Introduction

This topic examines weathering in tropical environments and the resultant landforms associated with granite and limestone landscapes.

You will study:

The formation of characteristic landforms:
- granite: (deep weathering profiles) tors, inselbergs, and bornhardts
- limestone: tropical karst (cone karst, tower karst, and cockpit karst).

Read and Make Notes

For this topic, you will need to work through pages 199 to 205 of your textbook, completing the Activities at the end of the Section.

Download and Print

Download and print out these resources to accompany your notes:

PRINT - Landforms of Tropical Environments

PRINT - Fig.7.16 Tor Formation

PRINT - Fig.7.18 Formation Bornhardts

PRINT - Fig.7.20 Cockpit Karst

Top Tips

Make sure that you understand the following key points:

Look back on your AS notes relating to weathering (unit 3.2) as you need to understand the application of these processes to create landforms.
Distinguish in your mind the different types of rock that form these landforms and do not muddle them up! Maybe a mnemonic may help you?
Practice drawing formation diagrams at speed and annotating them to show how the landforms formed and which processes formed them. You may have to draw sequential diagrams or use numbering to get your message across.

Key Terms

You may find it easier to put them into alphabetical order if you want them as a table (using a computer so you can add to them later) or if you want to get ahead then put them on flashcards with the word on one side and the definition on the reverse which you can use for revision before your exam. Some people like to colour-code their key terms by unit.

The words should be used in addition to those learnt in section 3.2 (AS units).

Hydrolysis is when orthoclase feldspar reacts with an acid water that coverts it to china clay (kaolin).
Humid tropics describes areas in the tropics that are wet all year round.
Exfoliation is a form of mechanical weathering in deserts, in which the outer layers of a rock expand and contract, due to heating and cooling, which leads to the eventual flaking/peeling of the rock.
Saprolite is weathered rock.
Weathering front or basal surface of weathering represents the depth to which rocks have been weathered – that is, the boundary between the weathered rock (saprolite) and the solid unweathered rock.
Tors are ridges or piles of spheroidal weathered boulders that have their bases in the bedrock and are surrounded by weathered debris.
Duricrusts are concentrations of minerals such as iron, aluminium, silica and calcium carbonate within the zone of weathering.
Equifinality is when different processes lead to the same end product.
Polygonal or cockpit karst is a landscape that is pitted with smooth-sided soil-covered depressions and cone-shaped hills.
Tower karst describes upstanding rounded blocks of limestone set in a region of low relief.
Stalactites are calcite (calcium) deposits that hang from the ceiling of caves.
Stalagmites are calcite (calcium) deposits that grow up from the floor of caves.
Deposition is the process of dropping material due to a decrease in energy/velocity.
Blue holes are drowned limestone swallow holes/sink holes that are now under the sea.

Consolidate

Now consolidate your understanding by working through these additional resources:

Compulsory Resources

READ – Granite Landforms (The Gneiss Blog)

READ - Karst Landforms (GeoHunter)

Important Resources

READ – Information on Granite Inselbergs of the Central Namib Desert (Migon & Goudie)

READ – Great Photo Article on Bahamas’ Blue Holes (National Geographic)

WATCH – 4-minute Video on Tor Formation (YouTube)

EXPLORE – Lots of Images of Chinese Karst Scenery (UNESCO)

Optional Resources

READ – Processes in Underground Karst Regions (BGS)

READ - Understanding Sinkholes and Karst (BGS)

READ - What Causes Sinkholes (BGS)

Synoptic Links

This unit has strong links with the AS unit 3.2 (Weathering).

Quiz

Complete the quiz. If you score less than 90%, try again.

QUIZ - Landforms of Tropical Climates

Assignment

When you have completed all the activities and are fully prepared and feel confident with the material, you should complete Assignment One and submit it to your tutor via Canvas for marking and feedback.