There’s not much point worrying much over geological existential risks. They come too infrequently too be a major risk, and those that do occur more often, are not big enough to matter in the big picture.
Still, if there’s one risk that is both potentially highly destructive and occurs at a relatively high rate, it is megatsunamis that occur as a result of submarine landslides (masses of land slumping into water as a result of earthquakes or volcanic eruptions). In the Canary Islands, there have been 14 such slides in the past million years (once every 100k years). In the Hawaiian archipelago, there were 68 big slides over the past 2 million years. In total, it is estimated there have been at least 100 big slides that caused megatsunamis during the Quaternary, or once every <25,000 years. This is >1 OOM more frequent than supervolcanoes (~once every million years), which are in turn 2 OOM more frequent than very big asteroid collisions (~once every 100M years).
So probably won’t happen within the lifetime of industrial civilization (250 years and counting). But megatsunamis are a more realistic concern on these timescales. The collapse of a part of Cape Verde 73,000 years ago created a 240 meter tall megatsunami that wiped the coast of West Africa clean. The Storegga Slide in 6170 BC flooded Doggerland and could have been the origin of the world’s flood myths. A slide in Réunion 4,000 years ago flooded West Australia. So this is something that happens within historical time.
According to some early modeling in 2001, a 500 km3 submarine landslide off the Cumbre Vieja volcano in La Palma could create huge waves that will retain a height of 10-25 meters by the time it reaches the Eastern Seaboard.
Such a 10-25 m megatsunami would advance ~30 km into low-lying Florida after just nine hours of warning time. The Caribbean and the West African coast would be wrecked. At least several 100,000sof people would die, a great deal of housing stock would be destroyed, and world markets would go into a hyperdepression. Portugal, Spain ,and the British Isles would sustain some more minor damage from 5-7 meter waves.
These projections have come under question as being too pessimistic or even entirely unrealistic. Nonetheless, it’s something to watch out for, given current developments.