Category: Geography Notes PPT

Before getting into the intricacies of Mercator projection, let us understand what is map projection. A map projection is one of the numerous methods to represent the 3-dimensional surface of the earth on a 2-dimensional plane in Cartography. It is a way to flatten a globe’s surface into a plane to make a map. This conversion requires a systematic transformation of the latitudes and longitudes from a particular location of the world on a plane. All projections of a sphere on a sheet distort the surface in some way or the other. Depending on the map’s purpose, some of the distortions are acceptable, and others are not. The primary mercator meaning of map projections is to preserve some of the original sphere-like properties at the expense of others. The study of map projections is the examination of the distortions.

What is a Mercator Projection?

The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer – Gerardus Mercator – in 1569. Now, you may ask what a cylindrical map projection is. In Cartography, any map projection of the terrestrial sphere done on the surface of a cylinder unrolled as a plane is known as a cylindrical projection. Mercator projection became the standard projection for navigation due to its ability to conserve lines of constant course; that is, it represents the north as up and south as down everywhere while preserving local directions and shapes. The Mercator projection is derived mathematically. The meridians are equally spaced vertical lines, and the latitudes are parallel horizontal straight lines that are spaced farther apart as the distance from the Equator increases.

The prime detriment of the Mercator projection is that it inflates the size of objects away from the Equator. The inflation is minuscule near the Equator and increases latitude, and becomes infinite at the poles. The result of such distortion is that areas like Greenland and Antarctica appear much more extensive than they are. For example, on a Mercator projection, the landmass of Greenland appears greater than that of the continent of South America; although, Greenland is even smaller than the Arabian Peninsula.

The Working of Mercator Projection

You can understand the construction of the Mercator projection by taking a cylinder with a globe inside. You should light up the globe from within so that you can project an image of the earth on the surrounding cylinder. As the cylinder only touches the globe at the Equator, the parallels along that specific region are entirely accurate. Furthermore, as the cylinder is perpendicular to the globe, the lines of longitudes and latitudes appear straight instead of curved lines when transferred to the cylinder. 

We can imagine the Mercator chart as a small section peeled from the cylinder and laid flat. The Mercator chart is mathematically constructed, which means that the distance representing the spacing between meridians and parallels is numerically derived.

The graticule transferred on to the cylinder has a consistent 90-degree angle between the parallels and meridians. Thus, the rhumb lines are also straight on the Mercator projection.

Uses of Mercator Projection

1. The Mercator projection is significant for navigation, and almost every marine chart is based on it.

2. Street mapping services such as Google Maps, Bing Maps, MapQuest, etc., use a Mercator called Web Mercator for their map images.

3. Mercator projections were vital for the mathematical development of plate tectonics during the 1960s.

Critique of the Mercator Projection

Owing to its expansive land distortions, many consider Mercator projection unsuitable for use in world maps. However, on account of its common usage, the Mercator projection has influenced people’s view of the world. Since it shows countries near the Equator as too small compared to Europe and North America, it has compelled people to consider those small countries as less critical. As a result, modern atlases no longer use the Mercator projection for world maps or areas far away from the Equator. Mercator projections, currently, are found in maps of time zones.

Conclusion

The topic of Mercator projection may seem very tricky to grasp. However, the concept does get manageable with thorough understanding, regularly solving questions and numerical, practising papers and proper revision. Before understanding the whole idea, we must grasp the basics of map projections and then move to Mercator. Past years’ question papers, along with ‘s concept pages, are the perfect companions to guide you through the journey of absorbing knowledge.

Facts About Mercator Projection

• The parallels and meridians on the Mercator are straight and perpendicular to one another. This phenomenon is typical among all cylindrical projections.

• The Mercator is a conformal map projection which means that the angles around all locations are preserved.

• All latitudes beyond 70 degrees north or south of the Mercator projection are unusable as the linear scale becomes infinitely large at the poles.

• A Mercator map can fully show the polar areas.

• The two features of a Mercator map – conformality and straight rhumb lines – make the projection uniquely appropriate for navigation.

• The Mercator projection was the most commonly used projection for world maps during the 19th and 20th centuries.

You must have visited the mountain regions or the hill stations for your holidays to enjoy the beautiful natural scenery and the smooth and relaxing weather of that region. The mountain regions matter a lot for especially those people who live in the hot climate regions and these mountain regions are considered as the perfect escape from those hot regions. In this article, we will be talking about one of the major landforms, the Mountains. We will learn about the rocky mountain landform’s meaning, definition, features, types and how they are formed, and other related concepts. This article will help you to cover one of the important topics of Geography of major landforms of the Earth and will help you in your studies as well.

Mountain Landform Definition and Meaning

It is one of the most important physical features of the Earth. It is a natural elevation due to various factors of the Earth and this elevation is higher than the surrounding areas. It can have a narrow shape at the top and a broader shape at the bottom. They can be of conical shapes or rounded figures. Temperature goes on decreasing with their heights and they are generally covered with snow. When a number of mountains are arranged in a line, then that landform is termed as mountain range landform.

As per the Cambridge dictionary, “mountain means a raised part of the Earth’s surface, much larger than a hill, the top of which might be covered in snow.”

Types of Mountain Landforms and Their Formation

The various types of mountain landforms and how they are formed is mentioned below:

Volcanic Mountain

These are the mountains that are formed because of volcanic activity. When the lava comes out at the surface through a crack in the earth called a vent and starts piling up around this vent, then after some time it takes the shape of a mountain with a conical shape. There can be different types of volcanic mountains such as,

• Shield volcanoes are those which are not too steep and lava usually flows up to a large distance. These are considered the largest of all the volcanoes.

• Cinder Volcanoes are those which are having a steep slope and a crater on the top. In this type of volcano, the lava blasts out explosively.

• Composite volcanoes are those in which there are one or more vents and lava gets collected in the form of layers over layers.

• Caldera is a kind of volcano in which a sudden volcanic eruption happens.

Fold Mountains

When two continental plates move towards each other and the rocks or debris etc. Start folding into a structure which leads to the formation of fold mountains. These are formed through an orogeny process which takes several years. These mountains are formed at convergent plate boundaries or continental collision zones or compression zones. The stress in these zones due to move towards each other leads to mountain formation. For example, the world-famous mountain ranges, the Himalayas, the Andes, the Alps are examples of fold mountains.

These kinds of mountains have rounded features and have low elevation because of denudation and are 500 million years old. Examples: Laurentian mountains, Algoman, etc.

Earlier these mountains were also very high but due to erosion, they have now rounded features with medium elevation. Their origin belongs to the territory period.

Examples, the Appalachians, the Aravallis, etc.

They belong to the territory period. They have high conical peaks and rugged relief. Examples, the Himalayas, the Andes, the Rockies, etc.

Block Mountains

These are the Mountains that are formed because of the faults in the Earth at a large scale and when large pieces or blocks of the Earth get displaced horizontally or vertically. They are formed when two tectonic plates go away from each other, leading to faulting in Earth and these are also called fault-block mountains. It can be seen in the following diagram that how they are formed. The uplifted part is called horst and the lower part is called graben. The formation of rift valleys is being seen between the block mountains. An example of it is the Eastern African Rift valley. 

These mountains are formed when the central part moves downwards and forms a rift valley but sometimes the central part remains the same and the surrounding sides subside which leads to Plateau formation.

Dome Mountains

Magma when reaching the surface we see a volcano but when it does not crack the surface and just pushes the rocks to create rounded swelling and when this magma cools with time, the hard rock will look like a dome. They are not as high as fold mountains. For example, Half dome mountain, Sierra Nevada Range, California. They are also not so easy to identify and usually, satellites are used to identify rounded structures.

Uses of Mountains

• They provide shelter to around 12% of the total population of the world.

• They are a great source of fresh water and many rivers generally originate from the mountains.

• They also support varieties of flora and fauna in the regions.

• The presence of the flora and fauna in the mountain regions varies and depends on the different locations.

• Several hill stations are also found here which attracts a large number of tourists and is a great source of income for that region. 

• It plays a vital role for mountaineers and rock climbers. People usually visit mountain regions for trekking and camping purposes as well.

Did you know?

• There are mountains under and above sea levels.

• Their heights are notes as per the height above the sea level.

• This mountain landform covers about 1/5th of the landscape of the Earth.

• They are sources of freshwater, recreation activities, livelihood, vegetation, and wildlife, etc.

• The Olympus Mons and Mount Everest are the highest mountains of the whole solar system and Earth respectively.

• The blue ridge mountains landforms are one of the most famous mountains in the world because of their blue appearance.

Conclusion:

Thus, in this article, we have covered one of the major landforms, the Mountains. These are the naturally elevated landforms of the earth. We have learned rocky mountain landforms, types of mountain landforms, their various features, highlands landforms, etc. This article will help you to understand one of the important landforms of the Earth and this will help you in studying landforms in Geography and Earth science. These notes will be helpful for students of Class 9 or upper classes. These will also increase your knowledge about mountains and how they are formed. You can find out more interesting articles on various subjects on our website which are written by subject matter experts to help you in your studies.

We have read about the old and young rocky mountains landforms, let’s practice some FAQs related to it:

Opal is naturally found in a white coloured semi-precious gemstone composed of a silicate mineral family recognized for its marvellous ‘play of colours’. This astrological alternative of precious diamond is worn for gaining success in innovative pursuits, lavish lifestyle, social/financial prominence, matrimonial harmony and good health. Over thousands of years, people have quarried and treasured opals. These striking opal stones have energized a rich body of folklore. (Thus, opal gemstones have been considered both the luckiest and unluckiest stones one can wear).

          

Factual Information About Opal Gemstone

Assembled Opal Gems

A triplet from assembled opal gems adds a transparent quartz cap and makes for a  good opal stone ring and opal earrings, since the hard quartz keeps the softer opal from scratching.

How to Determine Synthetic Opals?

Synthetic or lab-created opals are actually the real opals, but they’re grown in laboratories rather than yellowish-brown underground. They encounter the same formation processes, only at a stimulated rate in controlled settings.

Synthetic opals may exhibit an intense display of colour, generally in a mosaic pattern. With high magnification and backlighting, you can find a scale-like, snake skin or chicken wire structure in the pattern. When put under high magnification with transmitted light, synthetics may display a dendritic structure. Synthetic opals don’t phosphoresce (sparkle or twinkle) and may also stick to the tongue.

How to Detect Fake or Imitation Opal Gems?

Contrary to lab-created opals, imitations only simulate the physical look of opals. These imitations are essentially made from glass or plastic.

Plastic imitations or stimulants are soft and can be dissected with a sharp needle. They do not sparkle or twinkle (phosphoresce).

Glass stimulants essentially consist of glass bubbles and swirl marks. They also do not phosphoresce. Their refractive index (RI) and specific gravity (SG) are also generally higher than natural opal.

Care For Opal Stones

Nowadays, used frequently as opal necklace, opal rings and other opal jewellery, extra care of the delicate gemstone is well worth it. Highly sensitive to changes in temperature as well as a “crazing”, that implies they can easily form cracks or “craze” as they dehydrate, and must be kept cautiously.

Opals kept in water must be dried properly and cautiously before cutting.

Sometimes opals in rings can become chalky white and weary. This may owe to a network of scratches on the opal surface that dismantle the polish and dulls the colour play. However, a simple re-polishing can generally correct this. Having a hardness of only 5.5 makes them quite susceptible to scratching. Opals are thus usually not recommended for ring stones, unless the stone is positioned in a protective setting or a triplet for occasional wear.

Opal Stone Facts and Information

• Opal stone is sedimentary.

• Many ancient references to opal may actually indicate other gems, such as the iridescent iris agate.

• Under proper conditions, water seeps through the earth, becoming affluent in dissolved silicates. When water makes way through a cavity, it accumulates the silicates as microscopic spheres, forming opals.

Phyllite is a foliated metamorphic rock that is primarily composed of quartz, mica, chlorite, and sericite. The Phyllite rock is formed by the slate that is further metamorphosed so that the coarse-grained mica attain a preferred accommodation. The word Phyllite is derived from the Greek phyllon meaning “ leaf”. 

Phyllite metamorphic rock has an excellent tendency to split into the sheets and is generally black to grey or light greenish-grey. The appearance of the rock is commonly crinkled or wavy.  The Phyllite rock is commonly found in Dalradian metasediments of northwest Arran. The Tretorn phyllites rock and Woolgarden phyllites rock are found in North Cornwall.

Phyllite Properties

The Table Given Below Shows the Phyllite Mineral Composition

Phyllite Mineral Composition

Phyllite Composition

According to the Phyllite Composition Table Given Above, We Can Say:

• Phyllite has a coarse grain of mica such as Sericite and Muscovite.

• Phyllite includes almost half the amount of quartz mineral in its composition.

• Quartz and feldspar are found in large quantities in phyllite.

• Crystals of ratile, cordierite, andalusite, staurolite, and garnet are also found in phyllite.

• Large crystals or porphyroblast are found in the horizontal axis in phyllite.

• Organic minerals are metamorphosed into graphite and give phyllite black to dark colour shades and submetallic luster.

Phyllite Uses

Phyllite is a soft and durable metamorphic rock. It is often used as a floor tile, decorative aggregates, and decorative stone in counterparts. It is also used as an exterior building, or facing stone, and garden decoration. The other phyllite uses include commemorative tablets, cemetery markers, writing tablets, etc.  The slabs of Phyllite are often trimmed and used as a landscape, paving, or sidewalk stone. 

Phyllite Parent Rock

The phyllite parent rocks are shale, pelite, or slate which further comes from a shale protolith. Shale can be transformed into schist, slate or genesis depending on the degree of heat and temperature. 

Similar to slate, phyllite has a typical texture known as phyllitic sheen and has the feasibility or tendency to split into sheets like slate rocks.

Phyllite Rock Formation

The phyllite rock forms when Slate rock further transformation occurs, and very coarse grain mica attains perfect orientation.

• The slate rock consists of clay minerals in a semi-random orientation.

• When the slate rocks are buried further and attain a high temperature, the extremely fine clay transforms into mica and the flacks of clay minerals gain a horizontal positioning.

• The chemical reactions and heat transform clay mineral grain into chlorine or mica minerals. They are enlarged forms of coarse-grain clay flakes.

• Hence, they form phyllite rock. 

• Further metamorphosis and sedimentation process transform Phyllite into Schist, and then Geiss by enlarging mica flakes.

Where is Phyllite Rock Found?

Phyllite rock is found throughout the world  in many regions such as:

Did You Know?

• Large crystals or porphyroblasts are found in phyllite rock in parallel orientation.

• Organic minerals metamorphosed into graphite and give phyllite a black to dark grey shades that give it a submetallic luster.

• Phyllites are most commonly found in the Dalradian metasediments of northwest Arran.

• Quartz and feldspar are found in large quantities in phyllite.

• Phyllite has a good tendency to split into sheets.

• Fine grains of mica minerals such as Muscovite and sericite are also found in phyllite

• Tredorn Phyllite and Woolgarden phyllites are found in North Cornwall.

Pumice is a volcanic rock, which in powdered or dust form is called ‘pumice.  This rock has a feature of a highly vesicular rough-textured volcanic glass, which might contain crystals. The rock has a typical light-colored context. There is another volcanic rock known as Scoria which is different from this Pumice rock, the Scoria rock has larger vessels, thicker vesicle walls, and also it is darker in color and denser inconsistency.

Pumice is created when the rock is super-heated. The rock is formed in highly pressurized conditions, being violently ejected from the volcano. While due to simultaneous rapid cooling and rapid depressurization the rock gets its unusual foamy configuration.  

Pumice Rock

Pumice is a very light and porous volcanic rock that forms during the explosive eruptions of the volcano. During the volcanic eruption, the volcanic gases dissolve in the liquid portion of viscous magma, and then it expands very rapidly to create a foam or a froth. The liquid part of the rock is called the froth which quickly solidifies to glass around the gas bubbles. The volume of the gas bubbles present in this rock is generally so large that the rock is lighter than water and thus it floats in water. 

Pumice is a textural term for a type of volcanic rock which is a solidified frothy lava that is composed of highly microvesicular glass pyroclastic with very thin, this is translucent bubble walls of extrusive igneous rock. This is commonly, but not exclusively of a silicic or felsic to an intermediate in composition (e.g., rhyolitic, dacitic, andesite, Pantelleria, phonolite, trachyte), but the occurrences of this basaltic and other compositions are also known. The pumice is pale in color while ranging from white color or cream color or greyish in shade, also they can be green-brown or black. The rocks form when the gases exsolving from the viscous magma which nucleate the bubbles and cannot readily decouple from the viscous magma after chilling into the glass. Pumice is also a common product of explosive eruptions (Plinian and ignimbrite-forming) this commonly forms zones in the upper parts of silicic lavas. The Pumice has an average porosity of about 90%, and initially, the rock floats on water.

Pumice Uses 

• Pumice is an important rock for the industrial mine industries which is used to produce superior-quality cement and a lightweight, isolating for the building materials.

• Pumice is a very light weighted porous and abrasive material that has been used for quite a few centuries in the construction and the beauty industry as well as in early medicine. 

• This is also used as an abrasive, in polishes, or the pencil erasers, and the production of stone-washed jeans.

• This is abrasive in conditioning the “stonewashed” denim.

• This rock is an abrasive in the bar and liquid soaps such as the “Lava Soap”

• Works as an abrasive in pencil erasers.

• The rock is abrasive in skin exfoliating products.

• It works fine in the abrasive used for polishing.

• Also used in a traction material on snow-covered roads.

• A traction enhancer in the tire rubber.

Pumice Stone Meaning 

A pumice stone is a piece of pumice that is used in rubbing over the skin to clean the skin or make it even or smoother. Also, the term ‘pumice’ is an uncountable noun.

Pumice is a type of grey stone that is formed from a volcanic eruption and this is very lighter in weight which can be rubbed over the surfaces mainly the skin which is required to make it smoother.  

Is Pumice a Igneous Rock?

Pumice is a kind of igneous rock with a foamy texture. The name is derived from the Latin word which is “Pemex” this means “foam” and being evident of history this has been given many other names for its formation was unclear. In earlier times it was called “Spuma Maris”, which means froth of the sea in Latin word, as it was a frothy material that was thought to be a hardened sea foam. 

The hydrosphere is the total amount of water present on Earth. The water from water bodies such as lakes, seas and rivers, oceans, the water present under the ground and the water from the air, everything is included in the hydrosphere river and ocean waters. This water can be of any form – solid (in the form of ice), liquid or gas (vapours). The solid water is present in the form of ice sheets, glaciers and icebergs. Liquid water is present in the water bodies such as lakes, river and ocean waters. There is also groundwater which is in liquid form. The gaseous form of water can be found in the form of clouds and fogs.

River and Ocean Waters

Rivers are naturally flowing water bodies, generally freshwater bodies that flow towards another river lake and ocean. The rivers have a starting point from where it starts flowing. This starting point is known as the headwater. This starting point or headwater can be from a snow melting point or rainfall or a bubble up from groundwater or a lake or a pond. The other end of the river is called its mouth. The river empties into a river stream sea ocean through this mouth. 

Composition of Ocean Waters

The seawater is more uniform in composition with respect to the river water. Seawater has 3.5% of dissolved salts in it whereas river water has only 0.012% of dissolved salts. If we calculate the average density, the world’s ocean is approximately 2.75% denser than river water. 

Of the average of 35 parts per 1000 salts of the seawater, 30 parts are sodium and chlorine and 4 parts are magnesium and sulphate. The remaining 1 part of the saline water is constituted with 0.4 part of calcium and potassium each and 0.15 part of the carbon in the form of carbonate and bicarbonate. Along with these elements, the other nutrients found in the ocean or seawater are phosphorus, nitrogen and silicon.

Composition of River Waters

The water flowing in the rivers is freshwater. It contains less than 1% salt. In this 1% salt, 58 parts are carbon in the form of bicarbonate, 39 parts are calcium, sulfur in the form of Sulphate and silicone as dissolved monomeric silicic acid. The remaining 3 parts are chlorine, sodium and magnesium. 

Stream and Lake Waters

Lake waters contribute a small percentage of water in the hydrosphere but it is an important source of freshwater. The lake and stream waters are used for household purposes, agricultural purposes and also for industrial purposes. The composition of stream and lake water varies from place to place and season to season. The main source of the dissolved minerals of the stream and lake waters are the rocks through which this water flows. When slightly acidic water hits the rocks, the minerals start dissolving in them. Another factor affecting the composition of stream and lake water is biomass. The biomass helps in neutralizing the pH of the precipitation. Any biological activity in the stream or lake like photosynthesis can change the pH and dissolved oxygen content. Temperature also influences the number of dissolved gases in the water.

The composition of lake water is influenced by evaporation. When the water evaporates, the dissolved minerals are left behind. The more the evaporation will be, the more will be the concentration of dissolved minerals. And if the evaporation continues, minerals such as calcite (CaCO3) and gypsum (CaSO4.2H2O) can precipitate from the solution. 

Ground Water

The factors that influence the surface water such as river lake and ocean, sea, pond water also influence the groundwater. The groundwater is always in contact with the rocks. But they move slowly as compared to the surface waters. The surface water may move at a speed of a few kilometres per hour while the groundwater moves a few centimetres in a day.  As a result of this slow movement, the groundwater contains more minerals than the surface water. 

The composition of groundwater is influenced by the geological materials through which the water passes, the types of reactions taking place and the contact time. The contact time may be a few days to 10,000 years. 

Generally, the groundwater has a total dissolved solids content of less than 250 mg/L. But in some areas, groundwater with a total dissolved solid content of greater than 100000 mg/L has been found. This saline groundwater is found in marine sedimentary rocks and also in ancient metamorphic and igneous rocks. Saline groundwater is formed by the three ways –