Early Wednesday morning a 1,000-foot-wide section of a cliff on the island fell away, blocking the beach-side road below, The Seattle Times reported.
Police evacuated about a dozen people from homes below the cliff by boat because of the road blockage, KOMO-TV, Seattle, reported.
Another 17 people were evacuated from homes at the top of the cliff where at least one home is only 10 feet away from the newly formed edge of the cliff.
Two homes at the bottom of the cliff and two homes at the top have been deemed "at significant risk," said Central Whidbey Island Fire and Rescue Chief Ed Hartin.
Terry Swanson, a principal lecturer at the University of Washington's department of earth and space sciences told the Times the landslide was caused by unstable earth left behind by the Vashon glacier some 15,000 to 18,000 years ago.
The landslide caused no injuries, though one evacuee was transported to the hospital for an unrelated condition, KOMO said.