EM 1110-2-1100 (Part I)
30 Apr 02
River delta, marsh,
critical erosion in
Barriers and open bays
GULF OF MEXICO
Figure I-2-8. Gulf of Mexico coastal characteristics
are found with numerous lakes and meandering streams. Only a few mountain ranges extend as points into
the sea. The Yukon River has formed a large delta with many old lobes that form a vast plain connecting
small, elevated tracts. The oldest is located in the now drowned mouth of the Kuskokwim River. One reason
this coast differs from the glaciated southern coast of Alaska, is because it was largely ice- free during the
Pleistocene era. Permafrost becomes more important to the north where it greatly increases the number of
surface depressions in the summer when it melts forming thaw lakes. Rising above the coastal plain with
mountains over 1,000 m, the Seward Peninsula with Norton Sound and the Bering Sea to the south and
Kotzebbue Sound and the Chukchi Sea to the north provides a great contrast to the adjoining coasts. North
of Kotzebue Sound, barriers and cuspate forelands similar to those of North Carolina border the coast. The
first cuspate foreland is the unusual Point Hope. Three more cuspate forelands extend along the coast
terminating with Point Barrow, the most northern point of Alaska (Shepard 1982).
h. The Beaufort Sea: Deltaic coast. East of Point Barrow, the coast is dominated by river deltas.
Rivers draining the Brooks Range and father east the Mackenzie, draining the northern Canadian Rockies,
built these deltas even though the rivers flow only a short period each year. Where the deltas are not actively
building into the sea, extensive barrier islands can be found (Shepard 1982). One of the dominant processes
in shaping beaches in Alaska is the ride-up of shore ice (Kovacs 1983).