(a) Discuss in detail, with diagrams, the landforms and features resulting from deposition by rivers. (20 marks) (b) Describe…

Rivers deposit sediment where competence and capacity fall, so fluvial landforms record channel energy, sediment supply, and base level. Fluvial deposition. In-channel deposits are dominated by bedload: point bars build on inner meanders, channel bars include longitudinal, transverse and oblique forms in braided or high-energy reaches, and riffle–pool sequences reflect alternating coarse riffles and fine pools. In meandering rivers, lateral erosion and point-bar accretion produce scroll bars; in braided rivers, bar migration and channel switching produce braid bars and avulsion surfaces. Overbank deposits are finer: natural levees line channels with sand and silt, crevasse splays radiate where levees breach, and floodplains accumulate mud and organic matter. Floodplain deposits often show fining-upward sequences: sand in levee and splay, silt and mud in backswamp. Diagram 1 (meander scroll) would show abandoned channels and crescentic point-bar deposits; Diagram 2 (levee–backswamp) would show a raised sand levee, lower backswamp with fine silts, and a crevasse splay; Diagram 3 (terrace staircase) would show stepped remnants of former floodplains. Terraces are primarily erosional remnants of old floodplains, underlain by fluvial deposits, produced when base level falls or tectonic uplift incises the alluvium. Downstream fining occurs because stream power and competence decrease; hydraulic sorting keeps coarse grains in channels and fines on floodplains. Base-level rise causes aggradation, while fall causes incision and terrace formation. Alluvial fans form where gradient drops at mountain fronts; fan dynamics include progradation, avulsion, lobe stacking and fining-upward deposits. The Kosi megafan is a fluvial megafan built mainly by braided river processes, with radial drainage, channel avulsion, lobe progradation and fan surface aggradation, not a debris-flow fan. Deltas are major river deposits at base level, where distributaries split, sediment progrades, and lobes switch; deltaic deposits show progradational clinoforms and fining-upward sequences, as in the Ganga–Brahmaputra and Mahanadi deltas. Indo-Gangetic plains illustrate extensive alluvial deposition, terraces, fans and deltas.

Indian remote sensing satellites. IRS-1C/1D carried LISS-III (5.8 m, 8 bands) and PAN (2.35 m) with about 24 h revisit. Resourcesat-1/2 added LISS-IV (5.8 m) and AWiFS (8 m, 8 bands) for agriculture, soil moisture and wasteland mapping. LISS-III/IV and AWiFS use visible, near-infrared and shortwave-infrared bands. Cartosat-1 is a dedicated stereoscopic satellite (2.5 m) for DEMs; Cartosat-2 (1 m) and Cartosat-3 (0.5 m multispectral, 0.25 m PAN) are high-resolution mapping satellites, not primarily stereo, with about 24 h revisit. RISAT-1/2 X-band SAR provides all-weather data. These sensors support groundwater exploration, flood/drought monitoring, disaster management and land-use mapping.

Faults and stress ellipsoid. Anderson’s model uses σ1>σ2>σ3 as the stress ellipsoid axes, with σ1 the long axis and σ3 the short axis. The Mohr circle’s centre represents mean stress; failure occurs when it touches the envelope. In a normal fault, σ1 is vertical and σ3 horizontal; the fault plane dips steeply, the Mohr circle touches the failure envelope at relatively low shear stress, and focal mechanisms show extensional quadrants; the Sohan fault is an Indian example. In a thrust fault, σ1 is horizontal and σ3 vertical; the fault is a low-angle reverse plane, the Mohr circle is shifted to high normal stress, and focal mechanisms show compression; the Main Boundary Thrust exemplifies this. In a strike-slip fault, σ1 and σ3 are horizontal while the intermediate axis σ2 is vertical; the fault plane is vertical, the Mohr circle plots intermediate normal stress, and focal mechanisms show shear; the Kutch strike-slip system illustrates it. Fault plane solutions identify P, T and N axes: T-axis for normal, P-axis for thrust, N-axis vertical for strike-slip. These correspond to divergent, convergent and transform plate settings. Thus, fluvial forms, satellite mapping and fault mechanics together link sedimentation, surface processes and tectonic stress.