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GEOLOGY AND SOILS
The General Landform
The Andes in southern Ecuador are lower than in the
north. This lower elevation affects the appearance,
climate and vegetation of Loja province, including Vilcabamba.
It is generally a less rugged landscape than that of
northern Ecuador.
As the fragile mix of rock, sand and clay on Vilcabamba’s
hillsides is broken down by weathering, it erodes down
the mountains. It settles into a fairly stable slope,
at an angle of about 45 degrees. (This is the same type
of settling that happens as a sand castle dries.) As
the rivers cut into the valley bottom and carry away
deposited sediments, erosion and landslides re-establish
the slope. Over time, materials deposited by torrents
in the floodplains have built up a relatively deep soil
on the floor of the valley.
The Rock Below the Surface
The rock underlying the valley comes from different
periods and sources. It includes very old metamorphic
rock, and igneous rock of later, but still
ancient, origin. This bedrock is now mostly below the
surface, exposed in only limited locations. At various
places along the riverbeds, for example, slate and quartz
can be seen.
The Visible Sedimentary Materials
Sedimentary rock and sediments (loose rocks,
clays, and sands) blanket most of the valley. It is
easy to see the sedimentary nature of the rock in the
horizontal layering of the cliffs on the west side of
the valley.
The “Mandango”
The cliffs form where a relatively hard layer of sedimentary
rock resists erosion. This process can be most clearly
seen at the famed Mandango. This is the impressive rock-form
that caps the top of the mountain immediately west of
town. It resembles a reclining face, especially when
viewed from the north. A variety of legends are associated
with the Mandango. It is believed to be one of the reasons
that the valley was sacred to the indigenous people.
Vilcabamba’s name comes from the Quechua for “sacred
valley” (huilco = sacred, and pamba = valley).
It is also said that the treasure of the last Inca ruler,
Atahualpa, is hidden in a region marked by four masks;
and that the Mandango may be one of the four.
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 Boulder
Clay and Earth Pillars
Boulder clay is a type of unsorted sedimentary
rock. This chaotic jumble of rounded boulders, smaller rocks,
pebbles and sand is very striking. Spectacular examples are
visible in some of the cliffs around the valley, and in earth
pillars. The earth pillars (shown in the photo at right)
are columns of boulder clay that developed where small patches
on hillside spurs were protected from rain erosion by a harder
layer of rock, or by dense vegetation.
 The
Iron-Rich Cliffs
The red cliffs on the east side of the valley result from
iron leaching through the sedimentary rock and oxidizing.
The Agua de Hierro spring below the cliffs contains iron rich
water from these rocks. Both locals and tourists visit this
spring to splash its reputedly healing waters over their heads
and bodies.
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