Page 94 - (DK) Ocean - The Definitive Visual Guide

92 COASTS AND THE SEASHORE

Coastal Landscapes

A GREAT VARIETY OF LANDSCAPES ARE FOUND along the coastlines FRINGING REEF
of the world’s oceans. Coasts are shaped by processes such as sea-level This reef-fringed
coast, around the
change and wave erosion, as well as by land-based processes such south Pacific island
of Bora Bora, is a
as weathering, erosion and deposition by rivers, glacier advance secondary coast, as
and retreat, the flow of lava from volcanoes, and tectonic faulting. it has been modified
by the activities of
Some coastal features are made by living organisms, including living organisms,
the reefs built by corals and the harbors, coastal defenses, and notably corals.
artificial islands built by humans.

Classification of Coasts

Coasts can be classified as either primary or secondary. Primary coasts
have formed as a result of land-based processes, such as the deposition
of sediment from rivers (forming deltas), land erosion, volcanic action,
or rifting and faulting in Earth’s crust. Coasts formed as a result of
recent sea-level change, which include drowned coasts and emergent
coasts (see pp.88–89), are also usually considered primary, as are
coastlines consisting mainly of wind-deposited sand, glacial till, or
the seaward ends of glaciers. Coasts are considered secondary if they
have been heavily shaped by marine erosional
or depositional processes, or by the activities of
organisms, such as corals, mangroves, or, indeed,
people. A few coasts—for example, emergent
coasts that have undergone significant marine
erosion—display both primary and secondary
features and so fit into an intermediate category. VOLCANIC COAST
ARTIFICIAL COAST This land-eroded volcanic
Singapore Harbor, in Southeast cone is in the Galápagos Islands.
Asia, is an example of a coast The entire coastline around these
that has been heavily shaped islands was formed by volcanic
by human activity. Before activity and so is a primary coast.
human intervention, it was
a mangrove-lined estuary.

OCEAN ENVIRONMENTS SEA ARCH

This spectacular arch in southern England
is known as Durdle Door. A remnant of
a once much larger headland, it is a
classic feature of a marine-eroded coast.