**2. Genetic**

The research area was on tropical wet climate [18]. Annual precipitation in this area was more than 2000 mm per year [32]. The region's geography is characterized by rolling hills with a V valley shape, a medium to a steep slope, and an altitude of 850–1150 meters above sea level (see **Figure 2**). The landscape regulates the flow patterns of regional research into radial, parallel, and sub-dendritic (see **Figure 2**). An important aspect that forms the romance of the research area today is the Sumatra Fault that passes through the area. Geographical conditions of the research area and

**Figure 3.** *Tropical volcanic residual soil.*

**Figure 4.** *Volcanic breccias.*

**Figure 5.** *Rock photomicrograph.*

earth dynamics processes formed volcanic soil with a thickness of more than 20 m [28] (**Figure 3**).

Based on field findings and petrographic analysis, the research area consists of volcanic breccias with tuff components embedded in the tuff, sand, and clay matrix. (see **Figures 2** and **4**).

Tuff, the dominant rock, is characterized by crystal tuff and lithic tuff. Those tuff exhibit welded and flow structures, porphyritic and clastic textures, consisting of fragments and cement. The fragments consist of feldspar (partially insulated and alkaline feldspar type), quartz (showing embayment), plagioclase (andesine type), pyroxene, epidote, sericite, iron oxide, opaque minerals, and biotite embedded in the flow-textured volcanic glass base (**Figure 5**).

The rocks that make up the research area are deposited on land. The rock is deposited in a hydrothermal alteration environment. Evidence of hydrothermal alteration in the presence of geothermal manifestations around the research area, namely in the Mt. Seminung to the north and in the Suoh area, Mt. Sekincau, to the south [33].
