In that themes directory/css .... find the index.css file. In that file find the area that says
#upper_container (it should start at line 1326) in that section change the value from
height: 80px; to
height: auto; It should look like the following when done. I think that will fix what you want.
/* The logo and slogan. */
#upper_container {
line-height: 80px;
width: 100%;
height: auto;
padding: 0 2%;
}