tend to be more common in middle and high latitudes
(Figure 3), whereas carbonates (aragonite and calcite)
dominate tropical and subtropical zones. Although a small
feldspar fraction is usually present in terrigenous sands,
those few beaches that are rich in feldspar tend to be close
to the source rock from which the feldspar is derived, such
as glacial deposits derived from shield (cratonic) areas
containing feldspar-rich granites and gneisses. Beach
sands derived from granitic source areas sometimes contain heavy minerals (density > 2.9 g cm
3
) that tend to be
concentrated in the swash zone by the placering effect to
form dark-colored streaks that are sorted out from the rest
of the lighter-colored grains.
Beach color is determined by grain size and mineralogical composition so that silicates (derived from igneous
granitic rocks, metamorphic rocks such as gneisses and
schists, and preexisting sandstones) impart a light color
to beaches (Figure 3), whereas more mafic compositions
imbue black (Figure 4) to dark gray to dark green colors
in fragments of fine-grained rocks such as metamorphic
slates or volcanic ricks such as andesite and basalt
(Pilkey et al., 2011). The inherent color of the beach’s
grains does not always determine beach color because
grains may be stained by iron oxides, tannic acids, or
microorganisms that may produce distinctly red, yellow,
or green beaches, for example.
Types of beaches
Because beaches occur in all climatic zones, there are
some obvious morphological differences related to severe
conditions. In very high latitudes, for example, the water is
frozen but for a few weeks when beaches may be affected
by waves (Davis, 1978) and consequently beach morphology and texture is somewhat different from those in low
latitudes. Beaches in arid climates depend almost solely
on wave action to provide sediment from the bedrock
coast to form a beach. The best developed beaches are
associated with low-lying coasts where large quantities
of sediment are available. Beach development requires
an abundant sediment supply to produce characteristic
morphologies and environmental zonations (Masselink
et al., 2011).
The term beach type refers to the dominant nature of a
beach based on tidal, wave, and current regimes, spatiotemporal extent of the nearshore zone, morphodynamics
(beach width, shape, and processes) of the surf zone
including bars and troughs, and the subaerial beach
(Short, 1993). Irrespective of the specific beach type, most
beaches contain several morphogenetic zones: (1) the
backshore (nearly horizontal to gently landward-sloping
area called the berm), (2) inner swash zone (upper limit
of swash to the shoreline), (3) surf zone (from the shoreline to where waves break, the breaker zone), (4) nearshore
zone (from the breaker zone, commonly with sandbars, to
the wave base), and (5) wave base (depth where waves
begin to interact with the seabed to transport sand to the
beach and seaward to where sand is transported by large
waves that cause beach erosion) (Davis, 1978; Short and
Woodroffe, 2009). These zones are greatly variable,
depending on the processes and materials that affect
Beach, Figure 3 Siliciclastic beach sands on Amagansett Beach, Long Island, New York, USA, showing a reflective morphodynamic
beach state. As swash runs up the steep beach face, it carries sand grains that overtop the berm to the back beach area.
Interdigitating swash marks on the berm mark the landward most transport of sand grains that are dominantly quartz but which may
contain minor admixtures of biogenic (shell) fragments and organic matter (Photo: C.W. Finkl).
44
BEACH
(Figure 3), whereas carbonates (aragonite and calcite)
dominate tropical and subtropical zones. Although a small
feldspar fraction is usually present in terrigenous sands,
those few beaches that are rich in feldspar tend to be close
to the source rock from which the feldspar is derived, such
as glacial deposits derived from shield (cratonic) areas
containing feldspar-rich granites and gneisses. Beach
sands derived from granitic source areas sometimes contain heavy minerals (density > 2.9 g cm
3
) that tend to be
concentrated in the swash zone by the placering effect to
form dark-colored streaks that are sorted out from the rest
of the lighter-colored grains.
Beach color is determined by grain size and mineralogical composition so that silicates (derived from igneous
granitic rocks, metamorphic rocks such as gneisses and
schists, and preexisting sandstones) impart a light color
to beaches (Figure 3), whereas more mafic compositions
imbue black (Figure 4) to dark gray to dark green colors
in fragments of fine-grained rocks such as metamorphic
slates or volcanic ricks such as andesite and basalt
(Pilkey et al., 2011). The inherent color of the beach’s
grains does not always determine beach color because
grains may be stained by iron oxides, tannic acids, or
microorganisms that may produce distinctly red, yellow,
or green beaches, for example.
Types of beaches
Because beaches occur in all climatic zones, there are
some obvious morphological differences related to severe
conditions. In very high latitudes, for example, the water is
frozen but for a few weeks when beaches may be affected
by waves (Davis, 1978) and consequently beach morphology and texture is somewhat different from those in low
latitudes. Beaches in arid climates depend almost solely
on wave action to provide sediment from the bedrock
coast to form a beach. The best developed beaches are
associated with low-lying coasts where large quantities
of sediment are available. Beach development requires
an abundant sediment supply to produce characteristic
morphologies and environmental zonations (Masselink
et al., 2011).
The term beach type refers to the dominant nature of a
beach based on tidal, wave, and current regimes, spatiotemporal extent of the nearshore zone, morphodynamics
(beach width, shape, and processes) of the surf zone
including bars and troughs, and the subaerial beach
(Short, 1993). Irrespective of the specific beach type, most
beaches contain several morphogenetic zones: (1) the
backshore (nearly horizontal to gently landward-sloping
area called the berm), (2) inner swash zone (upper limit
of swash to the shoreline), (3) surf zone (from the shoreline to where waves break, the breaker zone), (4) nearshore
zone (from the breaker zone, commonly with sandbars, to
the wave base), and (5) wave base (depth where waves
begin to interact with the seabed to transport sand to the
beach and seaward to where sand is transported by large
waves that cause beach erosion) (Davis, 1978; Short and
Woodroffe, 2009). These zones are greatly variable,
depending on the processes and materials that affect
Beach, Figure 3 Siliciclastic beach sands on Amagansett Beach, Long Island, New York, USA, showing a reflective morphodynamic
beach state. As swash runs up the steep beach face, it carries sand grains that overtop the berm to the back beach area.
Interdigitating swash marks on the berm mark the landward most transport of sand grains that are dominantly quartz but which may
contain minor admixtures of biogenic (shell) fragments and organic matter (Photo: C.W. Finkl).
44
BEACH