Geoscience Reference
In-Depth Information
How Soil Is Formed
The flakes of inky thunderclouds
Above the convex whiteness of the glacier.
A lifeless river dressed in yellow till
And sun rays, glistering like spears at daybreak,
Pierce through the silent, silver sky
“Awake, oh Earth, awake!”—I cry
“Break free from this eternal coldness!
Transform your till and gravel into soil
And let the frigid puddles of the tundra
Be overgrown by reeds, green and unspoiled!”
The Earth is silent, and the pearly slabs of glaciers
Lie far beneath the icy sun, as in a trance.
Indeed, no human measure ever
Can wrap around this ancient, vast expanse.
N. Zagorskaya
Abstract Plants play a crucial role in the formation of soil; soil formation acceler-
ated when the first plants wandered onland 400 million years ago. One of the con-
ditions enabling plants to develop was that algae joined forces with fungi, which
were better at absorbing phosphorus from the ground. However the first soils were
formed by microorganisms. Their complex miniature worlds, so-called biofilms,
are described and compared with human cities. Acids secreted by microbes and
plant roots accelerate the weathering of minerals, and dead plant material helps
to build up humus in the soil. But soil formation is a slow process, and one has to
be ingenious to follow the phenomenon over long periods of time. You can take
soil samples where glaciers are receding, and along the gradients from the coast
towards the highest shoreline, in regions which are in a process of post-glacial
rebound still rising after being depressed under the weight of the ice during the
last ice age. This makes it possible to follow the soil formation process over thou-
sands of years.
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