Geoscience Reference
In-Depth Information
Fig. 13.11
Ultisol, suborder
Ustult. Below the ochric
epipedon (humus A horizon)
is the deep plinthite horizon
of
reddish
color caused by
free iron oxides that
originated during long-lasting
chemical weathering (WRB:
Plinthosol. Source: en.
wikipedia.org)
Fig. 13.12
Vertisol, suborder
Udert. Deep cracks penetrate
through the mollic epipedon
(A horizon) to the alluvium
sediment that forms the
parent material (C horizon)
(WRB: Vertisol. Source:
USDA Soil Taxonomy)
13.3
Granny Soils
We accept and use the terms of units in time spans from geology to defi ne and
appropriately discuss the ancient lives of granny soils. Era is for time span of several
hundred million years - there are 10 eras during the history of Earth. A shorter time
span of tens of millions of years is named Epoch. Millions of years has the term
Age. The term Period denotes a time span shorter than Era and larger than Epoch.
Simplifi ed: Era is for 10
8
years and more, Period for the range from 10
8
years to 10
7
