Base levelIn geology and geomorphology a base level is the lower limit for an erosion process. The modern term was introduced by John Wesley Powell in 1875. The term was subsequently appropriated by William Morris Davis who used it in his cycle of erosion theory. The "ultimate base level" is the plane that results from projection of the sea level under landmasses. It is to this base level that topography tends to approach due to erosion, eventually forming a peneplain close to the end of a cycle of erosion.
Congo RiverThe Congo River (Nzâdi Kôngo, Fleuve Congo, Rio Congo), formerly also known as the Zaire River, is the second-longest river in Africa, shorter only than the Nile, as well as the third largest river in the world by discharge volume, following the Amazon and the Ganges rivers. It is also the world's deepest recorded river, with measured depths of around . The Congo-Lualaba-Chambeshi River system has an overall length of , which makes it the world's ninth-longest river.
Drainage basinA drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern. Other terms for a drainage basin are catchment area, catchment basin, drainage area, river basin, water basin, and impluvium.
NileThe Nile is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest river in the world, though this has been contested by research suggesting that the Amazon River is slightly longer. Of the world's major rivers, the Nile is one of the smallest, as measured by annual flow in cubic metres of water.
RhineThe Rhine (raɪn ) is one of the major European rivers. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein, Swiss-Austrian, and Swiss-German borders. After that the Rhine defines much of the Franco-German border, after which it flows in a mostly northerly direction through the German Rhineland. Finally in Germany, the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea.
