Sedimentary rocks are formed when sediments, which are bits of rock, minerals, and organic matter, are compacted and cemented together over time. The sediments can be deposited by wind, water, ice, or gravity. When the sediments are buried deep underground, they are subjected to heat and pressure, which causes them to become cemented together into a solid rock.

The mountain in the desert is made from remains of ancient ocean organisms, which means that the sediments that formed the rock were deposited in an ocean environment. The sediments were likely deposited by waves or currents, and then buried deep underground over time. The heat and pressure of the overlying rock caused the sediments to become cemented together into a solid rock.

The type of sedimentary rock that makes up the mountain will depend on the composition of the sediments that were deposited. If the sediments were mostly sand, then the rock will be sandstone. If the sediments were mostly mud, then the rock will be mudstone. If the sediments were a mixture of sand, mud, and gravel, then the rock will be conglomerate.