In Dak Nong UNESCO Global Geopark, the two most abundant rock types are volcanic basalt and the sedimentary sandstone, siltstone and shale, each accounting for more than 40% of the Geopark’s area. Thus in a certain place, it is usually that one sees only one rock type.
However, along the experience route “Wind of change concerto”, at Long Son commune, Dak Mil district, there is an interesting geosite where the basaltic lava erupted and flowed down, covering the sedimentary rocks underneath – poetically it can be called the ‘lava-sandstone meeting place’.
Well before that, the sedimentary rocks were exposed, forming an undulating topography. The lava flow first filled the lowland before continuing to flow further. The hot lava heated the sedimentary rocks underneath, triggering the oxidation of iron-rich rock minerals, resulting in a red rim along the contact boundary between the two rock types.
It is amazing to imagine oneself standing right at this boundary, one step forward is the basalt, another step back is the sedimentary rock, the two being hundreds of million years different in ages; one step forward is one vegetation cover, another step back is already a totally different ecological environment. Maybe very different cultures, different ethnic groups existed on each side of the rock boundary – Mother Nature is really a wonder.