Volcano Haze Sunset
The famous Kilauea Volcano has been errupting since 1983. From time to time, lava from Kilauea reaches the ocean giving you a glimpse of nature at work. Recently, the fumes were so bad that local officials considered evacuating areas close to the volcano.
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Under the right conditions, the volcanic haze (aka "vog") can reach Oahu. You can actually follow this trail if you fly from Kona to Honoulu. Because the air is usually so clean in Hawaii, the sunsets are usually just a beautiful gradient of orange and yellow. But the vog in the air scatters more light showing off more colors resulting in purplish sunsets. Here's the view from a building near Pearl Harbor.