Lava from Mauna Lao, the world’s largest active volcano, is inching its way toward the Daniel K. Inouye Highway, a key transportation artery on Hawaii’s Big Island.

The Hawaiian Volcano Observatory said in its latest update that the lava flow has “slowed down significantly over the past couple of days, as expected.”

The observatory said, “Advance rates may be highly variable over the coming days and weeks due to the way lava is emplaced on flat ground. On flat ground, lava flows spread out and inflate. … There are many variables at play and both the direction and timing of flow advance are expected to change over periods of hours to days, making it difficult to estimate when or if the flow will impact Daniel K. Inouye Highway.”