Complex sentence: Mathematical analysis shows that this process operates on volcanoes at a wide range of scales and that spreading of a large volcano is mechanically identical to the larger-scale rifting that occurs at mid-ocean ridges (divergent plate boundaries).
Split into simpler sentences: Mathematical analysis shows that this process operates on volcanoes at a wide range of scales. Basal spreading of a large volcano is mechanically identical to the larger-scale rifting that occurs at mid-ocean ridges (divergent plate boundaries).