(GEOL 103) Exam II- Class 10: Surface Water

Q: How does water get into the atmosphere from the surface?

A: Through evaporation and sublimation.

Q: How does water get into the atmosphere from the subsurface?

A: Through transpiration from plants.

Q: Where does water from rain and snow go after it hits the surface?

A: It may re-enter the atmosphere, move into the ground, or stay on the surface as runoff.

Q: What are drainage divides?

A: Boundaries that define the limits of drainage basins—areas drained by a given stream or stream system.

Q: How do drainage divides relate to drainage basins?

A: They mark the boundaries between different basins; each basin collects water flowing toward a specific stream system.

Q: How do drainage divides relate to Continental Divides?

A: Continental Divides are special drainage divides that separate flow into different oceans, seas, or isolated basins.

Q: What is the meaning and importance of a stream’s base level?

A: The lowest level to which a stream can erode its channel. It controls the stream’s potential energy and erosion.

Q: What is a graded stream?

A: A stream that maintains a minimum flow rate needed to transport the sediment delivered to it—no net erosion or deposition.

Q: What are the different ways in which streams erode bedrock?

A: Quarrying (removing bedrock blocks), abrasion (scraping and rubbing by sediment), and corrosion (dissolving bedrock).

Q: What are the different ways in which streams transport sediment?

A: In solution (dissolved load), in suspension (suspended load), and along the bed (bed load).

Q: Why is sediment deposited when a stream empties into a body of water?

A: Flow velocity suddenly decreases, lowering competence and causing sediment to settle.

Q: Why is sediment deposited when a stream empties onto a flat plain?

A: The stream’s slope decreases, reducing flow velocity and competence, leading to deposition (e.g., alluvial fans).

Q: Are sediments deposited from the suspended load of a stream usually well sorted or poorly sorted?

A: Well sorted, because the largest suspended sediments are deposited first as stream velocity decreases.