What is the difference between An asteroid slammed into North America, an event that caused plant and animal extinction,which marks the end of the geologic era known as the Cretaceous Period and An asteroid slammed into North America, an event that caused plant and animal extinction that marks the end of the geologic era known as the Cretaceous Period ?

7 May 2017

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What is the difference between An asteroid slammed into North America, an event that caused plant and animal extinction,which marks the end of the geologic era known as the Cretaceous Period and An asteroid slammed into North America, an event that caused plant and animal extinction that marks the end of the geologic era known as the Cretaceous Period ?
Feel free to just provide example sentences.
The first one is told to be a false expression. My question is why can I use "which" to represent the event precedes in the sentence

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