9.0 Setting layer attributes

Now that we have created a new floating layer to represent the Weardale granite, lets assign it a bulk density so that we can model its gravity effect. We will also assign a background density used to represent the surrounding basement rock. The difference between these two values represents the density contrast used for calculating the gravity effect of the granite.

Kimbell et al., (2011) [6] suggest that 2780 \(kg\) \(m^{-3}\) is a reasonable bulk density for the Lower Palaeozoic rocks of the Alston Block, within which the Weardale granite was emplaced. While measurements made on rock fragments of the granite itself, recovered from the Rookhope borehole, suggest its bulk density is close to 2630 \(kg\) \(m^{-3}\) (Bott, 1967) [2].

Lets use these values to begin our modelling. To set the bulk density of the granite:

First, select the ``Weardale`` layer under the menu by double clicking on its name. We can now set the bulk density
and reference density values under the ``Layer Attributes`` top left control panel. Once you have assigned the
values click ``Set layer attributes`` to make the changes.

Important

Layer densities are entered using \(g\) \(cm^{-3}\) so for the reference and bulk densities we will use \(2.78\) and \(2.63\) respectively.