Any time you are on the ground in Hawaii you are on a volcano. The only active volcanoes at this time are on the Big Island of Hawaii, and the Loihi seamount, just off the Big Island coast line. The Hawaiian Islands are formed over a “hot spot” on the ocean floor that sits under the Pacific Plate. As the Pacific plate moves to the northwest, the volcano moves away from the hot spot. The magma will find another spot to poke through, and a new sea mount is formed. Sometimes these sea mounts grow large enough to rise above the ocean surface, and some times they don’t quite have enough mass to make it.
The Big Island is made up of 5 volcanoes that have meshed together to make one big island. The Big Island is the largest of the Hawaiian Islands and the newest. There are eight named islands that make up the Hawaiian Islands, although the Hawaiian Island chain is comprised of many islands and atolls.
Our Big Island first appeared above the ocean surface at least 500,000 years ago, although the island was slowly being built up under the ocean for millions of years. If you measure the mountains from the bottom of the ocean floor, they are the tallest mountains in the world. It takes a lot of lava to make a volcano big enough to breach the ocean surface, much less make a mountain that is 14,000 feet above sea level. If you measured the mountain from the ocean floor, the mountain is over 30,000 feet high!
The five volcanoes that make up the Big Island are Mauna Kea (White Mountain), Mauna Loa (Long Mountain), Kilauea, Hualalai, and Kohala. Kilauea, Hualalai and Mauna Loa are still active volcanoes. Mauna Kea is a dormant volcano and Kohala is an extinct volcano. The last eruption of Mauna Kea was 4,000 years ago while the last eruption of Kohala was about 120,000 years ago.
Kohala is the northwest tip of the Big Island and is the oldest volcano of the five. It used to be much larger than it is today. About 250,000 years ago the northeast flank of the volcano slide into the sea in a huge land slide. The rugged coastline of Kohala speaks to the power of the separation of the mountain as the landslide occurred. Lava flows from Kohala’s sister volcanoes Mauna Kea and Mauna Loa covered part of the gently sloping sides that were left. So while Kohala accounts for less than 6 per cent of the total area of the Big Island, it was on that gently sloping shield that the biggest island in the Hawaiian chain was born.
Mauna Kea, our dormant volcano and the tallest of the group, last erupted about 4,500 years ago. Mauna Kea is sandwiched between Kohala and Mauna Loa, and is the top northeast corner of the island. Mauna Kea has snow on her peaks in the winter months, and has had 3 glacial periods. Pretty impressive for a tropical island wouldn’t you say? Even though Mauna Kea is a dormant volcano, chances are there will be another eruption in the future.
Now to our active volcanoes, which is one of the reasons to visit this bit of heaven on earth. Hualalai formed the western most point of the Big Island of Hawaii. The last eruption was in 1801, so this volcano is still classified as active. In volcano time, 200 years is the blink of an eye. This volcano will likely erupt again in the future. The good news is, these volcanoes are the most studied volcanoes in the world. The USGS keeps constant vigilance on all the volcanoes in Hawaii, and there will be plenty of warning before Hualalai erupts again. That is all part of living with a volcano in your back yard.
Mauna Kea is the show piece of the Big Island. This is the largest volcano on earth, and one of the most active volcanoes. Mauna Loa comprises the southern most tip of the Big Island, and then stretches almost up to Kohala, and then over to the east past Mauna Kea. The last eruption was in 1984, and there will be eruptions in the future. This is one big volcano that loves to spew lava. In fact, the amount of lava that Mauna Kea has released would equal almost 90% of the total volume of all the other major Hawaiian Islands combined. Fortunately, before any eruptions occur, the volcano gives us warnings in the form of increased earthquake activity. This volcano is very careful monitored so warnings can be issued when needed.
Now to the star of the show, Kilauea, which has been erupting almost continuously since 1983. What an incredible show Kilauea has put on for all of us. Nick-named a drive-up volcano, because you can drive up and see it erupting; it is a wonderful opportunity to see first hand the awesome power of nature at work. For the most up-to-date information I have included a link to the USGS site on Kilauea. Click on the web cams at night and check out Halema’uma’u. At the time this article was written, you could look down into the pit and see the lava glowing. Awesome!
http://hvo.wr.usgs.gov/kilauea/update/images.html
