12 Topics.
0 of 17 Concepts Done
What to Study: Who was the first to suggest that the Atlantic continents were once joined, what was his nationality, and in which year? Remember what Pellegrini added. Understand why the Atlantic coastlines prompted this idea, and how it differs from Wegener's full argument.
Asked in UPSC PrelimsUPSC 2014
What to Study: Remember who Wegener was by profession and nationality, and the year he put forward his theory. Understand its central claim: what the continents and oceans looked like at first, and what happened to them later.
What to Study: Remember what each of these four names refers to and what the first two names mean. Around when did Pangaea begin to split? Be clear which part became the northern and which the southern landmass, and which sea lay between them.
Asked in UPSC PrelimsUPSC 2025
What to Study: Which two continents show the clearest match of coastlines? Remember who produced a computer fit of the Atlantic margins, and when. Why was the fit tried along the 1,000-fathom line and not along the present shoreline?
What to Study: How has radiometric dating helped link rocks on opposite sides of the Atlantic? Remember the belt of ancient rocks that matches between Brazil and western Africa, and its age. What does the Jurassic age of the earliest marine deposits suggest about the ocean?
Asked in UPSC PrelimsUPSC 2025
What to Study: What is tillite, and how is it formed? Which southern landmasses have counterparts of the Gondwana sediments found in India? Explain why glacial deposits in lands that are warm today support both drift and a change of climate.
Asked in UPSC PrelimsUPSC 2025
What to Study: What is a placer deposit, and how does it differ from gold found in rock veins? Why is the lack of a local source rock in Ghana puzzling? Understand how this points to a past link with Brazil.
What to Study: Where are lemurs and their fossil relatives found? What was the lost land of Lemuria proposed to explain, and why was the idea dropped? What kind of reptile was Mesosaurus, and where are its fossils found? Explain why identical land or freshwater species on either side of an ocean need an explanation.
What to Study: Wegener proposed two forces for drifting. What does each of them relate to? Understand why most scholars found them far too weak.
What to Study: Understand the main objections to the theory: weak forces, continents moving through the ocean floor as if it were passive, movement only towards the equator and the west, and no reason for the timing of the break-up. Which later ideas answered these objections?
What to Study: Who discussed convection currents in the mantle, and around when? Understand what causes these currents. Explain how the idea tried to answer the objection about the force behind drifting.
What to Study: Understand why mapping of the ocean floor after World War II shifted the debate from evidence on land to evidence under the sea. Remember what the mapping showed about relief, ridges, trenches, the age of oceanic rocks and the rocks on either side of the ridge crests.
What to Study: Remember the three major divisions of the ocean floor and the parts that make up a continental margin. Where do abyssal plains lie, and what collects on them?
What to Study: Remember how this ridge system compares with other mountain chains on earth, and why it is hidden from view. Understand its three parts (central rift, fractionated plateau, flank zone) and why the crest is a zone of volcanic activity.
What to Study: Know the path of the line of earthquake activity through the Atlantic and Indian Oceans, and where it splits near the Indian subcontinent. Which mountain system and which ocean rim form the other major belt? Understand how these belts coincide with ridges and young fold mountains.
What to Study: How does the depth of earthquake foci change with the type of plate boundary? Compare ridges, trenches, the Alpine-Himalayan belt and the Pacific rim. Understand where deep-focus earthquakes occur and why.
What to Study: Which region is called the rim (or ring) of fire, and why? Understand how plate movement around the Pacific explains its earthquakes and volcanoes.