Halliday & Matthiessen (2014: 481):
The combination of enhancement with hypotaxis gives what are known in traditional formal grammar as ‘adverbial clauses’. As with parataxis, these are clauses of time, place, manner, cause, and condition. Typically, hypotactically enhancing chains are limited to two clauses, with one clause (or sub-complex) qualifying another clause (or sub-complex);