Conventional flooring or crawlspace area issues are most commonly linked to over-spanned beams, the need for pier adjustment, and moisture related movements. Do keep in mind, there could be items not discussed here, that could be playing a role in your issues. However, that is a blog for another day.
Expansive soil, also know as a fatty clay, is a highly plastic soil characterized with swelling and contracting across changing soil moisture content. In Northeast Arkansas and Southeast Missouri, foundation issues are often times attributed to these type of soil movements.