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.
Arsia Mons
The volcano is in diameter, almost high (more than higher than the surrounding plains), and the summit caldera is 110 km (72 miles) wide. It experiences atmospheric pressure lower than 107 pascals at the summit. Excluding Olympus Mons, it is the largest known volcano in terms of volume. Arsia Mons has 30 times the volume of Mauna Loa in Hawaii, the largest volcano on the Earth.