Category: Geography Notes PPT

Sea level is the base level considered for measuring the elevation and depth on our planet Earth. Sea level is the position of the air-sea interface. The ocean is a continuous body of water and its surface tends to seek the same level throughout the world. But, various factors such as winds, currents, river discharges, and variations in gravity and temperature, prevent the sea surface from being at a true level. Sea levels are measured in relation to the adjacent land. Just like the oceans, the land elevation also rises and falls over time. 

Image: The graph portrays the sea-level changes since 1880

Sea Level Rise or Sea Level Change

Sea level rise is the increase in the sea level or ocean levels due to global warming. Two factors related to global warming are the primary cause of sea-level rise – the melting of ice sheets and glaciers and the expansion of seawater when it warms. Pollution is one of the main causes of global warming as carbon dioxide and other heat-trapping gases are released in the process into the atmosphere. The oceans absorb most of this heat and the ocean water becomes warmer. As a result, the ocean starts expanding, there is rising water and there is a rise in sea level. 

The glaciers and the ice sheets present in the land are also affected by global warming. Regions such as Greenland and Antarctica are covered with ice that melts in the summer (or warmer weather) and is again replenished in the winter. With an unexpected rise in temperature over the globe, these glaciers and ice sheets are experiencing a disproportionate amount of melting, and that too at a rapid rate.

Consequences of Sea Level Rise

The sea-level rise or the ocean rising is a serious threat to life on earth. Life along the coasts is at a greater threat. As the sea level rises, there could be flooding, storm surges, and heavy damage to the coastal areas. The people and the wildlife around the coasts can be displaced from their homes. The rising sea levels can contaminate the soil and the groundwater with its salt. 

Mean Sea Level

Mean sea level is the average height of the sea. It is the average level of the surface of a water body (mainly oceans) from which the heights (elevation) may be measured. Mean sea level is calculated as the average height of the sea over longer periods of time (months or years) and the shorter periods of time of tides and storm surges. The absolute mean sea level reflects the change in sea height and the relative mean sea level rise reflects the change in sea height and changes in the level of the land at a local scale. 

The changes in sea level are caused by factors such as changes in water volume and by variations in the shape of oceanic basins over geological time scales. The main factors that cause the increase in the volume of the ocean are:

• Melting of ice sources that are on lands such as glaciers, ice caps, and ice sheets of Greenland and Antarctica.

• The thermal expansion of seawater when it’s heated up. 

• When the water storage on land changes.

Vertical land movements are a result of natural geological and anthropogenic processes. Natural geological processes include tectonic movements and the glacial isostatic adjustment. Anthropogenic processes result in subsidence. 

Eustatic and Relative Sea-Level Changes

In Eustatic sea-level change, Eustatic came from the word “eustasy” which was coined by the Austrian geologist Edward Suess in the year 1888. It is derived from the ancient Greek words “eu” meaning well and “statikos” meaning static. As per Suess, change(rise) in ocean level and melting of ice sheets will result in global uniform mean sea level rise (change). Both mean sea level rise and solid earth surface, move vertically together and contribute to the uneven topographic and bathymetric variations. These factors which change the sea levels are called relative as the land and the ocean move together and with respect to each other. The sea-level change that is observed with respect to the land-based reference frame is the relative sea-level change.

The reconstruction of eustatic sea level at different time scales is used to study the melting of glaciers and ice sheets (mainly the ice) and the warming of water masses. The relative sea-level change is used to investigate regional or local processes. 

In Geology, Sill, also known as a sheet, is a flat intrusion of igneous rock that forms between the preliminary layers of rocks and has a large horizontal extent when compared with its thickness. To define sill, let us understand that it is a concordant intrusive sheet. This implies that it does not cut across preliminary rock beds. Sills can often resemble volcanic flows that were interspersed with the sedimentary unit. 

Sill Rock Meaning

Before learning what is a sill, let us understand the meaning of sill rock. A sill is a flat sheet-like igneous rock mass that is formed when magma intrudes into between the older layers of rocks and crystallizes. Sills can form from magma with a range of silica contents. 

A renowned example of the sill is the tabular mass of quartz trachyte found near the summit of Engineer Mountain near Silverton, Colorado.

What is a Sill?

A sill is a tabular sheet intrusion that is formed between the older layers of sedimentary rocks, beds of volcanic lava or tuff, along the direction of foliation in metamorphic rocks. Sills occur in parallel to the bedding of other rocks that surround them, and though they may have vertical to horizontal orientation, horizontal sills are most commonly found. Sills may weigh a fraction of an inch to hundreds of feet thick and up to hundreds of miles long. 

The rock compositions of different types are found in sills. The famous basic sills get much attention for the knowledge they provide related to the crystallization behavior of molten magmas.

Sills are split based on the number of intrusions that are formed and the variability of the types of rocks that are involved. A simple sill is formed by a single intrusion whereas multiple sills are formed by two or more intrusions. A composite sill is composed of more than one type of rock found between the older layers of rocks during more than one intrusive period.

Sill V/S Dykes

Both dykes and sills are geological formations that are made up of igneous rocks. These rocks are formed when the hot magma from the hot core or mantle of the Earth gets released upward through cracks, fissures, or joints. This magma does not reach the surface of the Earth in the case of the Sill and dyke as in the case with Lava that exploded from the opening of a volcano. Hence, sill and dyke are the results of the cooled down magma before it reaches the surface of the Earth. Understanding the difference between dyke and sill is important for students of Volcanology.

 

What is the Difference Between Dykes and Sills?

• The different colors of both a dyke or a sill from the surrounding rocks are exposure to volcanic activity.

• A sill is generally formed when the dyke cannot move upward further and starts to move horizontally. Hence, a sill is fed by a dike.

• When magma intrusion is found along the preexisting rocks, then the resulting formation is known as sill whereas when magma flows across the rocks, the dyke is formed.

Did You Know?

• Sills are considered to be a horizontal intrusion.

• Sills are formed underground and hence composed of plutonic igneous rocks.

• The texture of a sill ranges from aphanitic to phaneritic.  

• All the types of rock formations are found in sills.

• The measures of a sill range from a fraction of an inch to hundreds of feet thick and up to hundreds of miles long.

Spring water is the water that people get from an underground aquifer, and it is commonly a huge underground deposit of water. The majority of the aquifers do exist in some amazing places all across the world. To answer the question, “What is spring water?” You must know that spring water has huge quantities of minerals. Spring water is important for removing toxins and purification in the human body. It permits every organ to function the manner it must be. 

As the subject of drinking water remains shrouded in misinformation, it becomes tough to make some informed decisions regarding what kind of water people must consume. Some people love bottled water for avoiding the chemicals that remain present in a tap water system. 

Spring Water Uses

Springwater is used for various purposes all across the world. 

• Springwater is utilized for people’s basic survival, pleasure, entertainment. 

• Springwater has got lots of medicinal purposes too. 

• Ancient Greek physicians were fully versed in the mineral water therapy health benefits. In earlier periods, the Arabians, and Egyptians, utilized mineral waters to heal ill people.

• This helps in many biochemical processes such as producing ATP.

• Gradually eliminates bone diseases and keeps healthy muscle function intact

• Helps to maintain healthy blood pressure.

• Helps to maintain water balance in the body.

Does Spring Water Have Minerals?

Springwater has natural mineral content, and it can propose unmatched health benefits. This kind of water is rich in minerals naturally and stands apart when you compare it with bottled water or tap water as they have got respective levels of antibacterial chemicals, chlorine, and pharmaceuticals. Mineral water arises from underground reservoirs. When spring water flows through sedimentary rocks, soil, and other sources of natural minerals, those minerals get submerged in spring water naturally. Unlike packaged drinking water, it does not go through chemical processing so the minerals stay in spring water.

What is Natural Spring Water?

Natural spring water is referred to as water that flows from the underground aquifer to the surface of the earth. When water flows through the underground rocks, then minerals get dissolved. The filtration process of spring water happens naturally via chemical means, physical substrate, and also by biological means.

Minerals Present in Spring Water

Some typical minerals that are present in spring water are potassium, sodium, calcium, magnesium, besides some trace quantities of zinc and iron. Every mineral present in water happens to be in its ionic form, and it means a person’s gastrointestinal tract can absorb it easily compared to minerals present in supplements and food. When spring water remains in its purest form, it comprises the maximum mineral content of any kind of water.

Some Facts About Mineral Spring Water

Mineral springs are acknowledged as naturally occurring springs, and they produce hard water. This water comprises salts, dissolved minerals, gases, and sulfur compounds, besides various substances that do dissolve in the spring water when it makes its passages underground. So, they are pretty different from sweet springs and produce soft water without any remarkable dissolved gases. The dissolved compounds, at times, change the taste of the water. Mineral water that is gotten from mineral springs, as well as precipitated salts, has turned into a vital commercial product.

A few mineral springs might comprise substantial amounts of dissolved minerals, like arsenic, and so, they aren’t safe for drinking. Sometimes, sulfur springs do smell of rotten eggs because of the presence of hydrogen sulfide, and it is pretty hazardous, and most of the time, deadly.

Hydrogen sulfide is a gas, and commonly, it gets into people’s bodies when they breathe in. Mineral spring waters are claimed to possess therapeutic value, and so, mineral spas are developed close to mineral springs where patrons drink and bathe in the mineral water. Historical mineral springs happened to be outfitted with some elaborate stone works that include retaining walls, artificial pools, roofs, and colonnades.

Water in seeps, wells and springs commonly originates in the form of rainfall, and the soil soaks it. After this, it gets seeped into underlying rocks. Springwater proposes much-needed oxygen to people’s brains and bodies. This water is also helpful in digestion besides maintaining a healthy weight. The great thing is spring water tastes great and never tastes boiled or flat. So, it makes for a superb drinking experience.

Minerals that contain persulfide or sulfide as the major anion are sulfide minerals. What is Sulphide ? Compounds containing one or more sulphide ions are sulphides. Most of the sulfide minerals are economically important as metal ores. These are inorganic compounds. Sulfide minerals are structurally simple. They not only exhibit high symmetry in their crystal forms but also have many metallic characteristics, such as electric conductivity and metallic luster. Sulfide minerals have low hardness and higher specific gravity. Generally, sulfides are opaque, sectile, and have high density. Sulphide is more readily soluble in water and oxidizes the accompanying iron into double iron oxides. The chemical formula of sulphide  is S²⁻.

Types of Sulfides

Selenides, tellurides, arsenides, antimonides, bismuthinite, and sulfosalts are the major classes of sulphide ores. Sulfides are mostly opaque with different color variations and different streaks. The color of mineral powder obtained from sulfide minerals is known as the Streak. The non-opaque varieties have a high refractive index. Here are some common sulphide ores examples.

Bismuthinite

It is a name of sulphide ore. Bismuth is extracted from the Bismuthinite ore. Mostly found in complex mixtures of ores of gold, silver, etc and bismuth is extracted in form of a by-product. Their color varies from lead-grey to tin white, may have yellowish or varied tarnish. It is used in the pharmaceutical and chemical sectors and also as a fusible metal alloy.

Chalcopyrite

One of the most important minerals is copper (Cu). It has a metallic luster, greenish-black streaks, and is commonly tarnished in golden color. Chalcopyrite often occurs in crystals, they are usually found in massive chunks. The crystal is scalenohedral shaped. It is softer and yellower than pyrite. It is found in Japan, Spain, and South Australia, etc.

Galena – Lead Sulfide

 It has a dark grey streak and has a density that is about 7.5 times higher than water. It is very bright and lustrous. Mostly Galena is straight grey, very often it is found in bluish-grey color. Galena is formed in between low to medium temperature ore veins, along with sulfide and carbonate minerals. Silver is often found as an impurity and silver is also an important byproduct of the lead industry. It is used as a source of lead in ceramic glaze.

Marcasite

Same as pyrite but the crystal structure is different. It forms groups of cockscomb aggregates. Marcasite has lighter brass color than pyrite but its tarnishes are darker. The streaks of pyrites are greenish-black where the streaks of Marcasites are gray. They are unstable and often its decomposition creates sulphuric acids. Marcasite is used for powerful meditation, to heal the chakras. It is found in England, Dover and Derbyshire, Russia, France, Mexico, etc.

Pyrite 

Most common mineral Iron Sulfide. It is one of the most important sulfur-containing minerals. The Mohs hardness of Pyrite is around 6. It is brass-yellow with greenish-black streaks. It slightly resembles gold but pyrite is much lighter and harder than gold. Fool’s gold. formally known as pyrites In many places, Pyrites contain silver and gold as containment. Pyrites crystals are called pyritohedron. Pyrite is used in the paper industry and the manufacture of sulfuric acid.It is a sulphur ore .

Solved Examples

What is Fool’s Gold?

Fool’s gold is formally known as pyrites. Pyrites are usually brass-yellow and have a metallic luster. Due to which it gives a superficial resemblance to gold so it is termed as fools gold. The word pyrite is a greek derived word that means fire. Not only that Pyrites also contain gold as contamination. Pyrite also creates fire when struck with another rock. Pyrites are more brittle than gold and will break as it is not bendable like gold.

What is Molybdenite?

It is a metal sulphide. It is often confused with graphite. It is dark, very soft with a greasiness feel. Molybdenite forms hexagonal crystals like graphite. It is more metallic than graphite. Molybdenum in trace amounts is necessary for life because to fix nitrogen for building protein, an atom of molybdenum is required. It is also the primary source of molybdenum. 

 

Are Pyrites Toxic?

Pyrites are sulfide minerals. They are composed of sulfur and iron and act as one of the major contaminants of groundwater, lakes, and streams. Oxidation of Pyrite due to the burning of coal releases toxic metals like Arsenic. Miners are often affected with lung cancer due to this reason Lead is poisonous to humans as well as the environment. 

Conclusion

The symbol of sulphide is S²⁻ .Sulfide minerals are economically important. Sulfides can be toxic or not. It has metallic properties including electrical conductivity, refractive index, etc. There is a lot of variety in sulfide minerals. They also play an important role in pollution. Be it Air pollution, water pollution or soil pollution sulfide minerals play a major role. Smelting of iron ores and burning coal, which contain sulfur impurities causes air pollution. The breakdown of sulfides due to weathering at the earth’s surface releases toxic to both soil and water. But the fact cannot be denied that sulphide ores are common for metals like gold and silver as they are found in containment.

Thermosphere meaning is quite simple. The thermosphere is one of the layers of the earth’s atmosphere that extends in an outward direction. It lies in between the mesosphere and exosphere layers of the atmosphere, the thermosphere layer is above the mesosphere and below the exosphere layer and it covers a major part of the Ionosphere, which is a part of the earth’s atmosphere.

                  

About Thermosphere Layer in Detail

The altitude of the thermosphere layer begins from about 80kms above sea level and extends up to 700kms to space. The altitude makes the thermosphere enter the space and it’s a part of space too. In this layer the ultraviolet radiation causes photoionization of molecules, that is, ions are created in this layer of the atmosphere by the interaction of a photon with an atom or molecule. The thermosphere contributes majorly to the ionosphere of the earth’s atmosphere, that is why photoionization or dissociation takes place in the thermosphere, as it lies in the ionosphere region.

Thermosphere and its Temperature

Here you will get to know about the thermosphere temperature range. The temperature of the upper thermosphere layer ranges from 500-degree Celsius to 2000-degree Celsius. It can even range higher than 2000- degree Celsius. Another fact of the temperature in the thermosphere layer is it can get 200 degrees Celsius higher in the daytime than at night. And it can get 500-degrees hotter than usual when the sun is very active. Thermosphere is the name derived from the language Greek, it means Heat. The temperature is always high in this layer of the temperature and the name is apt for the layer.

Air Present in the Thermosphere

The thermosphere is composed of air. The major components are atomic oxygen, atomic helium and atomic nitrogen. Here due to turbulence in the atmosphere, the different types of gas molecules are mixed together thoroughly. 

In the thermosphere, there is an infrequent collision of gas particles that leads to the separation of gases according to the chemical elements the gas contains. 

Much More Information About the Thermosphere

In this layer of atmosphere, the particles are electrically charged because of the radiation. It enables radio waves to be refracted and it can receive beyond the horizon. Much of X-ray and UV radiation from the sun is largely absorbed by the thermosphere when the sun is much active. When it absorbs this radiation the thermosphere expands due to heat and puffs up.

As the thermosphere is below the exosphere layer of the earth’s atmosphere, the exosphere begins at 600km from above sea level and extends into space. There is a Karman line that defines the boundary between the earth’s atmosphere and outer space, according to that thermosphere is a part of outer space. Because the exosphere begins in outer space that is from 600km above sea level, the thermosphere layer is extended to 700 km above sea levels, hence that makes the thermosphere a part of outer space.

As we know oceans have tides and waves, similarly, the earth’s atmosphere including the thermosphere has tides and waves, which helps to move the energy along. This results in the production of electrical currents In some parts of the thermosphere.

The atmospheric pressure on the thermosphere is around the 0.0005 kPapressure level, there is a very minimal activity of air pressure at the top of the thermosphere.

Thermosphere and the Other Atmospheric Layers

Let’s understand the thermosphere atmosphere. The thermosphere is the fourth atmospheric layer which is above the mesosphere and below the exosphere. The thermosphere layer begins in the mesosphere region and ends in the exosphere region. But the atmospheric components don’t mix with the other. The transitional space between the mesosphere and thermosphere Is called mesopause. And between the thermosphere and exosphere, it’s called thermopause. There is another important fact here, that is the Ionosphere, parts of the thermosphere, mesosphere, and exosphere is included in the ionosphere. There is an interdependence of thermosphere and ionosphere here, as the thermosphere is very hot, it ionizes the atoms in its layer, and produces an electric current.

The thermosphere layer is a thicker layer than other layers of the atmosphere, but not as thick as the exosphere. The thermosphere is home to the International Space Station as it orbits Earth, this is also where you’ll find low Earth orbit satellites.

Tropical Storm occurs in the Earth’s Ocean Basins where tropical cyclones are found. They are precisely centered in the North Atlantic, Northeast and Central Pacific, Northwest and Southwest Pacific, and also in Indian. Tropical storms are quite similar to intense and mature tropical cyclones. These cyclones possess horizontal dimensions of about 160 km (which is around 100 miles). 

We will further know in detail about the tropical storms. Also, we will enlighten on Tropical Weather. 

Tropical Storm

A tropical storm is a storm that has an organized center and has low pressure which originates over the warm tropical oceans. The surface winds maximize their range from 63 to 118 km (that is 39 to 73 miles) on a per-hour basis. These kinds of storms represent the intermediate stage which is between the organized tropical depressions which are loosely formed and other intense tropical cyclones which are known as hurricanes or typhoons, they are named differently in different parts of the globe. 

The winds are the highest at the surface area but decrease with the increasing altitude. These winds typically attain the approximate intensity of about 30–50 km (that is 20–30 miles) which is away from the center of the circulation. 

Tropical Weather 

Two reasons why tropical weather is different from the weather in higher latitudes. The reason is here, the sun shines directly on the tropics rather than shining directly on the higher latitudes. They shine directly at least on an average over a year, this makes the tropics very warm compared to the higher latitude regions. Another reason is, the vertical direction, while one stands on the earth’s surface, is perpendicular to the Earth’s axis of rotation at its equator. The axis of rotation and the vertical are the same at the pole, this causes the rotation of the earth to influence the atmospheric circulation more intently at higher latitudes than at the lower latitudes. 

For these above-mentioned factors, clouds and rainstorms occur in the tropics more spontaneously than compared to that in the higher latitudes. In these, they are more tightly controlled by the larger-scale forces in the atmosphere. For these differences, the clouds and rain are very difficult to forecast in the tropics than at the higher latitudes. On the other hand, the temperature can be easily forecasted in the tropics, as it doesn’t differ much.

Heat, Moisture, Clouds, and Rain

With higher temperatures, more water vapour gets collected in the air without the process of condensing. When the sun shines strongly on the tropic regions mainly on the warm oceans they have an effectively infinite amount of water that evaporates into the open air. This is the time when the overlying atmosphere becomes humid.

Temperature and pressure both drop very quickly with the increasing altitude, this happens in the tropical regions as elsewhere on the Earth. If the warm air is lighter than the air surrounding it, this will expand and cool. Thus, it will cause water vapour in it to condense into these tiny liquid droplets and this forms a cloud. The latent heat of the condensation warms the air, this causes the air to become warmer, which further allows the air to updraft and rise. After enough water condenses, then the cloud droplets can become large enough to fall as rain.

Sometimes the tropical shower ends quite quickly when the rain evaporates. The evaporating rain cools the air which is located near the surface, the warm air rises into a new cloud. Also, the cooling effect with the weight of the rain itself can create a downdraft which will be enough to create turbulence which then turns and lifts the nearby warm, making the air humid, making a new updraft. This process then well feeds on itself to produce a large complex of storms that maintains the rainy weather over a couple of days. 

More on Tropical Storms

The tropical storms act as precursors for the more intense tropical cyclones, which occur more often. The yearly average tropical storms that occur in the various ocean basins are as follows:

• North Atlantic 

• North Eastern Pacific 

• North Western Pacific 

• Northern Indian 

• South Western Indian 

• Australian. 

In all the ocean basins, roughly around 45 percent of the tropical storms continue to intensify their motion to minimal tropical-cyclone strength or greater.

The above image depicts the data of the number of tropical cyclones and tropical storms that occur around the globe. 

There are a number of factors that might result in the failure of a tropical storm to continue to intensify a particular area. In some cases, the storm also moves into a region where the large-scale environment will not favor further growth. The sea surface temperature is quite low, the middle atmosphere is also too dry, or the winds which are blowing at the upper levels are too high to support the continued vertical development of the storm.