NPS Illustration Words You May Hear at Craters Of The MoonA'aA type of lava flow having a rough surface with sharp, spiny projections. A'a means "hard on the feet" in Hawaiian. Active VolcanoA volcano that is erupting or has erupted in recorded history. BasaltA fine grained, dark-colored rock rich in iron and magnesium and relatively poor in silica; the common lava of Hawaii and Craters of the Moon. Blue Dragon LavaA type of pahoehoe flow with a bright blue sheen on its surface. The blue color is produced by a thin veneer of crude "glass" that forms on the flow's surface. CinderSmall, very porous fragments of frothy rock ejected from a volcano. Cinder ConeA steep sided hill formed by the accumulation of cinders expelled from a volcanic vent. CraterA bowl- or funnel-shaped depression, generally in the top of a volcanic cone. The vent for volcanic material. Dormant VolcanoA volcano that has not erupted in a long time but may erupt again in the future. Extinct VolcanoA volcano that has not erupted in tens of thousands of years and is unlikely to erupt again. FissureA crack in the earth's surface from which volcanic material may erupt. LavaMagma which has reached the earth's surface. Lava TubeA hollow tunnel formed when the outer part of a flow has hardened and the inner, still molten material subsequently drains out. MagmaMolten rock beneath the earth's surface. Mantle Plume TheoryA theory which states that localized hot spots deep in the earth's mantle periodically release "plumes" of molten material which slowly rise to the surface. Hot spots are fixed and do not move. However, the crust of the earth slowly moves across them, generating volcanic activity. PahoehoeA type of lava flow with a smooth, billowy surface. Rafted Block (Monolith)A large block of old cinder-cone walls which has been transported by a lava flow to a new location. Shield VolcanoA volcano with a broad, low profile, the shape of a flattened dome, built up by repeated flows of very fluid lava. Common on the Snake River Plain, but not at Craters of the Moon. SpatterA thick, pasty clot of lava. Spatter ConeA low, steep-sided cone built of blobs of sticky lava that have piled up around a vent. Tree MoldAn impression left in the lava of the charred surface of a tree. VentA channel in the earth's surface from which volcanic material erupts. VolcanoA vent in the surface of the earth through which magma, gases and ash erupt. Volcanic Rift ZoneAn array of volcanic fissures along which repeated eruptions occur.
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Last updated: November 20, 2021