Editing Table Mountain (section)

==Geology==
{{further|Cape Peninsula#Geology|Cape Fold Mountains|Marine geology of the Cape Peninsula and False Bay}}

[[File:Table Mountain geology.jpg|thumb|left|Geological structure of Table Mountain. Compare with the map in this section.<ref name=compton />]]
[[File:Geology of Cape Peninsula 1.jpg|thumb|Geology of Table Mountain in relation to the geology of the rest of the Cape Peninsula.]]

The upper approximately {{convert|600|m|adj=on||}} portion of the {{convert|1|km|mi|spell=in|adj=mid|-high}} table-topped mountain, or [[mesa]], consists of 450- to 510-million-year-old ([[Ordovician]]) rocks belonging to the two lowermost layers of the [[Cape Fold Mountains]].<ref name=compton /><ref name=McCarthy>{{cite book |last1=McCarthy |first1=T. |last2=Rubidge |first2=B. |year=2005 |title=The Story of Earth and Life |pages=188–192 |publisher=Struik |location=Cape Town |isbn=1-77007-148-2 }}</ref> The uppermost, and younger of the two layers, consists of extremely hard [[quartz]]itic [[sandstone]], commonly referred to as "[[Table Mountain Sandstone (Geological Formation)|Table Mountain Sandstone]]" (TMS), or "[[Cape Fold Belt#Table Mountain Group|Peninsula Formation Sandstone"]] (as it is known as at present), which is highly resistant to erosion and forms characteristic steep grey crags. The {{convert|70|m|ft|adj=mid|-thick}} lower layer, known as the "Graafwater Formation", consists of distinctively maroon-colored mudstones, which were laid down in much thinner horizontal strata than the Table Mountain Sandstone strata above it.<ref name=compton /> The Graafwater rocks can best be seen just above the contour path on the front of Table Mountain, and around [[Devil's Peak (Cape Town)|Devils Peak]]. They can also been seen in the cutting along [[Chapman's Peak]] Drive. These rocks are believed to have originated in shallow tidal flats, in which a few Ordovician fossils, and fossil tracks have been preserved.<ref name=compton /><ref name=tankard>{{cite book |last1=Tankard |first1=A. J. |last2=Jackson |first2=M. P. A. |last3=Eriksson |first3=K. A. |last4=Hobday |first4=D. K. |last5=Hunter |first5=D. R. |last6=Minter |first6=W. E. L. |year=1982 |title=Crustal Evolution of Southern Africa. 3.8 Billion Years of Earth' History |pages=338–344 |publisher=Springer |location=New York |isbn=0-387-90608-8 }}</ref> The overlying TMS probably arose in deeper water, either as a result of subsidence, or a rise in the sea level.<ref name=compton /><ref name=tankard /> The Graafwater rocks rest on the [[Basement rock|basement]] consisting of [[Granite|Cape Granite]]. [[Devil's Peak (Cape Town)|Devil's Peak]], Signal Hill, the City Bowl and much of the "Cape Flats", however, rest on heavily [[Fold (geology)|folded]] and altered [[phyllite]]s and [[hornfels]]es known informally as the [[Marine geology of the Cape Peninsula and False Bay#The geological structure of the region|Malmesbury shales]]. The Cape Granite and Malmesbury shales form the lower, gentler slopes of the Table Mountain range on the Cape Peninsula. They are of late [[Precambrian]] age, pre-dating the "Graafwater rocks" by at least 40&nbsp;million years.<ref name=compton />

[[File:Erosion A5.svg|thumb|A west-east (left to right) geological cross section through Table Mountain on the [[Cape Peninsula]], the Cape Flats (the isthmus connecting the Peninsula to the African mainland) and the [[Hottentots-Holland]] Mountains on the mainland. It indicates how the Cape Fold Mountains have been eroded in this region, leaving what was once the bottom of a valley to form Table Mountain with its flat table-top structure.<ref name=compton>Compton, John S. (2004) ''The Rocks & Mountains of Cape Town''. Cape Town: Double Story. {{ISBN|978-1-919930-70-1}}</ref>]]
The basement rocks are not nearly as resistant to weathering as the TMS, but significant outcrops of the Cape Granite are visible on the western side of Lion's Head, and elsewhere on the Peninsula (especially below Chapman's Peak Drive, and The Boulders near [[Simon's Town]]).<ref name=compton /><ref name=uct-geology>{{cite web | url=http://web.uct.ac.za/depts/geolsci/cape.htm | archive-url=https://archive.today/20120719105740/http://web.uct.ac.za/depts/geolsci/cape.htm | url-status=dead | archive-date=2012-07-19 | title=Geology of the Cape Peninsula | work=[[University of Cape Town|UCT]] Department of Geological Sciences | access-date=2006-07-20}}</ref><ref name=geology>{{cite web | url=http://www.capetown.at/heritage/history/prehistory_geo_geol_art.htm | title=The Geology of Table Mountain | work=CapeConnected | access-date=20 July 2006 | archive-date=27 November 2019 | archive-url=https://web.archive.org/web/20191127134741/http://www.capetown.at/heritage/history/prehistory_geo_geol_art.htm | url-status=live }}</ref> The weathered granite soil of the lower slopes of the Peninsula Mountain range are more fertile than the nutrient-poor soils derived from TMS. Most of the vineyards found on the Cape Peninsula are therefore found on these granitic slopes of the Table Mountain range.

The mountain owes its table-top flatness to the fact that it is a [[syncline]] mountain, meaning that it was once the floor of a valley (see diagram on the right). The [[anticline]], or highest point of the [[Cape Fold Belt|series of folds that Table Mountain was once part of]], lay to the east, but that has been weathered away, together with the underlying softer Malmesbury shale and granite basement, to form the "Cape Flats", the isthmus that connects the Cape Peninsula to the mainland. The fold mountains reappear as the [[Hottentots-Holland]] Mountain range on the mainland side of the Cape Flats.<ref name=compton /> What has added to the mountain's table-top flatness is that it consists entirely of the very hard, lower layer of the [[Table Mountain Sandstone (Geological Formation)|TMS Formation]]. Originally this was topped by a thin glacial tillite layer, known as the Pakhuis Formation (see the diagram above, left), above which was the upper layer of TMS. Both these layers, but especially the tillite layer, are softer than the lower layer of Table Mountain Sandstone.  When these softer layers eroded away, they left a very hard, flat erosion-resistant quartzitic sandstone platform behind which today forms Table Mountain's top.

[[File:Table Mountain Cape Town South Africa 19Mar2018 SkySat.jpg|thumb|Satellite image of Table Mountain, surrounded by Cape Town]]
Table Mountain is the northernmost end of a {{convert|50|km|mi|adj=mid|-long|-1}} and roughly {{convert|6|to|10|km|mi|adj=mid|-wide|0|spell=in}} Cape Fold Mountain range that forms the backbone of the Cape Peninsula, stretching from the [[Cape of Good Hope]] in the south to Table Mountain and its flanking Devil's Peak (to the east) and Lion's Head and Signal Hill (to the west) in the north. Table Mountain forms the highest point of this range. The range runs parallel to the other Cape Fold Mountain ranges on the mainland to the east.