Geoscience Reference
In-Depth Information
by waves, tides, and the wind into the linear islands. At the
same time as these islands began to form, they were gradually
nudged toward their present position by the slowly rising water
and storms crashing into them.
A key factor in the overall topography of a barrier island
is the supply of sand fed to the system. In barriers with low
sand supply, the landform will have very low relief and lie
only a meter or two above sea level. Where barriers have high
sand supply, dunes typically form and provide additional re-
lief to the landscape. Barrier islands lie in various proximities
to the shoreline, with some being only several hundred meters
away and others many kilometers from the coast. An excel-
lent place to see barrier islands is along the Atlantic and Gulf
coasts of the southeastern United States, where approximately
280 barrier islands are found. Figure 19.27a shows a satellite
image of a reach of barrier islands along the Gulf Coast from
Louisiana (left) to Alabama (right). The Chandeleur Islands
are part of the complex, lying east of the Mississippi Delta.
These islands have very low relief due to limited sand supply
and are thus pounded when large waves from strong storms
and hurricanes wash over. As you can see in Figure 19.27b,
hurricanes Rita (2004) and Katrina (2005) dramatically al-
tered the shape of these islands, producing numerous gaps and
reducing island size.
Cat Island
Dauphin
Island
Horn
Island
Ship
Islands
Mobile
Point
Petit Bois
Island
Chandeleur Islands
Mississippi Delta
30 km
(a)
(b)
Figure 19.27 Barrier islands along the Gulf Coast.
(a) Satellite image of a complex of barrier islands east of the Mississippi Delta along
the coast of Mississippi and Alabama. (b) Time sequence of the Chandeleur Islands from 2001, 2004, and 2005. Notice the profound impact
hurricanes Rita and Katrina had on these inlands.