Preface

*Updates in Volcanology - Linking Active Volcanism and the Geological Record* provides an exciting snapshot of research around the hot topic of volcanic geology. Volcanic geology is a fast-growing research arena within volcanology in which the basic aspects of volcano science are revisited based on direct geological observations from the field. As field geology is the fundamental data provider for any geological research, such work examines the basic elements of how volcanoes work. In addition, the volcanic geology approach to understanding volcanic systems can provide a strong evidencebased approach to design analogue and numerical modeling of various volcanic processes ranging from the eruption-fed aspects to the more secondary elements governed by the background environment within which the volcanism takes place. In proximal settings, primary volcaniclastic successions are more abundant and complex (**Figure 1**), while in distal regions, volcanic eruptive products tend to form clear stratigraphy marker horizons. As volcanic rocks or rocks that formed under volcanic influence form vital elements of the geological record, tracing the transition from modern pyroclastic and volcaniclastic successions to rocks formed from such is key to providing valid and realistic reconstructions from preserved rocks in any geoenvironment. Naturally, this subject is too broad to be covered in a single book, but it is also a subject that can be evaluated through various locations, volcanic systems, and

#### **Figure 1.**

*Proximal region of the Lascar Volcano (northern Chile) complex primary pyroclastic successions and lava flows filling the landscape. Pyroclastic flows tend to fill the valleys such as the deposits of the 1993 eruption (light-colored zone in the middle of the view).*

geological times through specific research topics. This book discusses a wide range of volcanic systems and describes their volcanic geology.

Chapter 1 introduces and summarizes the subject matter. Chapter 2 provides a summary of the role of paleovolcanology within the context of volcanic geology based on past research. The chapter is a useful guide to identifying the correct scale of volcanism and linking it to the volcanic rock record. Chapter 3 discusses one of the largest volumes and potentially the most complex type of volcanism associated with convergent plate margins. It outlines some models that link the active subduction processes and what we can see in the geological record. Chapter 4 focuses on dispersed volcanic systems such as mafic monogenetic volcanic fields whose eruptions can span over millions of years despite the individual volcanoes being very short-lived in the geological time scale. The chapter provides an overview of using the geological record to define the most likely eruptive scenarios in future eruptions in long-lived volcanic fields. While mafic volcanism is the most common manifestation of volcanism on Earth, large silicic systems can be the most explosive or produce unusually effusive products, as outlined in Chapter 5. Volcanic systems act as part of the normal sedimentary environment; hence volcanism can alter, modify, or completely switch the nature of sedimentation. Chapter 6 describes this process, which can be traced

Overall, this book provides a representative overview of the problem geologists face when geological reconstruction involves volcanic successions in various time and space scales. This book is a useful reference for approaching and solving this problem.

**Károly Németh**

Sopron, Hungary Massey University, Volcanic Risk Solutions,

Bologna, Italy

Saudi Geological Survey,

Jeddah, Kingdom of Saudi Arabia

Palmerston North, New Zealand

Institute of Earth Physics and Space Science,

National Institute of Geophysics and Volcanology,

well along fluvial systems evolving in volcanic terrains.

The link between active volcanic processes, their eruptive products, and what is preserved in the geological record is fundamental to understanding the growth and erosion processes of volcanoes. Volcanic systems and volcanic rocks differ from other geological processes and rock types because they act and form during extremely short time scales and can also be voluminous (**Figure 2**). As such, volcanic rocks are commonly viewed as excellent chronostratigraphy markers that can present across large sedimentary basins but on a very large spatial scale, such as thin tephra layers in marine or terrestrial settings. On the contrary, massive landscape-forming successions can completely alter the sedimentation of entire regions and thus their impact on the geological record is huge. There is no other geosystem where such a dramatic range of time and space needs to be considered within a single volcanic system and commonly in repeated fashion over longer time scales. It is critical to acknowledge this issue in the geological mapping of volcanic terrains or regions influenced by volcanism in the past. The impact of volcanism on sedimentary basins far from an active volcano might just be an accumulation of thin volcanic ash layers that can be preserved in the geological record as sharp chronostratigraphic horizons. Information from these thin layers however is vital to identify and define the nature of volcanism interacting with the normal sedimentary environment. To be able to trace these gradual changes to obtain the maximum potential information volcanic rocks can provide in the context of sedimentary basin evolution, it is important to be able to assign the correct time and space scales of volcanism recorded in the rock successions.

#### **Figure 2.**

*Enormous spatial-scale variations of volcanism and their products in one photo in northern Chile. In the foreground, Cerro Overo maar represents a fast and small-volume eruption that cut through a landscape-forming ignimbrite succession (pink). Group of complex andesite stratovolcanoes are a magnitude less in edifice and eruptive volume than those exceptionally large ignimbrite sheets.*

Chapter 1 introduces and summarizes the subject matter. Chapter 2 provides a summary of the role of paleovolcanology within the context of volcanic geology based on past research. The chapter is a useful guide to identifying the correct scale of volcanism and linking it to the volcanic rock record. Chapter 3 discusses one of the largest volumes and potentially the most complex type of volcanism associated with convergent plate margins. It outlines some models that link the active subduction processes and what we can see in the geological record. Chapter 4 focuses on dispersed volcanic systems such as mafic monogenetic volcanic fields whose eruptions can span over millions of years despite the individual volcanoes being very short-lived in the geological time scale. The chapter provides an overview of using the geological record to define the most likely eruptive scenarios in future eruptions in long-lived volcanic fields. While mafic volcanism is the most common manifestation of volcanism on Earth, large silicic systems can be the most explosive or produce unusually effusive products, as outlined in Chapter 5. Volcanic systems act as part of the normal sedimentary environment; hence volcanism can alter, modify, or completely switch the nature of sedimentation. Chapter 6 describes this process, which can be traced well along fluvial systems evolving in volcanic terrains.

Overall, this book provides a representative overview of the problem geologists face when geological reconstruction involves volcanic successions in various time and space scales. This book is a useful reference for approaching and solving this problem.

> **Károly Németh** Saudi Geological Survey, Jeddah, Kingdom of Saudi Arabia

Institute of Earth Physics and Space Science, Sopron, Hungary

> Massey University, Volcanic Risk Solutions, Palmerston North, New Zealand

National Institute of Geophysics and Volcanology, Bologna, Italy

**1**

preserved as part of tectonically dissected terrains.

**Chapter 1**

Successions

*Károly Németh*

**1. Introduction**

Introductory Chapter: Linking

Modern and Ancient Volcanic

Understanding volcanic rocks plays a crucial role in reconstructing the environment

in various scales within volcanic rocks formations. Volcanic processes can act in a short time scale and still produce large volumes of eruptive products that commonly can misbalance the sedimentary budget of a sedimentary basin, regardless of their geoenvironmental position (e.g., marine, or terrestrial). Distal ash, on the other hand, can travel hundreds of kilometers away from their source and fall into the background sedimentary environment and can produce a very characteristic and sharp time marker across the entire region. This makes volcanic deposits excellent chronostratigraphy markers [1]. Volcanic processes are also diverse not only by the way coherent and fragmented source materials get generated (e.g., fragmentation style variations, eruption intensity diversity) but also by the way those materials get transported and accumulated. Large volumes of volcanic material can accumulate quickly (hours to days) and alter the entire drainage pattern of large regions. The same accumulated volcaniclastic deposits later can gradually get redeposited and altered by normal surface processes but can provide volcanic detritus over prolonged time along the transportation arteries that eventually lead to marine basins [2, 3]. While this process seems to be a slow and gradual way effectively remove large volume of volcanic deposits from source regions and disperse it over large territories, such processes can also take place in a dramatic and abrupt fashion. Massive breakout lahars can mobilize large volumes of water and damp their sediments suddenly over large areas. On many occasions, like in the Taupo Volcanic Zone in New Zealand, large volumes of calderaforming silicic eruptions had modified the landscape dramatically and promoted the formation of large lake systems, which, from time to time, initiated breakout lahars moving large volumes of volcaniclasts to other sedimentary basins [4]. Over time, major sedimentary basins from terrestrial to marine produce massive successions of complex multisource volcaniclastic aprons, fans, and basin fills. In ancient settings, such basins and their complex volcaniclastic successions can be the only "messengers" of former high-intensity volcanism, especially if the preserved volcaniclastic rocks are

Volcaniclastic sedimentology has evolved in recent years dramatically. Primary eruption-fed processes considered to produce fragmented volcanic materials generate pyroclasts that can start their journey through initial primary volcanic processes that later interact with the normal sedimentary environment, making it increasingly
