Desert Southwest Playas
High Plains Pluvial Lakes
(Sometimes Referred to as Playas)
Overlap Area
Figure 2. Distribution of desert southwest
playas and high plains pluvial lakes. (After
Stone 1956, Motts 1970, and Nelson et al.
1983.)
PLAYAS
The term playa as used for the past 100 years
kilometers or less in size. Fewer than 1,000 cover more
than 100 km2 (38.61 mi2). Motts (1970) is reluctant to
(Johnson and Oliver 1997) is broadly defined as the flat
and generally lower portions of arid basins with inter-
call the smaller features (<609.6-m- [2000-ft-] diameter)
nal drainage that periodically flood and accumulate sed-
playas and prefers the term "microplaya." Doub and
iment (Neal 1975) (Fig. 1). Playa is the Spanish word for
Colberg (1996) refer to playas under 15.2 m (50 ft) in
shore or beach, but in English-speaking countries has
width and/or diameter occurring in clusters within
generally come to mean the landform described. Neal
uplands as "playettes." Similarly, Rundel* refers to small
and Motts (1967) refined this definition by adding that
playas as "playitas." In the older literature (Stone 1956),
the surface is covered with water less than 50 percent
when playas contain water, they are referred to as playa
of the year, that is, playas are dry most of the time; Motts
lakes; when they are dry they are called dry lakes; when
later (1970, 1972) suggested this figure should be 25
wet by seepage they are termed salinas; other synonyms
percent. Shaw and Thomas (1989) add to this general
include clay flats, salt marshes, and borax marshes. On
definition that the margins show evidence of evaporite
USGS topographic maps, they are denoted as intermit-
accumulation and/or lacustrine activity. Rosen (1994)
tent lakes.
further added that playas have negative hydrologic
There are several sorts of playas and playa-like enti-
balances and that they be entirely continental (i.e., no
ties with distinctly different geologic origins; these are
connection to the ocean). Most recently, Briere (2000)
discussed below to the extent that they provide infor-
redefined them as having a negative water balance for
mation on possible indicators for use in delineation. The
over half of each year and dry for 75% of the time. Impli-
classification and nomenclature of these landforms are
cit or stated in all of these definitions is that playas of
discussed in Shaw and Thomas (1989), Rosen (1994),
the sort considered herein are typically vegetation-free
and Johnson and Oliver (1997); Stone (1956), Stevens
surfaces of Pleistocene lacustrine sediments.
(1988), and Briere (2000) present synonymies of playa
The playas covered by this review (primarily those
classification and terminology. For example, although
of the deserts of California, Nevada, Utah, and parts of
referred to as playas, the "pluvial lake basins" of west
Arizona, New Mexico, and southeastern Oregon [Fig.
Texas originated during the Pleistocene along pluvial
2]) originated as Pleistocene lakes (e.g., Kerr and Langer
streams (e.g., Reeves 1966) and developed further in
1965) but dried as a result of climatic change or from
response to a range of environmental factors; their cur-
change in stream inflow or outflow. In all of the United
rent soils and vegetation are in marked contrast to those
States, there are about 300 large playas, at least 120 of
under consideration.
which are the relicts of Pleistocene lakes (Cooke et al.
1993); Neal (1975) estimated that there are about 50,000
* Personal communication, Dr. Philip W. Rundel, Professor of
playas on earth, the vast majority being a few square
Biology, UCLA, Los Angeles, California, 1995.
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