Ceraunius Fossae is an area of intensely fractured terrain in the northern Tharsis region of Mars. It lies directly south of the large volcano Alba Mons and consists of ancient highland crust that has been deformed by numerous parallel faults and tension cracks. In places, younger lava flows cover the fractured terrain, dividing it into several large patches or islands. The faults are mainly narrow, north-south oriented graben. (wikipedia entry)
A fossa is a long, narrow, shallow depression. On Mars they are named after the nearest named albedo feature on the Schiaparelli or Antoniadi maps.