The reef's 'trench' structures were formed by the rapid cooling of volcanic lava, which created hardened rock formations subsequently carved out by long-term wave erosion.
The signature green color is produced by Ulva lactuca, commonly known as sea lettuce, which thrives in the nutrient-rich, cooler waters of early spring.
The entire site is subject to constant tidal changes, meaning the reef is often submerged during high tide, leaving only the water's surface visible.
The algae begin to fade and turn white as temperatures rise and the sun intensifies, making late spring the definitive end of the viewing season.
The location is part of the broader North Coast and Guanyinshan National Scenic Area, which manages the preservation of the delicate reef ecosystem.
Laomei Green Reef is a unique geological site located in Shimen District, known for its distinctive parallel volcanic rock trenches that become carpeted in vibrant green sea lettuce algae each spring. The reef is formed by the erosion of igneous volcanic rocks created by historic eruptions from the Datun Volcano Group. As the tide recedes, the exposed, moss-covered trenches create a striking visual contrast against the surrounding sea and dark stone. The algae growth is a seasonal phenomenon driven by the northeast monsoon and receding tide patterns. It is one of the most significant and accessible coastal reef formations on Taiwan’s northern coastline. The area is maintained by the North Coast and Guanyinshan National Scenic Area administration.
From the sandy beach area looking toward the sea during low tide to capture the leading lines of the parallel reef trenches.
Check local tide tables before departure, as the green reef is only fully visible and walkable during low tide.
Wear footwear with excellent grip, as the algae-covered rocks are extremely slippery and treacherous even when the tide is low.
Walk only on the designated wooden boardwalks or sand areas to protect the fragile algae from being crushed by foot traffic.
Visiting during high tide when the reef is fully submerged and invisible; attempting to climb on the slippery, mossy rocks.
The green algae is a seasonal phenomenon peaking in spring; the reef turns white and dies back as summer temperatures increase.
Do not step directly on the green-covered rock formations to prevent damage to the ecosystem; stay on designated viewing paths.
