Explain Wegener's theory of continental drift and its limitations.

a) Wegener's theory of continental drift explains the observed phenomena by proposing that all present-day continents were once joined together in a single supercontinent called Pangaea. This supercontinent later broke apart, and the individual continents slowly drifted to their current positions over millions of years. This explains:

• The jigsaw-puzzle fit of coastlines, such as South America and Africa.
• The presence of similar rock layers and mountain ranges on continents now separated by oceans, indicating they were once continuous geological features.
• The discovery of identical ancient plant and animal fossils on widely separated continents, suggesting these organisms lived on a connected landmass before it split.
• Paleoclimatic evidence, such as glacial deposits found in present-day tropical regions and coal deposits (formed in warm conditions) found in colder areas, which indicates that continents have moved through different climatic zones over geological time.

b) The primary limitation of Wegener's theory in justifying the occurrence of continental movement was its inability to provide a plausible mechanism for how the continents actually moved. While he presented compelling evidence for the fact of continental drift, he could not adequately explain the force or process driving this movement. He proposed forces like the Earth's rotation or tidal forces, but these were later proven to be far too weak to move massive continents, and the idea of continents plowing through the oceanic crust was geophysically unsound. This lack of a convincing mechanism led to widespread skepticism and delayed the acceptance of his theory until the development of plate tectonics in the mid-20th century.