Showbiz
Rex Features
The 24-year-old actor joins hip-hop star Lupe Fiasco, Jessica Biel, Elizabeth Gore and Australian soap actress Isabel Lucas for the Summit On The Summit expedition beginning on Thursday.
The Milk star told The AP that the climb combines "an epic adventure with an educational process on the global water crisis".
The journey is reportedly aiming to use star power to bring awareness to the need for clean water around the world. Fans can follow the climb online and donate as little as $1 to provide clean water to those who need it.
Hirsch added that he is ready for the 19,000ft challenge, saying: "Put this on the books: I'm making it to the top."
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