Hawaii Geology and Geography
The Volcanoes of the Big Island
Mauna Loa, the Big Island’s largest volcano makes up approximately 51% of the island, and most people still have a surprisingly hard time finding it when they are here. Mauna Loa means “Long Mountain” and is given this name due to its large shield shape. This shape makes it difficult to distinguish Mauna Loa as an actual mountain.
The name “shield volcano,” which is what all the islands in Hawai‘i are, comes from a perceived resemblance to the shape of a warrior’s shield. Molten lava rises from a hot spot in the earth’s crust, erupts through various vents and rifts on the surface, and proceeds to move down the gentle slopes toward the ocean, building up layer upon layer over millions of years. Kilauea Volcano, the world’s most active volcano and home to the fire-goddess, Pele, resides on the eastern slopes of Mauna Loa. At one time many believed Kilauea to be a vent of Mauna Loa, but today we know it has its own magma chamber and is completely separate from its larger cousin next door. Mauna Kea is the other major volcano on the island making up about 25% of the island’s total landmass. Mauna Kea is significantly easier to spot than Mauna Loa, often recognized in winter months by its snowy cap, hence the name Mauna Kea - meaning “White Mountain.” Reaching a total elevation of some 33,000 feet from the sea floor, of which only 13,780 (approx.) feet exist above sea level, the mountain is the highest point in the Pacific Ocean and the world’s tallest mountain from base to summit.
The Big Island’s other volcanic mountains are Hualalai in Kailua-Kona on the west side of the island and Kohala on the northwest tip of the island. Kohala is the oldest mountain on the island and shows much more geological wear than its younger counterparts. The amazing sea cliffs found in Kohala today were likely caused by a giant landslide some 200,000 years ago.
Mauna Kea and Hualalai are both considered dormant, like Haleakala on Mau'i. Chances are they will erupt again in the long-term future, though most likely to no significant degree (volume wise) as the hot spot no longer exists beneath them. Generally speaking, the only eruptions that occur beneath these dormant mountains are due to their subsidence into the ocean floor, usually a few thousand feet over time, which then heats and "pushes" any remaining magma up to the surface in the form of an eruption. Unfortunately, while these eruptions lack volume, they can be somewhat violent and even explosive. Mauna Kea owes its steep slopes to a explosive type of eruption in the recent geologic past. Explosive eruptions often produce widespread ash deposits, which help build a steeper sided volcano like those found in the western United States. Today the physical differences between Mauna Kea (fairly steep sided due to 'recent' explosive eruptions) and Mauna Loa (still in its shield-forming stage) are very distinct. In its prime, Mauna Kea likely reached a few thousand feet higher than it does today. As previously noted, Mauna Kea remains the tallest mountain, from top to bottom, on the planet. From base to summit it towers some 33,000 feet. That's taller than Mount Everest. Plus if you consider what's subsided (sunk) into the ocean floor, which the USGS does take into account for mountain height, then the mountain is 56,000 feet tall. That's just incredible!
Mauna Loa and Kilauea are both considered active volcanoes. Mauna Loa last erupted in 1984, and is likely to erupt fairly significantly again in the near future. Since 1843, the beginning of well-documented historical data, Mauna Loa has erupted 33 times. Geologically speaking that makes it a very active volcano. Mauna Loa is by far the bulk (51%) of the Big Island and remains the world's largest (in mass) volcano. Currently, Kilauea makes all the news and steals the show, but one day in the future Mauna Loa will remind us why it's the biggest volcano on the island. Mauna Loa can erupt significant amounts of lava in a very short time frame, dwarfing Kilauea.
Kilauea, once believed to be merely a side satellite vent of Mauna Loa but now recognized as its own distinct volcano, is the world's most active volcano, erupting continuously since 1983. Between January 1983, and June 2007, nearly 600 acres of land were added to the island by lava flows from Kilauea volcano. This growth has not been without cost however. Several towns have been destroyed by Kilauea: Kapoho (1960), Kalapana (1990), and Kaimu (1990). Today the remnants of these towns struggle to survive on the flanks of the world's most active volcano. In some aspects these towns are all but abandoned except by a few.
As previously mentioned, just 18 miles off Hawai'i's southeast coast is the undersea volcano known as Lo'ihi. Lo'ihi is an actively erupting seamount that lies approximately 3,178 feet below the surface of the ocean. If and when Lo'ihi breaks above the waves, it will likely join with Kilauea (which, in theory, will be much larger by that time) and become the sixth peak in what is now Hawai'i's largest island. Don't book your hotel room just yet though: it's a good 50,000 years or more in the making.
Page 2 of 3 pages for this article < 1 2 3 >
Topic Views: 29898
Author: J.C.Derrick
Destination Expert on
80°F
The comments below do not necessarily reflect the views of Hawaii-Guide or its affiliates.
Questions directed at our staff will be answered as quickly as possible.
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.