Near the edges of the lunar mare are dark layers of material that cover many thousands of square kilometers. They contain many small spheres of orange and black glass that probably formed from small drops of lava that cooled very quickly. Such droplets are believed to be ejecta from lava fountain eruptions that were larger than those on Earth. The largest known deposits occur at Taurus–Littrow, Sinus Aestuum, Sulpicius Gallus, Rima Bode, Mare Vaporum, Mare Humorum and the Aristarchus plateau in the central near side of the Moon.
