HaleakalÄ is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. The tallest peak of HaleakalÄ ("House of the Sun") is PuÊ»u Ê»UlaÊ»ula (3055m). From the summit one looks down into a massive depression some 11.25 km across, 3.2 km wide and nearly 800 m deep.