**1. Introduction**

The volcanoes of the Jos Plateau are aligned in four specific volcanic linesnamely Miango, Kassa, Panyam (Sura) and Gu volcanic lines [1]. There is no record of any actual activity in the Nigerian volcanic provinces in the recent past [2–5]. Recent K-Ar dating the volcanoes of the Kassa volcanic line revealed recent eruption during the Pleistocene ages [6].

Recently, biological and physico-chemical changes were observed within the Jos Plateau Volcanic Province within and around the Pidong Lake which is characterized by the occurrence and recurrence of floating 'mat' vegetation (Plate I & II). The physical changes are dominated by the intermittent color changes from its natural bluish to yellow brownish color and these activities call for a comprehensive study of these phenomena. In light of the intermittent activities in the lake, this study seeks to determine- (1) the hydrogeochemical characteristics of the lake, (2) constraint the origin and source (s) of the lake water and its chemical elements (3) to ascertain the factors responsible for the observed color change in the lake.
