Ecuador is divided into three continental regions--the Costa, Sierra,
and Oriente--and one insular region--the Gal�pagos Islands. The
continental regions extend the length of the country from north to south
and are separated by the Andes Mountains. The Gal�pagos Islands,
officially called the Archipi�lago de Col�n, are located 1,000
kilometers west of the Ecuadorian coast within 1 south of the equator.
The Costa, located between the Pacific Ocean and the Andes Mountains,
consists of coastal lowlands, coastal mountains, and rolling hills that
separate river valleys. The widest part of the region stretches 150
kilometers from Cabo San Lorenzo in Manab� Province to the foothills of
the Andes Mountains. In the southern part of Guayas Province, east of
the Gulf of Guayaquil, the narrow coastal plain is only fifteen to
twenty kilometers wide. The lowlands of the Costa do not exceed 200
meters in elevation, whereas the coastal mountains extend no higher than
1,000 meters. The coastal mountain chain, known as the Cordillera Costa�era,
divides the region into the Costa Externa, next to the coast, and the
Costa Internal, next to the Andes. The Cordillera Costa�era reaches
from Esmeraldas in the north to Guayaquil in the south. North of
Portoviejo in Manab� Province, the Cordillera Costa�era loses its
character as a mountain chain and becomes a series of hills and small
mountains.
The Sierra consists of two major chains of the Andes mountains, known
as the Cordillera Occidental (Western Chain) and Cordillera Oriental
(Eastern Chain), and the intermontane basin or plateau between the two
chains. Several transversal mountain spurs, known as nudos, cut
across the plateau. The Nudo del Azuay, at 4,500 meters the highest of
these transversal spurs, divides the Sierra into two subregions--the
area of modern volcanism to the north and the area of ancient volcanism
to the south. The former area consists of newer, higher mountains than
those in the ancient volcanism section, which with time have eroded to
lower levels.
The Sierra has at least twenty-two peaks over 4,200 meters in height.
Of the two cordilleras, the Cordillera Oriental is wider and generally
higher, with peaks averaging over 4,000 meters. The Cordillera
Occidental, however, contains the highest point in Ecuador, which is the
Mount Chimborazo at 6,267 meters. The Sierra also contains the highest
point on the equator, Mount Cayambe at 5,790 meters.
The Sierra has at least thirty peaks of volcanic origin, including
six still active. These peaks, which vary in width from 80 to 130
kilometers, are located in the area of modern volcanism known as the
Avenue of the Volcanos. The most active volcano is Mount Sangay, 5,230
meters high. Although its last major outpouring of lava occurred in
1946, specialists consider Mount Sangay to be in a constant state of
eruption because of fires and bubbling lava at its crater. Mount
Cotopaxi, at 5,897 meters the highest active volcano in the world, last
erupted in 1877 and is now listed as "steaming." Its crater is
800 meters in diameter. In addition to the other damage caused by
eruptions, volcanos in the Sierra have melted snowcaps, which in turn
generate massive mudslides and avalanches. Earthquakes and tremors also
are common in the region.
The intermontane plateau between the two cordilleras is divided by
the nudos into roughly 10 basins, or hoyas, that range
from 2,000 to 3,000 meters in altitude. The average altitude of the
plateau is 2,650 meters.
The Oriente to the east of the Cordillera Oriental consists of two
subregions: the Andean piedmont and the Eastern lowlands. The piedmont
drops from a height of 3,353 meters to the featureless lowlands, which
spread out at an altitude of 150 to 300 meters.
The Gal�pagos Islands consist of a chain of large, medium, and small
islands that have a combined area of roughly 8,000 square kilometers.
The largest island is Isabela Island, also known as Albemarle Island,
which is 120 kilometers long with an area of 4,275 square kilometers.
All of the islands are of volcanic origin, and some have active cones.
Santo Tom�s, located on Isabela Island, is the highest peak of the Gal�pagos
at 1,490 meters. Its crater is ten kilometers in diameter.
Ecuador - Rivers
Almost all of the rivers in Ecuador rise in the Sierra region and
flow east toward the Amazon River or west toward the Pacific Ocean. The
rivers rise from snowmelt at the edges of the snowcapped peaks or from
the abundant precipitation that falls at higher elevations. In the
Sierra region, the streams and rivers are narrow and flow rapidly over
precipitous slopes. Rivers may slow and widen as they cross the hoyas
yet become rapid again as they flow from the heights of the Andes to the
lower elevations of the other regions. The highland rivers broaden as
they enter the more level areas of the Costa and the Oriente.
In the Costa region, the Costa Externa has mostly intermittent rivers
that are fed by constant rains from December through May and become
empty riverbeds during the dry season. The few exceptions are the
longer, perennial rivers that flow throughout the Costa Externa from the
Costa Internal and the Sierra on their way to the Pacific Ocean. The
Costa Internal, by contrast, is crossed by perennial rivers that may
flood during the rainy season, sometimes forming swamps.
The Guayas River system, which flows southward to the Gulf of
Guayaquil, constitutes the most important of the drainage systems in the
Costa Internal. The Guayas River Basin, including land drained by its
tributaries, is 40,000 square kilometers in area. The
sixty-kilometer-long Guayas River forms just north of Guayaquil out of
the confluence of the Babahoyo and Daule rivers. Briefly constricted at
Guayaquil by hills, the Guayas widens south of the city and flows
through a deltaic network of small islands and channels. At its mouth,
the river forms a broad estuary with two channels around Pun� Island,
the deeper of which is used for navigation.
The second major Costa river system--the Esmeraldas--rises in the
Hoya de Quito in the Sierra as the Guayllabamba River and flows westward
to empty into the Pacific Ocean near the city of Esmeraldas. The
Esmeraldas River is 320 kilometers long and has a
20,000-square-kilometer drainage basin.
Major rivers in the Oriente include the Pastaza, Napo, and Putumayo.
The Pastaza is formed by the confluence of the Chambo and the Patate
rivers, both of which rise in the Sierra. The Pastaza includes the
Agoyan waterfall, which at sixty-one meters is the highest waterfall in
Ecuador. The Napo rises near Mount Cotopaxi and is the major river used
for transport in the Eastern lowlands. The Napo ranges in width from 500
to 1,800 meters. In its upper reaches, the Napo flows rapidly until the
confluence with one of its major tributaries, the Coca River, where it
slows and levels off. The Putumayo forms part of the border with
Colombia. All of these rivers flow into the Amazon River. The Gal�pagos
Islands have no significant rivers. Several of the larger islands,
however, have freshwater springs.
Ecuador - Climate
Each region has different factors that affect its climate. The Costa
is influenced primarily by proximity to warm or cool ocean currents. By
contrast, climate in the Sierra varies more as a function of altitude.
The Oriente has a fairly uniform climate that varies only slightly
between the two subregions. Climate in the Gal�pagos Islands is both
moderated by the ocean currents and affected by altitude. Throughout
Ecuador variation in rainfall primarily determines seasons. Temperature
is determined by altitude. With each ascent of 200 meters in altitude,
temperature drops 1� C. This phenomenon is particularly significant in
the Sierra.
The Costa has a tropical climate. Temperatures for the region as a
whole remain fairly constant, ranging from 23� C in the south to 26� C
in the north. Although seasonal changes in temperature are not
pronounced, the hottest period occurs during the rainy season,
especially from February to April. Near Guayaquil, the coolest months
are August and September. Rainfall in the Costa decreases from north to
south, with vegetation changing from tropical rainforest in the north to
tropical savannah to desert in the south.
Differences in temperature and rainfall in the Costa are caused by
the Peruvian Current and periodic appearances of El Ni�o. The Peruvian
Current, also formerly known as the Humboldt, is a cold ocean current
that flows north along the coasts of Chile and Peru. At Cabo Blanco,
where the Gulf of Guayaquil begins, the main current veers to the west;
a branch continues northward to Cabo Pasado, in Manab� Province, where
it also turns westward to merge with the main current near the Gal�pagos
Islands. The cold water and air temperatures associated with the
Peruvian Current inhibit rainfall along the coast, creating dry to arid
conditions. This effect is greatest along the southern coast of Ecuador.
The El Ni�o occurs periodically every six or seven years. Starting
in late December, a change in atmospheric pressure shifts ocean currents
so that warm waters come closer to shore and displace the cold waters.
During this time, air and water temperatures, tides, sea levels and wave
heights, and relative humidity all are higher than usual. These
conditions produce heavy rainfall that generally lasts until May in an
area that normally experiences nothing more than a drizzle. The
resulting flooding and landslides can be devastating.
When the Peruvian Current is dominant, the amount of precipitation
along the coast varies from north to south, with levels ranging from 300
centimeters to 30 centimeters, respectively. Two rainy seasons in the
northernmost part of the coast become a single season (December through
June) not far south. Near Esmeraldas, average annual rainfall is 250
centimeters. The rainy season shortens farther south, lasting only from
January to May at Guayaquil. Very little rainfall occurs on the end of
the Santa Elena Peninsula west of Guayaquil. Arid conditions prevail on
the border with Peru south of the Gulf of Guayaquil.
Separated from the effects of ocean currents by the Cordillera Costa�era,
the Costa Internal has a hot and humid climate. Temperatures can surpass
26� C, and the vegetation and cloud cover tend to retain and augment
the heat. Rain is constant during the winter months of December through
May, with the heaviest rainfall occurring in February and March.
Temperatures in the Sierra do not vary greatly on a seasonal basis;
the hottest month averages 16� C and the coolest month, 13� C in the
upper elevations. Diurnal temperatures, however, vary dramatically, from
cold mornings to hot afternoons. The almost vertical sun and the
rarified air in the higher Sierra region allow the land to warm quickly
during the day and lose heat quickly at night. Mornings typically are
bright and sunny, whereas afternoons often are cloudy and rainy. In
general, rainfall amounts are highest on exposed locations at lower
altitudes. Rain also can vary on a local basis. Sheltered valleys
normally receive 50 centimeters per year, whereas annual rainfall is 150
centimeters in Quito and can reach 250 centimeters on exposed slopes
that catch rain-bearing winds. On a seasonal basis, the driest months
are June through September.
Climate in the Sierra is divided into levels based on altitude. The
tropical level--400 to 1,800 meters--has temperatures ranging from 20�
C to 25� C and heavy precipitation. The subtropical level-- 1,800 to
2,500 meters--has temperatures from 15� C to 20� C and moderate
precipitation. The temperate level--2,500 to 3,200 meters- -has a
year-round temperature in the range of 10� C to 15� C and an annual
rainfall of 100 centimeters. The temperate level experiences rainstorms,
hailstorms, and fog. Winter, or the rainy season, lasts from January
through June, and the dry season or summer from July through December.
Most rain falls in April. There also is a short rainy period in early
October caused by moisture penetrating the Sierra from the Oriente.
Quito and most other populated areas in the Sierra are located at this
temperate level. The cold level extends from the temperate zone to 4,650
meters. Here, average temperatures are 3� C to 9� C, and the
precipitation often appears in the form of rain, hail, and thick fog.
Above 4,650 meters is the frozen level, where peaks are constantly
capped with snow and ice, and temperatures range from below zero to 3�
C. Precipitation frequently is in the form of snow, fog, and rain.
The Eastern lowlands in the Oriente experience an equatorial climate.
Rainfall is abundant, especially in the Andean piedmont, sometimes
exceeding 500 centimeters per year. Temperatures average 25� C in the
western parts of this region. The jungle-covered plains of the Eastern
lowlands register high levels of rainfall and temperatures surpassing 28�
C.
Being located on the equator, the Gal�pagos Islands would have an
equatorial climate were it not for the modifying effects of the Peruvian
Current. Instead, climate on the islands follows a pattern more like
that of the Sierra than the Costa. At sea level, the land is desertlike
with temperatures of 21� C. The eight summer months experience no
precipitation, whereas the winter months of January through April have
some fog and drizzle. Above sea level to an altitude of 450 meters, the
islands have a mixture of tropical, subtropical, and temperate climates.
In general, temperatures are around 17� C. There is constant fog and
drizzle in the summer and rain in the winter. The cold level above 450
meters has temperatures below 14� C.
