Mauna Kea Volcano, Hawai'i

Mauna Kea on the Big Island of Hawai'i i, is over 32,000 ft from its base on the ocean floor to its summit,

making it the worlds tallest mountain

The Mauna Kea summit is home to the Mauna Kea Observatory, 

which is the worlds largest astronomical observatory 

Mauna Kea's last eruption was approximately 4,600 years ago, making the volcano dormant

However the neighboring volcano of Mauna Loa, also on the Big Island is currently active