What was likely covered by later lava flows on Mauna Loa?
Mauna Kea is one of five volcanoes  that form the island of Hawaii, the largest and youngest island of the Hawaiian–Emperor seamount chain. Of these five hotspot volcanoes, Mauna Kea is the fourth oldest and fourth most active. It began as a preshield volcano driven by the Hawaii hotspot around one million years ago, and became exceptionally active during its shield stage until 500,000 years ago. Mauna Kea entered its quieter post-shield stage 250,000 to 200,000 years ago, and is currently dormant. Mauna Kea does not have a visible summit caldera, but contains a number of small cinder and pumice cones near its summit. A former summit caldera may have been filled and buried by later summit eruption deposits.
Mauna Kea is over 32,000 km3 (7,680 cu mi) in volume, so massive that it and its neighbor, Mauna Loa, depress the ocean crust beneath it by 6 km (4 mi).
Mauna Kea is the only Hawaiian volcano with distinct evidence of glaciation. Similar deposits probably existed on Mauna Loa, but have been covered by later lava flows. Despite Hawaii's tropical location, during several past ice ages a drop of a degree in temperature allowed snow to remain at the volcano's summit through summer, triggering the formation of an ice cap. There are three episodes of glaciation that have been recorded from the last 180,000 years: the Pōhakuloa (180–130 ka), Wāihu (80–60 ka) and Mākanaka (40–13 ka) series. These have extensively sculpted the summit, depositing moraines and a circular ring of till and gravel along the volcano's upper flanks. Subglacial eruptions built cinder cones during the Mākanaka glaciation, most of which were heavily gouged by glacial action. The most recent cones were built between 9000 and 4500 years ago, atop the glacial deposits, although one study indicates that the last eruption may have been around 3600 years ago.At their maximum extent, the glaciers extended from the summit down to between 3,200 and 3,800 m (10,500 and 12,500 ft) of elevation. A small body of permafrost, less than 25 m (80 ft) across, was found at the summit of Mauna Kea before 1974, and may still be present. Small gullies etch the summit, formed by rain- and snow-fed streams that flow only during winter melt and rain showers.
glaciation