2005 California Government Code Sections 25020-25022 Article 2. Chairman

25020.  The members of the board of supervisors shall elect a
chairman, who shall preside at all meetings of the board.  If he is
absent or unable to act, the members present shall select one of
their number to act as chairman temporarily by an order entered on
the records of the board.
25020.1.  Instead of selecting a temporary chairman whenever the
chairman is absent or unable to act, the members of the board of
supervisors may elect a vice chairman who shall preside at all
meetings of the board when the chairman is absent or unable to act.
25021.  The chairman of the board shall perform such duties as are
prescribed by law or by the board.
25022.  In any emergency affecting the interest of the county or
when any defalcation or official misconduct comes to his knowledge,
the chairman shall forthwith call a special meeting of the board to
consider the matter if the board is not then in session.