page_title: Hanauma Bay
section_title: Geology
hierarchical_section_title: Hanauma Bay / Geology
caption_attribution_description: English: Hanauma_Bay_Oahu_Hawaii_Photo_D_Ramey_Logan classic color reversal film shot kodak process and digitally transfered to disk
context_page_description: Hanauma
  is a marine embayment formed within a tuff ring and located along the southeast coast of the Island of Oʻahu in the Hawaii Kai neighborhood of East Honolulu, in the Hawaiian Islands.
  Hanauma is one of the most popular tourist destinations on the Island and has suffered somewhat from overuse. At one time, this popular tourist destination accommodated over three million visitors per year. In 1956, dynamite was used to clear portions of the reef to make room for telephone cables linking Hawaii to the west coast of the US.
context_section_description: The Hawaiian Islands are a group of volcanoes that have risen up over a hot spot, which is a section of the Earth's surface that has exhibited volcanism for an extended period of time. Volcanic chains such as the Hawaiian Islands form as a result of the movement of a tectonic plate across fixed hot spot beneath the surface. In the case of the Hawaiian Islands, the Pacific plate has moved slowly northwestward over such a hotspot.
  Approximately 3.9 million years ago, the Waiʻanae volcano created the island of Oʻahu.  About 2.5 million years ago, the Koʻolau volcano breached the ocean's surface and continued to grow in elevation until about 1.7 million years ago, when it went dormant.  Most of the eastern or windward portion of Oʻahu are remnants of this volcano.  Most of the familiar geographic landmarks of eastern Oʻahu were created by eruptions from Koʻolau from about 500,000 to 10,000 years ago.  The eastern flank of the Koʻolau volcano including the caldera slid into the sea, leaving the Koʻolau mountain range that can be seen today on the windward side of the island.
  The Hanauma Crater was created about 32,000 years ago during the Honolulu volcanic series, the latest (and perhaps final) round of volcanic activity to occur on Oʻahu. Tens of thousands of years ago, a series of volcanic vents opened along the southeast shoreline of Oʻahu. Unlike the gentle lava flows currently building the island of Hawaiʻi, the late-stage eruptions on Oʻahu were most often short-lived violent explosions. The volcanic vents that formed Hanauma Crater opened on the sea floor. Upwelling magma vaporized the ocean water and steam explosions blew the magma into fine ash. The explosions built cones or rings of ash, which solidified into tuff. The eruptions shattered the sea floor—coral reef and basalt—and scattered pieces that are now embedded in the tuff. Wave erosion eventually cut through the low, southeast wall of the crater, forming the current bay.
caption: Hanauma Bay Oahu Hawaii
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