There are many Genre (text) e.g. description that include a method of teaching based on Genre for Indonesia.
Description purpose is to explain why things are as they are, and how they are formed/made. It explains the stages of the process.Textual factors are subject matter (field) which is the information of natural phenomena and the processes involved.
Roles and relationships between writer and reader are Tenor which writer as an authority and , to unknown readers.
The Medium or sources can be took from Text books for Science and Geography, encyclopedias, geographical/science magazines.
There is an example of Description, if you interest to read more click FREE DOWNLOADTag Kinds of Genre