Remember the entrance to the Fiery Path? Go back there and walk to the right. You will find the cable car station open. Enter it and talk to the lady. She will provide you with a car and you will be off to Mt. Chimney.
Once you are out of the car. Start climbing the mountain. You will find many grunts bullying with their Pokemon. Battle them.
- Team Aqua/Magma Leader Archie/Maxie
Once you beat the Team leader, he'll give up the Mt. Chimney plans. The Leader of his rival team will come and congratulate you. Walk to the machine and remove the Meteorite kept in it. Now, the path to the south of the cable car station will be open. Head down the stairs here to enter the Jagged Pass.
If you return to Mt. Chimney anytime, a woman near the Cable Car station will offer Lava Cookies for 200 bucks each, which can cure all status problems. Stock up lots of them. After winning the Pokemon League, come back here to find and battle new trainers.