closest peak to peak A (along all ridges connected to A) that has a greater height than A, and satisfies some prominence criteria. The disadvantage of this concept is that it goes against the intuition that a parent peak should always be more significant than its child. However it can be used to build an entire lineage for a peak which contains a great deal of information about the peak's position. Other criteria To choose among possible parents, instead of choosing the closest possible parent, it is possible to choose the one which requires the least descent along the ridge. In general, the analysis of parents and lineages is intimately linked to studying the topology of watersheds. Issues in choice of summit and key col Alteration of the landscape by humans and presence of water features can give rise to issues in the choice of location and height of a summit or col. In Britain, extensive discussion has given rise to a protocol that has been adopted by the main sources of prominence data in Britain and Ireland. Other sources of data commonly ignore man-made alterations, but this convention is not universally agreed upon; for example, some authors discount modern structures but allow ancient ones. Another disagreement concerns mountaintop removal, though for high-prominence peaks (and for low-prominence subpeaks with intact summits), the difference in prominence values for the two conventions is typically relatively small. Examples The key col and parent peak are often close to the subpeak but this is not always the case, especially when the key col is relatively low. It is only with the advent of computer programs and geographical databases that thorough analysis has become possible. The key col of Denali in Alaska (6,194 m) is a 56 m col near Lake Nicaragua (unless one accepts the Panama Canal as a key col; this is a matter of contention). Denali's encirclement parent is Aconcagua (6,960 m), in Argentina, and its prominence is 6,138 m. To further illustrate the rising-sea model of prominence, if sea level rose 56 m, North and South America would be separate continents and Denali would be 6138 m above sea level. At a slightly lower level, the continents would still be connected, and the high point of the combined landmass would be Aconcagua, the encirclement parent. Note that, for the purposes of this article, man made structures such as the Panama Canal