self.total_crust = tf.transpose(crust)

        total_crust = tf.zeros((self.vertices.shape[0],), dtype=tf.float32)
        for k, v in self.crust_layers.items():
             if k != 'age':
                 total_crust += v
        self.crust_layers['total'] = total_crust

    def total_crust_mass(self):
        return tf.math.reduce_sum(self.total_crust, axis=1)