The base level of a river or stream is the lowest point to which it can flow, often referred to as the 'mouth' of the river. For large rivers, sea level is usually the base level, but a large river or lake is likewise the base level for tributary streams. A rather rare exception can be seen in the Jordan River, for which the base level is the Dead Sea, 417 m below modern sea level. For the Second World War frigate class, see River class frigate The Murray River in Australia A river is a large natural waterway. ... Running Stream The primary meaning of stream is a body of water, confined within a bed and banks and having a detectable current. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... A lake is a body of water surrounded by land. ... Northern part of the Great Rift Valley as seen from space (NASA) The Jordan River is a river in Southwest Asia flowing through the Jordan Rift Valley into the Dead Sea. ... The Jordan River flowing into the Dead Sea The Dead Sea (Arabic البحر الميت,Hebrew ים המלח) is the lowest point on the Earths surface. ...

When the source of a stream is very high, relative to the base level (high stream gradient), erosion proceeds rapidly due to the energy of the rapidly moving water; the topography becomes rugged; and we say the stream is young (geologicially speaking). When erosion has acted for a long geologic time, wearing down the high points and making a small difference between the source and the base level of a stream (low stream gradient), we say that it is mature. Mature stream valleys have gentle slopes, rounded higher points and meandering courses. Stream gradient is the ratio of drop in a stream per unit distance, usually expressed as feet per mile or meters per kilometer. ... The word meander has a number of senses. ...

A very hard layer of rock can form a temporary base level, until it is cut through. The Lockport dolomite has created a temporary base level for the Niagara River. Eventually this will be cut through as Niagara Falls recedes, and Lake Erie will be drained to near the lower base level of Lake Ontario. The Niagara River flows to the north from Lake Erie to Lake Ontario. ... The Horseshoe Falls, one of the three Niagara Falls. ... Lake Erie, looking southward from a high rural bluff near Leamington, Ontario Lake Erie is one of the five large freshwater Great Lakes in North America, the worlds largest such lakes. ... Lake Ontario seen from near Wolcott, New York Lake Ontario, bounded on the north by Ontario and on the south by Ontarios Niagara Peninsula and by New York State, is one of the five Great Lakes of North America. ...

Movements of land can greatly affect base levels. The uplift of the Colorado Plateau, combined with the opening of the Gulf of California to the sea, established sea level as the base level for the Colorado River and led to the (geologically) rapid erosion that resulted in the Grand Canyon. The Colorado Plateau, also called the Colorado Plateaus Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. ... The Gulf of California (also known as the Sea of Cortez or Sea of Cortés; locally known in the Spanish language as Mar de Cortés or, much less frequently, Golfo de California) is a body of water that separates the Baja California Peninsula from the Mexican mainland. ... Colorado River in the Grand Canyon from Desert View For other uses, see Colorado River (disambiguation). ... Grand Cañon at the foot of the Toroweap - looking east, by William Henry Holmes The Grand Canyon is a colorful, steep-sided gorge, carved by the Colorado River, in northern Arizona. ...

The many meaders of the Kentucky River shows that it was a mature stream with little relief. Uplift of the central Kentucky area rejuvinated the stream, causing it to cut a deep canyon, but preserving the meanders that indicate the stream existed prior to the uplift. The Kentucky River is a tributary of the Ohio River, approximately 259 mi (417 km) long, in the U.S. state of Kentucky. ... State nickname: Bluegrass State Other U.S. States Capital Frankfort Largest city Louisville Governor Ernie Fletcher (R) Official languages English Area 104,749 km² (37th)  - Land 102,989 km²  - Water 1,760 km² (1. ...

Other geologic processes can affect base levels. In the Finger Lakes of New York, Ice age glaciation greatly deepened the lake valleys and rejuvinated tributary streams. These streams have deep ravines and often waterfalls where hard rock layers slow erosion; they are said to be hanging valleys. A mature tributary stream has a greatly reduced stream gradient at it approaches the base level. New Yorks Finger Lakes The Finger Lakes are glacially formed lakes in upstate New York, mainly linear in shape, each lake oriented on a north-south axis. ... State nickname: Empire State Other U.S. States Capital Albany Largest city New York Governor George Pataki (R) Official languages None (English is de facto) Area 141,205 km² (27th)  - Land 122,409 km²  - Water 18,795 km² (13. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... This article is about the geographical formation. ...

Sea level can also change (primarily due to the formation or melting of continental ice sheets), and raise or drop the final base level for coastal rivers. Along the east coast of North America river valleys extend out onto the continental shelf indicating a time when erosion was possible due to the lower base level of a lower sea level in the past. Today many of these same rivers end in bays, indicating that sea level has risen in recent geologic time. This is referred to as a drowned coastline. World map showing location of North America A satellite composite image of North America North America is a continent in the northern hemisphere, bounded on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west... The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the one we live in by relatively shallow seas and gulfs. ...