the slow-moving, effusive eruptions typical of shield volcanism, known as Hawaiian eruptions. These eruptions, the least explosive of volcanic events, are characterized by the effusive emission of highly fluid basaltic lavas with low gaseous content. These lavas travel a far greater distance than those of other eruptive types before solidifying, forming extremely wide but relatively thin magmatic sheets often less than thick. Low volumes of such lavas layered over long periods of time are what slowly constructs the characteristically low, broad profile of a mature shield volcano. Also unlike other eruptive types, Hawaiian eruptions often occur at decentralized fissure vents, beginning with large "curtains of fire" that quickly die down and concentrate at specific locations on the volcano's rift zones. Central-vent eruptions, meanwhile, often take the form of large lava fountains (both continuous and sporadic), which can reach heights of hundreds of meters or more. The particles from lava fountains usually cool in the air before hitting the ground, resulting in the accumulation of cindery scoria fragments; however, when the air is especially thick with pyroclasts, they cannot cool off fast enough because of the surrounding heat, and hit the ground still hot, accumulating into spatter cones. If eruptive rates are high enough, they may even form splatter-fed lava flows. Hawaiian eruptions are often extremely long-lived; Puʻu ʻŌʻō, a cinder cone of Kīlauea, erupted continuously from January 3, 1983, until April 2018. Flows from Hawaiian eruptions can be divided into two types by their structural characteristics: pāhoehoe lava which is relatively smooth and flows with a ropey texture, and ʻaʻā flows which are denser, more viscous (and thus slower moving) and blockier. These lava flows can be anywhere between thick. Aā lava flows move through pressure— the partially solidified front of the flow steepens because of the mass of flowing lava behind it until it breaks off, after which the general mass behind it moves forward. Though the top of the flow quickly cools down, the molten underbelly of the flow is buffered by the solidifying rock above it, and by this mechanism, aā flows can sustain movement for long periods of time. Pāhoehoe flows, in contrast, move in more conventional sheets, or by the advancement of lava "toes" in snaking lava columns. Increasing viscosity on the part of the lava or shear stress on the part of local topography can morph a pāhoehoe flow into an ʻaʻā one, but