Enlarge / Lava pouring from a fissure in the Leilani Estates neighborhood. (credit: USGS)

Recent events in Hawaii have been producing some remarkable images. But if you’re not a geologist—or resident of Hawaii—you might be wondering what the heck is going on. We’re here to help: while lava spewing from back yards in a subdivision seems wild, it’s not really surprising.

Why is Kīlauea an active volcano in the first place?

The Hawaiian chain of islands (there are also seamounts that no longer reach above sea level) is the result of a “hotspot” in the Earth’s mantle. Hotspots in the Earth’s interior are areas of rising hot rock that can turn to liquid hot magma near the Earth’s surface. These hotspots are basically stationary, while tectonic plates slowly slide around on the surface. That means a hotspot will punch a line of eruptions through the plate a bit like a sewing machine.

The Big Island of Hawaii is the youngest in the chain, still straddling the hotspot that fuels its volcanoes—there are five individual volcanoes that make up the island. Of those five, Kīlauea is the youngest, comprising the southeastern edge of the island. Kīlauea’s summit is home to a collapsed crater called Halemaʻumaʻu Crater. In 2008, a new vent appeared in the floor of the crater, which has hosted a lake of roiling lava ever since.