Around 10,000 years ago, the planet emerged from its most recent glacial age. Large parts of volcanic summit cones became destabilized from melting glaciers, consequently plummeting to the valleys below. And now New Scientist reports that the same geological event is occurring over several mountaintops across the world, most notably in the past decade. Scientists are worried this could just be the beginning of mega-landslides capable of crushing major cities.

The last glacial period occurred when giant ice sheets covered most of North America and Eurasia. It reached its peak around 18,000 years ago when the Alps, the Himalayas and the Andes were mostly ice-covered. (The ice sheets of Antarctica remain today.) Permafrost functioned then and now as the glue holding soil together. As it disappeared during the last ice age, so did any real stability on some mountaintops.

Daniel Tormey is an environmental consultant studying a huge landslide in Chile that that occurred 11,000 years ago. Planchón-Peteroa is so high that it likely experienced the first warming temperatures at the end of the last ice age. Tormey reports that 10 billion cubic meters of rock slammed down onto 370 kilometers of land. Experts note that rainfall could not provide the “lubrication” necessary to cause such a landslide, and that glacier melt would have been the key to initiating this catastrophe.

And now such collapses are starting to happen again. Experts cite collapses at Mount Cook in New Zealand, Mount Dzhimarai-Khokh in Russia, and Mount Rosa in Italy — all which suffered great collapses after warmer temperatures. Climate change remains the likeliest impetus to these collapses.

Scientists are concerned with the potential collapse of the Andes, as temperatures are rising fastest along this volcanic mountain range. Tormey notes that such a landslide would be an epic disaster for the planet. According to Tormey, "There are far more human settlements and activities near the slopes of glaciated active volcanoes today than there were 10,000 years ago, so the effects could be catastrophic."

It’s not just the volcanic mountain tops with glaciers that have experts worried. If climate change continues to exacerbate rainfall, volcanic mountains without glaciers could also be influenced. Bill McGuire of University College London recently told New Scientist that there is cause for worry. According to McGuire, "We have found that 39 cities with populations greater than 100,000 are situated within 100 kilometers of a volcano that has collapsed in the past and which may, therefore, be capable of collapsing in the future.”

For further reading:

Climate change linked to increase in landslides
Thinning glaciers and loosening permafrost on volcanoes are destabilizing high mountain ranges, triggering collapses.