What were the advantages and disadvantages of popular sovereignty?

 Majority Rule. James Madison warned against this in his Federalist #10. This is along the same principle the United States has the Electoral College for Presidential elections, the Filibuster rule in the Senate, etc. By building a "larger consensus," more people are involved with decision-making, and a minority is not oppressed by a majority. Popular Sovereignty in terms of the Kansas-Nebraska Act led to Slave and Free-Soilers rushing into settling the territories and ultimately would lead to a violence, one that arguably was the spark of the Civil War.

Afine-grained igneous rock forms as a result of slow cooling.