When a volcano erupts on the sea floor, and continues to erupt slowly for thousands of years, it eventually results in formation of an island. This is exactly how the Hawaiian Islands - extending over a distance of around 1,500 miles in the North Pacific Ocean, were formed. As of today, there exist 500 active volcanoes on the planet, of which at least 50 are notorious for frequent eruptions. In fact, the United States of America alone is home to 50 active volcanoes, of which 5 are found in the state of Hawaii.
Classification of Volcanoes
In a broad sense, volcanoes are classified into three different groups: 'active volcanoes' - which tend to erupt frequently, 'dormant volcanoes' - which haven't erupted for a considerable period now, but the chances of eruption cannot be ruled out, and 'extinct volcanoes' - which haven't erupted since historic times and chances of eruption now virtually don't exist.
What is an Active Volcano?
With several overlapping definitions of the same, it is very difficult to come to a consensus on what an active volcano actually is. Add to it the fact that even the arguments put forth by volcanologists tend to differ, and it becomes all the more confusing. Smithsonian Institute, a renowned educational and research institute based in Washington D.C., United States of America, has a research program referred to as the Global Volcanism Program - wherein the volcanic activity of several active volcanoes of the world is documented and studied to assess the nature of volcanic eruptions on the planet. Going by the definition of an active volcano which is taken into consideration for this study, the term active volcano refers to a volcano which has erupted at least once in the last 10,000 years i.e. the 'holocene period'.
Active Volcanoes in Hawaii
As we mentioned earlier, the volcanoes which resulted in formation of Hawaiian Islands erupted on the sea floor, and eventually emerged above the water surface as a result of continuous eruptions over the period of several thousand years. While Kilauea, Mauna Loa and Hualalai have erupted in the last 200 years, Haleakala last erupted in the 18th century. There exists yet another volcano - Loihi which is active, but hasn't emerged out of the ocean as yet. Discussed below are the details of these five active volcanoes of the Hawaiian archipelago.
Kilauea Shield VolcanoKilauea volcano - which began erupting on 3rd July, 1983, and continues till date, is considered to be one of the most active volcanoes of the world. It is one of the five shield volcanoes that together form the islands of Hawaii. The oldest dated rock samples of Kilauea suggest that the rock formed here is around 23,000 years old. Other than being the most active volcano - with as many as 35 eruptions since 1952, Kilauea is also considered to be the most dangerous volcano in the United States by the United States Geological Survey (USGS).
Mauna Loa Shield Volcano
Mauna Loa boasts of being the largest active volcano of the world in terms of total surface area as well as volume. The oldest dated rock samples from Mauna Loa suggest that the rock here is around 200,000 years old. Even though the eruptions of this volcano are mostly non-explosive in nature, they do have the tendency to cause a great deal of destruction. Major eruptions of this volcano - which gutted down several villages in the periphery, were recorded in 1926 and 1950 respectively. The last of Mauna Loa eruptions occurred on 24th March, 1984, and continued till 15th April, 1984.
Hualalai Shield VolcanoA potentially active volcano in the Hawaiian archipelago - Hualalai is the third youngest of the five shield volcanoes which form the island of Hawaii. It is considered to be potentially active volcano owing to the fact that it has just erupted thrice in the last 1,000 years - which is in stark contrast of Kilauea and Mauna Loa which have erupted more than 100 times during the same period. Even though it has been calm for quite some time now, volcanologists are of the opinion that Hualalai will erupt once again within the period of next hundred years.
Haleakala Shield VolcanoAlso referred to as East Maui Volcano, Haleakala alone constitutes more than 75 percent of the Maui Island - the second largest island of the Hawaiian archipelago. This volcano has erupted several times over the period of last 10,000 years, of which as many as ten eruptions can be attributed to the last 1,000 years or so. Rock samples from Haleakala suggest that the rock here is around 1.1 million years old. It is the long eruptive history of Haleakala - along with some activity which has been seen over the last few years, that has made the volcanologists believe that it will erupt sometime in the future.
Loihi Submarine VolcanoIn contrast to the four active volcanoes that we have spoken about as of now, Loihi is an undersea active volcano which is located off the southeastern coast of Hawaii Islands. The newest volcano of the lot, it is around 3,000 ft below the sea level, which means it will take some more years to emerge out of the water and form a full-fledged island. Rock samples suggest that the age of rock in this region is somewhere around 400,000 years old. Loihi seamount last erupted in 1996, and has been considered relatively active since then.
Of these five volcanoes, Kilauea and Mauna Loa are located at the Hawaii Volcanoes National Park, which has become a renowned tourist attraction for its amazing landscape. This 505.36 sq mi park was declared an International Biosphere Reserve in 1980 taking a note of the rare species of flora and fauna found here. Eventually in 1987, the same was declared a UNESCO World Heritage Site which made it the only World Heritage Site in the state of Hawaii.