When the faults are ready, earthquakes can be triggered with a force of no more than a handshake. That’s all you need, and climate change can provide a lot more force than that. For instance, there are earthquakes in Japan that are linked to increases in snow. Similarly, there have been earthquakes in Taiwan linked to low-pressure storms that cross over. These are small earthquakes, but the fact that atmospheric pressure can have an effect 5-6 km deep is staggering. There’s loads of evidence of how very small weather-related or climate-related changes can trigger geological activity.
“Global warming won’t just change the weather—it could trigger massive earthquakes and volcanoes“ in Quartz, May 14th, 2016. Interview with Bill McGuire, professor of geophysical and climate hazards at University College London.
Climate change affects patterns of pressure in the Earth’s crust. The sea and the land warm, and expand. The Himalayas and Andes and Alaska are relieved of the burden of their glaciers (and sooner or later Greenland and Antarctica of their ice-sheets), and the ground beneath springs upwards. Sea levels rise, and vast new masses of water weigh down on the continental shelves. Similarly with unprecedented dumps of monsoon rainwater onto plains and basins.
Accelerating change among finely balanced stresses in the Earth’s crust means more frequent ruptures among those stresses. More seismic and volcanic activity. Hey presto: geological mayhem!