Streams that develop later along belts of weak rock, so that their direction is controlled by the rock structure, form which type of drainage?

Subsequent streams develop after the original drainage of an area has been established. They cut their valleys along belts or zones of weak, easily eroded rock, such as shale, clay or soft limestone, or along faults and joints. As a result, their direction is controlled by the structure of the underlying rocks, rather than by the original slope of the land.

How subsequent streams form:

When a land surface is first uplifted, the main rivers flow down its original slope.

Over time, tributaries develop. Those that grow along the strike of weaker rock layers erode faster and become longer, while harder rock layers stand out as ridges.

These tributaries usually join the main rivers at right angles.

Associated pattern:

Subsequent streams often produce a trellis drainage pattern, where tributaries run parallel to each other along valleys of weak rock between ridges of hard rock and join the main stream at right angles.

This is common in folded mountain areas, such as the Appalachian region of the USA. In India, it can be seen in parts of the Himalayan foothills and in the old folded rocks of the Singhbhum region (Jharkhand).

Classification of drainage based on origin (genetic classification):

Rivers are classified according to how they developed relative to the land's slope and structure. The main types include:

Antecedent: older than the uplift; keeps its course by cutting across rising land (example: the Indus, Sutlej, Brahmaputra).

Superimposed: develops on a younger rock cover and then cuts down into older rocks of a different structure, retaining its course.

Subsequent: controlled by rock structure, along zones of weakness.

Obsequent: flows in a direction opposite to the original slope.

Insequent: develops randomly, without any clear control from slope or structure, usually on uniform rocks; it often gives a dendritic pattern.

Why not the other options?

• ✗Antecedent drainage existed before the uplift of the land.
• ✗Superimposed drainage is inherited from an overlying cover of rock.
• ✗Insequent drainage shows no relation to rock structure.