Category: Geography Notes PPT

Bajada (Spanish: slope), also spelled as bahada, consists of a series of coalescing alluvial fans along a mountain front. Such fan-shaped deposits are formed by the deposition of sediments within a stream resting on the flat land at the base of the mountain. The term “ Bajada” is widely used to detail the landscape of geomorphology. 

What are Bajadas?

Bajadas are the shallow slopes that lie at the base of the rocky mountains, where the material gets accumulated from the weathering of the rocks. The bajadas typically have a mixture of sand, gravels, boulders, and silt particles, forming a  deep and complex soil structure that holds water and supports rich vegetation. 

Bajada Formation

When a stream slopes downwards, it picks up sediments along with the other material. As the stream comes up from a mountain front, the sediments that are carried begin to be deposited, such that the rough deposits are deposited at the base and the finer deposits arranged outwards in a fan – shape away from the mountain base. The sediments are further transferred to the opposite side of pediments into a close basin where the bajadas are arranged back into the pediments, making the boundary difficult to observe. 

Bajada Occurrence

Bajadas are moderately sloping depositional plains located between playa and pediments. They are commonly found in dry climates ( for example the Southwest US) where the flash flood deposits remain over time. Bajada is also commonly found in wetter climates where streams are almost constantly depositing sediments. 

Did You Know?

• Bajadas below the Hexie Mountains can be seen from Joshua Tree National park.

• Bajadas are found on both sides of Death valley (north of Stopevilles Wells), more well developed on the Panamint Range side.

• A bajada is generally composed of gravel alluvium and even has larger rocks interbedded in it.

• Pyara lake is found between the Bajadas and pediments.

• The Spanish term Bajada means inclination or descent is often used to describe a landscape or geomorphology.  

• When many alluvial fans come together at one place, or deposits in the same area it forms bajada. Due to the gathering of all the fans, it implies that there is much more water and sediments than usual, and is quite evenly spread out to the whole bajada.

The research and practice of making maps is cartography. Cartography, integrating science, aesthetics, and methodology, builds on the idea that reality (or an imaginary reality) can be modelled in ways that effectively convey spatial details.

The basic goals of conventional cartography are:

• Set the agenda for the map and pick the characteristics of the object that is to be mapped. This is the main focus of map processing. The traits might be physical, like roads or masses of land or might be abstract, like political borders or toponyms.

• Reflect the mapped object’s terrain on flat media. This is the problem with map projections.

• Decrease the sophistication of the features that are to be mapped. There is also the dilemma of generalisation.

• To better transmit its vision to its viewer, organise the components of the map. This is the major area of focus with map design.

Cartographic Process

Evaluating the viewer and using a diagram is the first step in mapmaking. It might help in deciding the map scale, the map size and text features that are most essential to show the map colour schemes, as well as what projection is being used. It is necessary to understand this data because it will allow the map to be transparent and simple to comprehend.

The cartographer can start with making the map only after the decisions regarding size, colour, essential characteristics, and projection are identified. Most maps are produced on computers in modern cartography. Through internet sources, cartographers can collect the details they require, upload the information into their mapping software, and modify the functionality to match the necessary requirements.

Types of Maps

There exist three basic types of maps namely, thematic maps, general reference maps, and cartometric maps.

• General Reference Maps: 

Geographical location details such as highways, rivers, lakes, seas, political borders, cities and mountains are displayed on a general reference map. Such maps can be used for political maps, road maps, some topographic maps, and a basic all-purpose map which can be used anytime and anywhere.

A particular theme and factors relating to a certain theme are represented by thematic maps. A crime map in a district, areas where a disease was already established, population size, the distribution of a species or the extent where a community can live, severe flooding, climate models and more are examples of thematic maps. Thematic maps are also used to examine spatial trends or the results of such studies.

Cartometric maps are the ones which concentrate on parameters such as area or distance that are unique. Such maps are mostly used for guidance, navigation and are also referred to as charts. Examples of cartometric maps are aeronautical and nautical diagrams. To navigate waterways such as oceans, lakes, and rivers, nautical charts can be used, whereas aeronautical charts enable airlines to navigate safely.

Cartographic Scale

• The size of a map determines the area that is depicted by the map. A fraction such as 1:250,000 or 1/150,000,000 typically denotes it. Such fractions mean that in the real world, standard measure on the map is equivalent to 250,000 or 50,000,000 of those same units.

• It is beneficial to use ratios to label the scale since they could be used in every measurement device without converting from one system to the other (such as from feet to meters). A map covering a large area is classified in cartography as a small-scale map, whereas a map covering a small area is defined as a large-scale map. This relates to the map’s representative fraction.

• The 1:250,000 fraction is greater than the 1:50,000,000 fraction, much like 1/2 is greater than 1/4 and 1/3 is greater than 1/6. A simpler way of describing the difference, though, is that the characteristics of a large-scale map (buildings, highways, rivers, etc.) are greater than the characteristics of a small-scale map.

• It must be remembered that although there is no standard unit of measurement for the absolute level of a map, like meters, feet, or miles, the scale bar is used as a reference bar for map readers.

Importance of Cartography

• Cartography is useful because it encourages spatial visualisation of data. This can display population spatial trends, economic growth, urbanization, as well as more.

• Cartography often aids in the preparation and rehabilitation of disasters and allows emergency responders to consider what is going on in the region where they operate.

• Cartography is useful because it encourages spatial visualisation of data. This can display population spatial trends, economic growth, urbanization, as well as more.

• Cartography often aids in the preparation and rehabilitation of disasters and allows emergency responders to consider what is going on in the region where they operate.

• Also, people use maps every day as they drive, locate restaurants, shops, and track their online transactions as they reach, with GPS and maps readily available on mobiles and other devices. The value of cartography is rising and becoming profoundly ingrained in our lives.

Fun Facts about Cartography 

• Ever since ancient times, lots of people are making maps. Thousands of years ago, cave drawings depicted hunting areas.

• Thanks to satellite imagery and GPS today’s mapmaking is very accurate because of such factors. However, the earliest maps were constructed using basic methods and mathematical equations.

There are different types of coal that are all rocks and minerals composed largely of carbon. This fossil fuel produces ~40% of the planet’s electricity and approximately 25% of the world’s primary energy. Perhaps, not all coal used is the same. There are different types of coal and their uses. Moreover, there are different quantity levels of carbon—which pronounce the quality of the coal. Higher quality coal or the best variety of coal yields less smoke, burns longer, and renders more energy than lower quality coal.

Coal is Which Type of Rock

Wanting to know coal is what type of rock? Coal is typically organic sediment which contains a complex mixture of compounds. Depending upon the evolutionary phase of coal formation there are essentially four types of coal. The variety of coal types is based on energy density and the carbon contents of coal. Furthermore, it reflects the moisture content before drying, and the amount of mercurial content, after it’s dried.

Types of Coal and their Uses

As mentioned above, there are primarily 4 types of coal that are distinguished from one another based on their process of formation.

The first evolutionary phase of coal formation is Peat that is a bit more than wood pulp which has been poorly decomposed. There are huge deposits of Peat in the Greenland and Scandinavian countries. Peat coal can strip mine it because it is usually very close to the ground level. The issue with Peat is that it consists of a very low British Thermal Units (BTU) production per pound of the fuel burned. Moreover, strip mining is ecologically very devastating unless the mining operative makes a deliberate effort to restore the countryside. Strip mining is a phenomenon of scraping the coal from the top surface of the ground.

The second in an evolutionary phase of coal is lignite. Lignite is found in a huge amount in the Western part of the United States. Again lignite is not specifically efficient in yielding energy per mass of fuel. There has been a little effort recently in the gasification and liquefaction of lignite. Liquefaction transforms lignite into liquid crude petroleum. Gasification plants transform lignite into natural gas products. The transformation process is very expensive, and with the current cost of other forms of fuel, it is economically impractical. However, if other fuels get too expensive, this could become a more economical process. Other research has been carried out scrutinizing other uses of lignite like a fertilizer in hydroponic plant growth.  Hydroponics is the use of nutrients containing water in place of soil for the growth of plant life.

The third phase included in the coal development is bituminous (soft coal) which is one of the two stages used as a fuel in producing electrical power. The fourth and the final phase outcomes in the formation of anthracite (hard coal). If anthracite coal is put under more heat and pressure, it would in the de course be compressed into a diamond.

• 4th Stage – Anthracite Coal

In this fourth stage in the coal formation, coal is formed due to the high pressure and high temperature for a long duration of time. It is hard, lustrous and has the greatest percentage of carbon among all the 4 coal types. This is also known as hard coal. Petroleum and natural gas deposits are generally found in the coastal areas.

Best Type of Coal

The best variety of coal is Anthracite It is also known as the hard coal and attained its name due to the compact carbon variety with a submetallic luster. It contains the greatest carbon content, minimal impurities, and massive energy density of all coal types, and is the top coals ranking. Moreover, anthracite is also the oldest variety of coal, having created from biomass that was buried 350 million years ago

Where is Coal Formed?

The energy in coal arises from energy stored in jumbo plants, which lived in wetland forests hundreds of millions of years ago, even before the dinosaurs! When those colossal plants and ferns perished, layers at the bottom of the swamps were formed. Water and soil started to amass around the remains of the dying vine.

You must have seen some holes or circular structures on the surface of the Moon or Mars. The same kind of holes or structures is also present on the Earth. In English, the simple meaning of this is hollow structures or dimples on the flat surface or in astronomy is a constellation.

This term has different meanings but generally, it is a bowl-shaped structure. In Ancient Greece, a large bowl was used for mixing wine which was called a crater. In Geomorphology or Physical Geography, it is a depression that can be found on the surface of any celestial object be it on the Earth or the Moon, etc. 

Most of these craters are formed because of the meteorites or volcanic activities or explosion of the bombs. Even the top of the volcano or its mouth is also known as a crater. The formation of the crater is very common and can be seen anywhere. Even in the flat painted wall, any small dimple will also be termed a crater. 

On this page, we will be talking about the concept of the crater which has different meanings as per different disciplines but majorly it is used in Geography/Geomorphology. We will learn what is a crater, define crater, features or types of craters, examples of craters on Earth along with important additional information which will solve a lot of questions about this concept. This topic will help you a lot whenever you talk about craters in Geography or Earth Sciences.

Features of Craters

Craters can have various distinct features. The floor is usually below the ground of the surrounding areas and generally either it is bowl-shaped or flat in nature. Sometimes central peaks are also seen in the craters which are formed in the central areas of the larger crater. Sometimes, the excavated crater collapses because it becomes so great and the material after the collapse of this leads to the formation of central peaks. 

If we talk about the interior of the crater, it usually has steep walls. Besides these, they also can have giant stair-like terraces that have been formed because of the slumping of walls. The edges of the crater are usually elevated as compared to the surrounding areas. It is also termed a rim. If we talk about ejecta, it is the material of the rock that is basically thrown out of the crater during the impact event and usually thrown out of the rim as debris of the crater on the surface of the planet. 

Crater Definition

Following are some of the definitions for a crater:

• “Crater is the round hole at the top of a volcano, or a hole in the ground similar to this” – Cambridge dictionary.

• “A crater is a very large hole in the ground, which has been caused by something hitting it or by an explosion.” – Collins dictionary.

• “Crater is the bowl-shaped depression around the orifice of a volcano or a depression formed by an impact (as of a meteorite) or a hole in the ground made by the explosion of a bomb or shell.” – Merriam-Webster

• “A crater is a bowl-shaped depression produced by the impact of a meteorite, volcanic activity, or an explosion.” – National Geographic

Simple and Complex Craters

There are different kinds of craters that can be seen. These are generally divided into these two categories. In the former category, they are small-sized and have smooth wall structure with a bowl-shaped appearance. Its size depends upon the planet. The latter are those large craters which are having complex features such as terraces, rings, central peaks, etc. The size of large impact craters is if more than 300 km then they are termed as impact basins. Among the following images, the left one is an example of a simple crater present on Mars whereas the right image is Copernicus which is an example of a large crater present on the Moon.

Meteorite Crater

These are the pieces of rocks that fall on the Earth from outer space. Some of them burn in the journey before reaching the Earth’s surface but some of them pass the atmosphere and reach the surface of the Earth because of which they create a huge depression on the ground. These kinds of the crater are most common on Mars or on the Moon or other planets as compared to the Earth because they usually burn out before reaching the surface of the Earth.

Volcanic Crater

It is a depression that is caused by volcanic activity in the ground and is circular. It is usually present at the top of the volcano which contains single or multiple vents. Magma erupts from this depression only and it is also deep sometimes. Sometimes at the top of the volcano, lakes are also found in these craters along with some vegetation as well.

Other Types of Craters

There are some other types of craters that can also be found that are described by the scientists:

• The craters in which, in addition to the main basin ring there are multiple basin rings of mountain chains ie. around 5 or 6 rings are surrounded.

• There are craters with irregular shapes whereas there are multiple impact craters that occur at the same time. Impact craters are nothing but meteorite craters.

• There are also craters found which have been eroded because of weathering activities.

• Usually, circular craters are found but elongated craters can occur when the impactor hits the surface at a very low angle, say less than 20°.

Craters on Earth

Different kinds of craters can be found on Earth as there are a number of volcanoes and even meteorites also sometimes reach the surface of the Earth and other types of craters can also be seen as they are one of the most common phenomena in the solar system. Some of the examples are given below:

Meteor Crater

It is also known as the Barringer crater which is present in Arizona with a diameter of 1300 meter and depth of 174 meters. Have a look at the depression of this:

Diamond Head Crater

It is one of the famous craters found on the Earth that formed because of volcanic activity. It is present in Hawaii and it is an example of a dormant volcano. 

Kelimutu Volcano

It is also famous for volcanic craters and thus is located in Indonesia at an elevation of 5,377 feet. This is more famous for crater lakes. Here, three acid lakes are found with different beautiful colours such as blue, dark green and red.

Fun Facts About Craters

• In Astronomy, a crater refers to a kind of constellation that appears like a cup and can be found between the constellations of Hydra and Corvus. The name of this constellation is inspired by the cup that was used to keep the wine in Ancient Greece. The diagram of the constellation is given below.

• Vredefort impact crater is one of the most famous craters found on the planet Earth and it is the oldest crater which is about 100 km larger present in Johannesburg in South Africa and formed almost over 2 billion years ago. It is not only the oldest but the largest recognised crater on the Earth. Originally, it is believed to be as large as 300 km but now has been eroded.

Additional Information

• The shapes and sizes of the craters along with the material excavated depend upon various distinct factors. For example, mass, the velocity of the impacting body, surface Geology, etc. If the speed of the impactor is faster then the formation of large craters usually occurs. Generally, objects from outer space hit the surface of the Earth with a speed of 20 km per second and this much speed leads to the occurrence of large craters. On the other hand, it also depends upon the size of the impactor as well. The larger size of the impactor when it hits the surface will create larger craters.

• Craters are very useful in understanding and determining the age of any planet or moon, etc. Scientists note down the size or shape, number of the craters and note how they are eroded, which helps in understanding their history. Usually, more impact craters can be found on older surfaces rather than younger surfaces. For example, the old surfaces of Mercury and Moon have a lot of impact craters. If we talk about the surface of the Earth, it is generally recycled by various geographical phenomena, thus there are few impact craters found.

• If we compare the Earth and the Moon, you will find more craters on the Moon as compared to the Earth. The first reason is the surface of the Moon ( almost 99% ) is older ie. around more than 3 billion years old whereas the surface of the Earth ( almost 80% ) is just 200 million years old. Another reason is there are erosional and weathering activities happening on the Earth which makes it harder to recognise the impact craters on the Earth whereas there is no such activity present, no atmosphere or no tectonic activities happening on the Moon.

Conclusion

Thus, to sum up we can say that a crater can be anything that has a bowl-like structure. It has different meanings in Science, Geography/Geomorphology, History, English, Astronomy, etc. Most commonly this word is used in Geography related to the depression that occurs because of volcanic activities or some object from outer space hits the Earth’s surface. There are different kinds of craters that can be found based on their features and geographic occurrence or conditions. This topic will help you in covering one of the important concepts and especially whenever you study volcanoes the meteorites in Science or Geography.

Before the evolution of life, Earth was a blurred place, a rocky globe with seas and a thin band of gases—mainly carbon dioxide, carbon monoxide, hydrogen sulfide, molecular nitrogen, and water vapour. Earth was a hostile and barren planet.

The biosphere is one of those thin layers of gas that supports life, by shielding the stratum of the Earth’s surface. The biosphere extends from a few kilometers into the atmosphere to the deeper in the sea vents of the ocean. This layer is a global ecosystem that is composed of living organisms like biota and the abiotic which are the nonliving factors that derive energy and nutrients.

The Efficiency of Solar Energy Utilization

Majorly the solar energy occurs at wavelengths that are unsuitable for the process of photosynthesis. The 98 and 99 percent of solar energy which reaches the Earth is reflected from the leaves and other surfaces and it gets absorbed by other molecules, which thereby gets converted to heat. So, we can estimate that only 1 to 2 percent is available for the plants which they capture eventually. The plant processing the photosynthesis process depends on the amount of light that reaches the leaves, it also depends on the temperature of the environment, and on the availability of water and other nutrients like phosphorus and nitrogen. The measurement is also included which indicates the rate at which the organisms convert the light energy (or the inorganic chemical energy) to the chemical energy of organic compounds, this is called the primary productivity. 

Thus, the total amount of energy that is being assimilated by the plants in an ecosystem during the process of photosynthesis varies in different environments. 

A major part of the energy that is assimilated by the plants through the process of photosynthesis is not stored as organic material, rather they are used in cellular respiration. This is the process where the organic compounds like carbohydrates, fats, and proteins are broken down, they get oxidized, in order to provide energy (in the form of ATP. The energy which is not being used in this process is stored in the tissue structure of the plant for further use and this is called net primary productivity.

Approximately about 40 – 85 percent of the gross primary productivity is not used during the process of respiration and thus, becomes net primary productivity. The highest net primary productivity in the terrestrial environments occurs in marshy lands, swamps, tropical rainforests. While the lowest occurs in the desert regions. In the aquatic environments, the highest net productivity happens in estuaries, reefs, and algal beds. These types of environments are critical for the maintenance of the world’s biological productivity.

Biosphere Efficiency of Solar Energy Utilization 

Viv Forbes – “Green energy is not so green after all. It reduces the supply of food, water, and energy available to all life on earth, and it often consumes large amounts of hydrocarbon energy for its manufacture, construction, maintenance, and backup.”

Our planet earth has three significant sources of energy, they are – Geothermal energy, combustible hydrocarbon minerals energy, and radiation or gravitational pull from the sun and moon energy.

The functioning of the biosphere is solely not dependent on the maintenance of the intimate interactions which are among the myriad species that are within the local communities but this is also on the loser yet the crucial interactions of all these species and communities living around the globe.

Our earth is covered with so many species and so many different kinds of communities, hence the populations have been able to adapt to any kind of environment on Earth through natural selection. Life-forms evolved who are able to survive in the ocean depths and even in the frigid conditions of Antarctica. Life forms are also existing in the near-boiling temperatures of geysers. The greatest richness of adaptations that are being found among the different populations and species of living organisms is the Earth’s greatest resource. This is a richness that has evolved over millions of years and this is quite irreplaceable.

In the process of photosynthesis, light energy gets absorbed by the chlorophyll molecules of the plants and this gets converted into carbon dioxide and water into carbohydrates and oxygen gas. The proteins, fats, nucleic acids, and other compounds also get synthesized during the process, this happens as long as the elements such as nitrogen, sulfur, and phosphorus are available here.

Worldwide Biological Productivity

Productivity is generally measured by an increase in biomass. World Biological Productivity is a term used to refer to the weight of all the living organisms living in an area. The Biomass is reported in grams or metric tons.

The effects of species richness on biological productivity are at an ecosystem level (which means inter-populational) or in the level of landscape-level (that is inter-ecosystemic) processes. This goes beyond the simple sorting of the species into their suitable portions with their own habitat. The contextual effects boost or reduce the productivity of the species that are occupying a given amount of habitat. 

Loreau and Hector in the year 2001, called the positive interspecific contextual effects “facilitation”. 

“Allelopathy” means the poisoning of one plant species by another, this is an example of a negative contextual effect. With this addition the processes occurring within ecosystems, and the interactions developing between the ecosystems (that is the landscape-level processes) it is conceivably and also affects the individual species’ productivity. For example, even more, diverse ecosystems resisted the invasion by the non-native species which is better than less diverse ecosystems. This depends on the way the invaders affect the productivity of the species which is already there.

The fluvial process is the physical interaction between the flowing water and the natural channels of flowing water such as rivers and streams. Such a fluvial process plays an essential and very significant role in the weathering of the land surfaces and the process causes the transportation which is known as fluvial transportation of the rock debris from higher to lower levels. Such fluvial transportation leads to the deposition and creation of landforms along the banks and at some distance from the edges of such flowing water bodies. 

Fluvial Processes and Its Effects

Most of the fluvial processes include the movement of the sediment as is clear from the fluvial processes definition. Such a movement of the sediments because of the flowing water causes erosion also known as fluvial erosion or deposition on the river bed which is a result of fluvial transportation. Thus, fluvial erosion meaning finds its basis in the fluvial processes definition. 

Fluvial erosion processes are carried out by the moving water mainly in two ways. The first manner in which the hydrology and fluvial geomorphology is determined is by the movement of water across the bed of the stream that exerts shear stress directly on the bed. If in some cases, the cohesive strength of the substrate is lower than the shear force exerted or there is a case in which the bed is formed of loose sediments that can be mobilized by such stress, then the steam bed will go low mainly because of the flow of clear water. But if the river maintains a significant quantity of sediment then the sediment material can act as a tool for the enhancement of the wearing of the bed. This process is known as abrasion. During this time, the fragments of the sediments themselves undergo weathering and the fragments become small and round which is known as attrition. Thus, both abrasion and attrition form a part in the determination of hydrology and the fluvial geomorphology.

Fluvial transportation of the river sediments is either caused by the bedload, which is formed by the coarse fragments that move close to the bed or are caused by the suspended load, which are the fine fragments carried with the flowing water. There is also some form of dissolved material that is flowing with the water in the river or stream affecting the stream geomorphology as well.

There is a specific velocity that is present for each grain of the sediment in proportion to its size. This velocity is known as the entertainment velocity which triggers it to move. There is no hard and fast rule that if the velocity of the sediment grain falls down below the entertainment velocity. The grain will continue to be transported by fluvial transportation processes such as the reduced or removed friction in-between the grains and the river bed. As the velocity decreases over time, eventually the sediment grain settles and gets deposited thus contributing to the hydrology and the fluvial geomorphology. 

As a river or stream moves continuously, it keeps on picking up and dropping solid particles of the rock and soil from the bed. It is observed that wherever the river flows towards the fast there is more possibility of the particles being picked up rather than being dropped while wherever the flow of water is slow, there is more possibility of the particles being dropped and deposited rather than being picked by the water. Thus, in this case, the rate of flow of the water determines the steam morphology. These areas where more such particles are dropped are known as alluvial plains or flood plains and the particles that are dropped are known as alluvium. Such alluvial deposits are also done by small streams but the most significant ones are the flood plains and the deltas of large rivers. 

Because of the fluvial erosion processes the amount of matter that is carried by the large rivers in enormous quantities. Because of such fluvial geography, the names of many rivers are derived from the colours that are obtained from the particles and matter moved by different types of fluvial erosion. An example of such an incident is the Huang He River in China which when translated means yellow river. Another one is the Mississippi River in the US which is also known as “the Big Muddy”. Another example, as given below in the image, is the White River in South Dakota which is known so because of the white colour derived from the sediments it carries.