SURFACE STRUCTURE OF THE

 

and ranges of Colorado, lies a region drained by the head-
waters of the Colorado. This region, together with the
country lying in the middle courses of the river, is a won-
derful section of country, traversed by streams that have
eroded their valleys and flow through deep cafions, some
of which are over 6000 feet deep. A view of apart of one
of the most noted of these cafions is shown in Fig. 126.

390. The Appalachian System, sometimes called
the Alleghany Mountains, extends from Georgia
to Maine, nearly parallel to the Atlantic. The
chain varies in breadth from 150 to 200 miles.
The system consists of an elevated plateau,
bearing several mountain-chains, separated by
wide valleys. In the northern and southern
parts of the chain, where the elevation is the
greatest, the system is formed of irregular groups,
without any definite direction. In the centre,
low parallel chains occur separated by fertile val-
leys. These valleys generally take the names of
the rivers which flow through them.

The system is highest in North Carolina, where
Mt. Mitchell, 6707 feet high, forms its culminat-
ing point.

Beginning in the north, the system includes the
White Mountains in New Hampshire, with Mount

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig, 127, The Natural Bridge (Virginia).

Washington, 6294 feet high ; the Green Mountains,
in Vermont; the Adirondacks, in New York, with

 

 

UNITED STATES. 149

 

the culminating peak of Mount Marcy, 5379 feet
high; the Catskill Mountains, the Blue Mountains,
the Alleghanies, the Blue Ridge, the Cumberland
Mountains, and others.

The Natural Bridge, in Rockbridge County, Virginia,

“is, from its peculiar formation, an object of interest to
tourists.

391. Plains—There are two great low plains
in the United States: the Atlantic Coast Plain
and the Plain of the Mississippi Valley.

The Atlantic Coast Plain lies along the eastern
flanks of the Appalachian Mountains. It varies
in width from 50 to 250 miles. Along the coast
the soil is comparatively sandy, and has been
formed by the combined action of the rivers and
ocean.

- The extensive swamps which occur in this region—such
as Cypress Swamp, in Delaware, Dismal Swamp, north of
Albemarle Sound, Alligator Swamp, between Albemarle
and Pamlico Sounds, and Okefinokee Swamp, in Southern
Georgia—are of fluvio-marine origin. The Everglades, in
Florida, are the result of a coral formation. Farther from

the coast, the plain is more elevated ; long valleys occur,
which are very fertile, particularly near the river bottoms.

The Mississippi Valley lies between the predomi-
nant and the secondary mountain-systems. It is
over 300,000 square miles in area, and includes
some of the most fertile land in the country.
Much of it is covered with forests or prairies.

392. River- and Lake-Systems.—The United
States is particularly noted for the number and
extent of its navigable rivers.

Oceanic Drainage—Atlantic System.—Among
the important rivers emptying directly into the
Atlantic Ocean are the Penobscot, Merrimac,
Connecticut, Hudson, Delaware, Susquehanna,

 

 

 

 

 

 

Fig. 128, Scene on the Mississippi.

Roanoke, Cape Fear, Santee, Savannah, Altar
maha, and the St. John’s.