Final answer:
The region in the United States most likely to experience the greatest mechanical weathering is one with steep slopes, varying temperature, and weak rock composition, such as the rugged and harsh climate areas of northern New England and the Canadian Maritimes, or regions like the Appalachian Mountains, the Rocky Mountains, and the Pacific Coastal Ranges where landslides are common.
Step-by-step explanation:
Mechanical weathering is greatly influenced by factors such as climate, topography, and the type of rock. Regions with dramatic temperature fluctuations, such as areas with a continental climate, experience significant mechanical weathering due to processes like frost wedging and thermal expansion and contraction. Moreover, areas with steep topography are subjected to increased mechanical weathering as gravity can drive the physical breakdown of rocks on slopes.
Considering the various physiographic provinces of the United States, the region most likely to experience the greatest mechanical weathering would be one with a combination of steep slopes, significant temperature changes, and the presence of weaker rocks. The northern New England and the Canadian Maritimes, which experience harsh climates with significant temperature changes and have rugged topography, are prime candidates for substantial mechanical weathering. Landslide activity provided by the debris flow scars in greater Los Angeles or the regions with severe landslide problems such as the Appalachian Mountains, the Rocky Mountains, and the Pacific Coastal Ranges also indicates substantial mechanical weathering. Moreover, the rain shadow effect leading to the semi-arid climates and the presence of high-grade metamorphic rocks on the surface due to erosion, as described in the western United States, further highlight the prominence of mechanical weathering processes in these regions.