Complex sentence: Around 1.9 billion years ago, the rift system at the Jiao-Liao-Ji Belt switched to a subductional and collisional system, which then combined the Longgang Block and the Langrim Block, forming the Eastern Block.
Split into simpler sentences: Around 1.9 billion years ago, the rift system at the Jiao-Liao-Ji Belt switched to a subductional and collisional system. The Longgang Block and the Langrim Block then combined, forming the Eastern Block.