From lava to sinking land: Hawaii faces unexpected threat of subsidence

BGR unveils in a latest article that Hawaii, once formed by powerful volcanic eruptions, is now facing an unexpected and alarming shift—certain parts of the islands are sinking. 

A new study from the University of Hawai‘i at Mānoa has revealed that several areas of Oʻahu, the state's most populated island, are sinking far faster than previously believed.

The findings of the study are not just a geological curiosity; they serve as a stark warning about the escalating flood risks across the region. The research focused on subsidence, the gradual sinking of land, and found that much of Oʻahu is sinking at a rate of 0.6 millimeters per year. However, some areas, like the industrial zone of Mapunapuna, are sinking at an alarming 25 millimeters per year—more than 40 times faster than the island’s average rate and outpacing the global rise in sea levels.

So, what’s driving this stark variation in subsidence rates? According to the researchers, not all land behaves the same way. Areas built on soft sediments or artificial fill, like Mapunapuna, are especially prone to compaction, causing the ground to sink more rapidly over time. This intensified sinking, combined with rising sea levels, means some areas could see up to 50 percent more land at risk of flooding by 2050.

While flood maps traditionally focus only on sea level rise, the rapid sinking of parts of Hawaii signals that these maps may only tell part of the story. When you account for both rising waters and shrinking land, the urgency for action becomes undeniable.

Fortunately, Oʻahu is already taking steps toward climate resilience. Initiatives such as Climate Ready O‘ahu are working to restore wetlands, reinforce dune systems, and protect shorelines. However, the study's authors stress that future strategies must incorporate subsidence rates to better combat the threat.

“As lead author Kyle Murray stated, ‘In rapidly subsiding areas, sea level rise impacts will be felt much sooner than previously estimated.’” This emphasizes the need for immediate decisions around urban planning, infrastructure, and emergency preparedness to address this growing risk without delay.

By Naila Huseynova