Geology Reference
In-Depth Information
Table 13.1 Beach types
Form
Name
Comment
Beaches attached to land at one end
Length greater than width
Barrier spit
A continuation of the original coast or
running parallel to the coast
a
Comet-tail spit
Stretch from the leeside of an island
Stretch from the coast at high angles
b
Arrow
Length less than width
Foreland (cuspate spit)
—
Beaches attached to land at two ends
Looped forms stretching out from the
coast
Looped barriers
Stretch from the leeside of an island
Looped spit
A spit curving back on to the land
Double-fringing spit
Two joined spits or tombolos
Connecting islands with islands or islands
with the mainland (tombolos)
Tombolo
Y-tombolo
Single form
Single beach looped at one end
Double tombolo
Two beaches
Closing off a bay or estuary (barrier
beaches)
Baymouth barrier
Midbay barrier
Bayhead barrier
At the mouth (front) of a bay
Between the head and mouth of a bay
At the head (back) of a bay
Forms detached from the land
A discrete, elongated segment
Barrier island
No connection with the land. Runs parallel to
the coast. Often recurved at both ends
and backed by a lagoon or swamp
Notes:
a
A winged headland is a special case. It involves an eroding headland providing sediment to barrier spits that extend
from each side of the headland
b
A flying spit is a former tombolo connected to an island that has now disappeared
Source:
Adapted from Trenhaile (1998, 244)
Tombolos
is a tombolo that is partly or completely submerged by
the sea at high tide.
Tombolos
are wave-built ridges of beach material con-
necting islands to the mainland or islands to islands.
They come in single and double varieties. Chesil Beach
in Dorset, England, is part of a
double tombolo
that
attaches the Isle of Purbeck to the Dorset mainland.
Tombolos tend to grow in the lee of islands, where a pro-
tection is afforded from strong wave action and where
waves are refracted and convergent.
Y-shaped tombolos
develop where comet-tail spits merge with cuspate forms
projecting from the mainland or where a cuspate barrier is
extended landwards or seawards. A
tombolino
or
tie-bar
Barriers and barrier beaches
Coastal barriers and barrier islands are formed on beach
material deposited offshore, or across the mouths of inlets
and embayments. They extend above the level of the
highest tides, in part or in whole, and enclose lagoons
or swamps. They differ from bars, which are submerged
during at least part of the tidal cycle.
Coastal barriers
are built of sand or gravel. Looped
barriers and cuspate barriers result from growing spits
