The Hawaiian Islands are the tops of volcanoes that grew from the ocean floor. Haleakala National Park is located on one of the largest volcanoes in the world.

Haleakala had an ancient summit, which towered about 15,000 feet (4500 m) above sea level.

Haleakala “crater” is actually a valley carved by streams and glaciers during the erosional stage of the volcano. The “crater” is 3,000 ft (900 m) deep, 7-1/2 miles (12 km) long, and 2-1/2 miles (4km) wide.

Haleakala is in the “renewed volcanism” stage. The renewed activity partially filled the eroded “crater” with lava flows and small hills called cinder cones. Each cones is a vent from a separate eruption.

Haleakala is classified by scientists as an active volcano. It erupted at least 6 times in the last 1,000 years, most recently in about 1790 near Makena.

Haleakala summit is 10,023 feet (3055 m) above sea level, but the volcano is actually about 28,000 feet (8500 m) high measuring from the ocean floor. Only about 5% of the volume of the volcano is above the sea.

Haleakala is mostly made of a lava rock called basalt, which contains about 61% silicon and aluminum oxides, and 21% iron and magnesium oxides. This composition results in the dark and red colors of the rocks.