Complex sentence: The first collapse faced by the men consisted of more than 100 long tons of debris, while another fall had been over 300 feet (91.5 metres) long and 30 to 40 feet (10--12 metres) high.
Split into simpler sentences: The first collapse faced by the men consisted of more than 100 long tons of debris. Another fall had been over 300 feet (91.5 metres) long and 30 to 40 feet (10--12 metres) high.