Geographic location:

Latitude:  12 40’ 24’’ N

Longitude: 107 54’ 04’’ E

Administrative location: Nhà Đèn village or Nui village, Ea Pô ward, Cư Jut district, Đắk Nông province.

Volcanic bombs in Nha Den village
Volcanic bombs in Nha Den village

During volcanic eruptions, many fragments of lava (at the temperature of 11000 C– 12000C) eject up above, contact with the environment at the temperature lower than 400C, rapidly cool down into solid fragments before reaching the ground. They are called volcanic bombs.

The presence of volcanic bombs which were found in Đray Linh 2 hydroelectricity dam and later transported to Nhà Đèn village) proves the existence of a rigorous volcanic explosion previously.

The size of volcanic bombs can be a factor to reflect the explosive energy, the distance moving through the air and the viscosity of lava flow. The higher explosive energy level is, the bigger the bombs’ size is created. At the same explosive energy level, a lava flow with more viscosity is able to generate the bigger bombs and the smaller the bombs are, the further distance they can travel from the vent. According to the investigation of the related volcanoes, the bombs are derived from a relatively close volcano on the north bank of Serepok river in Đắk Lắk province.

The glassy layer on the surface of each bomb indicates the rapid cooling down process due to the contact with the surrounding ambiance when it goes out of the vent.

Most of the bombs here have some cracks. These facts show that the bombs fell into the ground when their outside layer (the glassy layer) was solidified quickly into an amorphous structure while the inside lava still remained in high temperature. The crash into the ground triggered the cracks on the surface and enabled the lava to spread out.

The extremely rough surface and the thick glassy layer (more than 1cm) of the bombs here must have resulted from a sudden and very quick cooling process. It is believed that there might have been a heavy rain at the time of volcano eruption or the bombs dropped into water.