The giant appears asleep now, its crater filled with a frozen lake of rock…
Appearances can be deceiving.
If you train a thermal camera on that 600- to 750-year-old crater just before sunrise, after a long night of chilling at almost 13,700 feet, you will see the rocks radiating heat.
The giant is still awake.
One of the most active volcanoes on Earth, Mauna Loa is just taking a bit of a break right now. However, its inner activity continues. Per the HVO,
Re-inflation of Mauna Loa’s shallow magma storage reservoirs started immediately following the most recent eruption in 1984, then turned to deflation for almost a decade. In mid-2002, inflation started again, just after a brief swarm of deep long-period (LP) earthquakes. A more intense swarm of several thousand deep Long Period (LP) earthquakes occurred in late 2004, immediately preceding a dramatic increase in inflation rate. Inflation slowed again in 2006, ceased altogether in late 2009, and resumed slowly in late 2010.
When it’s ready, this Decade Volcano will belch forth fire again.
Mauna Loa’s lava is low in silica, unlike the stuff frequently erupted by, say, Mount St. Helens, and so it mostly just flows along the ground instead of exploding. This is why there haven’t been any fatalities in recent eruptions.
However, Mauna Loa did destroy some villages in the 20th century, and part of the city of Hilo sits on its 19th century lava flows.