Ternary Diagrams Display 3 Variables on the Same Plot

Ternary diagrams are used to show the relations between three variables on a two dimensional plane. Geologists commonly use ternary diagrams to show how different chemicals or rocks will interact.

Ternary diagrams show one variable on each of three axes, and can also show intermediate points along the axes. Lines connecting these intermediate points can show additional relationships between the constituents, such as zones of constant temperature or pressure.

In the example below, five variables are represented. The three ternary axes show the distribution of TiO2, FeO, and 1/3 Fe2O3. As the temperature and pressure change, these components combine in different ratios to create a variety of intermediate rock types. For example, as temperature increases, the Fe2O3 content increases. This is shown on the temperature axis (lower slanting axis). The horizontal axis in the center of the diagram shows how changes in pressure at constant TiO2 content will affect the ratio between FeO and Fe2O3. The resulting graph shows the possible zones of reaction.

This graph was created by overlaying a line/symbol graph onto an existing ternary diagram and hiding the line graph’s axes. The ability to create multiple graph types on the same page combined with the ability to hide any attribute of the graph allows you to create stunning graphics in minutes with Grapher 3.

The ternary diagram above is used for plotting rock compositions with respect to temperature and pressure.

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