Kent coastline of Kent is continuously changing, due to tectonic uplift and coastal erosion. Until about 960, the Isle of Thanet was an island, separated by the Wantsum channel, formed around a deposit of chalk; over time, the channels silted up with alluvium. Similarly Romney Marsh and Dungeness have been formed by accumulation of alluvium. Kent's principal river, the River Medway, rises near East Grinstead in Sussex and flows eastwards to Maidstone. Here it turns north and breaks through the North Downs at Rochester, then joins the estuary of the River Thames as its final tributary near Sheerness. The Medway is
Gibbon River Gibbon River The Gibbon River flows east of the Continental Divide in Yellowstone National Park, in northwestern Wyoming, the Northwestern United States. Along with the Firehole River, it is a major tributary of the Madison River, which itself is a tributary of the Missouri River. The Gibbon River rises in the center of the park at Grebe Lake. It flows for a short distance into Wolf Lake. Below Wolf Lake, the river flows through Virginia Cascades into the Norris valley. It flows near the Norris Geyser Basin and through the Gibbon Geyser Basin. From there it flows through the Gibbon