Match the List I with List II

List I (Theories of Mountain Building)		List II (Propounded by)
A	Geosynclinal orogen	I	Daly
B	Thermal contraction	II	Holmes
C	Sliding continent	III	Jeffreys
D	Thermal convection	IV	Kober

Choose the correct answer from the options given below:

Correct option is A

Information booster 

Mountain building, or orogeny, is a complex geological process that involves the formation of mountains through various physical and geological forces. Over the years, several theories have been proposed to explain how mountains form, and these theories have been associated with various geologists and scientists. Below, we will look at each theory, its proposer, and the significance behind these ideas.

• Proposed by: Daly (I)

• Explanation:

  • The geosynclinal theory explains mountain formation as a result of sediment accumulation in large geosynclines (broad depressions or basins in the Earth's crust).

  • Over time, these accumulated sediments, under pressure, experience compression, folding, and uplift, eventually forming mountain ranges.

  • The geosynclinal theory was a dominant explanation for mountain building during the early 20th century, especially for fold mountains. Daly's ideas contributed significantly to the understanding of mountain genesis in regions like the Appalachians and the Himalayas.

  • Significance: This theory emphasized the importance of sediment deposition and tectonic movements in shaping the Earth's surface and the formation of mountain ranges.

• Proposed by: Kober (IV)

• Explanation:

  • The thermal contraction theory suggests that the cooling of the Earth over time causes its outer layer to contract.

  • As the Earth’s crust cools, it wrinkles and forms mountainous structures due to the contraction of the outer surface.

  • Kober believed that the Earth’s outer shell was originally hotter and, as it cooled, it contracted, causing it to fold and form mountains.

  • Significance: This theory was one of the early explanations for the formation of mountain belts, especially during a time when plate tectonics had not yet been fully understood. It also highlighted thermal dynamics as a force influencing mountain building.

• Proposed by: Jeffreys (III)

• Explanation:

  • Jeffreys proposed the sliding continent theory, which suggests that continents move over the Earth's surface and collide with each other, leading to the formation of mountain ranges.

  • This theory supports the idea that continental drift causes tectonic plates to shift, leading to compressive forces that fold the Earth's crust, forming mountains.

  • Significance: Jeffreys' work laid the groundwork for later ideas of plate tectonics and continental drift. His theory was instrumental in moving away from the idea of static continents and toward understanding dynamic crustal movement.

• Proposed by: Holmes (II)

• Explanation:

  • The thermal convection theory proposes that convection currents in the Earth's mantle are responsible for shaping the surface of the Earth.

  • Holmes argued that the mantle's heat causes the material to move in convection currents, which leads to the uplift of the crust and the creation of mountain ranges. These currents move the lithospheric plates, leading to tectonic activity such as mountain building and volcanism.

  • Significance: This theory became a key element of the plate tectonics theory, explaining how earth's crust is shaped by forces within the mantle. It provided a dynamic model of mountain formation, incorporating the idea of subterranean heat and the movement of tectonic plates.