We construct a hyperbolic 3-manifold M (with ∂M totally geodesic)
which contains no essential closed surfaces, but for any even integer g>0
there are infinitely many separating slopes r on ∂M so that M[r],
the 3-manifold obtained by attaching 2-handle to M along r, contains an
essential separating closed surface of genus g and is still hyperbolic. The
result contrasts sharply with those known finiteness results for the cases
g=0,1. Our 3-manifold M is the complement of a simple small knot in a
handlebody.Comment: 25 pages, 14 figure