In soil science, soil that forms on unconsolidated deposits (rather than directly on solid bedrock) is known by what name?

Introduction / Context:
Soils can be classified based on how and where they form. One key distinction is between soil that forms directly on underlying rock and soil that forms on materials transported from elsewhere. This question asks you to recall the correct term for soil that forms on unconsolidated deposits rather than on solid bedrock.

Given Data / Assumptions:
- The soil in question forms on unconsolidated deposits, such as sediments transported by water, wind, or ice.
- We must differentiate between transported soil and residual soil.
- We assume standard school-level definitions of these terms.

Concept / Approach:
Residual soil forms in place directly from the weathering of underlying bedrock. Its composition closely reflects the rock beneath. Transported soil, on the other hand, forms from materials (like sand, silt, or clay) that have been moved by rivers, glaciers, wind, or gravity and then deposited elsewhere. Because the question explicitly mentions unconsolidated deposits rather than bedrock, it is pointing to transported soil.

Step-by-Step Solution:
Step 1: Note the phrase “unconsolidated deposits” in the question, which suggests loose material not attached to solid rock. Step 2: Recall that residual soil forms directly on solid bedrock with little transport. Step 3: Understand that transported soil develops on sediment that has been carried and then deposited by agents like rivers or glaciers. Step 4: Match this description with the option mentioning transported soil. Step 5: Select transported soil as the correct answer.

Verification / Alternative check:
Textbooks in physical geography often show diagrams with residual soil sitting directly on bedrock and transported soil overlaying a different type of rock or resting on loose sediments like alluvium. This visual distinction reinforces the idea that transported soil forms from material that has moved from its source.

Why Other Options Are Wrong:
Option A: Humus rich organic topsoil describes a layer with high organic content, but it does not specify whether the soil is residual or transported.
Option B: Bedrock is the solid rock beneath soil; if soil formed directly on bedrock, it would be residual soil, not transported soil on unconsolidated deposits.
Option D: Residual soil is exactly the opposite of what the question describes, since it forms in place on underlying rock rather than on transported deposits.

Common Pitfalls:
Students sometimes confuse unconsolidated deposits with bedrock or think that all soil is residual. Remember that river valleys, floodplains, and glacial valleys are classic locations for transported soils because sediments are moved and redeposited there. Residual soils are more likely found in stable upland areas where weathering acts on bedrock over long periods.

Final Answer:
The correct answer is transported soil formed from unconsolidated deposits because this type of soil develops on sediments that have been moved from their source and are not directly derived from the underlying bedrock.