The rugged coastline resembles the glacier-carved coasts of polar regions, but in this case, the coast was shaped by the movement of Earth's crust. The Arabian plate is slowly pushing under the Eurasian plate, creating the earthquake-prone mountains of Iran. On the leading edge of the Arabian plate, the Musandam Peninsula is sinking. The higher elevation mountains remain above the water, but the sea has rushed in to fill the valleys with fingers of water.