Definition of Volcanic Dust from Volcanic Eruptions

By McGeary, Plummer and Carlson (2002) volcanic eruption materials in the form of solids can be referred to as pyroclastic materials (pyro = fire, clastic = lumps). This solid material based on the particle diameter is divided into volcanic ash (< 0.26 mm) in the form of loose and fine material, sand (0.25 – 4 mm) which is loose and blunt, lapilli or 'little stone' (4 – 32 cm) which is round to round in shape. squares and bombs (> 32 mm) that are coarsely textured. Rocks resulting from volcanic eruptions based on their silica content can be grouped into acidic volcanic rocks (SiO2 content > 65%), moderate (35 – 65%) and alkaline / alkaline (<35%).

Volcanic ash deposited on the soil surface will undergo chemical weathering with the help of water and organic acids in the soil. The occurrence of chemical changes from volcanic ash itself and to the soil contained in the subsoil is very interesting to study and has been carried out by soil scientists in Japan, New Zealand, the United States and Italy. Indeed, theoretically this weathering process will take a very long time which can reach thousands and even millions of years if it occurs naturally in nature.

Volcanic Dust Pictures

Dahlgren and Ugolini (1989c) added a layer of tephra on the Spodosols surface for ten years after the eruption of Mt. St. Helens in 1980. After ten years there was an increase in the levels of cations (Ca, Mg, K and Na) in the soil by almost 50% from the previous state. The result of further weathering of the volcanic ash also produces non-crystalline clay minerals as evidenced by the increased levels of Alo, Feo and Sio, extracted with acid ammonium oxalate, between 200 to 500 percent higher than the original state.

Meanwhile, Shoji, Nanzyo, Shirato and Ito (1993) conducted an experiment on weathering volcanic glass derived from Tephra Andisols Northeastern Japan. This experiment was carried out in a laboratory using an environment with stratified temperatures ranging from 50, 150 and 250 C which resulted in a model to predict the age of the soil with a normal temperature of 100 C and resulted in a simulation of the weathering process of volcanic glass to produce secondary products, namely non-clay minerals. crystalline.