Flatirons are steep and plain triangle-shape slopes that are cut off and drained by a system of channels and waterways. The term, flatiron, comes from a row of stand steam irons, that these slopes resemble to.

Flatirons mainly develop in anticline limbs, which in the case the dominant direction of channels is coincide with the tensional joints perpendicular to the anti-form axis. These slopes are resulted from many geological features such as folded structures, alternating incompetent and competent

 Layers, and differential erosion. In the thin to intermediate-thick beds consist of non-uniform alternative layers such as limestone with marl, or sandstone with shale, eroding the incompetent beds results to more prominent exposing competent layer and forming rock walls. In that sense that the slopes coincide with the bedding surface and make a vast plain surface. These slopes due to its unstable situation are subject to gravity slumping and mass movements, so gradually became narrow form their apex, till make a triangle-shape like an iron.