Key Points
Planetesimal Hypothesis (Chamberlin): This hypothesis, proposed by Thomas C. Chamberlin and Forest R. Moulton, suggests that a star once passed near our Sun, pulling out a stream of solar material. Tiny solid particles formed within this stream and, over time, these particles coalesced through gravity, forming the planets in our solar system.
Thermal Contraction Theory (Jeffreys): Proposed by Harold Jeffreys, this theory suggests that our planet was once a molten sphere and that it has been cooling and contracting ever since. This contraction led to the formation of the planet's surface features, like mountains and valleys. However, this theory has been largely replaced by the theory of plate tectonics.
Geosynclinal Orogen Theory (Kober): This theory, developed by Leopold Kober, explains the development of major topographical features, especially mountain ranges. According to this theory, large linear troughs (geosynclines) filled with sediment eventually collapse under their weight, bend and fold upward, resulting in mountain ranges.
Hypothesis of Sliding Continent (Daly): Reginald Daly proposed this hypothesis as an early alternative to Alfred Wegener's drift theory. Daly suggested that continents moved due to their gravity, "sliding" down the flanks of the geoid and displacing the seafloor.
Propounder of given theories are as follows-
| (Hypothesis / Theory) | (Propounder) |
|---|
| Planetesimal hypothesis | Chamberlin |
| Thermal contraction theory | Jeffreys |
| Geosynclinal Orogen theory | Kober |
| Hypothesis of sliding continent | Daly |