Salt Lake Community College
Geography 1000 – Physical Geography
AJ Allred, Fall
2014
Study Guide for Chapters 15-17
As a supplement to studying the quiz questions, the following statements summarize and
correlate Earth processes that are inter-related and which are particularly relevant for
understanding human effects on the Earth’s lithosphere.
This study guide also integrates issues across many chapters of the book, in support of study for
the Geography 1000 Final Exam. The points below also help clarify test questions that are based
on current or relevant issues in class discussion that supplement concepts covered in the
textbook.
1. Changes in solar energy across hundreds of millions of years create vast alterations in
Earth landforms (lithosphere) based on very small changes in annual average air
temperature. A long-term increase in air temperature of just three or four degrees can
trigger melting of polar ice caps that:
a. raises ocean levels, covering vast land areas with water;
b. allows mid-latitude continental land masses to rise as the weight of ice is removed.
2. Mid-latitude climates exhibit freeze-thaw cycles that can break apart almost anything that
gets wet. In many regions, freeze-thaw cycles can occur daily during some seasons.
3. The effects of water on terrain take many forms. In Chapter 15 look for acidity, plant
roots, hydrolysis, oxides, salt, and air temperature. In particular, compare pages 450-454
to Chapter 19, especially for Final Exam study.
4. Water is a strongly controlling factor in all climates. In liquid state:
a. flowing water mechanically scours landforms;
b. chemically bonds to other compounds to make them softer and weaker
(hydrolysis);
c. supports plant growth and other chemical reactions that degrade landforms;
In frozen state, ice fractures, peels, plucks, crushes or carries off vast amounts of solid
Earth. In volcanic events, water adds explosive power to eruptions and contributes to
powerful lahars and pyroclastics. In dry regions, lack of water contributes to landforms
that are steep, easily eroded and fractured and subject to erosive flash flooding. For Final
Exam study, compare the effects of water in dry country to Chapter 18. In particular,
flash flooding is usually a greater problem in dry country than in humid regions because:
a.
b.
c.
d.
steep landforms shed water at high velocity;
hard-surfacing and lack of vegetation cover help water flow more quickly;
dry land surfaces often absorb very little water;
rainfall is often more sharp and brief than in rainy climates.
The amount of water in soil helps determine whether a mass waste event is solifluction,
creep, slump, flow, or fall. To make earth moves faster, just add water.
5. Human efforts to prevent flooding are often ineffective. The U.S. Army Corps of
Engineer is changing its long-standing policy of “channelizing” streams due to high cost
and gradual recognition that natural features along shorelines provide countless benefits,
including flood and storm management.
6. Geothermal resources are becoming more important worldwide. Extracting energy from
magma heated rocks requires water. Failure to protect geothermal water resources and/or
the drying effects of climate change over dry country can diminish or destroy natural and
man-made geothermal resources. Compare to page 509.
7. In chapters 9, 15 and 17, and in current news events it is clear that soil failure and
instability are often caused by either removing fluids and solids from the ground or
injecting them back into the ground. In Chapter 12 we see that climate change is making
frozen soils less stable. In humid regions, high air temperature and heavy precipitation
cause soil leaching and soil failures along with periodic mass wasting events such as
landslides caused by extreme events that include earthquakes and, volcanoes. Climate
change also enhances the acidic effect of hydrologic processes that dissolve or erode
landforms. Failure to understand or protect landforms along the Wasatch Front is causing
soil failures that damage property. The recent North Salt Lake landslide is a good
example of water causing soil failure even in a dry climate where hard-surfacing and
flood-control measures are intended to prevent such problems. A dangerous sinkhole
developed in Taylorsville in 2013 and three people were killed by a mud flow in Logan a
few years ago.
8. In previous chapters on climate, water and weather, we learned that dry country is prone
to brief, sharp or severe precipitation events that create momentary heavy run-off. In dry
country, with steep slopes and hard, rocky surfaces, such sharpness in water supply can
lead to flash flooding and cataclysmic failures of soil and rock formations. River
meanders are evidence of shallow or flat country where slopes are not steep enough to
provide quick, straight-line drainage.
9. The kind of climate change that Earth is now experiencing includes warmer air
temperatures in most, but not all places. Warmer air can evaporate more water that will
eventually fall as more precipitation. Rainy places, such as over oceans, should
experience more evaporation and more rain. Dry regions, such as Utah, may experience
slightly more rain, but much more evaporation, as warm air has much greater capacity
than cold air to hold moisture. Thus, rainy regions may experience more acid rain and
acid soils, while dry country loses ground water that is needed for geothermal
development. The western USA, including Utah, has vast geothermal potential that
requires water as a heat-transfer fluid. Warming air could evaporate and carry-off much
needed surface water that might otherwise go back into the ground for geothermal
heating.
10. Another example of integrating topics across chapters, consider that an off-set stream can
be created by an earthquake or landslide. Offset streams are more common in the
western United States where earthquakes are more common and where dry climate
conditions do not provide enough stream flow to quickly wash-away an off-set. Notice
also that stream offsets are more likely to occur in small, first and second-order streams.
A large river is almost impossible to off-set by anything but a rare cataclysmic quake.
11. Finally, human population growth is served by mining of water and mineral resources
that leaves voids underground, leading to earth failures. Population growth is very high
in many locations where soil failures are also caused by natural processes such as karst
caving in limestone bedrock. Rising ocean levels portends hydrologic softening by salt
water invasion and coastlines around the world are increasingly occupied by cities.
Heavy buildings put additional pressure on vulnerable landforms that may already be
under assault by all of the forces mentioned above.