Pakistan collapsed to 100-7 at tea against Mitchell Starc's searing pace in reply to Australia's mammoth 556-9 declared on the third day of the second Test in Karachi on Monday.
Starc picked up 3-24 in a superb spell of left-arm fast bowling which included the wickets of Azhar Ali and Fawad Alam off successive deliveries.
Pakistan lost six wickets in the middle session for only 62 runs and still needs 257 runs to avoid the follow-on.
Home captain Babar Azam was unbeaten on 29 with Hasan Ali yet to score. Babar survived a close lbw referral against Pat Cummins before he had scored.
Australia made early inroads when leg-spinner Mitchell Swepson ran out Abdullah Shafique before lunch.
Nathan Lyon then ignited the collapse immediately after lunch when Imam-ul-Haq played a terrible shot and holed out to mid-on before Starc ran through the middle order.
Azhar played away from his body and Cameron Green took an edge in the slips while Alam was out plumb lbw following a vicious yorker. Rizwan Ali was beaten off the hat-trick ball before eventually succumbing to Cummins.
Much like the first test, off-spinner Lyon came into the attack early and the occasional delivery by him and debutant Swepson turned off a slow wicket.
Earlier, Cummins (34 not out) helped add a rapid 51 runs after Australia resumed its first innings on 505-8.
Despite losing Starc (28) to the second ball, which gave Shaheen Afridi his first wicket, Cummins and Swepson (15 not out) scored freely against spinners Sajid Khan and Nauman Ali.
Cummins lofted two sixes off left-armer Nauman, who ended up with 1-134 from 48 overs. Sajid took 2-167 from 57 overs.