1. Calderas – a selective introduction

2. What is a caldera?
A caldera is a surface depression formed by draining a subsurface magma reservoir
Once a magma chamber has drained sufficiently, its roof can no longer be supported, so it collapses into the reservoir
Draining of the reservoir can occur by subsurface intrusion (basaltic systems) or by explosive venting (silicic systems) (can you think of some examples?)
The structural rim and topographic rim of a caldera are different
Calderas are filled with breccia and pyroclastic rocks
The caldera floor can be coherent or broken up into many pieces
Lipman 1997 BV

3. Smith and Bailey’s caldera cycle

4. Caldera-related magma reservoirs
How are they sustained?
What is their physical nature and rheology?
How do they evolve over time?
National Park Service

5. Triggers and causes of caldera eruptions
Changes in the physical state of the magma
Replenishment
Overpressure
Role of magmatic-hydrothermal fluids
Any other ideas ?

6. Styles of caldera collapse
Effects upon intracaldera ignimbrite and cooling
Role of regional structures
Lipman 1997 BV

7. Links between subsidence processes and magma chamber processes
Mixing and stirring of magma
Single blocks vs. multiple blocks
Temporally increasing magma diversity
Intensification of eruptions
Kennedy et al 2008 Nature Geosci

8. Calderas at stratovolcanoes
Crater Lake
Pinatubo

9. Basaltic calderas Miyakejima 2000
Sandbox experiments - Roche et al 2000 JGR

10. Miyakejima 2000 degassing caldera formation complete
Kazahaya et al Geology

11. Restless silicic calderas
Long Valley (USA)
Yellowstone (USA)
Rabaul (Papua New Guinea)
Campi Flegrei (Italy)
Maule (Chile)
Role of regional structure
Calderas as pull-apart basins
USGS

12. Resurgence and associated activity
Styles
Mechanisms
Timing of collapse and resurgence
Hydrothermal systems
Ore deposits
Smith and Bailey 1968

13. Global impact of caldera-related super-eruptions
Atmosphere
Land surface
Sea surface
Vegetation