UPSC Essentials | Mains answer practice — GS 1 Questions on ocean currents and geological time scale (Week 48)

QUESTION 2

What is the geological time scale (GTS)? Describe the historical evolution of the geological time scale.

General points on the structure of the answers

Introduction

QUESTION 1: What are ocean currents? Discuss the ways it influences human behaviour.

Introduction:

— Oceanic currents refer to the movement of water from one location to another.

— Currents are often measured in meters per second or knots (1 knot = 1.85 km/h or 1.15 miles/h).

— Wind, density changes in the water, and tides all contribute to ocean currents.

Tidal currents

— Tides cause currents in the oceans, which are strongest along the beach and in bays and estuaries along the coastline. These are known as “tidal currents.”

— Tidal currents follow a relatively consistent pattern and can be anticipated for future dates.

Wind

— Winds propel currents that flow at or near the ocean’s surface. Winds near coastlines tend to drive localised currents, resulting in phenomena such as coastal upwelling.

Thermohaline circulation

— This is a process characterised by density changes in water caused by temperature (thermo) and salinity (haline) fluctuations in different sections of the ocean. Thermohaline circulation drives currents at both deep and shallow ocean depths, and they move much slower than tidal or surface currents.

Body:

You may incorporate some of the following points in the body of your answer:

— Ocean currents have numerous direct and indirect effects on human activities. Cool waters border the west coasts of continents at tropical and subtropical latitudes.

— Their average temperatures are relatively modest, with limited diurnal and yearly fluctuations. There is fog, although the landscapes are mostly arid.

— Warm waters border the west coastlines of continents at middle and higher latitudes, resulting in a distinct marine climate.

— They have pleasant summers, generally warm winters, and a narrow yearly temperature range. Warm currents move parallel to the continents’ east coasts in tropical and subtropical latitudes.

— This leads to warm and rainy climates. These locations are located on the western borders of subtropical anticyclones.

— Mixing warm and cold currents helps to replenish oxygen and promotes the growth of plankton, the principal food source for fish populations.

— The best fishing grounds in the world are primarily found in these mixing zones.

Conclusion:

— A recent study notes that the Atlantic Meridional Overturning Circulation (AMOC) is losing its stability.

— Atlantic Meridional Overturning Circulation (AMOC) is a large system of ocean currents. It is the Atlantic branch of the ocean conveyor belt or Thermohaline circulation (THC), and distributes heat and nutrients throughout the world’s ocean basins.

— AMOC carries warm surface waters from the tropics towards the Northern Hemisphere, where it cools and sinks. It then returns to the tropics and then to the South Atlantic as a bottom current.

(Source: Why the Atlantic Ocean current system is slowing down, and its implications by Aswathi Pacha, oceanservice.noaa.gov, ncert.nic.in)

Points to Ponder

What happens if AMOC collapses?

Difference between warm currents and cold currents

Location of important water currents

Related Previous Year Questions

What are the forces that influence ocean currents? Describe their role in fishing industry of the world. (2022)

Explain the factors responsible for the origin of ocean currents? How do they influence regional climates, fishing and navigation? (2015)

QUESTION 2: What is the geological time scale (GTS)? Describe the historical evolution of the geological time scale.

Introduction:

— The Earth’s geological time scale is a crucial tool used by geologists, paleontologists, and other scientists to investigate the planet’s history.

— It is a system that divides the history of the Earth into discrete intervals of time, based on events, such as the evolution and extinction of different living beings and processes that have occurred.

— It is divided into five broad categories, eons, epochs, eras, periods, and ages.

Body:

You may incorporate some of the following points in the body of your answer:

Evolution

— The root of geological time scale origin goes back to the 1500s and 1600s when the first major breakthrough came in 1669 after Danish scientist Nicolas Steno published the first laws of stratigraphy — the science of interpreting the strata, or layers of rock, in the Earth’s outer surface.

— He laid out two basic geologic principles:

(i) Sedimentary rocks (formed on or near the planet’s surface, in contrast to metamorphic and igneous rocks, which are formed deep within the Earth) are laid down in a horizontal manner.

(ii) Younger rock units were deposited on top of older rock units.

— The second principle essentially means that layers closer to the Earth’s surface must be younger than layers below them which allowed scientists of the time to conclude that each rock layer represented a specific interval of geologic time.

— Italian geologist Giovanni Arduino classified the four main layers of the Earth’s crust as:

(i) Primary (the lowest metamorphic and volcanic layers),

(ii) Secondary (hard sedimentary rocks),

(iii) Tertiary (less hardened sedimentary rocks), and

(iv) Quaternary (the most recently laid rock layer, which is quite soft in comparison to other strata).

Diagram of the geological time scale. (Credit: US Geological Survey General Information/Wikimedia commons)

Issues related to Arduino’s classification and Steno’s principles

(i) The rocks were locally described by colour, texture, or even smell, comparisons between rock sequences of different areas were often not possible.

(ii) Unlike tree-ring dating, in which each ring is equivalent to one year’s growth, rock layers don’t tell the specific length of geologic time, meaning no one layer can convey how long a certain period lasted on the Earth.

Conclusion:

— These discrepancies were ultimately resolved in the 1800s by English surveyor William Smith. He noticed that fossils may be used to describe distinct periods of time because evolution and extinction are natural phenomena. A rock with a trilobite fossil on it, for example, indicates that it is Paleozoic in age (541-252 million years ago), not older or younger because trilobites existed exclusively during the Paleozoic era.

— He came up with the principle of faunal succession, which stated that fossils are found in the same order under the Earth’s surface from place to place. Fossil A was always found below Fossil B, which in turn was always found below Fossil C, and so on.

(Source: Advent of the Anthropocene epoch: Geological time scale, and how it has evolved over time by Alind Chauhan)

Points to Ponder

Different types of rocks

Soil profile

Difference between categories of GTS

Related Previous Year Question

Describe the characteristics and types of primary rocks. (2022)

Previous Mains Answer Practice

UPSC Essentials: Mains answer practice — GS 1 (Week 47)

UPSC Essentials: Mains answer practice — GS 1 (Week 46)

UPSC Essentials: Mains answer practice — GS 2 (Week 48)

UPSC Essentials: Mains answer practice — GS 2 (Week 47)

UPSC Essentials: Mains answer practice — GS 3 (Week 47)

UPSC Essentials: Mains answer practice — GS 3 (Week 48)

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