Review for Final: Chapters 14, 16, 17, 18
The most important concepts from each chapter that we have covered since the midterm are
summarized below. In addition, you should spend some time going over the review questions at
the end of each chapter – a good way to do this is to work together on this with some of your
classmates. The exam will be ~1 hour and 40 minutes long, and a mix of multiple choice, word
match, and fill in the blanks. Good luck with your studying!
The geology of rivers and streams
1. You should be familiar with stream channels and should be able to label a
diagram locating point bars, cut banks, oxbow lakes, and meander necks. You should know
how meanders form and how they migrate. You should understand how the establishment
of cutoff routes causes meanders to become isolated oxbow lakes. Relationships among
erosion, deposition, and current velocity should be understood, as well as geometrical
differences between braided and meandering streams and how streams become braided.
2. You should be able to identify the five major drainage networks (dendritic, radial,
rectangular, trellis, and parallel) and understand the conditions that give rise to each.
3. Rivers carry a sediment load in three components: dissolved ions, suspended grains
(the greatest portion volumetrically), and bed load (larger grains which tumble along the
stream bottom). Stream competence refers to the largest particle size a stream can carry; the
total volume of sediment carried by a stream is its capacity.
4. The total volume of water passing by a fixed point in one second is its discharge;
the Amazon has by far the greatest discharge of all the rivers on Earth. In moist climates,
discharge increases downstream with the addition of tributaries and rainfall; however, in
arid climates, discharge may decrease downstream because of evaporation (and human
usage in agriculture).
5. The farthest that a stream can downcut into underlying sediment or rock is termed
the base level. Sea level is the ultimate base level, but resistant rock and lakes may locally
raise the base level substantially.
6. Streams are important agents of erosion, carving out steep-walled canyons and
shallow-walled valleys. Water itself is not especially abrasive, but the sediment that it carries
is highly so.
7. When rivers meet the sea (or some other still body of water), their velocity and
competence decrease, and they deposit sediments, which form wedge-shaped bodies termed
deltas. The shapes of ocean deltas are controlled by sediment supply, the strength of ocean
waves and currents, and the tides.
8. Floods may be seasonal or episodic; they may arise suddenly or gradually (in the
floodplains of major river systems). Large, catastrophic floods are less common than small
floods. Floods of various magnitudes have been assigned estimated recurrence intervals
(average waiting times between floods of a specific magnitude over very long time periods).
For example, a flood with a 100-year occurrence interval has a 1% chance of occurring