Editing Nantes (section)

===Geology===
[[File:Plan relief Nantes.svg|thumb|upright=1.5|alt=Map showing the elevation and rivers in Nantes|Elevation and hydrology map of Nantes]]
Nantes is built on the [[Armorican Massif]], a range of weathered mountains which may be considered the backbone of Brittany. The mountains, stretching from the end of the Breton peninsula to the outskirts of the [[Sedimentary basin|sedimentary]] [[Paris Basin]], are composed of several parallel ridges of [[Ordovician]] and [[Cadomian Orogeny|Cadomian]] rocks. Nantes is where one of these ridges, the Sillon de Bretagne, meets the Loire. It passes through the western end of the old town, forming a series of cliffs above the quays.{{sfn|M. Ters|J. Marchand|G. Weecksteen|1970}} The end of the ridge, the Butte Sainte-Anne, is a natural landmark {{convert|38|m|abbr=off}} [[above sea level]]; its [[foothills]] are at an elevation of {{convert|15|m|abbr=off}}.{{sfn|D. Janjou|avec collaboration de M. Gruet et C. Penecki|1998}}

The Sillon de Bretagne is composed of [[granite]]; the rest of the region is a series of low [[plateau]]s covered with [[silt]] and [[clay]], with [[mica]] [[schist]] and sediments found in lower areas. Much of the old town and all of the Isle of Nantes consist of backfill.{{sfn|M. Ters|J. Marchand|G. Weecksteen|1970}} Elevations in Nantes are generally higher in the western neighbourhoods on the Sillon, reaching {{convert|52|m|abbr=off}} in the north-west.{{sfn|D. Janjou|avec collaboration de M. Gruet et C. Penecki|1998}} The [[Erdre]] flows through a slate fault.{{sfn|Lelièvre|2000|p=14}} Eastern Nantes is flatter, with a few hills reaching {{convert|30|m|abbr=off}}.{{sfn|D. Janjou|avec collaboration de M. Gruet et C. Penecki|1998}} The city's lowest points, along the Loire, are {{convert|2|m|abbr=off|ft}} above sea level.{{sfn|D. Janjou|avec collaboration de M. Gruet et C. Penecki|1998}}