village of Kemnay. Bedshiel Kaims is a 3km long example in Berwickshire, southeast Scotland, that is up to 15m high and is the legacy of an ice-stream within the Tweed Valley.

2. North America:

In Michigan, there are over 1,000 eskers, mostly in the south-central Lower Peninsula. The Mason Esker, which stretches south-southeast from DeWitt through Lansing and Holt before ending near Mason, is Michigan’s longest esker at 22 miles.

Esker systems can be traced for up to 100 miles in the U.S. state of Maine.

The Thelon Esker is an 800-kilometre (497-mile) river that runs through Canada’s Northwest Territories and Nunavut.

Uvayuq, also known as Mount Pelly, is an esker in the Kitikmeot Region of Nunavut’s Ovayok Territorial Park.