**13. Explosive eruption form pyroclastic density currents**

These eruptions, unlike the previous ones, are characterized by the development of eruptive dynamics with the main component horizontal sliding on the ground. They are divided into—(a) dense pyroclastic currents (pyroclastic flow), (b) diluted pyroclastic currents (base surge).

Both these eruptive types can be found in association with an explosive eruption from fall or develop independently during special types of explosive eruptions. A typical dense pyroclastic current is shown in **Figure 33**. A pyroclastic flow is formed by the collapse of an eruptive column (**Figure 31**). The dense pyroclastic currents can be seen in **Figures 32** and **33**. **Figure 33** also shows the fluidization and turbulence of dense pyroclastic currents. The head of a dense pyroclastic current often is characteristic of an ignimbrite eruption. It can form through a pyroclastic flow formed by the collapse of a volcanic dome (**Figure 34**). Sometimes, it can be easy to find pyroclastic density currents with a massive structure in **Figure 35**.

**Figure 35.**

*Shape of typical pyroclastic dense currents. Pyroclastic dense currents with fluidization and turbulence (modified from Branney and Kokelaar [31]).*

**Figure 36.** *Head of a pyroclastic dense currents and PDC channeled in a valley. Modified from Schmincke [14].*

**Figure 37.** *Pyroclastic flow deposit with massive structure. Modified from Schmincke [14].*
