First, preexisting rocks must weather/erode, forming the sediment that will eventually form the sedimentary rock. Then, that sediment must settle someplace, and over a long period of time, pressure begins to build. This causes the sediments to become compacted. After a long period of time (and a lot of pressure), the sediments cement together and form a sedimentary rock. In a nutshell, sedimentary rocks form through compaction, cementation, and eventually... lithification.
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A stationary front is the least likely to be associated with rainfall.
Volcanic eruptions may occur in both locations, as the movement can cause the tectonic plates to allow magma through.
The process is called diffusion
