The Weil-Petersson and Thurston symplectic forms

We consider the Weil-Petersson form on the Teichmüller space T(S) of a surface S of genus at least 2, and we compute it in terms of the shearing coordinates for T(S) associated to a geodesic lamination λ on S. In the corresponding expression, the Weil-Petersson form coincides with Thurston's intersection form on the space of transverse cocycles for λ.