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Subject: Geographical Features

  • What is Lunar Eclipse?

    A penumbral lunar eclipse will be observed today midnight. The Earth will imperfectly align itself between the Sun and the moon, casting a shadow on the latter, marking the second lunar eclipse of the year.

    Solar and Lunar eclipse has been quite frequent this year. Mark the major differences between them.

    Lunar Eclipse

    • A lunar eclipse occurs when the Moon moves into the Earth’s shadow.
    • This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned with Earth between the other two.
    • A lunar eclipse can occur only on the night of a full moon. The type and length of a lunar eclipse depend on the Moon’s proximity to either node of its orbit.
    • Any object that obstructs light will produce two shadows: one which will be dark and dense, is called the umbra; and the other which is light and diffused is called the penumbra.
    • The only light reflected from the lunar surface has been refracted by Earth’s atmosphere.
    • This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light. Due to this reddish colour, a totally eclipsed Moon is sometimes called a blood moon.

    Types

    • In a total eclipse of the moon, the inner part of Earth’s shadow, called the umbra, falls on the moon’s face. At mid-eclipse, the entire moon is in shadow, which may appear blood red.
    • In a partial lunar eclipse, the umbra takes a bite out of only a fraction of the moon. The dark bite grows larger and then recedes, never reaching the total phase.
    • In a penumbral lunar eclipse, only the more diffuse outer shadow of Earth – the penumbra – falls on the moon’s face. This third kind of lunar eclipse is much more subtle and much more difficult to observe than either a total or partial eclipse of the moon.

    How it is different from Solar Eclipse?

    • A solar eclipse happens when the moon passes in between the earth and the sun. A lunar eclipse happens when the earth passes in between the moon and the sun.
    • During a solar eclipse, the moon partially or fully hides the sun’s rays for a few minutes.
    • Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth.
    • Also unlike solar eclipses, lunar eclipses are safe to view without any eye protection or special precautions, as they are dimmer than the full Moon.

    What’s special this time?

    • This eclipse is also called a strawberry moon eclipse — the term, interestingly, originates from an American concept and has little to do with the Euro-Asia region.
    • June’s full moon usually coincides with the harvesting season of wild strawberries in America and the phenomenon was often addressed in reference to that.
    • India had already witnessed an eclipse earlier this year, in January.
    • The strawberry moon eclipse is going to be its second and probably the last visible lunar one in 2020.

  • What is South Atlantic Anomaly?

    New data obtained by the European Space Agency (ESA) Swarm satellites has revealed the existence of a mysterious anomaly weakening the Earth’s magnetic field. Termed as ‘South Atlantic Anomaly’, it extends all the way from South America to southwest Africa.

    The term ‘South Atlantic Anomaly’ at its first sight looks similar to any climate/oceanic current related phenomena. But it’s not! This is where you can end up losing 2.66 marks in the prelims!

    What is South Atlantic Anomaly (SAA)?

    • The SAA is referred to the behaviour of Earth’s Geo-Magnetic field in an area between Africa and South America.
    • The SAA is an area where the Earth’s inner Van Allen radiation belt comes closest to the Earth’s surface, dipping down to an altitude of 200 kilometres.
    • This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.
    • The effect is caused by the non-concentricity of the Earth and its magnetic dipole.
    • The SAA is the near-Earth region where the Earth’s magnetic field is weakest relative to an idealized Earth-centered dipole field.

    Weakening of the magnetic field

    • Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average.
    • A large and rapid shrink has been observed in the SAA region over the past 50 years just as the area itself has grown and moved westward.
    • The weakening of the magnetic field is also causing technical difficulties for the satellites and spacecraft orbiting the planet.
    • The study conducted between 1970 and 2020, said that the magnetic field weakened considerably in a large region stretching from Africa to South America, known as the ‘SAA’.
    • This area has grown and moved westward at a rate of around 20 km per year.

    Its impact

    • The magnetic shield has an important role to play in keeping unwanted radiation away as well as helping determine the location of magnetic poles.
    • Even though unlike global warming or any weather change, this anomaly doesn’t directly impact human lives, it could actually bring on a change in the way we access technology.
    • The reversal and apparent shift, which could keep extending could actually impact satellite and telecommunication system, which means that some of the internet and mobile phone functioning which depend on satellite signals can possibly get disrupted.
    • It could also affect the mapping and navigation systems in smartphones.
    • The weakening of earth’s magnetic field could also impact migratory movement.
    • Birds, animals- all those who migrate with the change in season depend on the earth’s mapping to move about can find it a little difficult.
    • This is only a possibility, but we don’t know the extent of the damage till now.

    About the Van Allen Radiation Belt

    • A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet’s magnetic field.
    • The belts are located in the inner region of Earth’s magnetosphere. The belts trap energetic electrons and protons.
    • Earth has two such belts and sometimes others may be temporarily created.
    • Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays.
    • By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

    Also read:

    https://www.civilsdaily.com/news/shifting-north-magnetic-pole-forces-urgent-navigation-fix/

    Back2Basics: Swarm  Constellation

    • Swarm is a European Space Agency (ESA) mission to study the Earth’s magnetic field.
    • It is ESA’s first constellation of satellites for Earth observation.
    • The Swarm constellation consists of three satellites (Alpha, Bravo and Charlie) placed in two different polar orbits, two flying side by side at an altitude of 450 km and a third at an altitude of 530 km.

  • Super Cyclone Amphan and its threats

    The storm system in the Bay of Bengal, Amphan, developed into a super cyclone and is expected to make landfall along the West Bengal-Bangladesh coast very soon.

    Realted PYQ:

    Q. In the South Atlantic and South Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (CSP 2015)

    (a) Sea Surface temperature are low
    (b) Inter Tropical Convergence Zone seldom occurs
    (c) Coriolis force is too weak
    (d) Absence of land in those regions

    Super Cyclone Amphan

    • Cyclone Amphan is a tropical cyclone formed over the Bay of Bengal that has intensified and likely to turn into a “super cyclonic storm (maximum wind speed is 224 kmph)”.
    • It has been named by Thailand.
    • Amphan is the equivalent of a Category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale.
    • By the time it makes landfall in West Bengal, Amphan is expected to tone down into a category 4 Extremely Severe Cyclonic (ESC) storm with a wind speed of 165-175 kmph and gusting to 195 kmph.

    What makes it a nightmare?

    • This is the first super cyclone to form in the Bay of Bengal after the 1999 super cyclone that hit Odisha and claimed more than 10,000 lives.
    • It is the third super cyclone to occur in the North Indian Ocean region after 1999 which comprises of the Bay of Bengal, the Arabian Sea and the northern part of the Indian Ocean.
    • The other two super cyclones were Cyclone Kyarr in 2019 and Cyclone Gonu in 2007.

    Recent cyclones in the region

    • From 1965 to 2017, the Bay of Bengal and the Arabian Sea collectively registered 46 ‘severe cyclonic storms’.
    • More than half of them occurred between October and December.
    • Seven of them occurred in May and only two (in 1966 and 1976) were recorded in April, according to data from the IMDs cyclone statistics unit.
    • Cyclone Phailin in 2013 and the super cyclone of 1999 — both of which hit coastal Odisha — have been the most powerful cyclones in the Bay of Bengal in the past two decades in terms of wind speed.
    • Last year, Fani, which was an ESC made landfall in Odisha and ravaged the State, claiming at least 40 lives.

    Back2Basics: Tropical Cyclones

    • Cyclones are formed over slightly warm ocean waters.
    • The temperature of the top layer of the sea, up to a depth of about 60 metres, need to be at least 28°C to support the formation of a cyclone.
    • This explains why the April-May and October-December periods are conducive for cyclones.
    • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
    • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
    • This induces the anticlockwise rotation of the air.
    • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea and adds to its heft.

    What strengthens them?

    • A thumb rule for cyclones is that the more time they spend over the seas, the stronger they become.
    • Hurricanes around the US, which originate in the vast open Pacific Ocean, are usually much stronger than the tropical cyclones in the Bay of Bengal, a relatively narrow and enclosed region.
    • The cyclones originating here, after hitting the landmass, decay rapidly due to friction and absence of moisture.

    Grading of Cyclones

    • Tropical cyclones in the Bay of Bengal are graded according to maximum wind speeds at their centre.
    • At the lower end are depressions that generate wind speeds of 30 to 60 km per hour, followed by:
    1. cyclonic storms (61 to 88 kmph)
    2. severe cyclonic storms (89 to 117 kmph)
    3. very severe cyclonic storms (118 to 166 kmph)
    4. extremely severe cyclonic storms (167 to 221 kmph) and
    5. super cyclones (222 kmph or higher)

  • [pib] River erosion in Ladakh Himalayas

    Indian researchers have studied rivers in Ladakh Himalaya, bringing out 35 thousand-year histories of river erosion and identified hotspots of erosion and wide valleys that act buffer zones.

    Click here to read more about the Himalayan river systems and its orogeny

    Erosion hotspot: Ladakh region

    • The Ladakh Himalaya forms a high altitude desert between Greater Himalayan ranges and Karakoram Ranges.
    • The Indus and its tributaries are major rivers flowing through the terrain.
    • The Zanskar River is one of the largest tributaries of the upper Indus catchment, draining orthogonally through highly deformed Zanskar ranges.

    Zanskar: A major river in Ladakh

    • Two prominent tributaries of Zanskar River are the Doda and Tsrap Lingti Chu, which confluence at Padam village in the upper valley to form the Zanskar River.
    • Zanskar catchment was explored to understand the landform evolution in the transitional climatic zone, using morpho-stratigraphy and study of landforms like valley fill terraces, alluvial fans (triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt).

    Zanskar Padam

    • Zanskar river makes a deep gorge in its lower reaches with the headwaters in upper Zanskar makes wide basin called as Padam.
    • The basin stores large amount of sediments in form of fans and river terrace deposits
    • The research suggested that the wide valley of Padam, with an area of 48 square km, in the upper Zanskar, has stored a vast amount of sediments in these landforms.
    • Thus Padam valley is a hotspot of sediment buffering in the Zanskar.

    Sediment study reveals the erosion

    • The study suggested that most sediments were derived from Higher Himalayan crystalline that lies in the headwater region of Zanskar.
    • It was found out that dominant factors responsible for sediment erosion were deglaciation and Indian Summer Monsoon derived precipitation in the headwaters despite the presence of a geomorphic barrier (the deep, narrow gorge).

    Significance of the study

    • The scientists have traced where the rivers draining Himalaya and its foreland erode the most and identify the zones that receive these eroded sediments and fill up.
    • The study will help understand river-borne erosion and sedimentation, which are the main drivers that make large riverine plains, terraces, and deltas that eventually become the cradle to evolving civilizations.
    • It will also help study the dynamics of devastating floods created by these Himalayan rivers in recent times.
    • Thus, the understanding of water and sediment routing becomes crucial while developing infrastructure and for other development works in the river catchment area.

  • New list of names of tropical cyclones over north Indian Ocean

    The India Meteorological Department (IMD) has released a new list containing 169 names of future tropical cyclones that would emerge in the Bay of Bengal and the Arabian Sea.

    When is the name of a Tropical Cyclone declared?

    • Names are declared when TCs are diagnosed with maximum sustained surface wind-speed of 34 knots (62 kmph) or more as per Global Data Processing and Forecasting System (GDPFS) Manual of WMO.
    • Panel Members’ names will be listed alphabetically country-wise.

    We can expect a statement based prelim question like – Which of the following criterion are followed while naming a tropical cyclone?

    Who is involved in the naming of Tropic Cyclone?

    • Worldwide there are six regional specialised meteorological centres (RSMCs) and five regional Tropical Cyclone Warning Centres (TCWCs) mandated for issuing advisories and naming of tropical cyclones.
    • IMD is one of the six RSMCs to provide tropical cyclone and storm surge advisories to 13 member countries under WMO/ESCAP Panel.
    • The panel countries include Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen.
    • RSMC, New Delhi is also mandated to name the Tropical Cyclones developing over the North Indian Ocean (NIO) including the Bay of Bengal and the Arabian Sea.

    Since when did naming begin?

    • The WMO/ESCAP Panel on Tropical Cyclones (PTC) at its twenty-seventh Session held in 2000 in Muscat, agreed in principle to assign names to the tropical cyclones in the Bay of Bengal and the Arabian Sea.
    • After long deliberations among the member countries, the naming of the tropical cyclones over the north Indian Ocean commenced from September 2004.
    • This list contained names proposed by the eight member countries of WMO/ESCAP PTC, viz., Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand.

    Why name Cyclones?

    The naming of Tropical Cyclones (TC) helps the scientific community, disaster managers, media and general masses to-

    • identify each individual cyclone.
    • create awareness of its development.
    • remove confusion in case of simultaneous occurrence of TCs over a region
    • remember a TC easily
    • rapidly and effectively disseminate warnings to a much wider audience

    Major criteria adopted for naming

    • The proposed name should be neutral to (a) politics and political figures (b) religious believes, (c) cultures and (d) gender
    • The name should be chosen in such a way that it does not hurt the sentiments of any group of the population over the globe
    • It should not be very rude and cruel in nature
    • The maximum length of the name will be eight letters
    • The Panel reserves the right to reject any name if any of the criteria above are not satisfied
    • The names of tropical cyclones over the north Indian Ocean will not be repeated. Once used, it will cease to be used again.

    Back2Basics

    https://www.civilsdaily.com/news/explained-naming-of-cyclones/

  • Rohtang Pass and its location

    The Border Roads Organisation (BRO) has opened the Rohtang Pass, three weeks in advance, for transporting essential supplies and relief materials to Lahaul and Spiti districts of Himachal Pradesh.

     Rohtang Pass

    • It is a high mountain pass (elevation 3,980 m) on the eastern Pir Panjal Range of the Himalayas around 51 km from Manali.
    • It connects the Kullu Valley with the Lahaul and Spiti Valleys of Himachal Pradesh, India.
    • The pass lies on the watershed between the Chenab and Beas basins.
    • On the southern side of this pass, the Beas River emerges from underground and flows southward and on its northern side, the Chandra River, a source stream of the river Chenab, flows westward.

    Another pass in new:

    https://www.civilsdaily.com/news/sela-pass-tunnel-project/

  • Daporijo Bridge and its significance

    A key bridge over the Subansiri River in Arunachal Pradesh close to the Line of Actual Control (LAC) was constructed by the Border Roads Organisation (BRO) in record 27 days.

    North-East has seen the construction of a series of bridges by BRO in recent times post-Doklam standoff. Make a note of all such bridges and the corresponding rivers over which they are built.

     Daporijo Bridge

    • This Bridge is one of the two over River Subansiri which connect Daporji in North Subansiri dist. with rest of state.
    • This and the other bridge at Tamin sustaining more than 600 villages and troops strength of around 3000 personnel manning the LAC which includes disputed Areas of Asaphila and Maza.
    • All supplies, rations, constructional material and medicines pass over this bridge.
    • The new bridge now can withstand 40 tonnes of weight allowing a safe passage for heavier vehicles catering for the requirements of the Indian Army as well as future infrastructure development requirements.

    Significance

    • India has speeded up the construction of critical infrastructure in its northeast in the past half a dozen years including airports, railways and roads with an eye on China that has motorable roads right up to the border.
    • Arunachal Pradesh was the scene of the 1962 India-China border conflict that ended badly for India. China on its parts claims all of the state as “Southern Tibet.”
    • Of the 3488 km long Line of Actual Control with China 1126 lies with Arunachal Pradesh alone.
    • The two countries are yet to demarcate their border with the two sides patrolling the LAC but reporting incursions by the other side since the frontier is not clearly marked.

  • Matterhorn Mountain of the Swiss Alps

    Switzerland has expressed solidarity with India in its fight against the coronavirus pandemic by projecting the tricolour on the famous Matterhorn Mountain in the Swiss Alps.

    It has been long time since a question on global mountains/mountain ranges has not been asked in the prelims. Gear up for the uncertainty. Make a special sheet of geographical locations in news.

    Mt. Matterhorn

    • The Matterhorn is a mountain of the Alps, separating the main watershed and border between Switzerland and Italy.
    • It is a large, near-symmetric pyramidal peak in the extended Monte Rosa area of the Pennine Alps, whose summit is 4,478 metres.
    • It is one of the highest summits in the Alps and Europe (Mont Blanc being highest).
    • The four steep faces, rising above the surrounding glaciers, face the four compass points and are split by the Hörnli, Furggen, Leone/Lion, and Zmutt ridges.

    Its formation

    • The Matterhorn is mainly composed of gneisses originally fragments of the African Plate before the Alpine orogeny.
    • The mountain’s current shape is the result of cirque erosion due to multiple glaciers diverging from the peak, such as the Matterhorn Glacier at the base of the north face.

    Back2Basics: Alps mountain range

    • The Alps are the highest and most extensive mountain range system that lies entirely in Europe.
    • It stretches approximately 1,200 kilometres across eight Alpine countries (from west to east): France, Switzerland, Monaco, Italy, Liechtenstein, Austria, Germany, and Slovenia.
    • The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided.
    • Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn.
    • Mont Blanc spans the French–Italian border, and at 4,809 m (15,778 ft) is the highest mountain in the Alps.

  • Earth’s seismic noise levels

    Scientists at the British Geological Survey (BGS) reported a change in the Earth’s seismic noise and vibrations amid the coronavirus lockdown. This change has been monitored through a space-based seismograph.

    Ever heard of space-based monitoring of seismic activities?  This topic creates a scope for potential prelims question…

    What is seismic noise?

    • In geology, seismic noise refers to the relatively persistent vibration of the ground due to a multitude of causes.
    • It is the unwanted component of signals recorded by a seismometer– the scientific instrument that records ground motions, such as those caused by earthquakes, volcanic eruptions, and explosions.
    • This noise includes vibrations caused due to human activity, such as transport and manufacturing, and makes it difficult for scientists to study seismic data that is more valuable.
    • Apart from geology, seismic noise is also studied in other fields such as oil exploration, hydrology, and earthquake engineering.

    How are vibrations generated?

    • We measure ground vibrations from earthquakes using seismometers.
    • These are incredibly sensitive so they also pick up other sources of vibration too, including human activity, such as road traffic, machinery and even people walking past.
    • All these things generate vibrations that propagate as seismic waves through the Earth.

    Reasons for the decline

    • Due to the enforcement of lockdown measures around the world to tackle the novel coronavirus pandemic, the Earth’s crust has shown reduced levels of vibration.

    How do the reduced noise levels help scientists?

    • The seismic noise vibrations caused by human activity are of high frequency (between 1-100 Hz), and travel through the Earth’s surface layers.
    • Usually, to measure seismic activity accurately and reduce the effect of seismic noise, geologists place their detectors 100 metres below the Earth’s surface.
    • However, since the lockdown, researchers were able to study natural vibrations even from surface readings, owing to lesser seismic noise.
    • Due to lower noise levels, scientists are now hoping that they would be able to detect smaller earthquakes and tremors that had slipped past their instruments so far.

     

  • Earth’s spin has slowed over time

     

    Earth spun 372 times a year 70 million years ago, compared to the current 365. This means the day was 23½ hours long, compared to 24 today.

    Faster Earth in the olden days

    • It has long been known that Earth’s spin has slowed over time.
    • Previous climate reconstructions, however, have described long-term changes over tens of thousands of years.
    • The new study looked at daily and annual variations in the mollusc shell.

    About the Mollusc

    • A mollusc is an invertebrate of a large phylum which includes snails, slugs, mussels, and octopuses. They have a soft unsegmented body and live in aquatic or damp habitats, and most kinds have an external calcareous shell.
    • The ancient mollusc, Torreites Sanchez, belonged to an extinct group called rudist clams.
    • At 70 million years ago, it belonged to the Late Cretaceous — it was around the time this epoch ended, some 65 million years ago, that dinosaurs went extinct.

    How did researchers conclude this variation?

    • Torreites sanchezi grew very fast, laying down daily growth rings.
    • Using lasers on a single individual, scientists sampled tiny slices and counted the growth rings accurately.
    • This allowed them to determine the number of days in a year 70 million years ago, and more accurately calculate the length of a day.

    Significance of the research

    • It is important to note that the period of Earth’s orbit has remained the same. In other words, one year 70 million years ago was as long as one year today.
    • However, if there were a calendar then, the year would have been 372 “days” long, with each “day” half-an-hour shorter than one day today.
    • Today, Earth’s orbit is not exactly 365 days, but 365 days and a fraction, which is why our calendars have leap years, as a correction.

    The Moon’s retreat

    • Friction from ocean tides, caused by the Moon’s gravity, slows Earth’s rotation and leads to longer days.
    • And as Earth’s spin slows the Moon moves farther away at 3.82 cm per year.
    • If this rate is projected back in time, however, the Moon would be inside the Earth only 1.4 billion years ago.
    • This new measurement, in turn, informs models of how the Moon formed and how closes it has been to Earth over their 4.5-billion-year gravitational relationship.