Category: Geography Notes PPT

In this article, you will learn about the meaning of seawater, origin, composition, and impacts, etc. Seawater, or saltwater, is sea or ocean water. On average, seawater in the oceans of the world has a salinity of about 3.5 percent. This means that every kg of seawater contains approximately 35 grams of dissolved salt. The average surface density is 1,025 kg/l. Seawater is denser than fresh water and pure water because dissolved salts raise the mass by a larger proportion than the volume. The seawater freezing point lowers down as the concentration of salt increases.

Seawater is a rich source of numerous commercially important chemical elements. Most of the world’s magnesium is obtained from seawater, but so are large amounts of bromine. In some parts of the world, sodium chloride (table salt) is still produced by the evaporation of seawater. In addition, when desalinated, water from the sea can provide an unlimited supply of drinking water. Several large desalination plants are designed in dry areas along the coastlines of the Middle East and elsewhere to ease freshwater shortages. 

Seawater Meaning

Seawater Meaning: Seawater is a mixture of 96.5 percent water, 2.5 percent salts, and smaller amounts of other substances, including inorganic and organic dissolved solids, particulate matter, and few other atmospheric gases.

Origin

Scientific findings on the roots of sea salt began with Sir Edmond Halley in 1715, who proposed that the salt and other minerals would be transported to the sea by rivers after the rain had washed it out of the ground. Upon reaching the ocean, these salts were concentrated as more salt arrived over time. Halley concluded that most of the lakes that do not have ocean outlets have a high salt content. Halley referred to this process as “continental weathering” Halley’s theory was partially correct. In addition, when the ocean formed, sodium leached out of the ocean floor. The presence of other dominant ions of salt, chloride, tends to result from the outgassing of chloride with other gasses from the Earth’s interior mostly through volcanoes and hydrothermal vents. Consequently, sodium and chloride ions were the most abundant components of sea salt. Ocean salinity has been steady for billions of years, most possibly as a result of a chemical/tectonic system that removes as much salt as it deposits; for example, sodium and chloride sinks include evaporite deposits, pore-water burials, and marine basalt reactions.

Composition

Seawater comprises more dissolved ions than any kind of freshwater. Nevertheless, the ratios of the solutes vary dramatically. For example, although seawater comprises about 2.8 times more bicarbonate than river water, the percentage of bicarbonate in seawater as a ratio of all dissolved ions is much lower than in river water. Bicarbonate ions account for 48 percent of river water solutions, but only 0.14 percent for seawater. Differences such as these are mainly owing to the varying residence times of seawater solutes; sodium and chloride have quite long residence periods, while calcium tends to precipitate much faster. Sodium, chloride, magnesium, sulfate, and calcium are the most abundant dissolved ions in seawater.

Due to their common chemical and physical properties, several of the features of seawater correspond to those of water in general. For instance, the molecular structure of seawater, like that of freshwater, favours the creation of bonds between molecules. Some of the distinct features of seawater are directly related to its salt content. For instance, the viscosity of seawater is higher than that of freshwater due to its higher salinity. Seawater density is also higher for the same reason. The freezing point of seawater is lower than that of pure water, and its boiling point is higher.

Human Impacts

Changing climate, increasing atmospheric carbon dioxide, heavy metals, and pollution in many ways are distorting global ocean geochemistry. The rate of change for some aspects is significantly higher than in the historical and recent geological record. Primary issues include increased acidity, reduced subsurface oxygen in waters, increased level of coastal nitrogen, and widespread increase in mercury and persistent organic pollutants. Most of these abnormalities are either directly or indirectly linked to human burning of fossil fuels, fertilizer, and industrial activity.

Even though oceans are an enormous reservoir, human activities have begun to affect their chemistry on a local and global scale. The accumulation of nutrients to coastal waters results in increased phytoplankton growth, high concentrations of dissolved and particulate organic materials, reduced penetration of light through seawater, and variations of the community structure of sub-dwelling organisms. Through industrial and automotive emissions, the concentration of lead on the surface of the ocean has increased dramatically on a global scale compared to pre-industrial levels.

Did You Know?

• Saltwater functions as a conveyor belt to transport heat around the planet. 

• Even though humans cannot remain healthy drinking saltwater, many creatures in the oceans and seas depend on saltwater for their very existence. 

• Fish living in saltwater will end up dying in freshwater, and vice versa.

In Geological time, the Silurian period is the third period of the Paleozoic era. It started 443.8 million years ago and ended 419.2 million years ago, extending from the ending of the Ordovician period to the beginning of the Devonian period. During this period, continents’ highlands were much lower and sea level was rising. Sea level rose drastically as the huge glacier from the Late Ordovician ice age melted.  

The immediate changes in climatic conditions permitted many faunal groups to recover from the extinction of Late Ordovician times. Large expanses of different continents became flooded with shallow seas, and mound-type coral reefs were common. Fishes were extensive. Vascular plants began to take over coastal lowlands during this period whereas the continental interiors became infertile. 

When Did the Silurian Period Start?

The Silurian period was the period from the end of the Ordovician period, at about 443.3 million years ago, to the beginning of the Devonian period, 419.2 million years ago. The Silurian period is considered to be the shortest period of the Paleozoic Era.

Silurian Period Significant Events

Life on Land

It was during this period that the first life came about from water and colonized the land. Increased ozone from photosynthetic water plants provided protection from the ultraviolet rays, making the terrestrial environment friendly to those organisms that could prevent desiccation.

First Vascular Plants

The first plant with an internal vascular channel was seen in Silurian period. Plants were not able to transfer food and gases to other parts of the structure, allowing a considerable amount of increase in size.

First Insect

The first insect seen in the Silurian period, was probably the first animal to come out of water.

First Jawed Vertebrates

The first fish with jaws appeared during the Silurian period, providing much better predictability and eventually giving rise to vertebrates known today. 

Silurian Period Climate

The climate was much warmer during the Silurian period. This caused the melting of glaciers and sea levels to rise.  Even though the sea level was rising, there was a place where the land was rising as well. This was due to the mountain building as the continental plates collided. In these places, the seas moved away from the coasts or evaporated from the shallow zones. Plants that had to live in coastal water had to live on land or die.

Fishes Gained Importance During the Silurian Period

Fishes gained much importance during the Silurian period. Most of the fishes were jawless at the beginning of the Silurian period. There were some earlier vertebrates, animals with soft cartilage bones. By the end of the Silurian period, animals with jaws and real bones were swimming in water. These animals soon would rule the seas.

Terrestrial

The most significant progressive development of this period was that of the first true terrestrial ecosystem. 

The first fossil records of vascular plants, that is, land plants with tissue was of those which carries food, occurred during the Silurian period. The vascular plants were simple plants that had not developed individual stems and leaves.

By the middle of the Silurian period, a very simple early terrestrial community with simple plant producers, millipede herbivores, centipede and arachnid carnivores, worm detritivores, and fungal decomposers had developed.

The Mid-Late Silurian terrestrial biota included small plants along with the water’s edge and arthropods such as trigonotarbids and myriapods. Fungi, nematodes, and perhaps earthworms were most likely present as well, although they did not leave a fossil record (except for possible fungi).

Did You Know?

• The name Silurian originated from the Celtic from Whales.

• During this period, the sea fluctuated between transgression and regression due to the climatic change and continental buildup.

• The first fossil record of the Vascular plants appeared in the second half of the Silurian period.

Many of the times you read in the newspaper or watch the news on television talking about the storms, reporters and the government ask the public to stay home for safety purposes. Ever thought about why they asked us to stay inside? Don’t worry if you are not aware of the answers. has brought detailed notes on the storms to help students understand the topic in detail. 

A storm is a disturbance caused in the atmosphere when the ocean develops a low-pressure zone. It brings heavy rain and destruction to the coastal areas. But, for the drought-affected areas, it is a blessing in disguise. 

In the notes, has also explained the different types of storms, for instance, tornadoes, hail storms, and many more.

Learn Storms with

physics experts have crafted the notes to make it easy for students to gain proper knowledge about the rated topic in today’s time. 

Since the past decade, storm occurrence has become very frequent and has already taken a lot of lives. Today is the right time for students to learn about it and the reasons for the occurrence of the storms. 

Storms are nothing but strong and gusty winds accompanied by snowfall or heavy rain. A wind that you may know as the air; feels so pleasant in the heat of summer, but it shows its ghostly powers as a storm that can even collapse the high story buildings. 

More About Storm

A storm is an acute disturbance of the atmosphere that is coupled with the mighty wind and usually by heavy or light rain, snow, hail, sleet, or thunder and accompanied by lightning. During a storm, the wind has a speed of 64 to 72 miles (which is 103 to 117 kilometers) per hour.

A storm is identified as a violent meteorological phenomenon where there is an occurrence of heavy rain and gusty strong winds. In our further section, we will know more about Storms, a common occurrence in our life. 

Storm Information 

Storms are raging atmospheric disturbance that is characterized by cloud cover, low barometric pressure, precipitation, and also with wild winds. They are also coupled with thunder and lightning. 

The cause of the storm is the moisture content in the air. The Formation of Hail and Lightning are also quite common encounters with the storms. A storm generally happens in bad weather and is accompanied by strong winds, thunder, lightning, and also heavy precipitation like ice.

The storm is a general term, which is popularly used to describe other disturbing varieties of atmospheric disturbances, that range from ordinary rain showers and snowstorms to the happening of thunderstorms, wind-related disturbances, and gusts of wind like gales, tornadoes, sandstorms, tropical cyclones.

Meteorologically, the storm is restricted to a cyclone that has a strong low-pressure center, strong winds that range from 103–117 kilometers per hour (which is 64–73 miles per hour), heavy precipitation, and also lightning and thunder. 

Description About Storm

Strom is the type of disturbance in the atmosphere which is manifested by gusty and strong winds which are accompanied by rain, snow, or other precipitation and are often struck by thunder and lightning.

A storm is described as a disturbed state in the environment or in the atmosphere which affects the surface, and this implies severe weather conditions. This is also marked by significant disruptions to normal conditions such as strong winds, tornadoes, hail, thunder, and also lightning with heavy precipitation which is known as a snowstorm, rainstorm with heavy rain like the ice storm, the storm is freezing as well. The tropical cyclone and windstorm or the wind transporting substances via the atmosphere as in the case of a dust storm, blizzard, sandstorm, etc.

These strong, gusty storms have the potential to harm the lives and property of human beings. Also, for this it causes rain or snow causing flood or road passing incapability, lightning and wildfires may also happen, and also causes of wind shear are witnessed. 

Storms with heavy rainfall and duration relieve the drought areas. The heavy snowfall also might allow other recreational activities like skiing and snowmobiling.

Storms are then created when a center of low pressure gets developed with the high-pressure system that surrounds it. These opposing forces can also create winds which result in the formation of the storm clouds like cumulonimbus. The localized areas of low pressure can also form from hot air rising off from the hot ground, which results in smaller disturbances like dust devils and whirlwinds.  

Types of Storms

Now that we have covered what is a storm, let us now learn about the different types of storms are as follows:

1. Deroche Storms: Deroche storms are the series of storms that have a large extent they all;l follow the path of each other even which at least 240 miles with wind gusts of at least 58mph.

2. Flooding: Floods also occur due to the rain and other water rises faster than the drains can handle. Flooding often leads to high damage to homes and other commercial buildings.

3. Hail Storms: Hail storms are the cause of a lot of damage which is hard and can fall up to high speeds of up to 120mph.

4. Snow Storms: Heavy snow may also be an inconvenience that can cause damage to the home, heavy build-ups of snow can also lead to collapsing of roofs, or gutters. It also causes blockage of drains.  

5. Hurricanes: Hurricane is the most powerful and dangerous type of tropical cyclone, they are identified by low-pressure systems, high winds, heavy rainfall, and storm surges and swells.

6. Ice Storms: Ice storms produce freezing rain that covers everything in ice, they make everything slippery and also cause hazardous conditions and a high potential of affecting homes and vehicles.

7. Lightning: Lightning happens to storm damage, and this usually causes trees to fall, wildfires, structural fires, and also power outages.

8. Thunderstorms: Thunderstorms cause a wide range of types of weather, like hail, flooding, and tornadoes. 

9. Tornadoes: Tornadoes are very dangerous, as the high winds often gush in excess of 300mph. Tornadoes are very much prevalent in certain states like Oklahoma, Kansas, Texas, and Missouri. They are named “tornado alley”. Minnesota, which lies on the northern edge, witnesses around 26 tornadoes per year, with an average of more than 2 per month.

10. Tropical Storms: Tropical storms have wind speeds of between 39 to 73mph, they are prevalent in the Pacific and Atlantic oceans.

The main damage is caused by tropical storms which include damage that happens to the water.

The term Syenite is derived from the original word “Syene” that comes from Egypt. It is associated with plutonic groups because it is one of the types of intrusive igneous rocks. It is considered to be similar to granite as well but some difference is there in terms of syenite minerals In this article, we will talk about this rock. We will learn syenite composition, distribution, uses, classification and syenite metaphysical properties and some examples as well. This topic is useful to increase our understanding of igneous rocks especially the Intrusive rocks which form below the surface of the Earth.

Meaning

It is an intrusive igneous rock that consists of ferromagnesian mineral & alkali feldspar and usually coarse-grained. If we talk about its composition, that is generally the same as granite. It contains medium quantities of silica & large amounts of alkalis and alumina. The texture of syenites is like granite, which is granular but these rocks differ from granite due to the lack of quartz. 

Definitions

Some of the standard definitions are mentioned below:

• “It is an igneous rock composed chiefly of feldspar. ” – Merriam-Webster

• “It is a light-coloured coarse-grained plutonic igneous rock consisting of feldspars with hornblende or biotite.” Or ” a greyish, intrusive igneous rock usually containing feldspar, hornblende, and some quartz. ” – Collins dictionary.

• “It is a type of intrusive igneous rock which consists of ferromagnesian minerals as well as alkali feldspar.” – General Definition.

Syenite Composition

• If we talk about syenite mineral composition, then the predominant mineral is alkaline.

• Plagioclase feldspar may present but with a small amount, generally less than 10%.

• If ferromagnesian minerals are present, most of all in syenite, then they usually occur in hornblende, amphibole or clinopyroxene, whereas Biotite is rare. 

• Some other common accessory minerals are titanite, apatite, zircon as well as opaques.

• Most of the syenites are considered as either peralkaline or peraluminous.

Classification

We can see the classification on the QAPF diagram. Here, we can observe that various types of syenitic rock cover a large part in the diagram but true syenite rock is that rock that fits into the area marked as red. These types of rocks are usually composed of alkali feldspar (A) along with minor amounts of quartz (Q). On the other hand, Plagioclase feldspar (P) is less important than the former i.e alkali feldspar whereas foid syenites contain a significant amount of rare silicate minerals which are generally known as feldspathoids (F), which in simple words also termed as foids. Here we should note that Q, as well as F, are mutually exclusive. The rock that contains quartz can not contain feldspathoids or vice versa.

Some of the types of syenite are explained below:

Nepheline Syenite

Nepheline syenite is a medium coarse-grained, intrusive igneous rock member. It is a holocrystalline plutonic rock. It consists of nepheline and alkali feldspar in large quantities. The rock of these is mostly in pale coloured, grey and pink colour. It is poor in silica and rich in alkaline. Generally, they are not similar to granite but because of their dark green varieties, they are known. Nepheline mineral is used to replace feldspar to manufacture ceramic glass and products.

Quartz Syenite

If we talk about this kind of syenite, then it is considered as a group of those plutonic rocks which are having the features of syenite along with a much larger amount of quartz, which is around 5 to 20%. Usually, syenite consists of less amount of quartz that is around less than 5% and when this quartz composition is between 5 to 20%, it is considered as quartz syenite.

Hornblende Syenite

Hornblende Syenite is the subgroup of amphibole minerals. It contains important amounts of calcium and is monoclinic. It is quite common. These rocks consist of a wide variety of rocks, such as syenites, granites, gneisses and gabbros. The minerals are typically opaque. It is dark green to black in colour with a vitreous to dull lustre. The crystals of hornblende are long and thin and they sometimes occur in massive granular aggregates. It can be found in New York ( USA ), Norway, Italy as well as Ontario ( Canada).

Syenite Properties

Physical properties of rocks are studied because they help not only in identifying the type of rocks but also to discover more about them. There are various syenite rock properties such as hardness, streak, lustre, compressive strength, specific gravity, etc. which defines this rock. The properties are important in determining its texture as well as uses. The hardness of Syenite on the Mohs hardness scale is 5.5 – 6 and compressive strength is 150.00 N/mm². If we talk about Streak which is considered as the colour of rock when it is crushed/ powdered, then it is white. Lustre is subvitreous to dull whereas cleavage is perfect. The specific gravity is said to be 2.6-2.7. Besides these, it is considered opaque in nature. Chemically, these types of rocks contain silica of moderate amounts, and relatively large amounts of alkalies, and alumina.

Distribution

It is not a common rock and thus some of the examples of the regions where it is found are mentioned below:

• Two giant nepheline syenite bodies lead to the making up of the Lovozero Massif as well as the Khibiny Mountains in the Kola Peninsula of Russia.

• Arkansas & Montana are regions where it is found in North America along with some parts of New England as well as New York and many other regions.

• Switzerland, Norway, Germany, Sweden, Portugal, Bulgaria and Romania are the countries where it is found in Europe.

• In Australia, it is found mostly in all of the states whereas in the Aswan & Malawi regions of Africa. 

Uses

• This rock is used for flooring, homes, hotels and interior decoration.

• It is used as a building stone, as a Facing Stone or paving stone along for garden decoration or the purposes of office buildings.

• It is also useful for curbing purposes. 

• It is used as a dimension stone, for cement manufacturing, construction or road aggregate, for landscaping, etc. 

• It is used for manufacturing natural cement as well as Magnesium & Dolomite Refractories.

• It is used for artefacts, monuments, sculpture making or small figurines, cemetery markers and the creation of various artwork.

Conclusion

Thus to conclude, in the end, we can say that syenite is an example of intrusive rock that forms beneath the surface of the Earth and consists of feldspar as its chief content. We learned about syenite rock and all related aspects along with some examples such as nepheline rock, nepheline syenite composition, quartz or hornblende, etc. We came to know that syenite is not a common rock found in some of the regions of the world and it is very useful for various purposes such as cement manufacturing, decoration, homes or buildings, sculpture or artworks making, etc. This topic is useful in Geography, Chemistry, Geomorphology, Physical Geography, Geology, Petrology and Earth Sciences. 

Let’s look at some frequently asked questions related to syenite:

A tidal bore, also known as the bore is a tidal phenomenon in which the highest incoming tides form a wave (or waves) of water that travels up a river or confined bay against the path of the river or bay’s current.  The word “bore”  is derived through Old English from the Old Norse word Bara meaning “ wave” or “swell”.

A bore occurs in some places worldwide, generally in areas with larger tidal range and where incoming tides are passed into a shallow narrowing of a river of the lake through a broad bay. 

The funnel-like shape not only increases the tidal range but also decreases the duration of the flood tide where the flood appears as an immediate increase in a water level. A tidal bore always occurs during the flood tide and never occurs during an ebb tide. 

Qiantang River Tidal Bore

Qiantang River tidal bore, also known as the silver dragon tidal bore, is the world’s largest tidal bore. It is a river in east china and runs from Hangzhou bay on China’s eastern coast. The Qiantang River tidal bore is a famous scenic spot of the Qiantang River.

Generally around  August 15, the Lunar calendar is the best time to observe the silver dragon tidal bores. Driving this time, this largest tidal bore can be several meters. Before the sea tide appeared, a white ting dot appeared in the distance, which transformed into a silver thread in a blink of an eye. Later, the white line rolled to the sea as it was accompanied by waves of dull thunder. 

In ancient Hangzhou, Phoenix mountain, the Jianggan area was the best place to watch the Qiantang River tidal bore. Due to the transformation of geographical location from the Ming dynasty, Haining, Hanguan was the first resort to observe the silver dragon tidal bore,  so it was also called “Haining Tidal Bore”.

Petitcodiac River Tidal Bore

The Petitcodiac River tidal bore – retrograde wave moving upstream over the downstream wavers. It occurs twice a day and comes from the world’s largest tide in the Bay of fundy. The first European mention of the Petitcodiac river tidal bore by the British Lieutenant Colonel George Scott on 17 November 1758.

The Petitcodiac River tidal bore ranges from 1 to 2 m (3.3 – 6.6 ft) in height, with a speed from 5 to 15 km/h. Peter Fisher in 1825, observed that the noise of the bore is heard at a great distance, and animals instantly take to the highland and manifest visible signs of terror if near it. Before the causeway, the value of the Petitcodiac river tidal bore was compared with the tidal bores of Qiantang, Hooghly, and Amazon river. The bore reached heights from about 5 to 75 cm after the causeway was built.

Bay of Fundy Tidal Bore

The Bay of Fundy tidal bore is the bay found between the Canadian province or territories of New Brunswick and Nova Scotia, with a small part touching the US state of Maine. The bay of fundy tidal bore has an extremely high tidal range. The name is derived from the French word Fendu meaning “split”.

The tidal range in the Bay of Fundyis around 16 m ( 52 ft). Some tides are higher than others, depending on the position of the moon, the sun, and other atmospheric conditions. Tides in the Bay of Fundy are semi-annual, meaning they have two highs and two lows on each day with about 6 hours and 13 minutes between each high and low tides.

As per the Guinness Book of World records, the World’s highest tides are found in the Bay of Fundy, where the mean spring range in the Minas basin is 14.5 meters (47.6 feet). The largest tide on record in the Bay was 21.6 meters ( 70.9 ft) in 1869.

Pororoca Surfing 

The Pororoca is a tidal bore, with waves up to 4 m (13 ft) high that travels as much as 800 km ( 500 mi) inland upstream on the Amazon river and other adjacent rivers. The word “ porocca” is driven from the indigenous tulip language where it could translate into “great roar”. The Pororoca tidal bores occur at the mouth of the river where its water meets the Atlantic ocean.

The Pororoca river waves have become popular with surfers. However, pororoca surfing is especially dangerous as water contains a significant amount of debris from the shores of the river ( often entire trees) along with the dangerous fauna.

Did You Know?

• Tidal bore can occur every day, like the tidal bore of the Batang River in Malaysia, known as benak.

• Tidal bore, like the porocca, occurs during spring tides.

• The bore is the fastest and highest in some of the small rivers like Salmon River in Truro, the St. Croix and Kennetcook river in the Minas Basin, and the Maccan river and River Hebert in the Cumberland basin.

• The second highest tides in the World is Severn Estuary-after the Bay of Fundy in Canada and the highest in Europe.

• There are around 60 tidal bores around the Globe.

• The World’s highest tidal bore occurs along the Qiantang River in Hangzhou,China, where tides reach upto 30 feet and travel at upto 40 kilometers per hour.

The tsunami definition states that “A series of waves triggered by the movement of a large amount of water in a water body, typically an ocean or a large lake”.

The tsunami definition tells us that these are waves so tsunamis are also known as tidal waves. Tsunamis and tides both create inland water waves, but the inland movement of water in the case of a tsunami can be much greater, giving the appearance of an extremely high and strong tide called a tsunami wave.

In this article on tsunamis, we will learn about the causes and effects of tsunamis, types of tsunamis, and more tsunami information.

What is the Spelling of the Tsunami?

Tsunami is derived from the Japanese word “soo-NAH-mee”. The tsunami meaning in Japanese is “harbour wave”. Since in Japanese words, there is no ‘T’. So when spelt the initial ‘T’ is often silent which fits with the phonological rules of English.

So, the correct spelling of Tsunami is “Tsunami” with ‘T’ a silent letter.

How Tsunami Occurs?

• Tsunamis may be caused by earthquakes, volcanic eruptions, and other underwater explosions such as detonations, landslides, glacier calvings, meteorite impacts, and other man-made disruptions above or below water.

• The movement of a large amount of water or the perturbation of the sea is the primary cause of a tsunami. Earthquakes, landslides, volcanic eruptions, ice calvings, and, more rarely, meteorites and nuclear tests are all accounted for the water displacement. 

• Earthquakes are the major cause of tsunamis that occur worldwide.

• Let us look into a detailed explanation of tsunami causes.

1. The Tsunami Caused By Earthquake

• When the seafloor suddenly deforms and vertically displaces the overlying water, tsunamis may occur.

• Tectonic earthquakes are a type of earthquake that is related to the deformation of the Earth’s crust. When these earthquakes happen under the sea, the water above the deformed region is displaced from its equilibrium state.

• Because of the vertical component of movement involved, a tsunami can be produced when thrust faults associated with convergent or destructive plate boundaries move suddenly, resulting in water displacement.

• Tsunamis have a small wave height offshore and a long wavelength, which is why they go unnoticed at sea, creating just a small swell about 300 mm (12 in) above the normal sea level. 

• When they enter shallow water, they rise in height, a process known as wave shoaling. A tsunami can occur at any tidal state, and coastal areas can be inundated even at low tide.

• Examples of tsunamis caused by earthquakes are the Aleutian Islands earthquake in 1946, the Valdivia earthquake in 1960, the Alaska earthquake in 1964, the Indian Ocean earthquake in 2004, the Tōhoku earthquake in 2011.

2. The Tsunami Caused By Landslides

• Landslides cause displacements mostly along the shallower sections of the coastline, and the extent of large landslides that hit the water is uncertain. 

• Water in enclosed bays and lakes has been shown to be disturbed as a result, but no landslide large enough to cause a transoceanic tsunami has ever occurred in recorded history.

3. The Tsunami Caused By Meteorological Conditions

• The tsunami caused due to Meteorological changes is called a Meteotsunami.

• Rapid changes in barometric pressure, such as those seen when a front passes through, can displace bodies of water enough to cause trains of waves with wavelengths similar to seismic tsunamis, but with lower energies.

• These are basically dynamically similar to seismic tsunamis, with the exception that Meteotsunami lacks the transoceanic scope of substantial seismic tsunamis and that the force that displaces the water is maintained over time, preventing Meteotsunami from being modelled as occurring instantly.

• Despite their lower energies, they can be strong enough to cause localised damage and loss of life on shorelines where they can be intensified by resonance.

Types of Tsunami

There are three basic types of tsunami that occur worldwide. Let us discuss in detail the types of tsunamis in this article on tsunami.

Local Tsunami

• A local tsunami is one that causes damage in close proximity to the event that triggered the tsunami.

• The underwater occurrence, which is typically an earthquake that triggers a local tsunami, occurs within 100 kilometres (just over 60 miles) of the land damage that results.

• Since the time between the underwater occurrence and the arrival of the tsunami can be less than an hour, and even less than 10 minutes, these tsunamis can be catastrophic.

• There is insufficient time to perform a thorough evacuation.

Regional Tsunami

• A regional tsunami is described as one that causes damage between 100 and 1,000 kilometres from the source of the tsunami. Outside the 1,000-kilometer perimeter, more contained damages will occur in some cases.

• Regional tsunamis have a significantly longer warning time than local tsunamis, arriving between one and three hours after the triggering incident.

• Within a 1,000-kilometer radius, one to three hours might not be enough time for people to safely evacuate.

Distant Tsunami

• A distant tsunami, also known as a Teletsunami or ocean-wide tsunami, is caused by a strong and devastating occurrence that occurs more than 1,000 kilometres away from landfall.

• A distant tsunami may appear to be a local tsunami at first, but it spreads through vast swaths of the ocean basin.

• A distant tsunami allows more time to evacuate and flee, but it also occupies a wider area of land and is more likely to cause extensive and widespread damage.

Effects of Tsunami

• Till now we have learned about what is a Tsunami and the types of the tsunami. So in this section, we will learn about the effects of the tsunami.

• A tsunami’s impact on a coastline can vary from mild to catastrophic. The characteristics of the seismic event that caused the tsunami, its distance from its point of origin, its duration, and, finally, the structure of the depth of water in oceans along the coast that the tsunami is approaching, all influence the effects of the tsunami.

• Here let us discuss a few of the catastrophic effects on nature, animals, and humans.

Destruction

• When a massive tsunami hits land, the amount of energy and water stored in it will cause massive damage.

• Tsunamis inflict damage by two mechanisms: the slamming force of a fast-moving wall of water, and the destructive strength of a large volume of water draining off the ground and bringing a large amount of debris with it, even with small waves.

• The initial wave of a large tsunami is extremely high, but it does not cause the majority of the damage. The vast mass of water behind the initial wavefront causes the majority of the damage, as the sea level continues to rise rapidly and floods the coastal region. 

• The strength of the waves, the never-ending crashing water, is what causes destruction and death. A tsunami’s huge breaking waves will kill everything in their way as they pound the shoreline.

• Tsunami waves wreck everything in their path: boats, houses, bridges, vehicles, trees, telephone lines, power lines, and just about everything else. 

• If the tsunami waves have swept away the shoreline’s infrastructure, they will proceed inland for several miles, sweeping away more trees, houses, vehicles, and other man-made objects. 

• Some tsunamis have also made some of the small islands unrecognisable.

Death

• The cost of human life is one of the most significant and destructive consequences of a tsunami since surviving a tsunami is virtually impossible. Tsunamis claim the lives of hundreds of thousands of people.

• Before a tsunami hits the ground, there is very little warning. When the water flows toward the shore, there is no time to plot an escape path.

• People who live in coastal areas, cities, and villages do not have the luxury of time to flee. The tsunami’s strong force causes instant death, most usually from drowning. Another cause of death is buildings collapse, electrocution, and fires from gas, broken tanks, and floating debris.

Disease

• In tsunami-affected areas, the disease could spread due to flooding and polluted drinking water. When water is stagnant and polluted, illnesses like malaria will spread.

• Since it is difficult for people to remain healthy and diseases to be treated in these environments, infections and illnesses will spread rapidly, resulting in more deaths.

Environmental Impacts

• Tsunamis not only kill humans, but also wipe out insects, livestock, plants, and natural resources.

• The landscape is changed by a tsunami. It uproots trees and plants, as well as animal habitats including bird nesting sites.

• Drowning kills land animals, and waste kills sea animals when toxic substances are washed into the sea, poisoning marine life.

• The environmental impacts of a tsunami include not just the landscape and animal life, but also the man-made elements of the climate.

More Facts About the Tsunami

• The most dangerous tsunami recorded till now is the Boxing day tsunami, also known as the Indian Ocean tsunami with at least 2,30,000 people killed or missing in 14 countries bordering the Indian Ocean, it was one of the worst natural disasters in human history.

• The most recent tsunami is the tsunami 2020 which occurred on the island of Samos (Greece) and the Aegean coast of the Izmir region (Turkey) on 30 October 2020. This significant tsunami was triggered by an earthquake of magnitude 7.0 Mw.

• Some zoologists claim that some animals can detect subsonic Rayleigh waves generated by an earthquake or tsunami. Monitoring their actions, if done correctly, may provide an early warning of earthquakes and tsunamis. The proof, on the other hand, is debatable and not generally accepted.

• About 80% of Tsunami occur in the Pacific Ocean, “Rings of Fire”.

• The first wave of Tsunami is not the strongest. However, the successive waves are stronger and bigger. 

• Tsunamis can travel up to the speed of 805 km/hrs or 500 miles almost as fast as a jet plane.

• The US states like Hawaii, Alaska, Oregon, California, and Washington are at the highest risk of Tsunami.

• If anyone is caught by a Tsunami wave, it’s better to not swim, instead, he must grab an object and let the wave carry him.

• Tsunamis can travel throughout the ocean with minimum energy loss.

• Hawaii is always at risk of a Tsunami- It gets hit by one each year and seven in every seven years. In 1946, Hawaii got hit by the biggest tsunami wave at Hilo Island. The reported height of the wave was 30ft and the speed was 500mph.

• In 2004, an earthquake caused a tsunami in the Indian Ocean with the energy of 23000 atomic bombs. After the earthquake, 11 countries were slammed by the radiation emitted from the epicentre. The total death toll was 283000.

 

Tsunami Safety

A Tsunami becomes dangerous when it approaches land. Its speed decreases from 30mph to 20mph when it enters shallow water near coastlines. The height increases, wavelength decreases, and the currents intensify. Tsunami warnings come in various forms. Tsunami warning centres broadcast warnings through local radio and television, weather radios, wireless emergency alerts, and social media. They may also be received by outdoor sirens, text message alerts, local officials, and telephone notifications.

It is better to recognize natural tsunami warnings instead of waiting for an official warning. These include long and strong earthquakes, a loud sound (similar to train or aeroplane) coming from the ocean, a sudden rise or fall in the sea level not related to the tide. Both natural and official warnings are equally important. One should be prepared to respond quickly to these warnings.

One can move to a safe place by following the evacuation signs. If an individual is unable to do so, then he must go to high ground or far away from the coastlines.

When tsunamis strike land, their height is less than 10 feet, but in some cases, it can exceed 100 feet near their source.

A tsunami can come to the shore like a wall of turbulent water or a fast-rising flood. Moreover, a huge tsunami wave can destroy low-lying coastal areas to a large extent.

Rushing water from floods, waves, and rivers is highly powerful. It can wash off everything coming on their way.

Tsunamis are destructive due to their volume and speed. They become more dangerous when they return from the sea carrying people, objects, and debris with them. Therefore, people are advised to stay out of the tsunami hazard zones until the conditions come under control.