Category: Geography Notes PPT

You must have seen extreme ecosystems at many places such as the forests which have an extreme variety of flora and fauna and on the other hand, there are deserts where very little flora and fauna are found. There is always a transitional zone between these two extreme ranges. These transitional zones are known by various names in the world and here in this article, we will be talking about one of them. In this article, we will cover what is a prairie and all the various related concepts so that you will be able to understand one of the most important concepts of the environment. Here, we will discuss this transitional zone in North America.

The grasslands mean a place that is covered with different kinds of grass which also includes small types of trees and shrubs. These are wild grasses and these grasslands serve as a transitional zone between the desert areas and the forest areas. They are kind of ecozones between these two ecosystems which have their own features, climate & weather, flora, and fauna, etc. Some of the famous grasslands of the world are the Pampas, the Prairies, the Velds, the Savannah, the Stepped, and the Downs. They can be divided into two major types i.e. Temperate and Tropical. 

Prairie Grassland

In different places of the world, the grasslands have named by different names which one is included is Prairie grasslands which is an example of temperate grasslands. It has emerged from the Rocky mountains. These types of grasslands are flat. It is a composition of grasses, herbs, and shrubs. These are normally tall and short. These are the grasslands which are referred to as golden wheat lands. The eastern regions have moisture whereas the western regions are much drier. These can be majorly divided into two types;

• Tall Grass Prairie: The regions of prairie which are having rich and fertile soil and receive moderate precipitation and where tall grasses are found which are over 5 feet in height.

• Short Grass Prairie: These are the areas with little precipitation and where short grass is found which are generally less than 2 feet and which are not suitable for agricultural purposes.

• Mixed Grass Prairie: This is a kind of prairie grass that serves as an ecotone between the above two grass types and it has more ecological diversity than the above-mentioned ones.

Location and Distribution in Map

• It is one of the major grasslands of the world.

• It is found in the continent of North America where it is distributed between the United States of America, Canada, and Mexico.

• It includes the areas of great plains as well as the wet and hilly land areas of the east.

• The Rocky Mountains are on the west whereas the Appalachian mountains are on the eastern side of these grasslands.

• It is a kind of major vegetation in North America and it covers almost 15% of the land area of this continent.

Features

Here we have the following features of the prairie grasslands:

• It is a region of flat, gently sloping, and hilly land.

• These grasslands formed around 8,000 years ago and they are one of the most recent developed ecosystems in the United States.

• There are no trees but at some places like near the lakes, Woodland can be found. Tall trees only reach up to the height of 2 meters.

• They also provide great habitat for the wild animals which are living there.

• There is no need for pesticides and any other chemicals because they can adapt themselves very well.

• They have a rich source of soil and there we can grow wheat and other crops.

• People also go for livestock and grazing here. 

• The most important and productive soils are black, dark grey, and dark brown soil found in the Aspen Parkland, tall grass as well as mixed-grass prairies.

• Bunchgrass Prairie can also be found here. Basically, it is a kind of grass that is found in bunches and found in the habitats of grasslands.

The Climate of Prairie Grassland

The climate of the grasslands is different according to the different types of places. The climate of the Prairie Grassland has the utmost temperature according to the region. It is present in the heart of the continent thus it experiences continental climate along with extreme temperatures. In the summer, a warm type of climate is found at 20°C and if there is winter then the temperature will reach up to – 20° C and also covered with snow during this season. It receives moderate rainfall which provides favourable conditions for this grassland. On the other hand, a local wind namely “Chinook” blows here. 

Vegetation

Let’s talk about the prairies vegetation:

• Tallgrass regions are completely cultivated with over 90% have been converted to crop production. The tall grasses include the big bluestem, the little bluestem, switchgrass as well as Indiangrass.

• About 75% of the areas of mixed-grass prairies are also diverted to cultivation or non-native species.

• The major crop found here is maize whereas potatoes, soybean, cotton, etc are the other crops.

• Naturally, this region is dominated by Speargrass, Wheatgrass as well as Blue Grama grass.

• The areas of lakes and wetlands are rich in vegetation. There are almost 1.6 to 7.1 million wetlands in the region of ecozone depending upon the different locations.

• Except in the eastern regions, some deciduous trees and shrubs are also grown in the ecozone regions.

• In the areas of water, willows, poplars, and alders trees can be found.

Prairie Animals

Various distinct types of animals are found here such as from large mammals to invertebrates. The various animals found here include bison, black-tailed jackrabbit, burrowing owl, American toad California condor, carrion beetle, common snipe, badger, black-footed ferret, coyote, deer, dragonfly, eagles, bumblebee, elk, ferruginous hawk, fox snake, golden owl, gopher snake, grasshopper, gray wolf, ground squirrels, etc. whereas the others are killdeer, monarch butterfly, northern grasshopper mouse, prairie chicken, prairie dog, prairie rattlesnake, prairie skink, pronghorn antelope, red fox, red-tailed hawk, lady beetle, larks, long-billed curlew, meadow vole, shrew, skunk, stink bug, tiger beetle, western tiger swallowtail, western meadowlark, white-tailed jackrabbit, and various others.

Among these animals, bison were hunted by the natives for food and clothing, and only 1000 species were left at the end of the 19th century and now it is no longer a keystone species here. If we talk about the Prairie dogs, they are not actually dogs but a squirrel which sounds like a dog’s bark and got their name because of this habitat.

Fires

• It is basically a naturally occurring event here and it also helps in maintaining its health.

• Vegetation found here in the prairies is actually adapted to warm temperatures and fires.

• They are important because it helps the grassland to become a forest and plays a vital role in the development of tall grass.

• Here, the fire can move at a speed of 600 feet per minute with around 700°F.

• These fires do not destroy the prairies but help in the renewal process of this grassland.

Did You Know?

There is National Prairie Day which is celebrated every year on the first Saturday of the month of June. This day of celebration was founded in 2016 by the National Prairie Foundation to spread awareness about the Prairie grasslands and for their protection, restoration as well as conservation.

Conclusion

Thus, to conclude we can say that grasslands have their own importance and equal distribution on the planet which serves as a transitional zone between two extreme ranges of deserts and forests and prairie is one of them which is a kind of temperate grassland that is found in North America and plays a great role in the geography of this continent. In this article we have comprehensively covered and learned what is a prairie and about prairie animals and vegetation, prairie grass, their temperature, and climatic conditions, etc. This article will surely help you in learning one of the most important grasslands of the world. You can learn the various features of other major grasslands as well that have been shown in the world map above.

Rhyolite is defined as an extrusive igneous rock with the maximum silica content. It is generally glassy or fine grain in texture but maybe porphyritic, consisting of large mineral crystals, known as phenocrysts. The rhyolite rock is predominantly composed of minerals like quartz, sanidine, and plagioclase. It is an extrusive rock similar to granite.

In 1860, the name rhyolite was introduced by German traveler and Geologist Ferdinand Von Richthofen from the Greek work “rhyax” (a stream of lava) and the rock name suffix – “lyte”.

Rhyolite Properties 

The table given below shows porphyritic Rhyolite physical properties.

Physical Properties

Rhyolite Texture

The porphyritic rhyolite texture is generally glassy or fine grain ( aphanitic), but maybe porphyritic, consisting of large mineral crystals (phenocryst). 

Rhyolite Composition

Rhyolite mineralogy composition  consisting of mostly quartz and feldspar with a total silica content of more than 68%. The percentage of quartz in porphyritic rhyolite may be as low as 10% but is generally more than 20%. Feldspar in rhyolite rock consists of 50%- 60%, with potassium feldspar consisting at least twice the amount of plagioclase feldspar.

The minerals cristobalite and tridymite in rhyolite are sometimes present along with the quartz. Biotite, augite, fayalite, and hornblende are common accessory minerals found in rhyolite rock.

Rhyolite Rock Type

Rhyolite is fine – grained extrusive igneous rock or volcanic rock. 

Rhyolite Uses

Rhyolite rock is used for different purposes starting from construction of bridges, roads, buildings to pot in the kitchen, as a gemstone or can be used for decorating your garden. Rhyolite use in the construction industry includes Arrowhead, building house or walls, like dimension stone, construction aggregate, for road aggregates, cutting tools, and knives. Rhyolite use in the medical industry is not yet defined. Some types of rocks have exceptional properties and can be used in the medical industry.

Rhyolite Metaphysical Properties

Rhyolite, often observed as a balancing stone is recommended to increase self-esteem, self-worth while helping to resolve the issues. It is a stone that is thought to facilitate change, variety, and progress while helping to tackle the challenges calmly. Rhyolite helps in achieving one’s goal and dream while strengthening the soul, body, and mind. The rhyolite has a strong connection with Earth. It is not a birthstone, but a zodiac stone of Aquarius, Gemini, and Saggitarius. 

Rhyolite Occurrence

The rhyolite rock has been found on islands far from lands. The rhyolite rock ocean occurrences are rare. 

Did You Know?

• Porphyritic rhyolite rock received its name from the German traveller and Geologist Ferdinand Von Richthofen.

• Rhyolite porphyritic magmas form highly viscous magma due to their higher content of silica and low content of iron and magnesium.

• Rhyolite that cools rapidly to grow crystals from a natural gas or vitrophyre or obsidian.

• Rhyolite formation generally takes place in continental or continental margin volcanic eruption where the granitic magma reaches the surface. The rock is rarely obtained during oceanic eruptions.

• The eruptions of magma may be highly explosive due to the sudden release of large amounts of trapped gas.

• The eruption not only obtains  rhyolite but also obtains obsidian, pumice, or tuff. They all have the same composition but different cooling conditions.

• Rhyolite porphyry is sometimes used as a crushed stone when other materials are not available.

• The percentage of silica content in rhyolite porphyry is generally between 60% to 77%.

• The countries in which rhyolite rock is found include  Germany, India, Iceland, and China, and the deposits that can be found near active or extinct volcanoes.

• Rhyolite is very rarely used in construction or manufacturing because it is highly fractured with too many cavities, though it can be used in cements.

• Gem deposits such as topaz, agte, beryl, jasper,and opal are sometimes present in rhyolite.

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

Why Do Seasons Change? 

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

Reasons 

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

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

How Do Seasons Change

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

• The Earth has a tilted axis 

• It revolved around the sun in 365 days approximately

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

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

Summer Solstice

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

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

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

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

Autumnal Equinox

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

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

Winter Solstice

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

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

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

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

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

Vernal Equinox

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

Did You Know

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

Silt is solid, dust-like sediment which is carried by wind or water or ice. Silt is composed of rock and mineral molecules that are bigger than clay but smaller than sand. Individual silt particles are so small that they are less likely to be seen with the naked eye. To be categorized as silt, a particle must be smaller than (.002 inches) across. Silt is most commonly found in soil, along with other kinds of sediment such as sand, clay and gravel. Silt sand or soil is slippery when wet, but not rocky or grainy. It is often referred to as fine silt because of being a non-plastic soil material.

             

Occurrence of Silt

Let’s see the three main processes that form silt:

1. Silt soil occurs when rock is weathered, or worn away, by water and ice. As flowing water carries tiny rock splinters, they scrape against the bottom and sides of stream beds, working away more rock.

2. The particles mince against each other, getting smaller and smaller until they become silt-size.

3. Glaciers can also weather away rock particles to form silt. Ultimately, wind can carry rock particles through a canyon or a landscape, thrusting the particles to grind against the canyon wall or one another.                                 

All three processes cause the formation of silt.

Soil and Its Different Types

Soil is formed by various particles such as clay, loam, humus, rock, gravel, sand and silt. Let’s discuss the types of soil in detail.

1. Sand

The widely used construction material, sand consists of particles of rock and hard minerals, like silicon dioxide. They are the biggest type of soil particles, where each particle is visible to plain sight. The large, comparatively stable sand-particle size enhances soil aeration, encourages drainage in tight soils and helps plants thrive or tilt.

When rubbed between the fingers, the larger particle sand size provides wet or dry sandy soil a grainy texture and even makes the soil crumbly and light when stuck together in your hand. The shape of sand particles is flat, rounded, elongated, angular, and subangular with a texture that is smooth, rough or polished.

2. Silt

Silt is a sediment substance with a size mediated between sand and clay. Transported by water during floods, the river silt creates a fertile deposit on the valley floor.

Being non-plastic or having low plasticity because of its fineness, silt soil allows it to be formed into balls or any desired shape when wet.

3. Clay

Finest of all the soil particles, clay measures less than 0.002 mm in size and is formed from the chemical decomposition of rocks. This fine-grained, cohesive soil glues together and creates a sticky texture when wet or dry.

Clay retains a high amount of water due to the spaces found between clay particles. Clay shrinks when getting dry but expands when in contact with water. Organic clay is extremely compressible and has very high strength when dry, which is why it is utilized in construction as mud mortar.

4. Loam

A mixture of clay, sand and silt is known to have to favour air circulation, water retention, drainage and fertility. These soils are greatly fertile, easy to work with and offer good drainage. Depending on their predominant constitution they can be either sandy or clay.

Black Silt  

Silt is granular soil whose mineral origin is quartz and feldspar. It is quite amazing to know that the fertile black river silt situated on the Nile river’s banks is a symbol of rebirth, linked with the Egyptian god Anubis.

Tank Silt

One of the silt types of soil, is fine soil transported from surface runoff during rainfall from catchment areas along with crop residue and is deposited as sediment in the tank water and decomposed over a period of time. Tank silt is believed to be rich in organic matter. However, the poor physical, chemical and biological property of the soil elevates the ill effects of climatic change, which substantially affects the rain-fed cropping.

Fun Facts

• Silt soil encourages air circulation and water retention.

• When there aren’t abundant trees, rocks, or other materials to prevent erosion, silt can accumulate quickly.

• The surplus of silt can also upset some ecosystems.

• The important and national symbol of India and Vietnam – Lotus plants have their roots in silty wetlands; however, their big, showy flowers blossom above water.

• Many species of frog lie torpid during the cold winters by embedding themselves in a layer of soft silt at the bottom of a pond or lake. Since the Water at the bottom does not freeze, and the silt renders some insulation, or warmth, for the animal.

• In some parts of the world, agriculture has blossomed in river deltas, where silt sediments are rich, and along the sides of rivers where annual floods freshen up silt.

• The Nile River Delta in Egypt is one classic example of a highly fertile area where farmers are harvesting crops for thousands of years utilizing river silt.

A very soft rock mostly consisting of the mineral Talc., also known as soapstone, is made up of hydrated magnesium silicate. It is simple to cut and has been used for carving since ancient times. Steatite is usually white, greyish green, brown, or, in extreme cases, red or black in colour. Bowls, boxes, and small items such as figurines, beads, seals, amulets, and scarabs were made from stones. Native steatite is so fragile that it can be scratched with a fingernail, but baking causes the stone to dehydrate and harden. Some ancient steatite carvings were glazed and fired, resulting in the formation of a mineral (enstatite) hard enough to scratch glass.

Steatite Formation

Steatite is typically formed at plate convergent boundaries. Periodites, serpentinites, and dunites are metamorphosed into soapstones in these areas of the Earth’s crust due to direct pressure and heat. It can also be produced by metasomatism, which is the alteration of dolostones by hot and chemically active fluids.

Composition

Its composition is determined by the parent rock material as well as the temperature/pressure conditions of its metamorphic climate. As a consequence, the physical properties of Steatite can differ from quarry to quarry, and even within a single rock unit. It is mostly talc with traces of chlorite and amphiboles (typically tremolite, anthophyllite, and cummingtonite) and traces of small iron-chromium oxide. It could be either schistose or huge. Metamorphism of ultramafic protoliths (such as dunite or serpentinite) and metasomatism of siliceous dolomites combine to form it.

Pure steatite consists of 63.37% silica, 31.88% magnesia, and 4.74% water. It usually contains smaller quantities of some other oxides like CaO or Al2O3.

Properties

Steatite is a low-cost material with excellent mechanical strength and a very low dielectric loss factor at high temperatures. Because of these characteristics, it is suitable for high frequency, low loss, and high voltage insulation. Furthermore, steatite is an excellent material for electrical engineering since it can be easily shaped into a wide range of shapes such as washers, bushings, resistor types, spaces, and beads.

Uses

We use rock steatite (also known as soapstone) for countertops, sinks, masonry heaters, flooring, and a variety of other architectural applications. Steatite is made up of many minerals, the most common of which is talc. Steatite, because of its additives, is tougher than talc and more ideal for the aforementioned applications. In its initial state, steatite only comes in grey shades, as opposed to talc, which comes in a number of colours.

This naturally quarried stone is softer than most other minerals found in nature. Soapstone, despite its softness, is a very dense (non-porous) stone, denser than marble, slate, limestone, and even granite. Since soapstone is impenetrable, it will not stain and will not allow liquid to permeate its surface. Other stones, such as granite, are prone to soiling, which is why soapstone (steatite) is commonly used in chemistry lab countertops and acid rooms. Steatite has long been used in large-scale industrial processes, consumer electronics, aerospace and automotive applications, and advanced electro-technical instruments such as cathode-ray tubes.

Inlaid patterns, sculpture, coasters, and kitchen countertops and sinks are all made from soapstone. Soapstone is frequently used in traditional Inuit carvings, and some Native American groups made bowls, cooking slabs, and other artefacts from it, especially during the Late Archaic archaeological era. Soapstone is often used for fireplace surrounds and woodstoves because it absorbs and distributes heat evenly while being simple to make. This is a popular feature in many upscale Alaskan homes. Griddles and other cookware are also made from it. Soapstone has been used as a soft medium for carving in India for decades, but global demand for soapstone is threatening the habitat of India’s tigers. Soapstone was used to construct the temples of the Hoysala Empire.

Steatite Manufacturing at Harappa

Steatite (soapstone) objects have been discovered at almost every excavated Harappan (2600-1900 BC) site and were also primary elements used to make seals. The Indus peoples used valuable ornaments and decorations made of steatite and faience as symbols of status and prosperity. The seals and tablets were even more significant because elites used them to legitimise and strengthen their political, economic, and ritual influence. Because of the importance of these artefacts to the Indus people, it is important to understand who was in charge of their production and how they were produced.

Overview of Applications

• Heating factor supports

• Insulators for electricals

• Stand-off insulators 

• Insulators for lighting (supports, bases, etc.)

• Spacers

• Insulating washers for bushings

Conclusion

Steatite is a magnesium silicate composite that has been used as an insulator or enclosure for electrical components for several decades. It has also been used in a variety of appliance, aerospace, and automotive applications where moderate power, low cost, and good electrical resistance are needed. Since this ceramic material can be moulded into complex shapes prior to sintering, it has found widespread use in a wide range of applications. In addition to the traditional formulation, the substance is also available in a Low Loss and White version.

A solstice is an event where a planet’s poles are extremely inclined towards or away from the star, it orbits around. On earth, solstices are defined by a solar declination or the latitude of the Earth where the sun stands directly overhead the moon. Solstices are phenomena that happen twice yearly, on earth where solar declination reaches the Tropic of Cancer and the Tropic of Capricorn in the north and south, respectively. The summer solstice happens two times during a year. Once, it happens when the path of the Sun is farthest north in the sky in the Northern Hemisphere (June 20 or 21). It happens the second time when the path of the Sun is farthest south in the sky in the Southern Hemisphere (December 21 or 22).

During Summer Solstice in the sky, the Sun travels the longest distance and the daylight is maximum that day. When the solstice happens in the Northern Hemisphere, the North Pole is tilted for about 23.4 degrees towards the Sun. Due to this, the Sun’s rays are slightly shifted from the Equator towards the north by the same amount it is tilted. During that time, the vertical noon rays stand directly overhead the Tropic of Cancer. 

When the second solstice happens six months later, the South Pole is inclined towards the Sun by about 23.4 degrees. This day, when the summer solstice happens over the Southern Hemisphere, the Sun’s vertical rays overhead move towards the southernmost position near the Tropic of Capricorn. 

What is Summer Solstice Definition Astronomy?

There are few astronomical definitions and explanations of the season according to the planetary position. According to the season’s astronomical definition, the summer solstice marks the beginning of the summer season. It lasts till 22nd or 23rd September in the Northern Hemisphere, or 20th or 21st March in the Southern Hemisphere, until the autumnal equinox. In Scandinavia, Midsummer’s Eve is celebrated during the summer solstice which is evidence of the fact that this day is celebrated in a lot of cultures. 

Many cultures around the world celebrate the longest day and shortest night of the year, which is the summer solstice. This day is traditionally celebrated throughout the world across cultures with festivals and bonfires. 

When Earth reaches a point in its orbit around the North Pole where it is angled closest to the sun, Astronomers are able to calculate the exact moment of solstice. Six months from this time, the sun will reach the southernmost point and pass overhead the Tropic of Capricorn. During this time the people in the Northern Hemisphere are going to experience the shortest days of the year, in their winter solstice. 

The sun’s angle in relation to the Earth’s equator moves gradually so close to the solstices that the shift is difficult to detect for about 10 days without any technical instruments. “Solar standstill” is the origin of the word ‘solstice’, due to the unique position of the Sun. 

The Earth’s atmosphere bends some amount of light over the horizon depending on the present weather. This phenomenon can introduce some changes of more than one minute to sunrise and sunset times. The calculation of the minutes done here is an approximation. The slow shift of the sun’s angle to the Earth’s equator means that 20th June is about a second longer than 19th June at the mid-northern latitudes. 

Solved Examples

Q1. When Does Summer Solstice Occur During the Year?

Answer: In the Northern Hemisphere, the summer solstice occurs on 20th or 21st June and in the Southern Hemisphere it occurs on 21st or 22nd December. 

Q2. Why is the Summer Solstice Important?

Answer: Most of the daylight is received by the Northern Hemisphere than any other day during the summer solstice. Apart from that, it also marks the beginning of the summer season, according to the astronomical definition.