Geology Reference
In-Depth Information
graveyard mounds, develops (Figure 8.14A, B). More widespread clearance, usually for
agricultural purposes, leads to the formation of large thermokarst (alas) depressions.
For example, one depression at Maya village, central Yakutia, is approximately 5-8 m
deep and between 200 m and 300 m in diameter. It formed in historic times (the last 200
years) following deforestation associated with establishment of the agricultural settlement
(Soloviev, 1973a). Similar human-induced thermokarst terrain has been described from
the Fairbanks region of central Alaska, where extensive areas were cleared for agricultural
purposes in the 1930s (Rockie, 1942). The following years saw the formation of mounds
and depressions in the fi elds, the mounds varying from 3 m to 15 m in diameter and up to
2-4 m in height. Eventually many fi elds had to be abandoned because it was impossible
to use mechanized equipment (Péwé, 1954).
(A)
(B)
Figure
8.14.
Human-induced thermokarst. (A) In borrow pits adjacent to the Sachs Harbour air-
strip, southern Banks Island, Canada, as seen in 1973, approximately 15 years after initial distur-
bance. (B) Baydjarakhii adjacent to the Maya-Abalakh road, Central Yakutia, Siberia, as seen in
July 1973. The topography developed following disturbance in 1966.
