Since geology began to enter a conversation online about “planetary risks,” I decided to compile a list of them that might put possibilities into perspective, and perhaps inform other conversations about infrastructure. Here’s a table:
| Event | Rough frequency | Primary reach | Planetary significance |
|---|
| Magnitude 7–7.9 earthquake | About 10–20 per year worldwide | Local to regional | Usually indirect, through damage to cities, infrastructure and supply chains |
| Magnitude 8+ earthquake | Roughly once a year | Regional; sometimes ocean-wide | Major economic and infrastructure shock |
| Magnitude 9-class earthquake and tsunami | Several per century, irregularly | Regional to transoceanic | Can devastate nations and disrupt global production |
| Krakatau-class eruption (VEI 6) | Several per century worldwide | Regional devastation; modest global climate effects | Serious, but normally not civilization-threatening |
| Minoan eruption of Thera/Santorini, circa 1600 BCE (VEI 6–7) | Events of this scale occur perhaps once every few centuries | Devastated Thera; spread ash and generated tsunamis across the eastern Mediterranean | A civilization-disrupting regional catastrophe; its precise role in the later decline of Minoan civilization remains debated |
| Tambora-class eruption (VEI 7) | Roughly once in many centuries | Global climatic and agricultural disruption | Credible worldwide systemic risk |
| Toba-class eruption (VEI 8+) | Extremely rare; on a geological timescale | Global | Potential civilization-level catastrophe |
| Tunguska-class airburst | Perhaps once per decades to centuries | Metropolitan to regional | Enormous local casualty potential |
| Kilometer-class asteroid impact | Roughly once per several hundred thousand years | Global | Potential civilization-level or existential event |
Am I missing some?
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