Mauna Kea
Mauna Kea ( or , ) is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii. Most of the mountain is under water, and when measured from its oceanic base, Mauna Kea is the tallest mountain in the world measuring over . Mauna Kea is about a million years old, and has thus passed the most active shield stage of life hundreds of thousands of years ago. In its current post-shield state, its lava is more viscous, resulting in a steeper profile. Late volcanism has also given it a much rougher appearance than its neighboring volcanoes due to construction of cinder cones, decentralization of its rift zones, glaciation on its peak, and weathering by the prevailing trade winds. Mauna Kea last erupted 6,000 to 4,000 years ago and is now considered dormant. The peak is only about higher than its more massive neighbor, Mauna Loa.
Hilina Slump
The Hawaiian Islands are volcanoes, the newest part of the Hawaiian-Emperor seamount chain, created by eruption of magma from the Hawaii hotspot. As the Pacific plate, moving to the northwest, carries the existing volcanoes away from the hotspot, new volcanoes form at the southeastern end. The newest and largest island is the Big Island of Hawaii, formed by the merger of seven volcanoes. The largest, at the trailing edge of the island, is Mauna Loa Volcano, and on its seaward flank is the younger Kīlauea, with the still submerged Lōʻihi Seamount just off-shore.