Creation of Table Mountain
From GeoClasses
Table Mountains are usually formed by eruptions underneath glaciers. After the eruption, the glacier begins melting. This results in the remainder of a table mountain. Table Mountain's creation began hundreds of billions of years ago. Initially the sediments and deposits created a mass of shale. Later, magma from the core of the earth was exposed to this mass of shale creating a very tough granite layer. As a result the shale had a very tough core of granite. Shale being a rock of clay or mud, weathers very easily. Soon after, the sediments and deposits from rivers resulted in various layers consisting of sandstone, granite and shale.
Eventually the table top surface of the mountain began forming as explained above. Ice sheets flattened the these layers of sandstone and glaciers of Maclear's Beacon. Table moutain was forming as Pangea began to break apart. At this time Africa was located in the center of Pangea. Plate tectonics caused shifting of the earth's major plates. Consequently, Pangea split into two parts. These shifts cause many folded mountains, but because of its extremely durable and erosion resistant granite base, Table Mountain withstood any folding. In a sense the granite base deflected the forces causing the folding in a downward direction. This caused a lifting force which explains the gradual proccess that brought the mountain above sea level today.
- This video shows continental drifting, as the great continent of Pangea breaks apart and forms into all 7 continents. Notice how for the most part Africa does not move much and no collisions happen between Africa and another continent.
The Malmesbury group is one of the oldest rock groups in the world making Table Mountain one of the five oldest mountains in the world. Table Mountain is so old because it was one of the first landforms to form. It was never destroyed due to the fact that it is at divergent boundary and thus new crust is being created (not destroyed) around it.
The Cape Peninsula is composed of three main rock formations of varying ages.
- The Malmesbury Group is around 540 million years old and made up of dark grey mudstones and light colored sandstones.
- Cape Granite is around 540 million years old and is much harder/coarse-grained with white feldspar crystals. This formation is the foundation for most of the Table Mountain chain.
- Table Mountain Group is 520 million years old and comprised of a further three formations:
1.The Graafwater formation: This layer is between 25m-65m thick and is made up of sandstone and mudstone.
2.The Peninsula Formation: This layer is comprised of light grey pebbly sandstone.
3.The Pakhuis Formation: This layer is found on the top of Table Mountain and is identifiable by glacially deposited pebbles-of sandstone.
