Limestone

In this section you will revise:

  1. How to identify Limestone Features on a map.
  2. How to explain the formation of both surface and sub-surfacec features of Limestone Formation.

Some useful advice would be to take notes while you watch. Sometimes I'll draw diagrams, you'd do well to attempt to do the same as we go along and then put the labels on from memory after the clip has ended. You can always go back and re-watch it to see if you're right. Some people prefer to write the answer in full underneath the diagrams, others to label the pcitures, you need to find the way that is best for you.

Recognising Limestone Features on a Map

In this clip you'll revise how to spot the basic features of a limestone landscape.

 

Watch this tour to understand Limestone geography better. Use a 1:25000 map of the Ingleborough area to follow along.

Limestone Pavements

In this video we'll revise the main processes behind limestone pavement formation:

 

Caverns, stalactites, stalagmites and rock pillars

 

Model answer:

When mildly acidic carbonic acid rain falls on an exposed limestone pavement it percolates down through the joints and along the bedding plains. This leads to carbonation where the limestone is dissolved. Where a particular joint or bedding plain is weathered away more an underground cavern may form. As the limestone solution makes its way along the bedding plains it is exposed to oxygen and so evaporates carbondioxide, this results in calcite being deposited where drips fall from the cavern roof. These build up layer on layer to form a stalactite. Where the drips land they splash and spread out to form a stalagmite. Where a stalagmite and stalactite meet a rock pillar forms.

Gorges

Gorges are most easily understood as a cavern who's roof has fallen in to leave a very steep sided narrow valley or 'gorge'. In explaining this feature you should go through the processes which explain the formation of a cave and then add this point to the end of that answer. You could also refer to a gorge being formed as a result of waterfall retreating back up stream, cutting a gorge as it does so. Take care not to do this if the a question is set in a limestone environment.

Scars

Where the side of a limestone pavement is eroded by the glacial processes of abrasion and plucking a steep cliff of 'scar' will be evealed. the name comes form the revealing bedding planes which lend it a scar like appearance. You should also refer to freeze thaw in your explanation of why the scar is so steep and why it will often have a scree slope beneath it. Use the map below to identify a scar and then compare it to the satelite image to find the same features.