When the Doctor shorts the circuit to the Daleks' control room, the electrical flash is triggered by the crew about a second before he actually completes the circuit.
When Ian and Barbara are crawling along the rock-face, part of the wall breaks away in Barbara's hand. The damage to the set reveals it to have been constructed from polystyrene.
When Ian jumps and grabs on the rock wall, his left hand breaks off a piece of the wall revealing that it is fake.