a. Typical algal crust on a hard playa. The first algal crust
formed after evaporation of surface water (dark gray) is
one coincident with the polygons subtended by the larger
cracks (black) below. With time, the first-formed algal
crust breaks down into smaller crusts ("flakes") as evi-
b. Closeup of algal crusts. The crust has bro-
ken into smaller flakes and been removed.
c. Algal crusts in 5-ha hard playa. Note the con-
spicuous curling and layering (darker upper/
inner surface), both of which indicate previous
Figure 5. Algal crusts.