so what do you do when you beat the gym leader in humilau city and when you battle terrakion and beat him. i've tried going into the giant chasm but some team plasma guys are blocking the way and they just talk about something when I walk up to them and press the button a. also i've gone through route 22 and also that other scientest gave me a colress machine
Go south onto Route 21.
See this guide. This is an amazing walkthrough.