**11. Conclusion and volcanic eruption scenarios**

Volcanism always cause a range of significant hazards to human societies. Not only to the life expectancy but they can also harm the foundations of infrastructures, exposed communities, disrupt the business, and put additional risks on the surrounding environments [42]. The hazards and threats from volcanic eruptions and its related tectonic disasters are increasing annually to vulnerable societies. This is caused by the specific natural features of a volcanic field. The volcanic products, especially the mapped PDC deposits at Tongxin Volcano, can generate a range of very fertile soils and lands, which are utilized intensively for agriculture. However, the presence of thick and extensive PDC deposits indicate the threat of violent phreatomagmatic explosive events that can devastate large regions are ever present. On the other hand, the lava flows common at ACVF, which constitute the bulk of the volcanic products, are the very good construction materials. In general, the major effective regions under the shadows of volcanic eruptions are the proximal and intermediate areas, which can be impacted by the significant and severe threats from lava flows as well as deadly PDC flows.

In ACVF, several volcano types have been identified, but all of them show features of typical monogenetic volcanoes with small eruptive volume, small edifice size, typical deep sourced magma systems and suspected short eruption duration. The majority of the volcanoes identified formed through dry magmatic explosive eruptions forming lava spatter cones (**Figure 17A**), scoria cones (**Figure 17B**) or complex fissure aligned volcano chains (**Figure 17C**). These volcanoes pose hazards to their immediate surroundings; however, because we do not know where the next eruption will take place, they pose prediction uncertainty. The strong fissure alignments of the vents in hundreds of metres to tens of kilometers length, however, suggests that new vents likely will open along those main regional structure-controlled zones. The identification of fissure-fed, dominantly Hawaiian and Strombolian style eruptions suggests that once a new vent opens, the active vents likely will migrate along the fissure axis within the hundreds of metres to several kilometers length, making it difficult to mitigate the volcanic hazard. Due to the propagation of fissure through periods, volcanoes can be classified not only by type but also by eruption types. Generally, Strombolian eruptions, phreatomagmatic eruptions are the two major eruption types. Otherwise, the transition type or switching of the eruption types between two major eruptive behaviors is another major hazard event. It seems that phreatomagmatism occurred at ACVF (**Figure 17D**), but it is not the most significant type of volcanism. Phreatomagmatism seems to have occurred in low lying areas and/or along major fluvial networks. This style of volcanism formed a very violent event at Tongxin (**Figure 17D**). Similar eruptions in the fluvial valleys, where most of the human population lives today, could be catastrophic. It is also evident that the Tongxin eruption started just like any other volcanic eruption at ACVF, as lava fountaining along a migrating fissure (**Figure 17D1**). Once the rising magma along the fissure hit an active hydrogeological zone, violent phreatomagmatic explosions took place (**Figure 17D2**). Similar situations were suggested at Dichi Lake only on a significantly smaller scale. (**Figure 17E**) The nature of this eruption style transition accompanied by the fissure-fed nature of the volcanism needs further study to develop realistic eruptions scenario-based volcanic hazard study of the region.

Effects to the local topography are represented as the lava pouring into the fluvial systems changes the river flow patterns (**Figure 17F**). By damming rivers, temporary lakes can form changing the local hydrogeology that may promote explosive phreatomagmatism in the course of the ongoing eruption.

The lava ponding has also been recognized as an important process in the development of the lava fields. The complex high altitude volcanoes with multiple vents, shifting active vent locations and lava ponding in large craters are features that need to be considered in volcanic hazard eruption scenarios, as sudden collapse of scoria cone sectors and outpour of ponded lava could initiate large lava flows to areas that normally would not be considered as regions susceptible to lava flow hazards (**Figure 17G**).

**243**

**Figure 17.**

**Acknowledgements**

*eruptions (G). Horizontal scales are approximate only.*

The authors wish to thank the support of the School of Agriculture and Environment, Massey University PhD Fellowship, the China – New Zealand Academic Exchange Program as part of the Royal Society of New Zealand Catalyst

*Typical volcano types identified at ACVF and their inferred schematic volcanic eruption scenarios. The ACVF has abundant individual lava spatter cones (A) and individual scoria cones (B) separated from other volcanoes by large (few kilometres) distances. More common volcano types of the ACVF are closely spaced spatter-and-scoria cone chains inferred to formed due to fissure-fed magmatic explosive eruptions (C). Phreatomagmatic volcanoes are rare at ACVF and their eruptive sequence commonly starts with a succession indicates initial magmatic explosive phases (D1) and thick laterally extensive pyroclastic density current (eg. base surge) deposited pyroclastic successions (D2). Occasionally, fissure-fed spatter-and-scoria cones terminate to a maar-forming eruption in low-land such as the Dichi Lake (E). Large-volume and long lava flows tend to dam syn-eruptive river network forming lakes where lava blisters such as tumuli field can form (F). Large and complex scoria cones in elevated ridges form multiple cone complexes, where outbreak of lava lakes can cause cone rafting and trigger sustained ash plumes to create ash and lapilli plains through violent-Strombolian style* 

*Basic Volcanic Elements of the Arxan-Chaihe Volcanic Field, Inner Mongolia, NE China*

*DOI: http://dx.doi.org/10.5772/intechopen.94134*

*Basic Volcanic Elements of the Arxan-Chaihe Volcanic Field, Inner Mongolia, NE China DOI: http://dx.doi.org/10.5772/intechopen.94134*

### **Figure 17.**

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

from lava flows as well as deadly PDC flows.

and its related tectonic disasters are increasing annually to vulnerable societies. This is caused by the specific natural features of a volcanic field. The volcanic products, especially the mapped PDC deposits at Tongxin Volcano, can generate a range of very fertile soils and lands, which are utilized intensively for agriculture. However, the presence of thick and extensive PDC deposits indicate the threat of violent phreatomagmatic explosive events that can devastate large regions are ever present. On the other hand, the lava flows common at ACVF, which constitute the bulk of the volcanic products, are the very good construction materials. In general, the major effective regions under the shadows of volcanic eruptions are the proximal and intermediate areas, which can be impacted by the significant and severe threats

In ACVF, several volcano types have been identified, but all of them show features of typical monogenetic volcanoes with small eruptive volume, small edifice size, typical deep sourced magma systems and suspected short eruption duration. The majority of the volcanoes identified formed through dry magmatic explosive eruptions forming lava spatter cones (**Figure 17A**), scoria cones (**Figure 17B**) or complex fissure aligned volcano chains (**Figure 17C**). These volcanoes pose hazards to their immediate surroundings; however, because we do not know where the next eruption will take place, they pose prediction uncertainty. The strong fissure alignments of the vents in hundreds of metres to tens of kilometers length, however, suggests that new vents likely will open along those main regional structure-controlled zones. The identification of fissure-fed, dominantly Hawaiian and Strombolian style eruptions suggests that once a new vent opens, the active vents likely will migrate along the fissure axis within the hundreds of metres to several kilometers length, making it difficult to mitigate the volcanic hazard. Due to the propagation of fissure through periods, volcanoes can be classified not only by type but also by eruption types. Generally, Strombolian eruptions, phreatomagmatic eruptions are the two major eruption types. Otherwise, the transition type or switching of the eruption types between two major eruptive behaviors is another major hazard event. It seems that phreatomagmatism occurred at ACVF (**Figure 17D**), but it is not the most significant type of volcanism. Phreatomagmatism seems to have occurred in low lying areas and/or along major fluvial networks. This style of volcanism formed a very violent event at Tongxin (**Figure 17D**). Similar eruptions in the fluvial valleys, where most of the human population lives today, could be catastrophic. It is also evident that the Tongxin eruption started just like any other volcanic eruption at ACVF, as lava fountaining along a migrating fissure (**Figure 17D1**). Once the rising magma along the fissure hit an active hydrogeological zone, violent phreatomagmatic explosions took place (**Figure 17D2**). Similar situations were suggested at Dichi Lake only on a significantly smaller scale. (**Figure 17E**) The nature of this eruption style transition accompanied by the fissure-fed nature of the volcanism needs further study to develop realistic eruptions scenario-based volcanic hazard

Effects to the local topography are represented as the lava pouring into the fluvial systems changes the river flow patterns (**Figure 17F**). By damming rivers, temporary lakes can form changing the local hydrogeology that may promote

The lava ponding has also been recognized as an important process in the development of the lava fields. The complex high altitude volcanoes with multiple vents, shifting active vent locations and lava ponding in large craters are features that need to be considered in volcanic hazard eruption scenarios, as sudden collapse of scoria cone sectors and outpour of ponded lava could initiate large lava flows to areas that normally would not be considered as regions susceptible to lava flow

explosive phreatomagmatism in the course of the ongoing eruption.

**242**

study of the region.

hazards (**Figure 17G**).

*Typical volcano types identified at ACVF and their inferred schematic volcanic eruption scenarios. The ACVF has abundant individual lava spatter cones (A) and individual scoria cones (B) separated from other volcanoes by large (few kilometres) distances. More common volcano types of the ACVF are closely spaced spatter-and-scoria cone chains inferred to formed due to fissure-fed magmatic explosive eruptions (C). Phreatomagmatic volcanoes are rare at ACVF and their eruptive sequence commonly starts with a succession indicates initial magmatic explosive phases (D1) and thick laterally extensive pyroclastic density current (eg. base surge) deposited pyroclastic successions (D2). Occasionally, fissure-fed spatter-and-scoria cones terminate to a maar-forming eruption in low-land such as the Dichi Lake (E). Large-volume and long lava flows tend to dam syn-eruptive river network forming lakes where lava blisters such as tumuli field can form (F). Large and complex scoria cones in elevated ridges form multiple cone complexes, where outbreak of lava lakes can cause cone rafting and trigger sustained ash plumes to create ash and lapilli plains through violent-Strombolian style eruptions (G). Horizontal scales are approximate only.*

## **Acknowledgements**

The authors wish to thank the support of the School of Agriculture and Environment, Massey University PhD Fellowship, the China – New Zealand Academic Exchange Program as part of the Royal Society of New Zealand Catalyst Programme and the support from the Institute of the Geology and Geophysics of the Chinese academy of Sciences, Beijing. An earlier version of the manuscript was kindly reviewed by Dr. Gaby Gomez (U Morelia, Mexico) what for we are really thankful. Formal Anonymous reviewers' comments helped to elevate the quality of the chapter we thank for.
