A complex sentence is a sentence consisting of an independent clause and a subordinating clause. Or, to put it more simply, complex sentences involve more than just a straightforward noun + verb. Complex sentences include extra phrases added to a base sentence, but which cannot stand alone as a sentence. For example:
Published 4:00 am, Thursday, January 9, 1997. 1997-01-09 04:00:00 PDT Yosemite National Park -- Yosemite Valley is slowly drying out after what park rangers are calling the worst flood here in recorded history, leaving behind hundreds of upturned tent-cabins and acres of wrecked camping sites.
On October 21, 2007, wildfires broke out across San Diego county and other parts of Southern California. By October 23, the Rice Canyon Fire had crossed Interstate 15 and spread into the east area of Fallbrook along Reche Road, prompting a mandatory evacuation order for all residents.