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The USGS completed a leveling survey along the Ka'u trail in Hawaii's Volcanoes National Park. The 10 mile route runs inland from the south coast of the Big Island. It follows a trail that's existed since 1778. The Ka'u trail was first leveled in 1921, when six permanent benchmarks were placed on the route. The last survey was done in 1976, following a 1975 earthquake.
From the survey, scientists discovered that deformation has continued along the Ka'u trail since 1976. The inland region has subsided gently, only about 5 cm. In contrast, the area close to the coastal plain has risen as much as 15 cm. The survey findings indicate that a narrow zone forms the current boundary between moderately deformed and less deformed crustal blocks of Kilauea volcano. The unanswered question is how much can the inland region deform before the crust once again ruptures on this zone? Or perhaps earthquakes elsewhere in the region will relieve the vertical changes that have accumulated in the past 25 years. Scientists suspect they will get their answer within the next few years.