The shield volcano stage cycle begins with the submarine pre-shield, which is a lowvolume underwater eruption occurrence. This is due to submarine vents in the earths crust. The low-volume eventually accumulates into rising earth creating a submarine shield, which is known as the submarine shield stage. The magma cools during this time and deteriorates calderas, allowing new calderas to form. This pattern repeats and recycles which is why the shield continues to create height above the original ocean floor. The explosive shield stage describes when the volcano breaches sea level and oxygen exposure allows more frequent eruptions. The sub aerial shield stage is a time when the violent eruptions lessen becoming less frequent and less aggressive. This allows landmass to expand from cooling magma, resulting in the resemblance of a shield above the sea level. The post-shield stage is a reverse from the sub aerial time and the eruptions create large volumes of sticky lava. Lastly is the rejuvenated stage, where small eruptions take place and lava plumes are visible infrequently. The final stage is the coral atoll, marking the end of the volcano life. This is when erosi
on and activity break down the volcano to sea level and it becomes a lagoon which is evident by geological occurrence on Kauai.
The Big Island is the main island of Hawaii chain, and the landmass is comprised of five volcanoes. Kohala, the oldest, is the northwestern-most located volcano on the island and is estimated to be million years old. The oldest recorded rock emitted from the volcano however is only 460,000 years old. The last eruption that has occurred from Kohala was 20,000 years ago, lending itself to be a less risky zone of the island. A major event that Kohala has experienced was a sign of the post-shield, when a massive landslide carried debris 8 miles out into the ocean. The volcano in particular traps low viscosity lava. Its main geographic features are the large faults, caused by the landslide. It has completed its shield stage and is now post-shield for the last 245,000 years. Having completed its shield stage, life forms have been able to thrive on the dormant land. Heavy moss covers the lava covered floor, which effectively traps frequent rain water. This has attracted 55 native species, making it the most thriving ecosystem on the big island.