Hawaii Geology and Geography
The 'Hot Spot'
So what exactly is this 'hot spot' you hear so much about, and how does it form these beautiful islands? The answer to this question is fairly simple. The Hawaiian Islands are situated near the middle of the "Pacific Plate" on top of a 'hot spot.' This Pacific Plate is almost always moving northwestward at a rate of several centimeters per year, about the same rate as your fingernails grow. This constant northwestward movement of the Pacific Plate over a local volcanic "hot spot," or plume, has produced a series of islands, one after another in assembly line fashion. The result is a chain of volcanic islands (Hawaiian archipelago) that consists of eight major islands and 124 islets stretching from the Big Island of Hawai'i along a northwest line for 1,500 miles toward Japan and the Aleutian Islands of Alaska. In total, the islands spread across an area of 6,459 square miles. The link above shows one perspective of this chain of islands. This link shows another view of the Hawaii archipelago.
The Big Island of Hawai'i is currently the largest landmass in the Hawaiian island chain. The eight major islands at the western end of the chain are, from west to east, Ni'ihau, Kauai`i, O`ahu, Moloka`i, Lana`i, Kaho`olawe, Maui, and the Big Island of Hawai`i.
Hawai'i, also the youngest island in this chain, began over a million years ago as five separate volcanoes on the ocean floor. As the five volcanoes erupted time and time again (not necessarily simultaneously but rather sequentially), they created thin new sheets of lava spread upon the old, building and building until the volcanic heads emerged from the sea. These mountains often would have flows that overlapped the other mountain's flows, and eventually the five peaks would become the single island we see today (note the diagram on the next page). First the Kohala Mountains formed as they sat over the 'hot spot' in the plate. But as the plate shifted, so did the location of the rising magma, moving to Mauna Kea, Hualalai, Mauna Loa, and eventually Kilauea. Even now there is a new seamount, named Lo'ihi, which is also forming off the southeast coast of the Big Island. In another 50,000 years or so, it too may become the next Hawaiian island, or it may even join to become the sixth peak of the Big Island. Currently, only the volcanic remnants of Kohala are completely extinct, never to erupt again. The rest of the volcanoes on the Big Island aren't quite done yet. Consider this a history lesson that's still evolving.
So what exactly is this 'hot spot' you hear so much about, and how does it form these beautiful islands? The answer to this question is fairly simple. The Hawaiian Islands are situated near the middle of the "Pacific Plate" on top of a 'hot spot.' This Pacific Plate is almost always moving northwestward at a rate of several centimeters per year, about the same rate as your fingernails grow. This constant northwestward movement of the Pacific Plate over a local volcanic "hot spot," or plume, has produced a series of islands, one after another in assembly line fashion. The result is a chain of volcanic islands (Hawaiian archipelago) that consists of eight major islands and 124 islets stretching from the Big Island of Hawai'i along a northwest line for 1,500 miles toward Japan and the Aleutian Islands of Alaska. In total, the islands spread across an area of 6,459 square miles. The link above shows one perspective of this chain of islands. This link shows another view of the Hawaii archipelago.
The Big Island of Hawai'i is currently the largest landmass in the Hawaiian island chain. The eight major islands at the western end of the chain are, from west to east, Ni'ihau, Kauai`i, O`ahu, Moloka`i, Lana`i, Kaho`olawe, Maui, and the Big Island of Hawai`i.
Hawai'i, also the youngest island in this chain, began over a million years ago as five separate volcanoes on the ocean floor. As the five volcanoes erupted time and time again (not necessarily simultaneously but rather sequentially), they created thin new sheets of lava spread upon the old, building and building until the volcanic heads emerged from the sea. These mountains often would have flows that overlapped the other mountain's flows, and eventually the five peaks would become the single island we see today (note the diagram on the next page). First the Kohala Mountains formed as they sat over the 'hot spot' in the plate. But as the plate shifted, so did the location of the rising magma, moving to Mauna Kea, Hualalai, Mauna Loa, and eventually Kilauea. Even now there is a new seamount, named Lo'ihi, which is also forming off the southeast coast of the Big Island. In another 50,000 years or so, it too may become the next Hawaiian island, or it may even join to become the sixth peak of the Big Island. Currently, only the volcanic remnants of Kohala are completely extinct, never to erupt again. The rest of the volcanoes on the Big Island aren't quite done yet. Consider this a history lesson that's still evolving.
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Now all that said, the lava may occasionally thicken to a`a, blocking the vent. Or pyroclastic materials (cinders, pumice and the like) may block the vent. Either way, an explosion can (but rarely does) result. Kilauea has had two major explosions during recent human history. Native Hawaiians noted an explosion around 1790 which killed several soldiers of an army encamped near the volcano, while the other explosion occurred in 1924. The latter was studied extensively by volcanologists. The most recent explosion in March of 2008 is what creating the relatively small smoking vent inside Halema`uma`u Crater. It was the first explosion in Kilauea's main Halemaumau Crater since 1924, scattering debris over an area of about 75 acres of the park.