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Mountain Weather: A Climber's Story
Grades 6 12
In this video segment adapted from
Interactive NOVA, mountain-climber Rob Taylor gives a
harrowing account of his failed attempt to scale the peak of Africa's
Mount Kilimanjaro. Because it is a free-standing mountain
the tallest in the world climbers must ascend from the
base through several climate zones before reaching the arctic
summit. After being rescued from a fall near the summit, Taylor
thought his worst problems were behind him when an unanticipated
consequence of his descent to warmer temperatures presented an
equally dangerous challenge.
Africa's Mount Kilimanjaro is a fascinating
study in climate. Located near the equator, it has six distinct
ecological zones from base to summit, each with its own climate,
flora, and fauna. The conditions that characterize each zone are
dictated largely by the combination of temperature, altitude,
and moisture. It's these conditions that ultimately influence
the types of species suited (or not suited) to inhabit each zone
even for a short time.
Temperatures in Earth's troposphere
-- the lower atmosphere, up to about 9,100 meters (30,000 ft)
at the poles and 16,800 meters (55,000 feet) at the equator
decrease rather predictably with altitude. With each 300 meters
(1,000 ft) climbed, air cools by about four or five degrees Fahrenheit.
As an air mass approaches a mountain, it is forced upward to an
area of lower pressure, and it expands and cools as it rises.
Once the air temperature falls to the dew point, water vapor in
the air condenses to form clouds that drop precipitation onto
windward slopes. As the air passes over the summit, conditions
change. Because the air now contains less moisture, conditions
on the leeward side are drier. As a result, climbers attempting
to reach the summit of mountains like Kilimanjaro may experience
very different weather conditions, depending on their ascent route.
Every living thing, from single-celled
microbes to megafauna, is adapted to thrive in the conditions
that characterize the particular ecosystem it inhabits, whether
it is a rainforest, high desert, or host life form. Bacteria,
such as those that infect human hosts, can only live and reproduce
within a certain range of conditions. Temperature is a key determinant.
At lower temperatures, molecules move slower. Enzymes that mediate
critical biochemical reactions no longer function, and the increasing
viscosity of the cell interior can cause cellular activity to
slow or cease. By contrast, in warmer temperatures, molecules
move faster, enzymes metabolize more quickly, and cells grow and
This explains mountain-climber Rob
Taylor's final ordeal the one he endured after being rescued
from Kilimanjaro's arctic summit. His descent through warmer zones
reinvigorated bacteria whose activity had slowed inside him during
his ascent. As a result, his badly broken and infected leg raged
with further swelling.
To learn more about challenges of mountain
climbing, check out Trying to Breathe on Mount Everest.
Questions for Discussion
You may think of changes in climate occurring
as you go north or south. This climber stayed at the same
latitude and went up. What explains the difference in temperature
and climate between the top and bottom of Mt. Kilimanjaro?
Why may glaciers be found on mountains near the
What are the positive and negative effects of
the mountain-climbing trade on the local environment and
Interactive NOVA: "Earth"