The Big Island of Hawaii is entirely formed by volcanic activity. There are five separate volcanoes which have, over the past million-or-so years, combined to form the island. Of these five volcanoes, one is considered to be extinct and in transition between its post shield and erosional stage; one is considered dormant; and the three remaining volcanoes are categorized as active.
Hualalai, on the western side of the Big Island of Hawaii, is the third youngest and third-most active volcano on the island. The 1700's were years of significant volcanic activity with six different vents erupting lava, two of which produced lava flows that reached the sea. The Kona International Airport is built atop the larger of these two flows.
Despite much building of businesses, homes, and roads on the slopes and flows of Hualalai, it is anticipated that the volcano will again erupt within the next 100 years.
Once believed to be an offshoot of its large neighbor, Mauna Loa, scientists now have concluded that Kilauea is actually a separate volcano with its own magma-plumbing system, extending to the surface from more than 60 km deep in the earth.
Kilauea Volcano, on the south-east side of the Big Island, is one of the most active on earth. Its current eruption (known as the Puʻu ʻOʻo-Kupaianaha eruption) started in Jan. 1983 and continues to this day. During this eruption over 500 acres have been added to the Big Island's shoreline.
In the course of the eruption, lava flows have destroyed a famous 700-year-old Hawaiian temple, (Wahaʻula heiau), overrun many houses including a housing subdivision known as Royal Gardens, permanently blocked several highways, and even destroyed the old National Park Visitor Center.
There are no indications that the current eruption will come to an end anytime soon.
Kohala Volcano is the oldest of volcanoes that form the Big Island of Hawaii, having emerged from the sea more than 500,000 years ago. Over 200,000 years ago it is believed that an enormous landslide removed the volcano's northeast flank forming the amazing sea cliffs that mark this part of the island. The height of the summit has reduced over time by over 1,000 meters.
Over the centuries, Kohala has continued to sink and lava flows from its two much larger neighbors, Mauna Kea and Mauna Loa have buried the southern part of the volcano. Kohala is today considered to be an extinct volcano.
Mauna Kea, which in Hawaiian means "White Mountain", is the tallest of Hawaii's volcanoes and in fact the tallest mountain in the world if measured from the floor of the ocean to its summit. It received its name, no doubt, because snow is frequently seen on the summit even from the distant shores. The snow occasionally reaches several feet deep.
The summit of Mauna Kea is home to numerous observatories. It is considered one of the best places to view the heavens from the surface of the planet. Several tour companies offer evening trips to the summit of Mauna Kea to view the sunset and then view the stars.
The Onizuka Center for International Astronomy, located near the summit, is an excellent place to learn more about the history of the mountain and the work done by the observatories.
Mauna Kea is categorized as a dormant volcano, having last erupted about 4,500 years ago. However, Mauna Kea is likely to erupt again someday. The periods between eruptions of Mauna Kea are long compared to those of the active volcanoes.
Mauna Loa is the second youngest and second-most active volcano on the Big Island. It is also the largest volcano on the face of the earth. Extending to the northwest near Waikoloa, to the entire southwest part of the island and to the east near Hilo, Mauna Loa remains an extremely dangerous volcano which can erupt in many different directions.
Historically, Mauna Loa has erupted at least once in every decade of recorded Hawaiian history. It has, however, since 1949 slowed its pace with eruptions in 1950, 1975 and 1984. Scientists and residents of the Big Island constantly monitor Mauna Loa in anticipation of its next eruption.