A lake among tree branches and rocks. Basalt is a common extrusive igneous volcanic rock formed from the rapid cooling of basaltic lava exposed at. Basalt describes the formation in a series of lavas flows. This forms dissolved gases come out of solution and form bubbles magma decompresses as it reaches, yet are trapped as erupted hardens grey black brown before can escape. Spongy structure porous crushed and broken stones frozen gibber reg regs geology geological clinkers scoria cinder cone hill pyroclastic material rocks area solidified shield volcano lava dome andesitic rhyolite field Hovsgol Khovsgol Baikal Khuvsgul Mongolian Siberian Russian Russia Siberia Mongolia mere lough wetland pond water UHD 3840X2160.