The question asks to identify the mode of river transport where particles roll along the riverbed. We need to understand the different ways a river transports its sediment load.
Correct Option: D) Traction is the mode of river transport where larger, heavier sediment particles are rolled or dragged along the riverbed by the force of the water.
The question asks about the cross-sectional shape of a river valley in its upper course. Understanding the geomorphic processes active in different stages of a river's life cycle is key to answering this question.
A) Deep, narrow V-shaped. This accurately describes the valley cross-section in the upper course due to dominant vertical erosion in steep gradients.
The question asks about the formation of interlocking spurs, a characteristic landform found in the upper course of a river. We need to identify the geological and geomorphological processes that lead to their creation.
D) A river with limited lateral power winds around hard rock ridges projecting alternately from each valley side — This accurately describes the formation of interlocking spurs. In the upper course, the river's main action is vertical erosion (downcutting). When it encounters resistant rock spurs extending from the valley sides, its limited lateral erosional power forces it to flow around these obstacles, creating the characteristic interlocking pattern.
The question asks about the geological conditions necessary for the formation of a waterfall. We need to identify the option that accurately describes the rock structure and erosional processes involved.
C) A band of resistant rock overlying softer rock — the softer rock is undercut creating a plunge pool, causing the cap to collapse
This option accurately describes the classic geological conditions and erosional processes leading to waterfall formation. The resistant rock forms the cap of the waterfall, while the softer rock beneath is eroded more rapidly, creating an overhang and a plunge pool. Eventually, the overhang collapses, causing the waterfall to retreat upstream.
The question asks to identify the landform left behind as a waterfall retreats upstream. This involves understanding the erosional processes associated with waterfalls and the resulting landscape features.
A) Gorge or canyon — As a waterfall retreats upstream due to erosion, it carves out a deep, steep-sided valley in its wake. This valley is known as a gorge or a canyon, depending on its scale and characteristics.
The question asks about the formation of potholes in riverbeds. This is a geomorphological process related to river erosion. We need to identify the specific erosional mechanism responsible for creating these distinctive features.
B) Corrasion — pebbles trapped in depressions rotated by eddying currents drill cylindrical holes into bedrock. This option accurately describes the process of pothole formation. The swirling motion of water creates eddies, which rotate abrasive material (pebbles, sand) within existing depressions, gradually drilling deeper and wider cylindrical holes into the bedrock.