  We study the evolution and scaling of the entanglement entropy after two
types of quenches for a 2+1 field theory, using holographic techniques. We
study a thermal quench, dual to the addition of a shell of uncharged matter to
four dimensional Anti-de Sitter (AdS_4) spacetime, and study the subsequent
formation of a Schwarzschild black hole. We also study an electromagnetic
quench, dual to the addition of a shell of charged sources to AdS_4, following
the subsequent formation of an extremal dyonic black hole. In these backgrounds
we consider the entanglement entropy of two types of geometries, the infinite
strip and the round disc, and find distinct behavior for each. Some of our
findings naturally supply results analogous to observations made in the
literature for lower dimensions, but we also uncover several new phenomena,
such as (in some cases) a discontinuity in the time derivative of the
entanglement entropy as it nears saturation, and for the electromagnetic
quench, a logarithmic growth in the entanglement entropy with time for both the
disc and strip, before settling to saturation.
