Page 177 - (DK) Ocean - The Definitive Visual Guide

SEAMOUNTS AND GUYOTS 175

MOUNTAINS IN THE SEA
This false-color map shows how a chain of chain of
8,850 ft (2,700 m) seamounts has arisen, close to where two large N
seamounts
spreading tectonic plates have been
9,000 ft (2,750 m) displaced sideways by a transform
fault. Other seamounts occur isolated
transform fault
9,200 ft (2,800 m) singly away from the ridge. seamount
isolated
9,350 ft (2,850 m) crest of East guyot
Pacific Rise
9,500 ft (2,900 m)
9,700 ft (2,950 m)

9,850 ft (3,000 m)
10,000 ft (3,050 m)
10,200 ft (3,100 m)

10,300 ft (3,150 m)
10,500 ft (3,200 m)

10,700 ft (3,250 m)
10,800 ft (3,300 m)
11,000 ft (3,350 m)

11,150 ft (3,400 m)
11,300 ft (3,450 m)

11,500 ft (3,500 m)
11,650 ft (3,550 m)
11,800 ft (3,600 m)

12,000 ft (3,650 m)
12,150 ft (3,700 m)
East Pacific Rise
12,300 ft (3,750 m) fracture zone
12,500 ft (3,800 m)
HUMAN IMPACT
ROUGHY
DEPTH
TROUBLE
Life on a Seamount PRIMNOID CORAL THREAT Fishermen thought they had
Scientists fear some primnoid
Some seamounts were first detected when coral species may be wiped out found a bonanza in the 1980s
when they discovered the huge
by bottom-trawl fishing before
fishermen discovered large shoals of fish in the area. shoals of fish that live over
they have even been named.
The nutrient-rich waters trapped above seamounts seamounts. For example, they
support dense concentrations of phytoplankton as could catch 100 tons of orange
well as the zooplankton that feed on them. roughy (see below and p.352) in
Free-swimming animals are attracted by this feast, a single day. However, roughy,
which can live for almost 150
including fish at densities found nowhere else in years, is slow-growing, and does
the open ocean. Predators such as sharks and seals also gather to feed. not produce eggs until it is 20–30
Seamount rock is colonized by suspension feeders—animals that catch years old. Such heavy fishing
plankton and detritus as it floats past. Only about one in a thousand cannot be sustained. World
seamounts has been explored underwater. However, in studies of 25 catches have declined hugely,
seamounts in the Tasman and Coral seas, 850 species (some previously and the roughy is now in danger.
thought extinct) were recorded.
Seamounts are important
biodiversity hotspots,
with up to one-third OCEAN ENVIRONMENTS
SEAMOUNT FEEDER
of species found there restricted to a Found in the tropics, this
single seamount or group of seamounts. octocoral is a colony of
soft corals. The feeding
FEEDING FROM THE CURRENTS polyps, lined up along
This squat lobster, or pinch bug, is a scavenger the branches, catch food
living on rock faces. Currents welling over from currents sweeping
the Bowie Seamount in the northeast over the seamount.
Pacific supply rich pickings.