Geography: December 2022 UPSC Current Affairs | Current Affairs & Hindu Analysis: Daily, Weekly & Monthly PDF Download

Western Disturbances

• Context
  • The days have been unusually warm for winter in New Delhi with the maximum temperature remaining above normal mostly on account of fewer western disturbances affecting this year.

• Western Disturbances

  • A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.

  • They are labelled as an extra-tropical storm originating in the Mediterranean, is an area of low pressure that brings sudden showers, snow, and fog in northwest India.
  • In the term “extra-tropical storm”, storm refers to low pressure. “Extra-tropical” means outside the tropics. As the WD originates outside the tropical region, the word “extra-tropical” has been associated with them.
  • It is a non-monsoonal precipitation pattern driven by the westerlies.
  • The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
  • Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
  • In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
  • Western disturbances are more frequent and strong in the winter season.

  • Impact: Winter Rainfall and Extreme Cold

  • Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.

  • They are the cause of most winter and pre-monsoon season rainfall across northwest India.

  • An average of four to five western disturbances forms during the winter season.

• Its significance

  • Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.

  • Wheat among them is one of the most important crops, which helps to meet India’s food security.

Cyclone Mandous

Why in News?

Recently, it has been reported that a cyclone may impact the Tamil Nadu and Puducherry coasts from 8th December 2022 onwards.

What is Cyclone Mandous?

• Mandous is a slow-moving cyclone that often absorbs a lot of moisture, carries a humongous amount of rainfall and gains strength in the form of wind speeds.
• The name has been suggested by the United Arab Emirates.
• India Meteorological Department’s (IMD) predicted that the storm system may move in the west and northwestward directions and intensify into a depression by the evening of December 6.
• It may subsequently strengthen further into a cyclone over southwest Bay of Bengal and move towards the Tamil Nadu and Puducherry coasts by the morning of December 8.

What is a Cyclone?

• Cyclones are rapid inward air circulation around a low-pressure area. The air circulates in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.
• Cyclones are usually accompanied by violent storms and bad weather.
• The word Cyclone is derived from the Greek word Cyclos meaning the coils of a snake. It was coined by Henry Peddington because the tropical storms in the Bay of Bengal and the Arabian Sea appear like coiled serpents of the sea.
• There are two types of cyclones:
  • Tropical cyclones;
  • Extra Tropical cyclones (also called Temperate cyclones or middle latitude cyclones or Frontal cyclones or Wave Cyclones).
  • The World Meteorological Organisation uses the term 'Tropical Cyclone’ to cover weather systems in which winds exceed ‘Gale Force’ (minimum of 63 km per hour).
  • Tropical cyclones develop in the region between the Tropics of Capricorn and Cancer.
  • They are large-scale weather systems developing over tropical or subtropical waters, where they get organized into surface wind circulation.
  • Extra tropical cyclones occur in temperate zones and high latitude regions, though they are known to originate in the Polar Regions.

How are Names of Cyclones Decided?

• Cyclones that form in every ocean basin across the world are named by the regional specialised meteorological centres (RSMCs) and Tropical Cyclone Warning Centres (TCWCs). There are six RSMCs in the world, including the India Meteorological Department (IMD), and five TCWCs.
• In 2000, a group of nations called WMO/ESCAP (World Meteorological Organisation/United Nations Economic and Social Commission for Asia and the Pacific), which comprised Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand, decided to start naming cyclones in the region. After each country sent in suggestions, the WMO/ESCAP Panel on Tropical Cyclones (PTC) finalised the list.
• The WMO/ESCAP expanded to include five more countries in 2018 — Iran, Qatar, Saudi Arabia, United Arab Emirates and Yemen.

Semeru Volcano of Indonesia  

Why in News?

• Recently, Semeru volcano erupted in Indonesia’s Eastern Java Island.

What is Semeru Volcano?

• Semeru - also known as "The Great Mountain" - is the highest volcano in Java and one of the most active.
• It previously erupted in December, 2021.
• Indonesia, with the maximum number of active volcanoes in the world, is prone to seismic upheaval due to its location on the Pacific’s Ring of Fire.
• Semeru volcano is also part of the Island arcs formed by the subduction of the Indo-Australian plate below Sunda Plate (part of the Eurasian Plate). The trench formed here is called the Sunda trench whose major section is the Java Trench.

What is Pacific Ring of Fire?

• The Ring of Fire, also referred to as the Circum-Pacific Belt, is a path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes.
• It traces boundaries between several tectonic plates—including the Pacific, Cocos, Indian-Australian, Nazca, North American, and Philippine Plates.

What are Island Arcs?

• They are long, curved chains of oceanic islands associated with intense volcanic and seismic activity and orogenic (mountain-building) processes.
• An island arc typically has a land mass or a partially enclosed, unusually shallow sea on its concave side.
• Along the convex side there almost invariably exists a long, narrow deep-sea trench.
• The greatest ocean depths are found in these depressions of the seafloor, as in the case of the Mariana (deepest trench in the world) and Tonga trenches.
• Prime examples of this form of geologic feature include the Aleutian-Alaska Arc and the Kuril-Kamchatka Arc.

What are the Other Volcanoes?

• Recently Erupted:
  • Sangay Volcano: Ecuador
  • Taal Volcano: Philippines
  • Mt. Sinabung, Merapi volcano: Indonesia
• Volcanoes in India:
  • Barren Island, Andaman Islands (India's only active volcano)
  • Narcondam, Andaman Islands
  • Baratang, Andaman Islands
  • Deccan Traps, Maharashtra
  • Dhinodhar Hills, Gujarat
  • Dhosi Hill, Haryana

Coastal Red Sand Dunes

Why in News?

Recently, geologists have suggested to protect the site of Coastal Red Sand Dunes, of Visakhapatnam, Andhra Pradesh.

What are the Key Points of the Sites?

• About:
  • The Coastal Red Sand Dunes is also known as ‘Erra Matti Dibbalu’. It is one of the many sites of Visakhapatnam, which have geological importance.
  • The site is located along the coast and is about 20 km north-east of Visakhapatnam city and about 4 km south-west of Bheemunipatnam.
  • This site was declared as a geo-heritage site by the Geological Survey of India (GSI) in 2014 and the Andhra Pradesh government has listed it under the category of ‘protected sites’ in 2016.
• Distribution:
  • Such sand deposits are rare and have been reported only from three places in the tropical regions in south Asia such as Teri Sands in Tamil Nadu, Erra Matti Dibbalu in Visakhapatnam and one more site in Sri Lanka.
  • They do not occur in equatorial regions or temperate regions due to many scientific reasons.

What is the Uniqueness of these Sediments?

• Continuous Evolution:
  • The red sediments are a part of the continuation of the evolution of the earth and represent the late quaternary geologic age.
  • The Quaternary Period is a period on the Geologic Time Scale that's known mainly for the spread of humanity and climate change. This period runs from about 2.6 million years ago to the Present Day.
• Different Geomorphic Features:
  • With a height of up to 30 m, they exhibit badland topography with different geomorphic landforms and features, including gullies, sand dunes, buried channels, beach ridges, paired terraces, the valley in the valley, wave-cut terrace, knick point and waterfalls.
  • Badland topography is a dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded by wind and water.
• Geochemically Unaltered:
  • The top light-yellow sand unit, which is estimated to have been deposited around 3,000 years ago, could not attain the red colouration as the sediments were geochemically unaltered.
  • These sediments are unfossiliferous (not containing fossils) and deposited over the khondalite basement.
  • Khondalite is a regional rock with high-grade metamorphism and granulite rock formation. It was named after the Khond tribe of Odisha.

What is the Significance of Protecting this Site?

• It is significant to protect this site, because its study can help understand the impact of climate change, as Erra Matti Dibbalu has seen both the glacial and the warm periods.
• The site is about 18,500 to 20,000 years old and it can be related to the last glacial period.
• It is a lively scientific evolution site, which depicts the real-time effects of climate change.
• About 18,500 years ago, the sea (Bay of Bengal) was at least 5 km behind from the present coastline. Since then, it has been undergoing continuous active changes till about 3,000 years ago and still the changes are on.
• The site also has archaeological significance, as studies of artifacts indicate an Upper Palaeolithic horizon and on cross dating assigned to Late Pleistocene epoch, which is 20,000 BC.
• The site was home to the pre-historic man as the excavations at several places in the region revealed stone implements of three distinctive periods and also the pottery of the Neolithic man.

Bomb Cyclone

Why in News?

Recently, a Bomb cyclone hit the United States and Canada, which triggered road accidents that results in the death of more than 30 people.

What is a Bomb Cyclone?

• About:
  • A bomb cyclone is a large, intense midlatitude storm that has low pressure at its center, weather fronts and an array of associated weather, from blizzards to severe thunderstorms to heavy precipitation.
  • Bomb cyclones put forecasters on high alert because they can produce significant harmful impacts.
• Reasons for the Formation:
  • Storms form when a mass of low-pressure air (warm air mass) meets a high-pressure mass (cold air mass). The air flows from high pressure to low, creating winds.
  • It occurs when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours.
  • A millibar measures atmospheric pressure.
  • This quickly increases the pressure difference, or gradient, between the two air masses, therefore making the winds stronger.
  • The formation of this rapidly strengthening weather system is a process called bombogenesis.

How does a Bomb Cyclone Differ from a Hurricane?

• Hurricanes tend to form in tropical areas and are powered by warm seas. For this reason, they’re most common in summer or early fall, when seawater is warmest.
• Bomb cyclones generally occur during colder months because cyclones occur due to cold and warm air meeting.
• During the summer, there’s generally not much cold air across the atmosphere; this means a bomb cyclone is much less likely to occur.
• Hurricanes form in tropical waters, while bomb cyclones form over the northwestern Atlantic, northwestern Pacific and sometimes the Mediterranean Sea.