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Digital Archive of Toyo Bunko Rare Books
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| 0085 |
Explorations in Turkestan : Expedition of 1904 : vol.2 |
Captions
| [Photo] 469 |
A Ruined Citadel on the Lower Zerafshan. |
Citation Information
OCR Text
PHYSIOGRAPHIC CLASSIFICATION OF OASES
Before answering these questions it is important to understand the present
distribution of oases and cast them into a type classification based on natural
forces and their products with man. Such a physiographic classification results
in five types remarkably distinct in their reactions upon civilization.
(I) Delta Oases: (a) of rivers; (b) of small streams.
(II) River-bank and flood-plain oases.
(III) High-valley oases.
(IV) Spring and well oases.
(V) Lake-shore oases.
Examples of all five are still to be found in their full life. At the ends of the
Murg-ab and Zerafshan lie Merv and Bokhara, our two best examples of type Ia,
while type Ib is found all along the edge of Central Asia's desert plains, where
small streams discharge from the border of its inclosing ranges. The important
difference between Ia and Ib lies in the effect of climatic change. Oscillating
degrees of precipitation over the catch-basins of larger rivers involve a correspond-
ing oscillation of the distances to which they penetrate the desert, so that the
positions of type Ia were ever shifted out and back, whereas smaller streams,
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