 Lopoliths are believed to have a more mafic, and therefore less viscous, source.Lopoliths tend to be larger than laccoliths, and are believed to get their lenticular shape from the weight of the intruding magma compressing the underlying country rock, or the shape comes from the evacuation of a magma chamber below the intruding magma, causing the country rock to collapse and creating a basin.Some of these terms might be outdated, and not accurately describe the shape of a pluton but they are still commonly used.