Examkin

Question

Difficulty: HardDrainage Patterns and River Basin Analysis

An aerial reconnaissance map of a catchment area displays primary tributaries flowing parallel to each other in elongated valleys, with short secondary streams joining them almost at right angles along structural strike lines of tilted, alternating hard and soft rock strata. Which drainage pattern is depicted, and what main geological control governs its formation?

  1. Trellis pattern, controlled by dipping or folded sedimentary rocks with alternating bands of hard and soft strataAnswer
  2. B
    Dendritic pattern, controlled by massive homogeneous crystalline rocks of uniform resistance
  3. C
    Radial pattern, controlled by central volcanic cones or elevated isolated domes
  4. D
    Centripetal pattern, controlled by circular inland drainage basins lacking external outlets

Answer

Trellis pattern, controlled by dipping or folded sedimentary rocks with alternating bands of hard and soft strata
The correct answer identifies a trellis pattern governed by dipping or folded sedimentary rocks. In folded terrain (such as ridge-and-valley topography formed by anticlines and synclines), main streams erode along weak strata in parallel valleys, while smaller tributaries flow down ridge slopes to join the main streams at nearly 90-degree angles.

Step-by-Step Solution

1
Analyze the stream geometric arrangement described in the scenario
Primary streams flow parallel to each other in main valleys, and secondary streams join them at approximately 90-degree right angles.
Identifying the characteristic right-angle tributary junction pattern narrows down the pattern type.
2
Examine the underlying geological structure described
The bedrock consists of tilted/dipping strata with alternating bands of hard (resistant) and soft (non-resistant) rocks.
The differential erosion of soft bands forms main strike valleys, while resistant ridge slopes direct short streams straight down at right angles.
3
Match stream geometry and geological structure to the correct drainage pattern classification
The combination of parallel main streams, right-angle tributary junctions, and folded/tilted rock belts defines a trellis drainage pattern.
Trellis patterns form specifically under these structural controls, distinguishing them from dendritic, radial, or centripetal patterns.

Key Concept

Trellis Drainage Pattern and Structural Geological Control
Estimated Time:1m 30s
Rate this question

Topics

Drainage Patterns and River Basin Analysis

More questions from this topic