Rocks formed of any of the materials that accumulate at Earth's solid surface at ambient temperatures, regardless of their consistency. Together with lava flows, sedimentary rocks form a cover of stratified material, known as the stratisphere, that, lying on igneous and metamorphic rocks, covers over two-thirds of the lands and nearly all of the ocean floor. Generally measured in hundreds to a few thousand meters, it locally reaches up to 15 km (9 mi) in thickness.