Melting Arctic ice isn't just bad news for sea levels. In Greenland, ice that previously held mountains together is melting, shaking loose unstable rock, according to New Scientist. That triggers huge landslides, which in turn leads to deadly tsunamis.

In June, 39 people were evacuated and several were killed after a tsunami flooded the remote island of Nuugaatsiaq, Greenland. Initially, authorities thought the tsunami was the result of a 4.1 earthquake off the coast. But it turned out that it wasn't an earthquake at all. The tsunami was triggered by part of a mountain collapsing, creating a giant landslide of seismic proportions that fell into the sea.

As the world gets warmer, we may have to deal with more incidents like these. Where previously ice might have been able to hold together the unstable rock of a mountain, if that ice melts, there's nothing to keep that rock from coming down. As a glaciologist told New Scientist, the melting and freezing cycles of ice in Greenland have created a dire situation.

Greenland and other fjord-dominated landscapes are at high risk for these sorts of disasters as ice melts. The sharp, steep cliffs of fjords make it easy for unstable rocks to go tumbling into deep water, causing dangerously strong waves. These tsunamis can reach speeds of more than 500 miles per hour. The deeper the water that the mountain collapses into, the stronger the tsunami, which means more bad news from rising sea levels.

[h/t New Scientist]