Activity No. 1A: Check each statement that shows an idea consistent with the plate tectonics concept. 1. A plate is composed of hard, mechanically strong rock. 2. Each plate moves like a small, intact sheet of rock. 3. Tectonic plates move at a very slow rate. 4. The margin or boundary of a plate is tectonically stable. 5. A plate glides horizontally over the hot plastic asthenosphere.​