Which landforms are primarily produced by the processes of unloading and thermal expansion, respectively?

Correct Option

The correct option is Exfoliation domes and Tors.

Explanation

Physical weathering processes involve the mechanical disintegration of rocks without a change in their chemical composition. Two significant mechanisms driving this disintegration are unloading (pressure release) and thermal expansion (insolation weathering).

Detailed Analysis

• Unloading and Exfoliation Domes:
  • Process: Unloading occurs when overlying rock layers are removed through continuous erosion. This removal releases the vertical pressure on the underlying rock mass.
  • Result: The rock expands upwards, causing fractures to develop roughly parallel to the ground surface. This leads to the peeling off of rock layers in large sheets, a process known as sheeting or exfoliation.
  • Landform: This process creates large, smooth, rounded landforms known as Exfoliation Domes.
• Thermal Expansion and Tors:
  • Process: Thermal expansion occurs due to the diurnal range of temperature. Rocks heat up and expand during the day and cool down and contract at night. Since different minerals within a rock expand at different rates, internal stresses are generated.
  • Result: This repeated stress leads to granular disintegration or block separation, particularly in crystalline rocks like granite.
  • Landform: In many contexts, this weathering creates piles of rounded boulders or residual rock masses known as Tors (though chemical weathering also plays a role, thermal stress is a key physical agent in their shaping).

Therefore, Exfoliation domes are primarily produced by unloading, and Tors are associated with thermal expansion and subsequent weathering processes.

Key Takeaway

Unloading leads to the formation of large-scale Exfoliation Domes through pressure release and sheeting, whereas Thermal Expansion contributes to the disintegration of rocks into boulder-like structures known as Tors.