**1. Introduction**

Juwangsan volcanic field, located in the northeastern part of Gyeongsang basin, comprises several calderas associated with the succession of ash-flow tuff caldera—ring dike. The evolution of Guamsan caldera, in the central part of the volcanic field, has been reported on in detail by a previous study [1, 2]. However, the eruption types in the caldera were not investigated. This study thus intends to interpret eruptive types and volcanic processes of the volcanic rocks associated with the caldera.

The strata in the Gyeongsang basin are so deeply eroded that the volcanic rocks are dominantly left inside the calderas. Likewise, the Guamsan caldera area has been so significantly eroded and so deep in valleys that it provides us with an excellent laboratory field that not only reveals almost all of the volcanic rocks related to the caldera but also reveals the intrusions corresponding to volcanic roots. Thereby, the Guamsan caldera area exposes the Guamsan Tuff as well as diverse intracaldera

**Figure 1.**

*Generalized geological map in and around the Guamsan caldera in the northeastern Gyeongsang basin. RI, ring intrusions (RI, inner ring dike; RI2, intermediate ring dike; RI3, outer ring dike); CI, intracaldera intrusions; F1, Sampo fault; F2, Jayangcheon fault; EW, trending fault.*

intrusions and ring dikes (**Figure 1**). The lithofacies and sequences of these extrusive rocks and intrusive rocks are sufficient to interpret eruption types and reconstruct volcanic processes in the Guamsan caldera.

Eruption types and volcanic processes before and after caldera collapse will be discussed in this study. The ultimate results reveal that the volcanic activities in Gyeongsang Basin are not only related with caldera volcanisms but are also significant for understanding the characteristics of the igneous processes. Further, the consequences will contribute to the understanding of other volcanisms and processes in the calderas as well as their comparative effects.
