Adding relatively minor factors like crystals, water, ice, and metal can drastically affect how lava moves, cools, and creates formations. When lava meets water, for example, the results can be explosive. Understanding these interactions is vital for keeping communities who reside in hazardous zones — like the volcanic and oceanic Hawaii — safe from lava flows. Plus, it can tell us about how volcanoes might work on other planetary bodies. Here’s how lava reacts to four different environmental factors.