Spatter Vents


Spatter refers to blobs of lava thrown a little ways into the air (by expanding gases) that is still molten when it lands.


Spatter Vents

Spatter ramparts and spatter cones are the vent structures formed by this type of activity. Spatter ramparts are elongate along the trace of an eruptive fissure whereas spatter cones occur as discrete mounds. They range between 1 and 5 m high, are steep-sided, and are composed of agglutinated (stuck-together) spatter. They are steep-sided because the hot spatter blobs are able to stick to each other when they land, and don't flow or roll away.

Small spatter cones forming near Pu'u 'O'o on the east rift zone of Kilauea in July of 1985. Note that the ability of molten spatter to stick together allows the spatter cones to be steep and even vertical. The pahoehoe toes in the foreground are picking up pieces of scoria that cover the ground in this area, and via a "reverse caterpillar motion" are placing these pieces (the dark spots) on top of themselves - stratigraphy is being reversed.




The fountaining associated with the formation of spatter ramparts is usually less than 10 m high.



A small spatter cone on Kilauea erupting in 1992. Note the fluid nature of the individual blobs making up the cone, and their ability to form a steep structure. The glowing orifice from which the spatter is erupting is ~30 cm across. The profile of Pu'u 'O'o can be seen in the background.





At the end of the eruption, lava often drains back into the fissure, forming prominent drainback features. Even if nobody actually witnessed a particular eruption, if you find spatter ramparts or cones associated with it, you can say that the fountaining that formed the cone or rampart was not very high.



Spatter vents from the 1974 eruption of Kilauea along the upper SW rift zone. Note that the last thing that happened was the drain-back of lava into the fissure (red arrows). The higher areas on the left and right are spatter ramparts and are 1-2 m high.