In order to activate an island on the map for teleportation, you must first fly to that location. When you're running low on speed and at risk of stalling, make a quick dive and pull back up again to gain velocity without losing much altitude. Pull back when you hit a thermal to slow down and gain greater altitude. At any time you can recalibrate the accelerometer by tapping the altimeter in the lower-right corner. The atoll of Perpetua, which is located to the southeast of Spiral Heights, doesn't have any crystals but offers a speed challenge activated by landing on the platform there.