Page 389 - Laboratory Manual in Physical Geology

BIG IDEAS PRE-LAB VIDEO

Drylands are lands of arid-to-dry, subhumid climates
that generally have sparse vegetation and receive
precipitation just a few days or one season of the year.
Even so, water is one of the primary agents that produces
characteristic dryland landforms and flood hazards.
Wind is also a factor in the erosion and transportation
of sediment, especially dust and the sand that makes
dunes. Although many people live in drylands, true
deserts do not support any agriculture without irrigation
or a well.

FOCUS YOUR INQUIRY

|
THINK What are some characteristic processes,
About It landforms, and hazards of drylands?
ACTIVITY 14.1 Dryland Inquiry (p. 358 )

|
THINK What can we learn from topographic maps and
About It satellite images about dryland processes and
landforms?
ACTIVITY 14.2 Mojave Desert, Death Valley,
California (p. 358 )

ACTIVITY 14.3 Sand Seas of Nebraska and the Arabian
Peninsula (p. 363 )
|
THINK How can topographic maps and aerial
14 ACTIVITY 14.4 Dryland Lakes of Utah (p. 365 )
About It photographs of drylands be used to interpret
how their environments have changed?

L ABOR A T OR Y
Introduction
Dryland Drylands are lands in arid, semi-arid, and dry-sub-humid
climates. The United Nations Environment Programme
(UNEP) estimates that drylands make up 41% of all land on
Landforms, Earth and that they support one-third of the world’s human
population. Sixteen percent of all existing drylands (about 6%
Hazards, and Risks of all land areas on Earth) are so dry that their biological pro-
ductivity is too poor to support any type of agriculture (unless
irrigation or wells are used). These regions are true deserts .
C ONTRIBUTING A UTHORS When people rely on land for farming or ranching,
they must assess the potential for land degradation —a state
Charles G. Oviatt • Kansas State University
James B. Swinehart • Institute of Agriculture & Natural Resources, of declining agricultural productivity due to natural and/
University of Nebraska or human causes. Humid lands (lands in humid climates)
may undergo degradation from factors such as soil erosion
James R. Wilson • Weber State University
(wearing away), farming without crop rotation or fertilization,
Rain is rare in drylands, so there are few plants to trap and bind overgrazing, or dramatic increases or decreases in soil
loose rocks among their roots or aid in the development of soil that moisture. However, degraded humid lands always retain the
would absorb rainwater. When it does rain, flash floods cut channels
and shape the landscape. (Photo by Michael Collier) capability of some level of agricultural production. This is
357