Geoscience Reference
In-Depth Information
Evolution of the Louisiana Coastline
Rising sea levels threaten many coastlines around the world. Perhaps
the most sensitive coastal zone in the United States is the Gulf shore
from Texas to Florida. The coast of Louisiana is particularly suscep-
tible to rising sea levels because of the close relationship it has with
the Mississippi River and its delta. Large areas of coastal loss have
already occurred in the past few decades. To see the complex his-
tory of coastal zone, and the rates of projected sea-level change in
the future, go to the
Geo Media Library
and select
Evolution of the
Louisiana Coastline
. Once you complete the animation, be sure to
answer the questions at the end to test your understanding.
nourishment is an active process involving the physi-
cal transport of sand to the beach, whereas groins
take advantage of the natural behavior of the long-
shore current.
4.
Jetties are long walls built along river channels and
inlets to maintain a passageway from the open ocean
to the interior. These features project some distance
into the water to provide a safe coastal approach for
ships.
3.
Beach and bluff protection is mostly accomplished
through the installation of sea walls and revetments,
which armor the shore. Although these features work
in the sense that they protect the portion of shore they
front, they transfer wave energy to adjacent localities
where it is concentrated as an erosive force.
5.
Global warming appears to be causing a rise in sea
level. In this context, significant parts of global coast-
lines are susceptible to increased erosion and, in some
extreme cases, ultimate submergence. Warmer oceans
are also contributing to coral bleaching.
S U M M A R y O F K E y C O N C E P T S
1.
A coastline is a narrow zone where the hydrosphere,
lithosphere, and atmosphere interact on a very large
scale. These interactions result in very distinctive
processes and landforms. Most coastlines are
associated with the world's oceans, seas, and gulfs, but
some prominent coastlines occur along very large lakes
such as the North American Great Lakes.
of (1) longshore current in the water along the shore
and (2) swash/backwash of water moving up and down,
respectively, on the beach.
4.
Erosional coastlines evolve when sediment is removed
by coastal processes. Prominent erosional landforms
along coastlines are headlands, bluffs, sea stacks,
and marine terraces. Depositional coastlines develop
where sediment accumulates. These landforms include
beaches, spits, baymouth bars, tombolos, and barrier
islands.
2.
The world's oceans collectively constitute the largest
component of the hydrological cycle. Smaller bodies of
water associated with oceans are seas and gulfs.
5.
A slight majority of people on Earth live near coastlines.
Given this population distribution, coastlines are
impacted greatly by human behavior. Most of this
impact occurs in the form of engineered structures, such
as seawalls and jetties, which protect the shore and
maintain the location of shipping channels.
3.
The most important agents of coastal change include
water fluctuations, tides, waves, and littoral processes.
The most extensive water fluctuations occurred when
continental glaciers advanced and retreated during
the Pleistocene. Tides are daily fluctuations caused
by the gravitational pull of the Moon (mostly), and to a
lesser degree the Sun. Waves form when wind blows
across the water, causing energy within the water to
roll forward due to friction. Waves often approach
coastlines obliquely, resulting in the littoral processes
6.
It appears that global warming is having a major impact
on coastlines around the world. These impacts include
bleaching of coral reefs and rising sea levels, which are
threatening coastal communities.