Some Topographical Observations about the Mountainland of Formosa

Abstract

1. Glaciated topoyrapity. A cirque has been found by the writer just to the north of the top of Mt. Tugitaka (3931m) in Formosa. It is enclosed by the two ridges that are projected out to the north and to the northeast from the main ridge, respectively, opening its mouth northeastward. The floor of the cirque has an elevation of 3818 nM. The lower part o f the wall which is composed of sandstone and shale, is buried by the detritus that has been produced by the vigorous weathering of the high mountains in the' tropical region. 2. Peneplain remnants. It is a. noteworthy fact that flat topped surfaces are often found upon the interstream ridges and at the high level. They are erosion levels truncating the steeply inclined strata of sandstone and shale, and may well be regarded as peneplain remnants. The best examples of this kind are found In a long ridge stretching from Nokosan (3333m) to Antogunzan (3088m), and in a ridge near Tugitakayama (See Fig. 3, 5, 10 & Plate). The former lies at an elevation of 2900-3000m with its area about 32km2, and the approximate elevation of the latterr is about 3500m The prominent peaks that protrude from the peneplain level are regarded as monadnocks. 3. Piedmont steps. Several steps of erosion levels that have been formed in the course of the succesive uplifts of the mountain lands are well preserved on some of the mountain slopes. The typical example is found near the hiking road that leads from Arisan' to Mt. Niitaka, where three steps of erosion levels are clearly observable at the heights of 2600m, 2800m in, and 3200m. 4. River terraces. River terraces are very well developed in the upperstream regions of the river Daikôkei, And Dakusuikei. The most conspicuous ones are found in the upstream of a tributary of the river Dakusuikei, where many steps of river terraces are observed between 1200m & 1820m. An astonishing heights of 2730m is measured at a river terrace that lies at the southern flank of Mashozokanzan (3246m).