Biology Reference
In-Depth Information
Louisiana are both amused and appalled at how those living in isolated parts
of the swamp are often depicted—particularly with regard to their distinc-
tive music (zydeco), culture (admittedly somewhat taciturn with strang-
ers but joyously effusive among friends), humor (a bit earthy), language (a
combination of French and Spanish), transportation (in fl at-bottomed boats
called pirogues), and religion (Catholic but with broad options including
the still-practiced voodoo). Nonetheless, the beauty of the cypress swamps,
approximating the
Glyptostrobus/Taxodium
association of the mid-Tertiary
in the New World, is frequently captured in these fi lms with dramatic
effectiveness.
The Western Cordillera
The complex of mountains known as the western cordillera formed as the
continent was forced westward by spreading from the Mid-Atlantic Ridge.
The leading edge crumpled as it was pushed against the subducting Pacifi c
Plate and accreted a complex mosaic of land fragments located on the plate.
Volcanic material from extensive volcanism associated with these events
was added later as an overlay of fl ood basalts, such as the Colorado Pla-
teau (circa 24 Ma) and the Columbia Plateau (largely formed 16-14 Ma).
The oldest of the highlands are the Rocky Mountains, west of which the
ranges become progressively younger. In the far north along the coast of
Alaska is the Brooks Range, brought to public attention because of the large
oil deposits around adjacent Prudhoe Bay, construction of the 800-mile-
long Alaskan pipeline, and most recently by corrosion of that pipeline after
decades of inadequate maintenance. Along the south coast is the Alaska
Range, with the magnifi cent scenery of Denali National Park, including Mt.
McKinley, the highest point in North America at 6194 m, and Prince Wil-
liam Sound, famous site of the 1989 Exxon Valdez oil spill.
The Rocky Mountains extend from northern British Colombia to the
Río Grande, but they are part of a system that continues into Mexico as
the Sierra Madre Occidental and Sierra Madre Oriental. They began as a
depression that was folded and uplifted to approximately 1 km above sea
level by about 65 Ma, followed by a period of intense orogeny 55-40 Ma.
By that time the landscape resembled the present-day High Plains along the
eastern front of the mountains, which locally had reached at least half of
their present altitude. The remaining height was attained afterward with
continued movement of the continent away from the Mid-Atlantic Ridge
and subduction of the Pacifi c Plate. The western cordilleras have higher
