Geology Reference
In-Depth Information
Plate 13.1
Horizontal shore platform at low tide,
Atia Point, Kaikoura Peninsula, New Zealand.
Higher Pleistocene coastal terraces are also visible,
the highest standing at 108 m.
(
Photograph by Wayne Stephenson
)
Figure 13.5
Three major forms on rocky coasts: shore
platforms and plunging cliffs
including cliffs, notches, ramps and ramparts, and several
small-scale weathering (including solution pools and
tafoni, p. 157) and erosional features. Indeed, shore
platforms, cliffs, stacks, arches, caves, and many other
landforms routinely form conjointly.
and upon biological factors. Tidal effects are also signif-
icant as they determine the height of wave attack and
the kind of waves doing the attacking, and as they may
influence weathering and biological activities. The tide
itself possesses no erosive force.
Plunging-cliff coasts
lack any development of shore
platforms. Most plunging cliffs are formed by the drown-
ing of pre-existing, wave-formed cliffs resulting from a
fall of land level or a rise of sea level.
Cliffs, notches, ramps, ramparts, and
potholes
Cliffs
are steep or vertical slopes that rise precipitously
from the sea or from a basal platform (Plate 13.3). About
80 per cent of the world's oceanic coasts are edged with
cliffs (Emery and Kuhn 1982). Cliff-base
notches
are
sure signs of cliff erosion (Plate 13.4). Shallow notches
are sometimes called
nips
. The rate at which notches
grow depends upon the strength of the rocks in which
the cliff is formed, the energy of the waves arriving at the
Landforms of cliffs and platforms
Several coastal features of rocky coasts are associated with
the shore platforms and plunging cliffs (Figure 13.6),
