Complex sentence: The Gila Mountains of Yuma County are a northwest-southeast trending mountain system, about 26 miles long; the fault-blocked mountain range is attached on the south to the Tinajas Altas Mountains which continue southeast into Sonora, Mexico for another 30 miles.
Split into simpler sentences: The Gila Mountains of Yuma County are a northwest-southeast trending mountain system. The fault-blocked mountain range is attached on the south to the Tinajas Altas Mountains which continue southeast into Sonora, Mexico for another 30 miles.