1:45 PM - 3:15 PM
[O08-P105] On the agglutinate with red surface found in Aso Sensuikyo
Keywords:Nakadake volcano, Agglutinate, oxidation
[Background and Objectives]
Pyroclastic rocks and tuff from the Nakadake volcano and pyroclastic rocks from the Washigamine volcano are distributed in the Aso Sensuikyo (Ono and Watanabe,1985). Agglutinates with red coloration only on the surface are found in them. In addition,most of them have a mixture of red-colored (discolored) and unred-colored (uncolored) areas on the surface(pic.1). In this study, we investigated what substances are responsible for the red coloration using field surveys and methods used in high school science courses.
[Method 1]Field survey and investigation of rock properties
We investigated whether volcanic products that have undergone similar changes along the trail from Sensuikyo to the Aso Nakadake crater can be found at other sites.We would use binocular stereomicroscopes to observe the undiscolored areas, the discolored areas, the inside of the rock, and the surface that has been discolored by heating to determined what the discolored areas and the surface that has been discolored by heating have in common. Magnetic properties, electrical conductivity, reaction with concentrated hydrochloric acid, and reaction with dilute sulfuric acid were also examined.
[Method 2]Identification of iron oxide
In the Kamikomeduka area around Mt. Aso Nakadake, there are reddish-brown colored scoria discolored by high-temperature oxidation of iron (Ejima, 2015; Ikebe, 2015), and the experiment was conducted assuming that the same mechanism is applied to the present subject. Undiscolored areas were heated with an external flame of a gas burner until the entire area became red-hot (about 5 minutes) and cooled in air, tap water, highly refined oil, or anhydrous ethanol, respectively. After that, they were examined as "surfaces discolored by heating" in the same way as Method 1.
The original reddish discolored surface and the surface discolored by heating were powdered and qualitatively analyzed using a precipitation reaction with sodium hydroxide solution to confirm whether iron was contained (Matsumoto, 2023). To further confirm whether iron oxide was contained, 3 g of aluminum powder and 8 g of the powder produced in the previous experiment were mixed and heated, referring to a demonstration experiment of the thermite reaction conducted at our school.
[Result 1]
In this survey, more discolored volcanic products were found in the eastern part of the Sensuikyo Observatory than in the western part of the Sensuikyo. The surface condition of the volcanic products, called "Saraishi," which are found in Aso Nakadake, was very similar to that of the target in this study. The results of the observations and the reactions with magnetism, electrical conductivity, concentrated hydrochloric acid, and dilute sulfuric acid are shown in Tables 1 and 2. Regarding the interior of the rocks, there were clinker, basalt and tuff samples with the same surface but different interior conditions.
[Result 2]
The percentage of discoloration after heating is shown in Table 2. In the experiment with anhydrous ethanol, combustion continued for a while when the cooled sample was brought close to a fire. In the experiment of precipitation reaction using sodium hydroxide solution, reddish brown precipitation was observed in both samples. However, no reaction was observed in the experiment using the thermite method.
[Discussion and Future Prospects]
The results suggest that the reddish discoloration was caused by the cooling of the high-temperature rocks in Senanmenkyo as well, since the surfaces of the originally reddish discolored rocks and those discolored by heating have the same characteristics. The surface of the rocks was also found to contain iron. However, in the case of the discoloration of the Kamikomeduka scoria, it is said that rapid cooling produces black ferric oxide (FeO), while slow cooling at high temperatures leads to oxidation and the formation of reddish brown ferric oxide (Fe2O3) (Ikebe, 2015). However, in the present study, the reddish discoloration occurred in many areas even after rapid cooling in liquid and cooling in air, which is different from the results of the reference study. In the experiments with highly refined oil and anhydrous ethanol, the assumption of iron oxide was inconsistent because each liquid functioned mainly as a reducing agent. Therefore since this study only verified the iron oxide hypothesis using the thermite method, we would like to continue our research on the identification of iron oxide, including cooling in high-temperature air and quenching with various types of liquids.
Pyroclastic rocks and tuff from the Nakadake volcano and pyroclastic rocks from the Washigamine volcano are distributed in the Aso Sensuikyo (Ono and Watanabe,1985). Agglutinates with red coloration only on the surface are found in them. In addition,most of them have a mixture of red-colored (discolored) and unred-colored (uncolored) areas on the surface(pic.1). In this study, we investigated what substances are responsible for the red coloration using field surveys and methods used in high school science courses.
[Method 1]Field survey and investigation of rock properties
We investigated whether volcanic products that have undergone similar changes along the trail from Sensuikyo to the Aso Nakadake crater can be found at other sites.We would use binocular stereomicroscopes to observe the undiscolored areas, the discolored areas, the inside of the rock, and the surface that has been discolored by heating to determined what the discolored areas and the surface that has been discolored by heating have in common. Magnetic properties, electrical conductivity, reaction with concentrated hydrochloric acid, and reaction with dilute sulfuric acid were also examined.
[Method 2]Identification of iron oxide
In the Kamikomeduka area around Mt. Aso Nakadake, there are reddish-brown colored scoria discolored by high-temperature oxidation of iron (Ejima, 2015; Ikebe, 2015), and the experiment was conducted assuming that the same mechanism is applied to the present subject. Undiscolored areas were heated with an external flame of a gas burner until the entire area became red-hot (about 5 minutes) and cooled in air, tap water, highly refined oil, or anhydrous ethanol, respectively. After that, they were examined as "surfaces discolored by heating" in the same way as Method 1.
The original reddish discolored surface and the surface discolored by heating were powdered and qualitatively analyzed using a precipitation reaction with sodium hydroxide solution to confirm whether iron was contained (Matsumoto, 2023). To further confirm whether iron oxide was contained, 3 g of aluminum powder and 8 g of the powder produced in the previous experiment were mixed and heated, referring to a demonstration experiment of the thermite reaction conducted at our school.
[Result 1]
In this survey, more discolored volcanic products were found in the eastern part of the Sensuikyo Observatory than in the western part of the Sensuikyo. The surface condition of the volcanic products, called "Saraishi," which are found in Aso Nakadake, was very similar to that of the target in this study. The results of the observations and the reactions with magnetism, electrical conductivity, concentrated hydrochloric acid, and dilute sulfuric acid are shown in Tables 1 and 2. Regarding the interior of the rocks, there were clinker, basalt and tuff samples with the same surface but different interior conditions.
[Result 2]
The percentage of discoloration after heating is shown in Table 2. In the experiment with anhydrous ethanol, combustion continued for a while when the cooled sample was brought close to a fire. In the experiment of precipitation reaction using sodium hydroxide solution, reddish brown precipitation was observed in both samples. However, no reaction was observed in the experiment using the thermite method.
[Discussion and Future Prospects]
The results suggest that the reddish discoloration was caused by the cooling of the high-temperature rocks in Senanmenkyo as well, since the surfaces of the originally reddish discolored rocks and those discolored by heating have the same characteristics. The surface of the rocks was also found to contain iron. However, in the case of the discoloration of the Kamikomeduka scoria, it is said that rapid cooling produces black ferric oxide (FeO), while slow cooling at high temperatures leads to oxidation and the formation of reddish brown ferric oxide (Fe2O3) (Ikebe, 2015). However, in the present study, the reddish discoloration occurred in many areas even after rapid cooling in liquid and cooling in air, which is different from the results of the reference study. In the experiments with highly refined oil and anhydrous ethanol, the assumption of iron oxide was inconsistent because each liquid functioned mainly as a reducing agent. Therefore since this study only verified the iron oxide hypothesis using the thermite method, we would like to continue our research on the identification of iron oxide, including cooling in high-temperature air and quenching with various types of liquids.