Continental plateaus are formed mainly through extensive volcanic outpourings. Oceanic islands formed by volcanic eruptions on the ocean floor may grow to such huge dimensions that they reach the waterline. Over a geological period, the continuous rise of the ocean floor by volcanic activity causes the once submerged basaltic rocks to rise above the sea level to exist as an island. With the passage of a long time, the volcanic action ceases and the volcanic features get subdued by erosional activities. Consequently, the rugged island topography changes into more subdued landscapes, where the remnants of volcanic peaks still stand out as monadnocks or residual hills. The Deccan Plateau of India is an excellent example of a Continental plateau formed by such volcanic activity.