page_title: Koa'e Fault Zone
section_title: Features
hierarchical_section_title: Koa'e Fault Zone / Features
caption_attribution_description: English: Large ground cracks in the Koa'e Fault Zone on Kilauea Volcano on the Big Island of Hawaii.
context_page_description: The Koa’e Fault Zone or Koa’e Fault System is a series of fault scarps connecting the East and Southwest Rift Zones on Kilauea Volcano on the Big Island of Hawaii. The fault zone intersects the East Rift near the Pauahi Crater and extends nearly 12 km in an east-northeast direction towards the westernmost boundary near Mauna Iki and the Southwest Rift Zone. Boundaries of the Koa’e Fault Zone also cover 2 km in a north-south orientation along the 12 km length. It is believed that the fault zone has been active for tens of thousands of years. The area is infrequently visited by park patrons due to the lack of eruptive activity and closure of certain areas to the general public.
context_section_description: The Koa’e Fault Zone contains numerous thrust fault scarps and ground cracks that are slowly moving towards the Pacific Ocean. The area is covered with pahoehoe lava flows dated between 700 and 500 years old. The exact number of lava flows in this region is debatable. Numerous exposed scarps have very poor distinctions between various lava flows due to weathering of the basalt. Because Kilauea has erupted explosively in the past, the Koa’e Fault Zone is also covered with tephra deposits. The stratigraphy of the sediments contains many clues to the eruptive history of Kilauea Volcano.
  A layer of scoria overlies the basaltic lava flows. The age of these deposits has been determined to be roughly 400 years old. Groundwater penetration into Kilauea most likely created a steam explosion followed by an eruption of these tephra deposits.
  Above the scoria is a layer of orange ash roughly 3 cm (1.2 in) thick. The fined grained texture of the ash also suggests an explosive style of eruption sometime after the tephra was deposited. Biologists believe that this layer of ash served as a soil horizon for native and invasive plants to colonize the area.
  The top layer is a sandy material which is also the product of an explosive eruption.
  In order to get a stratigraphy like this, a large eruption with tephra reaching the jet stream is required, suggesting that energetic pyroclastic eruptions have occurred in the past, making Kilauea significantly more hazardous than once thought.
  Fault scarps in the Koa’e Fault Zone create a Horst and Graben type of terrain. Some of the scarps (called “pali” in native Hawaiian) face northwards, towards the summit of Kilauea Volcano and Halemaʻumaʻu Crater. This is unusual because the scarps usually face in the direction of flow. Monitoring data of the fault zone has revealed that at the Pacific Ocean, the land mass is moving at a rate of 2.5 cm (0.98 in) per year. In the upper regions of the fault zone, the crust is moving at a rate of 8 cm (3.1 in) annually. This vast difference in movement rates has over time created numerous antiforms in the region.
  Kulanaokuaiki Pali is the southernmost fault in the Koa’e Fault Zone. During a period of intense earthquakes in December 1965, Kulanaokuaiki Pali was vertically displaced by more than 2.4 m (7.9 ft) meters. The region has been intensively studied since then. Displacements in other parts of the Koa’e Fault Zone based on historical data suggest that movements as great as 15 m (49 ft) have occurred.
caption: Large ground cracks in the Koa'e Fault Zone on Kilauea Volcano
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