INFLUENCE OF VOLCANO ERUPTION TO WEATHERABLE MINERALS AND CHEMICAL PROPERTIES OF RED SOILS IN SOUTH SUMATRA, INDONESIA

Abstract

The red soils spread over South Sumatra are generally derived from the materials of the late
Tertiary Period, are more than 1 million years old, and have fully developed and ultimately weathered. Thus,
these soils commonly have weatherable minerals and chemical properties with low values. The eruption of
Mount Krakatau, more than a hundred years ago, brought about the spreading of fresh volcanic materials
particularly to the surface horizons of the soils. Therefore, it is expected that the weatherable minerals and
chemical properties of the soils in South Sumatra will increase. The aim of this research is to study the
weatherable minerals and some chemical properties of the red soils distributed in the southern part of
Sumatra Island due to their exposure to the Krakatau eruption of 1883. The results show that all the soils
have colors of 10YR to 10R; and thus, they can be classified as red soils. The eruption of Mount Krakatau
has significantly increased the percentage of weatherable minerals and the CEC of the clay in the surface
horizons of the soils in the southern part of Sumatra Island.