Some volcanic islands feature rare beaches with vibrant green sand.

Papakōlea Beach on Hawaii's Big Island was formed approximately 49,000 years ago by the eruption of the Puʻu Mahana cinder cone. The green color comes from olivine, a magnesium iron silicate mineral that is one of the first crystals to form as lava cools. Because olivine is significantly denser than the surrounding basaltic glass and ash, it resists being swept out to sea by the powerful Pacific tides.Geologists note that these beaches are temporary on a geological timescale. Since the olivine is eventually crushed into fine silt or chemically weathered by the ocean's acidity, the green color will one day disappear if the cinder cone stops eroding. The specific variety of olivine found here is often called peridot when it reaches gemstone quality, which explains the sand's emerald-like shimmer.Besides Hawaii, the only other major green sand beaches are located in the Galápagos Islands (Punta Cormorant), Norway (Hornindalsvatnet), and Guam (Talofofo Beach). Research published in journals like 'Nature Communications' highlights how olivine weathering can actually help sequester carbon dioxide from the atmosphere. This makes these rare geological formations not only beautiful but also significant in the study of natural climate regulation.