How Soil Is Formed - Soil: Reflections on the Basis of our Existence - page 33

Nature's Own Soil Archive
If you want to study soil formation over a long period of time, the place to go is
the Franz Josef glacier in Westland National Park on New Zealand's South Island.
The area receives high annual snowfall of three to five metres in liquid equiva-
lent, which has resulted in one part of the glacier almost reaching the coast and a
milder climate zone. The temperate rainforest just below the glacier edge stands
in sharp contrast to the wall of ice. Franz Josef has left deposits along the narrow
valley that leads to the sea and has retreated many kilometres since the Ice Age.
Uniquely, the glacial deposits here date back to the last interglacial period, around
one hundred and twenty thousand years ago, allowing scientists to study soil for-
mation over a much longer time frame than in areas where glaciers are shrinking.
Soil composition is ever-changing, with no end point at which one can say
the soil is “finished”. In fact, it is preferable to view soil formation as a two-
step process consisting of an accumulation phase and a depletion phase—a pro-
cess that begins all over again when a new ice age arrives. This is because the
ice scrapes away the old weathered soil, paving the way for soil formation in
the moraine left behind when the glacier melts. Nitrogen-fixing plants tend to
Between the ice. It snows copiously on the Franz Josef glacier in New Zealand—three to five
metres per year in melted form. The high precipitation affects the moraine left behind by the
melting glacier, weathering it faster than on many other glaciers. The rainwater slowly dissolves
the phosphorus in the soil and carries it away. Moss grows close to the glacier edge and a temper-
ate rainforest covers the valley. However, soil phosphorus decreases with distance from the ice,
eventually falling to such a low concentration that shrubs replace the rainforest