Page 114 - (DK) Ocean - The Definitive Visual Guide

112 COASTS AND THE SEASHORE

PACIFIC OCEAN SOUTHWEST and fronts a series of dunes. Waves
generally break too close to the
Ninety Mile Beach beach for good surfing, and strong
rip currents make the conditions
TYPE Dissipative coastal hazardous for swimmers. In its
plain beach northeastern part, several large lakes
COMPOSITION Yellow and shallow lagoons, known as the
sand Gippsland Lakes, lie behind the dunes.
LENGTH 90 miles Beneath the sea, vast plains of sand
(145 km) stretch in every direction and are
LOCATION Southeast of Melbourne, Victoria, home to a large variety of small
southeastern Australia invertebrate life, including crustaceans,
worms, and burrowing mollusks.
Australia’s Ninety Mile Beach, on the
coast of Victoria, has a solid claim to AERIAL VIEW
be the world’s longest uninterrupted Facing out onto the Bass Strait, Ninety
natural beach. The beach runs in a Mile Beach is subject to strong waves
southwest to northeasterly direction during the winter months.

PACIFIC OCEAN SOUTHWEST PACIFIC OCEAN CENTRAL
Moeraki Beach Punalu’u Beach
TYPE Embayed beach TYPE
Pocket beach
COMPOSITION Dark
sand and large COMPOSITION
boulders Black sand
LENGTH 2 miles (3 km) LENGTH
1 / 3 mile (500 m)
LOCATION Northeast of Dunedin, southeastern LOCATION Northeast of Naalehu, Big Island,
New Zealand southeastern Hawaii
The beach north of Moeraki on Punalu’u Beach on Hawaii’s Big Island
New Zealand’s South Island is strewn is a steeply shelving pocket beach. It is
with groups of large, near-spherical best known for its dramatic-looking
boulders. Scientists believe they are black sand, which is composed of
mineral concretions that formed grains of the volcanic rock basalt.
over a few million years within The sand has been produced by wave
60-million-year-old mudstones— action on local cliffs of black basaltic
thick layers of sedimentary rock lava. Punalu’u, in common with about
making up the sea floor. These half the land area of Hawaii, lies on
mudstones were later uplifted the flank of Mauna Loa, the world’s
and now form a cliff at the most massive volcano. Lava produced
back of the beach. There, by the volcano dominates the local
gradual erosion exposes and landscape—although no lava has
releases the boulders, which reached Punalu’u from Mauna Loa
eventually roll down onto or the nearby active volcano Kilauea
the beach. for several hundred years.
The beach is a popular location
SUPERSIZED BOULDERS for swimming and snorkeling, but
The boulders are up to 7 ft (2.2 m) in underwater springs that eject cold
diameter, and some weigh several tons. water into the sea close to the beach
Some are half-buried in the sand. can cause discomfort. Punalu’u Beach
is also visited by green turtles, which
come to eat seaweed off rocks at the
PACIFIC OCEAN NORTHEAST location by ancient glaciers, remaining the shoreline. Such is the case in edge of the beach and bask on the
there when the glaciers melted. The Columbia Bay, a region within Alaska’s warm, heat-absorbing sand.
Columbia Bay till has usually been reworked by wave Prince William Sound. Many of the
action, with the lighter material (clay, beaches in this area have old tidal lines
TYPE Series of embayed silt, and sand) washed away and the visible above the present ones, the
beaches heavier gravel and rocks sorted by size result of a huge earthquake in 1964
COMPOSITION Gravel and deposited in different areas along that raised the land by 8 ft (2.4 m).
and rocks
OCEAN ENVIRONMENTS Many beaches in southern Alaska, and BLACK AND BLUE
LENGTH 31 miles (50 km)
LOCATION Southwest of Valdez, southern
Alaska, US

other beaches at high latitudes in the
Northern Hemisphere, consist of
gravel, small rocks, and boulders. These
materials come from coarse glacial
till—mixtures of clay, silt, sand, gravel,
and rocks that were carried to a

BEACH AND BAY
The sand on Punalu’u is almost perfectly black,
The backshore area visible here, which has
contrasting with the deep blue Pacific waters.
been colonized by plants, was foreshore prior
Removal of the sand is prohibited.
to the 1964 earthquake.