It preserved a 100% start to the defence of their Women's Rugby World Cup title, topping pool C in the process.
The Black Ferns scored six tries in front of a sell-out 30,000 crowd, going 12-0 ahead after 20 minutes, as Stacey Waaka sped over in the 15th minute before prop forward Chryss Viliko powered over five minutes later from close range.
The 18-year-old Sorensen-McGee jinked past two defenders to score the first of her three tries to put New Zealand 19-0 up at the break, before showing another impressive turn of speed in the 58th minute to go over for the Kiwis' fourth try.
New Zealand, who won the last World Cup on home soil four years ago, also had the opportunity to show their defensive qualities, which will come in handy in the knockout stages, as they tigerishly kept Ireland at bay in the latter stages of the game, thwarting efforts at a comeback.
Sorensen-McGee then ran past a tiring Irish defence to complete her hat-trick with a minute to go and straight from the kick-off she was part of a sweeping move downfield that Maia Joseph finished off.
The Black Ferns will now play South Africa in their quarterfinal, beginning at midnight on Sunday morning.
They will take on Ireland at Sandy Park in Exeter next Monday morning, while New Zealand will kick off the quarterfinals at the same venue on Saturday against South Africa.
In the other quarterfinals, second ranked Canada take on Australia in Bristol on Sunday at 3am, followed the next day by hosts England against Scotland.
Japan came from behind to beat Spain 29-21 earlier this morning in York to finish third in pool C but both teams had already been eliminated.
Italy's Vittoria Ostuni Minuzzi got a hat-trick of tries as her side proved much too strong for World Cup newcomers Brazil, winning 64-3 at Northampton to claim third spot in pool D.
