Several causes for the faults have been suggested, including regional stresses created by the Tharsis bulge, volcanic dikes, and crustal loading by Alba Mons itself. The faults of Ceraunius and Tantalus Fossae are roughly radial to the center of Tharsis and are likely a crustal response to the sagging weight of the Tharsis bulge. The faults ringing Alba's summit region may be due to a combination of loading from the Alba edifice and magma uplift or underplating from the underlying mantle. Some of the fractures are likely the surface expression of gigantic dike swarms radial to Tharsis. An image from High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) shows a line of rimless pit craters in Cyane Fossae on the Alba's western flank (pictured right). The pits likely formed by the collapse of surface materials into open fractures created as magma intruded the subsurface rock to form dikes.