Which do the following is an example of constructive force?
A: buildings collapse in an earthquake**
B: river erosion within the Grand Canyon’s rock walls
C: weathering of a mountin due to rain.
D: a volcanic eruption.
The correct answer is D: a volcanic eruption.
To determine which of the options is an example of a constructive force, we must understand what a constructive force is. Constructive forces are geological processes that shape the Earth's surface by building or creating new landforms and features. They contribute to the growth and formation of the Earth's features.
When we examine the options provided:
A: buildings collapsing in an earthquake - This is an example of a destructive force as it causes the destruction of structures.
B: river erosion within the Grand Canyon's rock walls - This is an example of a destructive force as it wears away and erodes the rock walls of the Grand Canyon.
C: weathering of a mountain due to rain - Weathering is a process of breaking down rocks into smaller fragments, but it is not necessarily a constructive force. It can be both constructive and destructive, depending on the context.
D: a volcanic eruption - This is an example of a constructive force. Volcanic eruptions create new landforms such as volcanic islands, volcanic mountains, and volcanic cones. The lava and ash expelled during an eruption contribute to the growth and formation of the Earth's surface.
Therefore, the correct answer is D: a volcanic eruption, as it exemplifies a constructive force.