Halliday & Matthiessen (2014: 272):
In the case of ‘time phase’, in particular ‘inceptive’, the tense may be like that of ‘material’ clauses rather than like that of ‘relational’ ones; … That is, coming into being is construed on the same model as activities as far as time is concerned; but it is still construed as a configuration of being, with Carrier (the scope of European trade) + Process (was becoming) + Attribute (oceanic and worldwide). If the Attribute is an ‘entity’ rather than a ‘quality’, the nominal group realising it may be marked by the preposition into; alongside ‘become’ + nominal group, we thus have ‘turn’, ‘grow’ + into + nominal group…