Reason why Kasparov resigned in the "Enrage the Beast" game [White "Garry Kasparov"]
    [Black " Vassily Ivanchuk"]
[fen ""]
[StartPly "62"]

1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. e5 b6 5. a3 Bf8 6. Nf3 Ne7 7. h4 h6 8. h5 a5 9. Bb5+ c6 10. Ba4 Nd7 11. Ne2 b5 12. Bb3 c5 13. c3 Nc6 14. O-O Qc7 15. Re1 c4 16. Bc2 Nb6 17. Bf4 Be7 18. Bg3 Rb8 19. Nh2 Qd8 20. Ng4 b4 21. axb4 axb4 22. cxb4 Nxb4 23. Bb1 Bd7 24. b3 Ra8 25. Rxa8 Qxa8 26. bxc4 Nxc4 27. Nc1 Ba4 28. Qe2 Qa7 29. Ne3 Qxd4 30. Nxc4 dxc4 31. Qf1 O-O 0-1


This is a game from  Horgen 1995, well-known because of Ivanchuk's 5th move ("enrage the beast"). As a fairly limited player, it is not obvious to me why Kasparov resigned at this stage. Is it obvious that the c-pawn cannot be stopped without losing material? Is there another reason to resign?
White's position is just bad overall. The main reasons:


The passed c-pawn is a huge asset. It's likely it will eventually cost White a piece, but in the meantime it cramps White's forces.
All Black's pieces are far more active than their White counterparts, with the sole exception of the rooks (which are roughly equal in activity).
Knowing Kasparov, he was probably disgusted with his play at this point and fed up with the game. White's position is already objectively resignable in any case due to the two points above.