  We study elliptic fibrations by analyzing suitable deformations of the
fibrations and vanishing cycles. We introduce geometric string junctions and
describe some of their properties. We show how the structure of the geometric
string junctions is naturally related to the Lie algebra structures of the
associated singularities. One application in physics is in F-theory, where our
novel approach connecting deformations and Lie algebras describes the structure
of generalized type IIB seven-branes and string junction states which end on
them.
