The Ever Changing Landscape of the Light Station
On Sunday, January 20, 2019 our Grounds Keeper Justin York discovered a significant sinkhole on the Gazebo Peninsula. Measuring about 12′ by 15′ and apparently at least 30′ deep, the sinkhole has obviously been forming for quite some time but only just appeared that day. We are fortunate that no guests were standing on it when it collapsed (at least as far as we know – we did check!). We immediately installed a security fence across the entire Gazebo Peninsula in front of the sinkhole. We also determined that there is very possibly another, larger sinkhole that may open up. An approximately 20′ by 40′ area east of the new sinkhole was observed to have sunk up to 2′ over the last week. We took as close a look as we could at the bluff near the sinkhole and it appears that there are two sea caves that likely allowed the ocean into the area under the sinkhole and it has been eroding the soil for some time. Our resident Geologist, Tom Cochrane, came out on Tuesday and placed marking stakes around the site so we can monitor further erosion. You can get a great view of the sinkhole from the top of the Lighthouse Tower, just ask the Guide to focus our big binoculars on it!
February 7 Update: The sinkhole has enlarged on its east and north edges, and there is moisture in the bottom of the hole now. We can hear water coming into the sinkhole but can’t see it from the safe vantage points. There has been more erosion at the bottom of the sinkhole as well. Our thanks to the Independent Coast Observer, Fort Bragg Advocate News and Mendocino Beacon for their coverage of this geologic phenomenon!
February 8 Update: The bottom of the sinkhole has now opened up slightly to the ocean and water can be seen flowing in and out with the waves (left photo below, the dark slot in the center is open to the water). The west edge has also eroded to the point that the fence post is now completely exposed and hanging in the air. The Mendocino Beacon had us on their front page last week! It was also covered by the Independent Coast Observer in its February 1, 2019 issue.
February 14 Update: After our big week of rains our sinkhole has enlarged significantly. Now measuring 16′ by 16′ the western edge lost about 2′ which left two of the fence posts hanging in midair. The Lighthouse team removed that section of fence so as not to have it fall into the sinkhole. As we were working on it some chunks of topsoil on the eastern edge fell off into the hole.
February 17 Update: Not much change, but the bottom of the sinkhole appears to be a face!
February 23 Update: Significant enlargement of the opening, up to about 16′ by 16′. Note the difference in the distance to the marker stakes between today and February 14:
The bottom is now clearly open to the ocean, you can hear the water churning in the opening and see it going in and out. We believe that the water is entering via a sea cave on the north part of the peninsula, you can see the waves roll into the opening and then they surge back out a few seconds later. The edges of the opening are significantly undercut, up to what appears to be anywhere from 5 – 10 feet deeper than the opening above it.
February 27 update: All of the stakes that Tom Cochrane put out around the perimeter when the sinkhole first opened are now gone. The opening is about 25′ by 30′, and the bottom is closed again due to all of the soil that has fallen into it. It has now expanded to the edge of the bluff and is starting to erode along the top. We had to remove another section of fence and also move the temporary rope perimeter fence back as one of the posts was hanging in the air.
March 2 update: The opening is about 30′ by 35′ and the bottom has now opened back up. Looks like another face! Bluff edge erosion hasn’t increased.
March 9 update: The opening is about 35′ by 35′ and the bottom has a smaller hole surrounded by the dirt that has fallen in, and we do not see or hear water coming in. The bluff edge erosion hasn’t increased.
March 10 update: The opening is about 40′ by 35′ and the bottom has opened up to the ocean waves again and we see and hear water coming in. The bluff edge erosion on the sinkhole’s western edge hasn’t increased, but other areas of the bluff to the south of the sinkhole have experienced some erosion.
March 16 update: The opening has grown to about 40′ by 45′ and the bottom has a significantly larger, rock outlined opening. The bluff edge erosion on the sinkhole’s western edge has increased very slightly. At the southwestern edge of the Gazebo peninsula bluff we lost about 10′ x 20′ that fell down onto the beach below. Looks like Justin will be moving more fencing this Spring!
March 26 update: The bluff edge erosion on the sinkhole’s western edge has increased by about 2 feet. A good sized rock is at the bottom of the sinkhole next to the opening where the ocean flows in and out. Overall diameter of the sinkhole has not measurably increased.
June 7 update: The bluff edge erosion on the sinkhole’s western edge has increased slightly. Overall diameter of the sinkhole has not measurably increased. Frequent Lighthouse lodging guest and kite photographer David Weese took a great aerial shot showing the gazebo and sinkhole.