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Caldera Volcanism

E-BookEPUBDRM AdobeE-Book
516 Seiten
Englisch
Elsevier Science & Techn.erschienen am22.09.2011
This volume aims at providing answers to some puzzling questions concerning the formation and the behavior of collapse calderas by exploring our current understanding of these complex geological processes. Addressed are problems such as:

- How do collapse calderas form?
- What are the conditions to create fractures and slip along them to initiate caldera collapse and when are these conditions fulfilled?
- How do these conditions relate to explosive volcanism?
- Most products of large caldera-forming eruptions show evidence for pre-eruptive reheating. Is this a pre-requisite to produce large volume eruptions and large calderas?
- What are the time-scales behind caldera processes?
- How long does it take magma to reach conditions ripe enough to generate a caldera-forming eruption?
- What is the mechanical behavior of magma chamber walls during caldera collapse? Elastic, viscoelastic, or rigid?
- Do calderas form by underpressure following a certain level of magma withdrawal from a reservoir, or by magma chamber loading due to deep doming (underplating), or both?
- How to interpret unrest signals in active caldera systems?
- How can we use information from caldera monitoring to forecast volcanic phenomena?

In the form of 14 contributions from various disciplines this book samples the state-of-the-art of caldera studies and identifies still unresolved key issues that need dedicated cross-boundary and multidisciplinary efforts in the years to come.

* International contributions from leading experts
* Updates and informs on all the latest developments
* Highlights hot topic areas and indentifies and analyses unresolved key issuesmehr
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Produkt

KlappentextThis volume aims at providing answers to some puzzling questions concerning the formation and the behavior of collapse calderas by exploring our current understanding of these complex geological processes. Addressed are problems such as:

- How do collapse calderas form?
- What are the conditions to create fractures and slip along them to initiate caldera collapse and when are these conditions fulfilled?
- How do these conditions relate to explosive volcanism?
- Most products of large caldera-forming eruptions show evidence for pre-eruptive reheating. Is this a pre-requisite to produce large volume eruptions and large calderas?
- What are the time-scales behind caldera processes?
- How long does it take magma to reach conditions ripe enough to generate a caldera-forming eruption?
- What is the mechanical behavior of magma chamber walls during caldera collapse? Elastic, viscoelastic, or rigid?
- Do calderas form by underpressure following a certain level of magma withdrawal from a reservoir, or by magma chamber loading due to deep doming (underplating), or both?
- How to interpret unrest signals in active caldera systems?
- How can we use information from caldera monitoring to forecast volcanic phenomena?

In the form of 14 contributions from various disciplines this book samples the state-of-the-art of caldera studies and identifies still unresolved key issues that need dedicated cross-boundary and multidisciplinary efforts in the years to come.

* International contributions from leading experts
* Updates and informs on all the latest developments
* Highlights hot topic areas and indentifies and analyses unresolved key issues
Details
Weitere ISBN/GTIN9780080558974
ProduktartE-Book
EinbandartE-Book
FormatEPUB
Format HinweisDRM Adobe
Erscheinungsjahr2011
Erscheinungsdatum22.09.2011
Seiten516 Seiten
SpracheEnglisch
Dateigrösse20825 Kbytes
IllustrationenIllustrated
Artikel-Nr.2745127
Rubriken
Genre9200

Inhalt/Kritik

Inhaltsverzeichnis
1;Front cover;1
2;Caldera Volcanism: Analysis, Modelling and Response;4
3;Copyright page;5
4;Contents;6
5;Contributors;12
6;Preface;16
6.1;References;23
7;Chapter 1. Residence Times of Silicic Magmas Associated with Calderas;26
7.1;1. Introduction;27
7.2;2. Methods for Obtaining Time Constraints of Magmatic Processes;30
7.3;3. Residence Times of Magmas Associated with Selected Calderas;36
7.4;4. Interpretation of Residence Times and Integration with Thermal and Mechanical Constrains;60
7.5;5. Summary and Conclusions;70
7.6;Acknowledgments;72
7.7;References;72
8;Chapter 2. Sedimentology, Depositional Mechanisms and Pulsating Behaviour of Pyroclastic Density Currents;82
8.1;1. Introduction: What are Pyroclastic Density Currents?;83
8.2;2. Key Concepts;85
8.3;3. Sedimentology: Main Particle Support and Segregation Mechanisms in PDCs;88
8.4;4. Depositional Processes in PDCs;95
8.5;5. Field Evidences of Stepwise Aggradation in Pulsating PDCs;109
8.6;6. Conclusive Remarks and Future Perspectives;112
8.7;Acknowledgments;115
8.8;References;115
9;Chapter 3. The Use of Lithic Clast Distributions in Pyroclastic Deposits to Understand Pre- and Syn-Caldera Collapse Processes: A Case Study of the Abrigo Ignimbrite, Tenerife, Canary Islands;122
9.1;1. Introduction;123
9.2;2. Review of Lithic Component Studies and Inferred Caldera Processes;124
9.3;3. Case Study of the Abrigo Ignimbrite;131
9.4;4. Conclusions;160
9.5;Acknowledgments;161
9.6;References;161
10;Chapter 4. The Ignimbrite Flare-Up and Graben Calderas of the Sierra Madre Occidental, Mexico;168
10.1;1. Introduction;169
10.2;2. The Sierra Madre Occidental Volcanic Province;170
10.3;3. Regional Stratigraphy of the Sierra Madre Occidental;174
10.4;4. Graben Calderas of the Sierra Madre Occidental;178
10.5;5. Conclusions;198
10.6;Acknowledgments;198
10.7;References;199
11;Chapter 5. Characterisation of Archean Subaqueous Calderas in Canada: Physical Volcanology, Carbonate-Rich Hydrothermal Alteration and a New Exploration Model;206
11.1;1. Introduction;208
11.2;2. Abitibi Greenstone Belt Geology;208
11.3;3. Notion of Calderas;211
11.4;4. Hunter Mine Caldera;212
11.5;5. Normetal Caldera;227
11.6;6. Sturgeon Lake Caldera, Wabigoon Subprovince;236
11.7;7. The Link: Subaqueous Calderas with Chert-Iron Formation and Hydrothermal Carbonates;239
11.8;8. Discussion;245
11.9;9. Conclusions;250
11.10;Acknowledgements;251
11.11;References;252
12;Chapter 6. A Review on Collapse Caldera Modelling;258
12.1;1. Introduction;259
12.2;2. The Role of Experimental Models in Caldera Studies;260
12.3;3. Theoretical Models on Collapse Calderas Formation;269
12.4;4. Geophysical Imaging and Its Value for Caldera Studies;284
12.5;5. Discussion and Implications;298
12.6;6. Conclusions;302
12.7;Acknowledgements;302
12.8;References;303
13;Chapter 7. Structural Development of Calderas: a Synthesis from Analogue Experiments;310
13.1;1. Introduction;311
13.2;2. Analogue Modelling;312
13.3;3. Experimental Studies on Calderas;314
13.4;4. Discussion;324
13.5;5. Comparison to Nature: Guidelines;327
13.6;6. Towards a New Caldera Evolution Scheme;330
13.7;7. Conclusions;332
13.8;Acknowledgments;333
13.9;References;333
14;Chapter 8. Magma-Chamber Geometry, Fluid Transport, Local Stresses and Rock Behaviour During Collapse Caldera Formation;338
14.1;1. Introduction;339
14.2;2. Collapse Caldera Structures;342
14.3;3. Geometry of the Magma Chamber;349
14.4;4. Behaviour of Crustal Rocks;351
14.5;5. Magma-Chamber Rupture and Fluid Transport Along a Dyke;354
14.6;6. Stress Fields Triggering Ring-Fault Initiation;357
14.7;7. Discussion;365
14.8;8. Conclusions;369
14.9;Acknowledgments;370
14.10;References;370
15;Chapter 9. Facilitating Dike Intrusions into Ring-Faults;376
15.1;1. Introduction;377
15.2;2. Modeling Method;380
15.3;3. Results;381
15.4;4. Discussion;392
15.5;5. Conclusion;396
15.6;Acknowledgments;396
15.7;References;396
16;Chapter 10. A New Uplift Episode at Campi Flegrei Caldera (Southern Italy): Implications for Unrest Interpretation and Eruption Hazard Evaluation;400
16.1;1. Introduction;401
16.2;2. Recent Ground Deformation Data at Campi Flegrei Caldera;404
16.3;3. Displacement Shapes and Maximum Vertical to Horizontal Ratios;409
16.4;4. Discussion and Conclusion;413
16.5;Acknowledgments;415
16.6;References;415
17;Chapter 11. Hydrothermal Fluid Circulation and its Effect on Caldera Unrest;418
17.1;1. Introduction;419
17.2;2. The Hydrothermal Fluid Circulation;420
17.3;3. Modelling of Hydrothermal Fluid Circulation;422
17.4;4. Hydrothermal Systems and Volcano Monitoring;425
17.5;5. An Example of Assessing the Role of Hydrothermal Processes During Unrest: Solfatara (Phlegrean Fields Caldera, Italy);429
17.6;6. Discussion and Conclusions;434
17.7;Acknowledgments;435
17.8;References;435
18;Chapter 12. Deciphering Causes of Unrest at Explosive Collapse Calderas: Recent Advances and Future Challenges of Joint Time-Lapse Gravimetric and Ground Deformation Studies;442
18.1;1. Introduction;443
18.2;2. The Subsurface Beneath Calderas: Hydrothermal Versus Magmatic Reservoirs;444
18.3;3. Joint Ground Deformation and Gravimetric Survey;445
18.4;4. Vertical Gravity-Height Gradients;448
18.5;5. Single and Distributed Sources;449
18.6;6. The Search for Causative Sources of Unrest: Recent Examples of Integrated Studies from the Long Valley, Campi Flegrei and Las Cañadas Calderas;452
18.7;7. The Problem of Aliasing of Time-Lapse Micro-Gravity Data;462
18.8;8. The Effect of Lateral Discontinuities on Ground Deformation and Residual Gravity Changes;462
18.9;9. Summary, Conclusions and Outlook;464
18.10;Acknowledgments;467
18.11;References;467
19;Chapter 13. The Failure Forecast Method: Review and Application for the Real-Time Detection of Precursory Patterns at Reawakening Volcanoes;472
19.1;1. Introduction;473
19.2;2. Theory of Precursors;474
19.3;3. The Theory of the Material Failure Forecast Method (FFM);475
19.4;4. Techniques of Analysis;478
19.5;5. Viscoelastic Model;478
19.6;6. Seismicity as the Observable for FFM;479
19.7;7. FFM Applied to the Studies of Volcanoes;481
19.8;8. Conclusions;490
19.9;Acknowledgments;491
19.10;References;491
20;Chapter 14. Perspectives on the Application of the Geostatistical Approach to Volcano Forecasting at Different Time Scales;496
20.1;1. Introduction;497
20.2;2. The Probabilistic Approach;498
20.3;3. The Geostatistical Approach;499
20.4;4. Case Studies;502
20.5;5. Conclusions and Perspectives;509
20.6;Acknowledgments;510
20.7;References;510
21;Subject Index;514mehr
Leseprobe


Chapter 1 Residence Times of Silicic Magmas Associated with Calderas


Fidel Costa*,

CSIC, Institut de Ciències de la Terra Jaume Almera , Lluís Solé i Sabarís s/n, 08028 Barcelona, Spain.

* Corresponding author. Tel.: ++34-93-4095410; Fax: ++34-93-4110012

E-mail address: fcosta@ija.csic.es



Abstract

This paper reviews the times that silicic magmas related to major caldera systems spend in the crust prior to eruption. The significance of the time information is evaluated and combined with magma volumes and temperatures to quantify the mass and thermal fluxes associated to calderas. The data discussed includes the largest explosive eruptions on Earth: Taupo Volcanic Zone (New Zealand), the Youngest Toba Tuff (Indonesia), Yellowstone system (USA), Long Valley (USA), Carter Lake (USA), Valles-Toledo complex (USA), La Garita caldera (USA), La Pacana (Chile) and Kos (Greece). Magma residence times are calculated from the difference between the eruption age and the age obtained by radioactive clocks and minerals that are a closed system at high magmatic temperatures (e.g., U-Pb system in zircon).

Large ranges of residence times between different systems are found. The shortest residences (4-19 ky) are those of some magmas from the Taupo Volcanic Zone (Oruanui and Rotoiti) and Yellowstone (Dry Creek and Lava Creek). There is not a good correlation between magma volume and residence time, although most eruptions 100 km3 have longer residences, some up to 300-500 ky (Fish Canyon, La Pacana). The residence times of some small (500 km3 are within 2±2×10â2 km3 yâ1. These high magma production rates are probably transient and comparable to global eruptive fluxes of basalts (e.g., Hawaii). Magma cooling rates for deposits >100 km3 were calculated from the difference between the liquidus and pre-eruptive temperatures over their residence times, and they vary between 2×10â4 and 3×10â3 K yâ1. Integration of the calculated residence times and magma fluxes with a simple rheological model of the crust is not possible and should be a main topic of research if we are to understand the mechanisms and rates which permit large amounts of silicic magma to be stored below calderas.


1 Introduction

Caldera-forming eruptions produce the most voluminous (up to 5,000 km3) explosive eruptions on Earth, and their activity appears to provide clues for understanding climatic and evolutionary biological changes (e.g., Lipman, 2000a; Francis and Oppenheimer, 2003). Collapse calderas are among the most investigated geological objects also because of their association with economic deposits and geothermal energy. The distinctive feature of caldera-related silica-rich volcanism is the topographical depressions left after the eruption. These are thought to be the result of either tremendous explosions that blew apart a pre-existing volcanic cone or due to subsidence of the roof of the reservoir after or during magma evacuation. High-level magma emplacement (typically Smith, 1979; Hildreth, 1981; Shaw 1985; Jellinek and DePaolo, 2003). These issues were addressed by Shaw (1985) who noted that the interaction of magma generation rates, stress domains and injection rates leads to a spectrum of residence times which effectively determine the types of intrusive and volcanic suites seen at high crustal levels and at the surface. Almost 25 years later, progress in analytical techniques have enabled the quantification of the time over which crystals and magma are stored before a caldera-forming eruption. This allows analysing the relations between the volumes, compositions, temperatures and depths of magma reservoirs below calderas from a new perspective. The purpose of this manuscript is to describe the approaches used to obtain the time scales of magmatic processes, to compile the data on residence times of major caldera-related complexes, and to use this information for deriving modes and rates of silica-rich magma production and storage in the Earth's crust.

1.1 What is the residence time of a magma?

It can be defined as the time elapsed since the magma was formed and its eruption. Uncertainties arise with the meaning of when a magma is formed because what is finally erupted is a mixture of phases that might have very different origins in time and space (e.g., Bacon and Lowenstern, 2005). The most widespread use of residence time involves pinpointing when a given mineral started to crystallise, presumably during storage in a magma reservoir. This is different from the definition used in oceanic geochemistry or in highly active volcanic systems where it refers to the (mean) time that a given element or isotope spends in a reservoir before being removed (e.g., Holland, 1978; Albarède, 1993). In practice, one can calculate the residence time as the difference between the eruption age as obtained by K-Ar (or 40Ar/39Ar), (U, Th)/He and 14C methods (for prehistorical eruptions) and the age provided by other radioactive clocks, such as Rb-Sr, and U-Th-Pb. From this definition it is apparent that the residence time does not need to be a single value, and might depend on the phases and radioactive isotopes that are used. Multiple values of residence times may arise from different crystallisation ages of different minerals, but also from the fact that the very definition of an age requires knowledge of when the radioactive system became closed. This condition depends on several factors but strongly on the diffusion rate of the daughter isotope, and has been quantified with the use of a closure temperature (Dodson, 1973). This explains the a priori paradoxical situation that, for example, a sanidine might have two different ages and both could be correct: dated by the K-Ar system the mineral gives the eruption age but using Rb-Sr clock it may give a much older crystallisation age, simply because the K-Ar system becomes closed at much lower temperatures (e.g., on quenching of the magma upon eruption). Most of the age data used in this manuscript were obtained using zircon and the U-Th-Pb decay system and thus reflect the time since the beginning of zircon crystallisation and final eruption. It is worth mentioning that there might be a systematic bias between the radioactive clocks of the K-Ar and that of U-Pb systems, the latter giving slightly older ages (Renne et al., 1998; Min et al., 2000; Renne, 2000; Villeneuve et al., 2000; Schmitz and Bowring, 2001; Schoene et al., 2006). Since the issue is not resolved at the time of writing it has not been considered for calculating residence times. Recent reviews of the methods and time scales of magmatic processes can be found in Condomines et al. (2003), Reid (2003), Turner et al. (2003), Hawkesworth et al. (2004) and Peate and Hawkesworth (2005).


1.2 Magma production and cooling rates

Aside from compiling residence times and rates of processes, two other parameters were calculated. One is a magma production rate, which is the ratio of the erupted volume over the residence time (e.g., Christensen and DePaolo, 1993; Davies et al., 1994). It is not sensu stricto a magma production rate because it only accounts for the erupted magma. It should be called erupted magma production rate but this would be very cumbersome. These rates are different from the average magma eruption rate (or output rate) calculated using the total erupted volume and time span of magmatic activity at a given volcanic system (Crisp, 1984; White et al., 2006). They are also different from the rates obtained from the erupted volume divided by the time interval between two subsequent eruptions (Bacon, 1982). A magma cooling rate has also been calculated for eruptions >100 km3. This is the difference between the magma temperature at pre-eruptive conditions and its liquidus calculated by MELTS (Ghiorso and Sack, 1995), over the residence time. The significance of such cooling...



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