Sedimentary rock forms when sediments are pressed and cemented together, or when minerals form from solutions. Magma forms when any type of rock is melted, a process driven by energy from Earth's interior. The plate motion that occurred near the Great Plains and Rocky Mountains uplifted igneous rock that formed underground.

When fragments are pressed and cemented together, the resulting rock is known as sedimentary rock. Sedimentary rocks are formed through a process called lithification, which involves the compaction and cementation of sediment particles over time. Examples of sedimentary rocks include sandstone, shale, limestone, and conglomerate.

Magma, on the other hand, is formed when molten rock material, typically containing a combination of minerals, gases, and dissolved solids, rises to the surface or remains underground. The process of magma formation is known as magmatism. Magma is primarily generated within the Earth's mantle, which is the layer beneath the crust.

The exact location where magma forms within the Earth's crust or mantle can vary. It typically occurs in areas where there is a significant amount of heat and melting of rock materials. Magma can form in subduction zones, where one tectonic plate is forced beneath another, leading to the melting of the subducted plate. Magma can also form at mid-ocean ridges, where tectonic plates are moving apart, creating space for the upwelling of molten material from the mantle.

Once magma is formed, it can either cool and solidify underground, forming intrusive igneous rocks like granite, or it can reach the Earth's surface through volcanic eruptions, resulting in extrusive igneous rocks like basalt. The specific location of magma formation and the subsequent rock types that form depend on various geological processes and tectonic settings.