 A paved trail less than 1 / 4 mile ( 400 m ) long at North Crater Flow ( photo ) crosses the North Crater Lava Flow , which formed about 2200 years ago , making it one of the youngest lava flows on the Craters of the Moon Lava Field . This lava is named for the purplish @-@ blue tint that tiny pieces of obsidian ( volcanic glass ) on its surface exhibit . Good examples of pahoehoe ( ropey ) , aa ( jagged ) , and some block lava are readily visible along with large rafted crater wall fragments . The rafted crater wall fragments seen on the flow were once part of this cinder cone but were torn away when the volcano 's lava @-@ filled crater was breached . A 1 @.@ 8 @-@ mile @-@ long trail ( 2 @.@ 9 km ) includes the 1 / 2 mile ( 800 m ) overlook trail but continues on through the crater and to the Big Craters / Spatter Cones parking lot . 
