GEOLOGY101 question help?

Most basaltic intrusives rise along fractures in the crust, related to uplift, stretching of the crust and rifting. This is fairly typical in areas overlying a mantle plume, which may be a precursor to continental splitting and the formation of a spreading ridge. The rifting allows decompression melting in the mantle, and the magmas rise along the fractures as s, and spread laterally between the crustal layers to form sills, or erupt at the surface as basalts. Palisades is a sill, and the Watchung Basalts are surface flows.