ASBOG Drainage Patterns/Stream Types 2

Question 1

What is a trellis drainage pattern, and what does it indicate about the underlying geology?

Accepted Answer

A drainage pattern with long parallel main streams joined at right angles by short tributaries, indicating alternating ridges and valleys of tilted, folded, or faulted rock

Answer

Trellis drainage develops on alternating bands of resistant and weak tilted rock (such as folded sedimentary sequences), producing long main streams in weak rock valleys connected at right angles by short tributaries crossing the resistant ridges.

Question 2

In the Strahler stream ordering system, how is the order of a stream reach determined?

Accepted Answer

All streams are assigned order 1 at the headwaters, and order increases by 1 each time two streams of equal order join; the junction of unequal orders retains the higher order

Answer

In the Strahler system, unbranched headwater streams are order 1; when two order-1 streams join, they form order 2; when two streams of the same order n join, they form order n+1; junction of streams of different orders retains the higher order.

Question 3

What is an antecedent stream, and how does its drainage pattern provide evidence for tectonic uplift history?

Accepted Answer

A stream that predates tectonic uplift and maintains its course by eroding downward as a barrier rises across its path, creating a water gap or gorge through an otherwise wind-gap ridge

Answer

An antecedent stream existed before tectonic uplift and maintained its original course by incising downward at a rate equal to or greater than the rate of uplift, cutting a gorge or water gap through the rising structure.

Question 4

What is the primary difference between a braided river and an anastomosing river system?

Accepted Answer

Braided rivers have multiple unstable, shifting channels separated by transient bars with high width-to-depth ratios; anastomosing rivers have multiple stable, vegetated channels with low width-to-depth ratios separated by floodplain islands

Answer

Braided channels are wide, shallow, shifting, and separated by unstable mid-channel bars — typical of high sediment load and flashy discharge; anastomosing rivers have multiple stable channels separated by vegetated floodplain islands with low width-to-depth ratios and finer, cohesive banks.

Question 5

What is the geomorphic significance of a 'yazoo stream' on a river floodplain?

Accepted Answer

A yazoo tributary runs parallel to the main river on the floodplain because natural levees block its direct entry into the main channel, forcing it to travel long distances to find a low point to join

Answer

A yazoo tributary runs parallel to and alongside a major river for long distances on the floodplain because the main channel's natural levees are high enough to prevent the tributary from joining the main river until a low point in the levee system is found.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG Drainage Patterns/Stream Types 2