GS Paper 1
Syllabus: Geography: Geology
Source: TH
Context: A recent study has revealed that India hosts remarkably well-preserved volcanic and sedimentary rocks as old as 3.5 billion years, and has similar geologic history to parts of South Africa and Australia.
- These rocks, found in the Daitari greenstone belt within the Singhbhum Craton in east India, provide valuable insights into the geological history of the region and shed light on past Earth processes.
- Cratons are pieces of ancient continents that formed several billions of years ago. Their study provides a window into how processes within and on the surface of Earth operated in the past.
Key Findings:
- The presence of silicic rocks rich in silica indicated explosive sub-marine to sub-aerial volcanic settings. Furthermore, the researchers determined that sub-marine turbidity current deposits, comprising sedimentary rocks, were formed after the volcanic vent drowned.
- By studying these ancient greenstones, researchers gain insights into various volcanic processes and uncover well-preserved minor sedimentary rocks that formed under sub-marine conditions.
Significance:
- The well-preserved greenstones serve as time capsules, providing clues about habitable environments on Earth during its early stages and aiding in the comprehension of the planet’s evolution.
- It provides evidence for various theories of plate tectonics
Various theories of Plate tectonics:
| Theory | Description | Key Proponents |
| Continental Drift | Suggested that continents were once a supercontinent (Pangaea) and have drifted apart over time | Alfred Wegener |
| Seafloor Spreading | Proposed that new oceanic crust forms at mid-ocean ridges and spreads outward | Harry Hess |
| Subduction Theory | Described the process of one tectonic plate descending beneath another at subduction zones | Charles Darwin, Eduard Suess |
| Plate Tectonics | Integrated the concepts of continental drift and seafloor spreading into a comprehensive theory | Tuzo Wilson, Jason Morgan, Dan McKenzie |
Key evidence in support of plate tectonics:
| Evidence | Description |
| Fit of Continents | The coastlines of continents, such as the east coast of South America and the west coast of Africa, fit together like puzzle pieces, indicating their past connection. |
| Fossil Distribution | Similar fossils of plants and animals are found on different continents, suggesting that they were once joined and have since separated. |
| Rock and Mountain Belts | Matching rock types, geological formations, and mountain ranges are found across continents that were once part of the same landmass. |
| Palaeomagnetism | The alignment of iron minerals in rocks, recorded by Earth’s magnetic field, shows that the magnetic poles have moved over time and continents have shifted. |
| Mid-Ocean Ridges | Underwater mountain ranges with a central rift where new crust forms and moves away, supporting the idea of seafloor spreading and the creation of a new oceanic crust. |
| Subduction Zones | Deep ocean trenches where one tectonic plate is forced beneath another, provide evidence of plate convergence and subduction. |
| Earthquake and Volcanic Activity | Distribution of earthquakes and volcanoes along plate boundaries, demonstrating the association between plate interactions and geological activity. |
