300
WORLD ATLAS OF CORAL REEFS
Part IV
The Pacific Ocean
This
is a vast region, incorporating the
eastern shores of Australia and stretching
towards the coastline of the Americas.
There are more coral reefs here than in any
other part of the world: over ^iO percent of
the global total, including the most extensive areas of
barrier reefs and coral atolls. It was by looking at this
region that Darwin developed many of his ideas on the
development of reefs.
Although a contiguous ocean, the underlying plate
tectonics are a little more complex. Much of the region
lies on the main Pacific plate, however the IndoAustrallan plate stretches far Into the southwest. The
boundary between these two plates, and the associated
tectonic activity, has driven the development of a
number of the island groups Including Tonga and Fiji.
Further north a similar boundary occurs between
the Philippines plate and the Pacific plate. This is the
location of the Mariana Islands, but also the deepest
point In all the worlds oceans - the Challenger Deep at
1 1
034 meters. Away from plate margins, a number of
island groups have formed over mid-plate hotspots. The
movement of the ocean crust over these hotspots has
led to classic Island chains such as Hawai'l. with active
volcanoes at one end, and a subsequent line of Islands
Illustrating atoll development as the central volcanic
islands subside but the reef structures continue to grow.
Given the size of this ocean, it Is dominated by a
relatively simple system of ocean currents which are
broadly consistent throughout the year. From the
southern hemisphere up to the equator there Is a westward flowing South Equatorial Current. Immediately
north of this is the Equatorial Counter Current, flowing
to the east, typically between 3-5° and 10°N. To the
north of this, the North Equatorial Current again flows
westwards. South of the equator, air movements are
dominated by the southeast trade winds which flow
from the sub-tropical high pressure areas towards the
equator, and tend to be particularly strong from
around June to October. The northeast trade winds
WORLD ATLAS OF CORAL REEFS
Part IV
The Pacific Ocean
This
is a vast region, incorporating the
eastern shores of Australia and stretching
towards the coastline of the Americas.
There are more coral reefs here than in any
other part of the world: over ^iO percent of
the global total, including the most extensive areas of
barrier reefs and coral atolls. It was by looking at this
region that Darwin developed many of his ideas on the
development of reefs.
Although a contiguous ocean, the underlying plate
tectonics are a little more complex. Much of the region
lies on the main Pacific plate, however the IndoAustrallan plate stretches far Into the southwest. The
boundary between these two plates, and the associated
tectonic activity, has driven the development of a
number of the island groups Including Tonga and Fiji.
Further north a similar boundary occurs between
the Philippines plate and the Pacific plate. This is the
location of the Mariana Islands, but also the deepest
point In all the worlds oceans - the Challenger Deep at
1 1
034 meters. Away from plate margins, a number of
island groups have formed over mid-plate hotspots. The
movement of the ocean crust over these hotspots has
led to classic Island chains such as Hawai'l. with active
volcanoes at one end, and a subsequent line of Islands
Illustrating atoll development as the central volcanic
islands subside but the reef structures continue to grow.
Given the size of this ocean, it Is dominated by a
relatively simple system of ocean currents which are
broadly consistent throughout the year. From the
southern hemisphere up to the equator there Is a westward flowing South Equatorial Current. Immediately
north of this is the Equatorial Counter Current, flowing
to the east, typically between 3-5° and 10°N. To the
north of this, the North Equatorial Current again flows
westwards. South of the equator, air movements are
dominated by the southeast trade winds which flow
from the sub-tropical high pressure areas towards the
equator, and tend to be particularly strong from
around June to October. The northeast trade winds