In earth science, what is the process called by which sediment is removed from its source area and transported away?

Introduction / Context:
This question belongs to basic earth science and physical geography. It asks you to identify the correct term for the process that removes sediment from its source and moves it elsewhere. Understanding the difference between erosion, weathering and deposition is important for topics such as river systems, soil conservation and landscape formation. These concepts are frequently tested in school exams and competitive tests.

Given Data / Assumptions:

The focus is on sediment being removed from its source area and transported away.
Sediment can include particles of rock, soil or sand loosened from the earth surface.
Four processes are listed deposition, erosion, weathering and composition.
Only one option accurately describes both removal and transport of sediment.

Concept / Approach:
Weathering is the process of breaking down rocks into smaller pieces through physical, chemical or biological actions, but it does not necessarily move the material. Erosion involves both the loosening and the movement of sediment by agents such as water, wind, ice or gravity. Deposition is the process by which transported sediment is laid down or settles in a new location. Composition is not a standard term for sediment movement in this context. Therefore, we need the term that combines removal from the source with transport, which is erosion.

Step-by-Step Solution:
Step 1: Note that the question stresses removal of sediment from its source, not just breaking it down.Step 2: Recall that erosion includes both picking up sediment and carrying it away by rivers, glaciers, wind or waves.Step 3: Evaluate option B, Erosion, and see that it matches this definition perfectly.Step 4: Evaluate option A, Deposition, which occurs after transport when sediment is dropped in a new place, the opposite of removal.Step 5: Evaluate option C, Weathering, which breaks rocks into sediment but does not necessarily transport the particles.Step 6: Evaluate option D, Composition, which does not describe any recognised geomorphological process in this context.

Verification / Alternative check:
You can verify this understanding with a river example. When a river cuts into its banks, it lifts soil and rock fragments and carries them downstream. That entire process, from loosening to transport, is called erosion. When the river slows down and drops the material in a delta or on a floodplain, that is deposition. Weathering may have produced the initial loose particles on the valley sides before the river picked them up. This simple scenario clearly separates the three processes and confirms that erosion is the correct answer.

Why Other Options Are Wrong:
Option A, Deposition, is wrong because it refers to the settling and accumulation of sediment, not its removal from the original location.
Option C, Weathering, is wrong because it describes the breakdown of rocks into smaller pieces and soils without necessarily involving movement to a new site.
Option D, Composition, is wrong since it does not represent a standard process in sediment transport and is more associated with the makeup of rocks rather than their movement.

Common Pitfalls:
Students often confuse erosion and weathering, treating them as if they were the same. A helpful rule is that weathering breaks, erosion moves. Another common pitfall is to think of deposition as part of erosion because both involve sediment, but they are different stages in the cycle. Being precise with these definitions is important for correctly answering geography and geology questions and for understanding environmental issues such as soil loss and land degradation.

Final Answer:
The correct answer is Erosion. Erosion is the process that removes sediment from its source and transports it to a different location.