8.0 Creating a model layer

Now we have loaded our observed anomaly data into the model environment, we are ready to start constructing our model.

To add a new layer to the model navigate to the ‘Layers’ menu and select ``New Layer``:

Layers -> New Layer

Alternatively, use the keyboard shortcut, n key.

You will be prompted with the option of adding a ``New fixed layer`` or a ``New floating layer``.

Floating layers:

Floating layers are polygons with all nodes defined by the user. This layer type is useful for modelling features that will be full contained within the model profile, for example, a narrow salt dome or volcanic dyke.

Fixed layers:

Fixed layers span the entire width of the model and are useful for modelling features such as sedimentary basin strata that will span the entire model profile width. Fixed layers have fixed boundary nodes (at the edge of the model profile) that can only be moved vertically along the model edges.

Note

Fixed layers are automatically ‘padded’ horizontally from the boundary nodes by an additional 400 km in order to avoid edge effects.

Lets chose to create a new floating layer, which we will use to represent the Weardale granite.

After selecting to create a floating layer your next four mouse clicks will define the initial position of the first four nodes for the new layer. Note that these nodes must be input in anti-clockwise order to ensure layers field effects are calculated with the correct sign. Besides the ordering of the nodes, there actual positions of the nodes are not particularly important, as then can be easily modified once the layer has been created.

We can rename the layer from its default name of layer 1 by right clicking its name under the Layers menu on the middle left Controls panel and selecting Rename layer. Lets rename the layer Weardale.