This Area graph example shows two groups of data sets plotted as Area plots in separate layers (i.e. panels). The two layers are stacked on top of one another with no vertical gap between them. The area plots within each layer are stacked on top of each other as well. This aspect of the Area plot is its default behavior. Stacking them allows you to see the overall affect of all variables in your experiment.
The data used to make this graph is the property of the US Geological Survey (USGS).