New Brunswick is divided into several regions. The Maritime Plain is a triangular region that covers 1/3 of the province. It is flat to gently rolling. It has sedimentary rocks and soils built on stone free glacial deposits. The New Brunswick Highland region is the highest region in the north. It has an average elevation that exceeds 610m (2,000 ft). Mount Carleton is the highest peak. The Bay of Fundy varies from 305-425m (1000-1400 ft). It is underlain by hard granite rocks and thin stony soils. The St. John's River has fertile alluvial soils. The Chaleur Uplands is a plateaulike region. The average elevation is about 305m (1000 ft). The soils are like the New Brunswick Highlands. A small portion of the Notre Dame Mountains are in New Brunswick. This area is rugged terrain. The main river in New Brunswick is the Saint John's. It has high tides that flow upstream causing the famous phenomenon of reversing falls. The largest lake is Grand Lake. It is 2m (7ft) above sea level.