Geological History of South America.--Rise of the Andes.--Creation
of the Amazon.--Characteristic Features of the Continent.--Andean
Chain.--The Equatorial Volcanoes.
Three cycles ago an island rose from the sea where now expands the vast
continent of South America. It was the culminating point of the
highlands of Guiana. For ages this granite peak was the solo
representative of dry land in our hemisphere south of the Canada hills.
In process of time, a cluster of islands rose above the thermal waters.
They were the small beginnings of the future mountains of Brazil,
holding in their laps the diamonds which now sparkle in the crown of Dom
Pedro II. Long protracted eons elapsed without adding a page to the
geology of South America. The Creator seems to have been busy elsewhere.
Decorating the north with the gorgeous flora of the carboniferous
period, till, in the language of Hugh Miller, "to distant planets our
earth must have shone with a green and delicate ray," he rubbed the
picture out, and ushered in the hideous reptilian age, when monstrous
saurians, footed, paddled, and winged, were the lords of this lower
world. All the great mountain chains were at this time slumbering
beneath the ocean. The city of New York was sure of its site; but huge
dinotheria wallowed in the mire where now stand the palaces of Paris,
London, and Vienna.
At length the morning breaks upon the last day of creation, and the fiat
goes forth that the proud waves of the Pacific, which have so long
washed the table-lands of Guiana and Brazil, shall be stayed. Far away
toward the setting sun the white surf beats in long lines of foam
against a low, winding archipelago--the western outline of the coming
continent. Fierce is the fight for the mastery between sea and land,
between the denuding power of the waves and the volcanic forces
underneath. But slowly--very slowly, yet surely--rises the long chain of
islands by a double process; the submarine crust of the earth is
cooling, and the rocks are folded up as it shrivels, while the molten
material within, pressed out through the crevices, overflows and helps
to build up the sea-defiant wall. A man's life would be too short to
count even the centuries consumed in this operation. The coast of Peru
has risen eighty feet since it felt the tread of Pizarro: supposing the
Andes to have risen at this rate uniformly and without interruption,
seventy thousand years must have elapsed before they reached their
present altitude. But when we consider that, in fact, it was an
intermittent movement--alternate upheaval and subsidence--we must add an
unknown number of millennia.
Three times the Andes sank hundreds of feet beneath the ocean level, and
again were slowly brought up to their present height. The suns of
uncounted ages have risen and set upon these sculptured forms, though
geologically recent, casting the same line of shadows century after
century. A long succession of brute races roamed over the mountains and
plains of South America, and died out ages ere man was created. In those
pre-Adamite times, long before the Incas ruled, the mastodon and
megatherium, the horse and the tapir, dwelt in the high valley of Quito;
yet all these passed away before the arrival of the aborigines: the wild
horses now feeding on the pampas of Buenos Ayres were imported from
Europe three hundred and thirty-three years ago.[50]
[Footnote 50: At Paita, the most western point of South America, there
is a raised beach three hundred feet high. The basal slate and sandstone
rocks, dipping S. of E., are covered by conglomerate, sand, and a
gypseous formation, containing shells of living species. Additional to
those described by D'Orbigny we found here _Cerithium læviuscula_,
_Ostrea gallus_, and _Ampullina Ortoni_, as determined by W.M. Gabb,
Esq., of Philadelphia. Darwin found shells in Chile 1300 feet above the
sea, covered with marine mud. President Loomis, of Lewisburg University,
Pa., informs the writer, that in 1853, after nearly a day's ride from
Iquique, he came to a former sea-beach. "It furnished abundant specimens
of _Patellæ_ and other shells, still perfect, and identical with others
that I had that morning obtained at Iquique with the living animal
inhabiting them." This beach is elevated 2500 feet above the Pacific.
The same observer says that near Potosi there is one uninterrupted mass
of lava, having a columnar structure, not less than one hundred miles in
length, fifty miles wide, and eight hundred feet thick. It overlies a
bed of saliferous sandstone which has been worked for salt. Fifty feet
within a mine, and in the undisturbed rock which forms its roof, the
doctor found fragments of dicotyledonous trees with the bark on,
undecomposed, uncharred, and fibrous.]
And now the Andes[51] stand complete in their present gigantic
proportions, one of the grandest and most symmetrical mountain chains in
the world. Starting from the Land of Fire, it stretches northward and
mounts upward until it enters the Isthmus of Panama, where it bows
gracefully to either ocean, but soon resumes, under another name, its
former majesty, and loses its magnificence only where the trappers chase
the fur-bearing animals over the Arctic plains. Nowhere else does Nature
present such a continuous and lofty chain of mountains, unbroken for
eight thousand miles, save where it is rent asunder by the Magellanic
Straits, and proudly tossing up a thousand pinnacles into the region of
eternal snow. Nowhere in the Old World do we see a single well-defined
mountain chain, only a broad belt of mountainous country traversing the
heart of the continent.
[Footnote 51: The name Andes is often derived from _anta_, an old
Peruvian word signifying metal. But Humboldt says: "There are no means
of interpreting it by connecting it with any signification or idea; if
such connection exist, it is buried in the obscurity of the past."
According to Col. Tod, the northern Hindoos apply the name Andes to the
Himalayan Mountains.]
The moment the Andes arose, the great continental valley of the Amazon
was sketched out and moulded in its lap. The tidal waves of the Atlantic
were dashing against the Cordilleras, and a legion of rivulets were
busily plowing up the sides into deep ravines; the sediment produced by
this incessant wear and tear was carried eastward, and spread out
stratum by stratum, till the shallow sea between the Andes and the
islands of Guiana and Brazil was filled up with sand and clay. Huge
glaciers (thinks Agassiz), afterward descending, moved over the inclined
plane, and ground the loose rock to powder.[52] Eddies and currents,
throwing up sand-banks as they do now, gradually defined the limits of
the tributary streams, and directed them into one main trunk, which
worked for itself a wide, deep bed, capable of containing its
accumulated flood. Then and thus was created the Amazon.
[Footnote 52: On this point see Chapter XVII.]
In South America Nature has framed her works on a gigantic scale. Where
else combined do we see such a series of towering mountains, such a
volume of river-water, and such wide-spreading plains? We have no proper
conception of Andine grandeur till we learn that the top of the tallest
mountain in North America is nearly a mile beneath the untrodden dome of
Chimborazo; nor any just view of the vast dimensions of the Amazonian
Valley till we find that all the United States could be packed in it
without touching its boundaries; nor any adequate idea of the Amazon
itself till we ascertain that it drains a million square miles more than
the Mississippi.
South America is a triangular continent, with its axis, the Andes, not
central, as in Europe, but lying on its extreme western edge, and in
harmony with the well-known law that the highest mountains and the
grandest volcanoes face the broadest ocean. The highlands of Brazil and
Guiana have neither volcanic nor snow-clad peaks.[53] Like all the dry
land which first appeared, these primitive mountains on the Atlantic
border trend east and west. The result of this position is a triple
river system--the Orinoco, Amazon, and La Plata, draining three immense
plains--the llanos of Venezuela, the sylvas of Brazil, and the pampas of
the Argentine Republic. The continuity and extent of these vast
depressions are more remarkable even than the height and length of the
mountain chains.[54]
[Footnote 53: "The interior plateau of Brazil (says Dr. Lund) is
composed of horizontal strata of the transition period, which are
nowhere covered with the secondary or tertiary formations." The highest
point in Brazil is 5755 feet. Darwin speaks of "some ancient submarine
volcanic rocks (in the province of La Plata) worth mentioning, from
their rarity on this eastern side of the continent." With the exception
of the coast of Venezuela, the eastern system is little exposed to
earthquakes.]
[Footnote 54: These three plains constitute four fifths of all South
America east of the Andes. The west slope of the Ecuadorian Andes is
about 275 feet per mile; on the east it is 125 feet.]
Such are the characteristic features of South America; they are not
repeated in any other continent.[55] Not one feature could be changed
without destroying those peculiarities of soil and climate which so
remarkably distinguish South America. Its position on the equator places
it in the path of the vapory trade winds, which continually sweep over
it westward till they strike the Andes, which, like a great condenser,
roll a thousand streams eastward again to feed the mighty Amazon. So
effectual is that barrier, not a drop of moisture passes it, and the
trade wind is not felt again on the Pacific till you are one hundred
and fifty miles from the coast. Were the Andes on the Atlantic side,
South America would be turned into a vast Sahara. As it is, the interest
which attaches to this continent, save a few relics of the Incas, is
exclusively that of pure nature. Nowhere does Nature affect us more
deeply with the feeling of her grandeur; nowhere does she exhibit wilder
freaks or more startling contrasts; nowhere do we find such a theatre
for the free development of vegetable and animal life.
[Footnote 55: There is, however, a striking coincidence between the
mountain and river systems of the northern and southern continents of
this hemisphere. Thus,
The Andes represent the Rocky Mountains,
" Highland of Guiana represent the Canadian Mountains.
" " Brazil " Appalachian "
" Amazon " Saskatchewan.
" La Plata " Mississippi.
" Orinoco " Mackenzie.
]
The long and lofty chain of the Andes is certainly one of the grandest
results of the plications and uplifts of the earth's crust. While the
waves of the Pacific, from Panama to Patagonia, submissively kiss the
feet of the Andes, and the showers that swell the Amazon fall within
sight of the mariner on that peaceful ocean, the Rocky Mountains are
situated five hundred miles from the sea. The space west of the Andes
does not contain 20,000 square leagues, while the country east of it
equals 424,600. While the compact Andes have an average width of only
sixty miles,[56] the straggling mountain system beyond the Mississippi
has the breadth of the Empire State; but the mean elevation of the
latter would scarcely reach the bottom of the Quito Valley. The
mountains of Asia may surpass the Cordilleras in height, but, situated
beyond the tropics, and destitute of volcanoes, they do not present that
inexhaustible variety of phenomena which characterizes the latter. The
outbursts of porphyry and trachytic domes, so characteristic of the high
crests of the Cordilleras, impart a physiognomy quite distinct from that
presented by the mountains of Europe. The Andes offer, in the least
space, the greatest possible variety of impressions.[57] There is near
Huanca, Peru, a coal-bed lifted up to the enormous height of 14,700
feet, and on the side of Chimborazo there is a salt spring 13,000 feet
above the sea. Marine shells have not been found in Europe above the
summit of the Pyrenees, or 11,700 feet; but the Andes can show some a
thousand feet higher. A strange sight, to see shells once crawling on
the bottom of the ocean now resting at an elevation twice the height of
Mount Washington!
[Footnote 56: The width of the chain south of the equator varies with
that of the continent.]
[Footnote 57: "No mountains which I have seen in Hungary, Saxony, or the
Pyrenees are as irregular as the Andes, or broken into such alternate
substances, manifesting such prodigious revolutions of nature."--_Helms_.
"More sublime than the Alps by their _ensemble_, the Andes lack those
curious and charming details of which Nature has been so lavish in the
old continent."--_Holinski_.]
Beneath the Southern Cross, out of a sea perpetually swept by fearful
gales, rise the rocky hills of Terra del Fuego. It is the starting-point
of that granite chain which winds around the earth in a majestic curve,
first northwesterly to the Arctic Sea, thence by the Aleutian and
Japanese Isles to Asia, crossing the Old World southwesterly from China
to South Africa.
Skirting the bleak shores of Patagonia in a single narrow sierra, the
Andes enter Chile, rising higher and higher till they culminate in the
gigantic porphyritic peak of Aconcagua. At the boundary-line of Bolivia,
the chain, which has so far followed a precise meridional direction,
turns to the northwest, and, at the same time, separates into two
Cordilleras, inclosing the great table-land of Desaguadero. This
wonderful valley, the Thibet of the New World, has four times the area
of New York State, and five times the elevation of the Catskill Mountain
House. At one end of the valley, perched above the clouds, is silvery
Potosi, the highest city in the world; at the other stands the once
golden capital of Cuzco. Between them is Lake Titicaca[58] (probably an
ancient crater), within which is an island celebrated as the cradle of
the strange empire of Peru, which, though crushed by Pizarro in its
budding civilization, ranks as the most extraordinary and extensive
empire in the annals of American history. The Cordillera, of which
Sahama, Sorata, and Illimani are the pinnacles, so completely inclose
this high valley that not a drop of water can escape except by
evaporation. At the silver mines of Pasco the Andes throw off a third
cordillera, and with this triple arrangement and a lower altitude, enter
the republic of Ecuador. There they resume the double line, and surpass
their former magnificence. Twenty volcanoes, presided over by the
princely Chimborazo and Cotopaxi, rise out of a sublime congregation of
mountains surrounding the famous valley of Quito. In New Granada there
is a final and unique display of Andine grandeur: the Cordilleras
combine just above the equator into one dizzy ridge, and then spread out
like a fan, or, rather, like the graceful branches of the palm. One
sierra bends to the east, holding in its lap the city of Bogota, and,
rolling off a thousand streams to swell the Orinoco, terminates in the
beautiful mountains of Caracas; the central range culminates in the
volcanic Tolima,[59] but is soon lost in the Caribbean Sea; the western
chain turns to the left, humbling itself as it threads the narrow
isthmus, and expands into the level table-land of Mexico. You may cross
Mexico from ocean to ocean in a carriage, but no wheeled vehicle ever
crossed South America.
[Footnote 58: This lake is the largest fresh-water accumulation in South
America. It has diminished within the historic period. Its surface is
12,795 feet above the Pacific, or higher than the highest peaks of the
Pyrenees.]
[Footnote 59: This is the loftiest summit of the Andes in the northern
hemisphere, being 18,200 feet. It is also remarkable for being situated
farther from the sea (120 miles) than any other active volcano.]
[Illustration: Profiles of Ecuadorian Volcanoes
10,000 ft. Chimborazo.
10,000 ft. Cotopaxi.
10,000 ft. Caraguairazo.
10,000 ft. Pichincha.
]
We will now speak more particularly of the Andes of the equator. The
mountain chain is built up of granite, gneissoid, and schistose rocks,
often in vertical position, and capped with trachyte and porphyry.[60]
Large masses of _solid_ rock are rarely seen; every thing is cracked,
calcined, or triturated. While in Bolivia the Eastern Cordillera shows a
succession of sharp, ragged peaks, in contrast with the conical summits
of the Cordillera of the coast, there is no such distinction in the
Andes of the equator.[61] The Eastern Cordillera has a greater mean
height, and it displays more volcanic activity. Twenty volcanic
mountains surround the valley, of which twelve are in the oriental
chain. Three of the twenty are now active (Cotopaxi, Sangai, and
Pichincha), and five others are known to have erupted since the Conquest
(Chiles, Imbabura, Guamani, Tunguragua, and Quirotoa). The truncated
cone of Cotopaxi, the jagged, Alpine crest of ruined Altar, and the dome
of Chimborazo, are the representative forms of the volcanic summits. The
extinct volcanoes usually have double domes or peaks, while the active
peaks are slender cones. Antisana and Cayambi are fashioned after
Chimborazo, though the latter is table-topped rather than convex;
Caraguairazo, Quirotoa, Iliniza, Sincholagua, Rumiñagui, and Corazon,
resemble Altar; Tunguragua, Sangai, Llanganati, Cotocachí, Chiles, and
Imbabura, imitate Cotopaxi; Pichincha, Atacatzo, and Guamani are
irregular. The Ecuadorian volcanoes have rarely ejected liquid lava, but
chiefly water, mud, ashes, and fragments of trachyte and porphyry.
Cotopaxi alone produces pure, foam-like pumice, and glossy,
translucent obsidian.[62] The paucity of quartz, and the absence of
basalt, are remarkable. Some of the porphyroids are conglomerate, but
the majority are true porphyries, having a homogeneous base. Dr. T.
Sterry Hunt calls them porphyroid trachytes. They have a black, rarely
reddish, vitreous, or impalpable base, approaching obsidian, with a
specific gravity of 2.59 in pure specimens, and holding crystals or
crystalline grains of glassy feldspar, and sometimes of pyroxene and
hematite. They differ from the Old World porphyries in containing no
quartz, and seldom mica.[63] D'Orbigny considers the porphyries of the
Andes to have been ejected at the close of the cretaceous period, and
formed the first relief of the Cordillera. The prevalence of trachyte
shows that the products have cooled under feeble pressure.
[Footnote 60: "As a general rule, whenever the mass of mountains rises
much above the limit of perpetual snow, the primitive rocks disappear,
and the summits are trachyte or trappean porphyry."--_Humboldt_. In
general, "the great Cordilleras are formed of innumerable varieties of
granites, gneiss, schists, hornblende, chloritic slates, porphyries,
etc., and these rocks alternate with each other in meridional bands,
which in the ridges frequently present the appearance of a radiated or
fan-shaped structure, and under the plains are more or less
vertical."--_Evan Hopkins, F.G.S_.]
[Footnote 61: Von Tschudi makes the incorrect statement that "throughout
the whole extent of South America there is not a single instance of the
Western Cordillera being intersected by a river." Witness the
Esmeraldas.]
[Footnote 62: It is a singular fact that true trachyte, pumice, and
obsidian are wanting in the volcanic Galápagos Islands, only 700 miles
west of Pichincha.]
[Footnote 63: As many of the crystals are partly fused, or have round
angles, the porphyries were probably formed by the melting of a
crystalline rock, the base becoming fused into a homogeneous material,
while the less fusible crystals remain imbedded.--_Dr. Hunt_.]
From the deluges of water lately thrown out have resulted deep furrows
in the sides; and from the prevalence of the east wind, which is always
met by the traveler on the crest of either Cordillera, there is a
greater accumulation of ashes, and less snow on the west slope. Cotopaxi
is a fine example of this. In Pichincha, Altar, and Rumiñagua, however,
the western wall is lowest, apparently broken down.[64] There is no
synchronism in the eruptions of Cotopaxi and Pichincha. These volcanoes
must have independent reservoirs, for the former is 3000 feet higher
than the latter, and only thirty miles distant. The reputed eruptions of
Pichincha are dated 1534, 1539, 1566, 1575, 1588, and 1660; that of 1534
resting on the assertions of Checa, Garcilazo, and Herrera, indorsed by
Humboldt. Excepting the traditional eruption in 1534, which probably is
confounded with that of Pichincha, Cotopaxi did not open till 1742; then
followed the eruptions of 1743, 1744, 1746, 1766, 1768, 1803, 1851, and
1855. We must mention, however, that, since the recent awakening of
Pichincha, Cotopaxi has been unusually silent. There is also a
remarkable coincidence (which may not be wholly accidental) in the
renewed activity of Pichincha, and the great eruption of Mauna Loa, both
occurring in March, 1868. It is generally believed by the natives that
Cotopaxi and Tunguragua are sympathetic.
[Footnote 64: In the Galápagos volcanoes the south wall is lowest, while
the craters in Mexico and Sandwich Islands are lowest on the northeast.]
There are fifty-one volcanoes in the Andean chain. Of these, twenty
girdle the Valley of Quito, three active, five dormant, and twelve
extinct.[65] Besides these are numerous mountain peaks not properly
volcanic. Nowhere on the face of the earth is there such a grand
assemblage of mountains. Twenty-two summits are covered with perpetual
snow, and fifty are over ten thousand feet high.[66]
[Footnote 65: The altitudes of the most important Ecuadorian volcanoes
are:
WESTERN CHAIN.
_Chimborazo_, 21,420 feet (Humboldt).
_Caraguairazo_, 19,183 feet (Humboldt).
It is variously estimated from 15,673
feet to 19,720 feet; 18,000 feet is
not far from the truth.
_Iliniza_, 17,370 feet (Wisse); 16,300
(Hall).
_Cotocachí_, 16,440 feet (Humboldt);
16,409 (Wisse).
_Pichincha_, 15,922 feet (Humboldt);
15,827 (Orton).
EASTERN CHAIN.
_Cayambi_, 19,648 feet (Humboldt);
19,358 (Wisse).
_Antisana_, 19,148 feet (Humboldt);
19,279 (Wisse).
_Cotopaxi_, 18,880 feet (Humboldt);
18,862 (Wisse).
_Altar_, 17,400 feet.
_Sangai_, 17,120 feet (Wisse).
_Tunguragua_, 16,579 feet (Humboldt).
_Sincholagua_, 16,434 feet (Humboldt).
]
[Footnote 66: The snow limit at the equator is 15,800 feet. No living
creature, save the condor, passes this limit; naked rocks, fogs, and
eternal snows mark the reign of uninterrupted solitude. The following is
the approximate limit of perpetual snow in different latitudes:
0° 15,800 feet.
27° 18,800 "
33° 12,780 "
40° 8,300 feet.
54° 3,700 "
70° 3,300 "
The limit appears to descend more rapidly going south of the equator
than in going north.]
All of these would be visible from a single stand-point--the summit of
Cotopaxi. The lofty peaks shoot up with so much method as almost to
provoke the theory that the Incas, in the zenith of their power, planted
them as signal monuments along the royal road to Cuzco. The eastern
series is called the _Cordillera real_, because along its flank are the
remnants of the splendid highway which once connected Quito and the
Peruvian capital.[67] It can also boast of such tremendous volcanoes as
Cotopaxi and Sangai. The Western Cordillera contains but one active
volcano; but then it can point to peerless Chimborazo and the deep
crater of Pichincha. These twenty volcanic mountains rise within a space
only two hundred miles long and thirty miles wide. It makes one tremble
to think of the awful crevice over which they are placed.[68]
[Footnote 67: We traveled over a portion of this ancient road in going
from Riobamba to Cajabamba. It is well paved with cut blocks of dark
porphyry. It is not graded, but partakes of the irregularity of the
country. Designed, not for carriages, but for troops and llamas, there
are steps when the ascent is steep.]
[Footnote 68: Grand as the Andes are, how insignificant in a general
view! How slightly they cause our globe to differ from a perfect sphere!
Cotopaxi constitutes only 1/1100 of the earth's radius; and on a globe
six feet in diameter, Chimborazo would be represented by a grain of sand
less than 1/20 of an inch in thickness.]