![]() One lasted 1,200 years, ending in about 1000 CE the other lasted 300 years, between about 15 CE. Scientists estimate that during Kīlauea's past 2,500 years a deep caldera has existed about 60 percent of the time, which included two long periods of sporadic violent explosions. Prolonged periods of explosive eruptions at Kīlauea may require the presence of a caldera to sustain them. Eventually, magma supply increases and effusive eruptions dominate as many lava flows fill the caldera and erupt from the rift zones. When the caldera floor is deep enough to be at or near the water table (about 500 m (1640 ft) deeper than present), water can seep into the vent to trigger steam explosions. When the magma supply drops, the caldera collapses. When magma supply is high, the summit caldera fills and feeds voluminous lava flows from the summit and rift zone vents. Scientists infer that the eruption style is determined by the amount of magma being supplied to the volcano. ![]() Long periods of explosive (tephra-dominated) and effusive (lava-flow-dominated) activity have alternated at Kīlauea for the past 2,500 years. Visit Media to see details.Īt Kīlauea, when the lava column drops below the water table, groundwater may come into contact with magma or hot rocks, causing violent steam explosions. Map of Kīlauea's activity over the past ~200 years Current research indicates the first alkali-basalt lava flows erupted onto the ocean floor between 210,000 and 280,000 years ago, and the volcano transitioned from its pre-shield to the shield-building stage about 155,000 years ago. Estimates for the age of Kīlauea's first-erupted lavas continue to evolve as more samples are collected and various dating methods are used. Older rocks have been recovered from Kīlauea's submarine slopes and drill cores, providing some clues to the volcano's origin. The Hilina Basalt formation, exposed in Hilina fault scarps on Kīlauea's central south flank, includes the oldest lava flows found above sea level, which erupted around 50,000 to 70,000 years ago. The other 90 percent of the volcano's surface is covered by lava flows younger than 1,000 years, and about 20 percent of those flows are less than 200 years old. Only about 10 percent of Kīlauea's surface consists of rock older than 1,000 years. There is a lack of old exposed rock at Kīlauea, which makes it difficult for geologists to piece together its complete eruption history. (Public domain.) Kīlauea Volcano Erupts in Explosive and Effusive Cycles Located on the southeastern side, Kīlauea Volcano is 90% covered with young flows. The Island of Hawai‘i with lava flows erupted in approximately the past 1,000 years shown in red.
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