Understanding Volcanoes and Drainage Patterns

The question asks us to identify the incorrect statement among the given options regarding volcanoes. Let's examine each statement carefully to determine its accuracy.

Analyzing Each Statement

1. Statement 1: "Stratovolcanoes produce lava flows that initially follow valleys but are highly resistant to erosion."

   Stratovolcanoes (also known as composite volcanoes) are known for erupting viscous lava. While these lava flows can initially follow existing topography like valleys, once cooled and hardened, they form durable rock layers (like basalt or andesite) that are often much more resistant to erosion than the surrounding softer rock or ash layers. Over time, these resistant lava flows can stand out as ridges or plateaus as the less resistant material around them erodes away. This statement appears to be correct.

2. Statement 2: "The surrounding areas can remain highlands, lava ridges or mesas."

   Following on from the erosion resistance of lava flows mentioned in statement 1, the areas covered by these flows can indeed resist erosion better than adjacent areas. This differential erosion can leave the lava-covered areas elevated relative to the surroundings, forming features like highlands, elongated lava ridges, or flat-topped mesas (if the flow was extensive and flat). This statement also appears to be correct.

3. Statement 3: "Hawaiian shield volcanoes are eroded by streams that form deeply carved valleys with steeply sloping heads."

   Hawaiian shield volcanoes are large, gently sloping volcanoes built by highly fluid basaltic lava. While their slopes are gentle, they are subjected to significant rainfall, especially in tropical environments. Over long periods, streams develop on the flanks of these volcanoes. These streams erode the volcanic rock, carving out valleys. Erosion is often more intense at the heads of these valleys, especially where waterfalls may form, leading to steep valley heads that gradually migrate upstream. This process is characteristic of the dissection of large shield volcanoes. This statement is correct.

4. Statement 4: "The system of streams on a dissected volcano cone is not a radial drainage pattern."

   A volcano cone is a conical landform with a peak at the center. When rainfall occurs on such a conical shape, the water flows downslope away from the central peak in all directions. This type of drainage pattern, where streams radiate outwards from a central high point, is specifically known as a radial drainage pattern. Therefore, a dissected volcano cone, with streams eroding its slopes, will typically exhibit a radial drainage pattern. The statement claims it is *not* a radial drainage pattern, which contradicts this fundamental concept of geomorphology regarding conical landforms.

Identifying the Incorrect Statement

Based on the analysis, Statement 4 is incorrect because the stream system on a dissected volcano cone is characteristically a radial drainage pattern, not something different from it.

Conclusion

The statement that is not correct with regard to volcanoes and their associated features or processes is the one claiming that the stream system on a dissected volcano cone is not a radial drainage pattern. In reality, it is a prime example of a radial drainage pattern.

Revision Table: Key Volcano Concepts

Additional Information: Drainage Patterns and Landforms

Drainage patterns describe the arrangement of streams and rivers in a landscape. They are influenced by geology, topography, and erosion processes. Understanding drainage patterns helps in interpreting the underlying structure and history of an area.

• Radial Drainage: Streams flow outwards from a central high point. Commonly found on volcanoes, domes, or isolated hills.
• Dendritic Drainage: Tree-like branching pattern, common in areas with uniform underlying rock resistance.
• Trellis Drainage: Rectangular pattern, common in folded mountain areas with alternating resistant and less resistant rock layers.
• Rectangular Drainage: Streams follow joints or faults, creating a network of channels with right-angle bends.
• Parallel Drainage: Streams flow parallel to each other, often on steep, uniform slopes or in areas with parallel faults.

Volcanic landforms are shaped by both constructive processes (eruptions building the cone) and destructive processes (erosion by wind, water, and ice). The stage of erosion can significantly alter the original volcanic shape, leading to features like eroded craters, volcanic necks, and dissected flanks with distinct drainage patterns.