What this lesson teaches
I can identify cockpit karst, tower karst and caves in the humid tropics.
Syllabus 9173, Topic 2.2, 2. Karst Landforms in the Humid Tropics. What karst landforms can be found in the humid tropics?
I can explain the processes and factors that form tropical karst landforms.
Syllabus 9173, Topic 2.2, 2. Karst Landforms in the Humid Tropics. What factors influence the formation of karst landforms in the humid tropics?
Make a guess
A limestone landscape has steep-sided hills standing alone on a flat plain. How did the hills keep such steep sides?
- Wind blew away the softer rock around them.
- The hills grew upwards from the plain.
- Water undercut their bases, and sides collapsed.
- Each cockpit hill turns into a tower at a set age.
Show the answer
Water undercut their bases, and sides collapsed.
In tower karst, water dissolves the base of the hills near the water table or flood level. Undercut sides collapse, keeping them steep.
Karst forms where water dissolves limestone, and rock structure, drainage and time decide whether cones, hollows or towers remain.
Karst forms where soluble rock, usually limestone, is dissolved by water. In the humid tropics, plenty of rain and carbon dioxide from active soils drive carbonation. Joints and layers in the rock let water in. Thick, pure limestone can form large karst areas.
Cockpit karst has cone-shaped hills surrounding enclosed, often star-shaped hollows. Water gathers in the hollows and along cracks, dissolving and lowering the ground. Slopes wear back as weathered rock is removed. The cone hills are what remains between the hollows.
Tower karst has steep-sided hills rising sharply from flat plains. Water dissolves the base of the hills, especially near the water table or where floods reach. The undercut sides collapse, keeping them steep, while the plains around are lowered.
Water supply, joints, rock purity and thickness, uplift, base level and time all matter. Base level is the lowest level a river can erode to, often sea or river level. Rivers from nearby non-limestone areas can bring extra water.
Cones and towers can exist side by side. They are not fixed stages of one sequence.
- Karst
- Landscape formed by dissolving limestone.
- Cockpit karst
- Cone hills around star-shaped hollows.
- Tower karst
- Steep hills rising sharply from flat plains.
Step by step
Open pathways
Acidic water widens joints and removes rock.
Lower and wear back
Hollows deepen; slopes retreat.
Explain the result
Link cones or towers to drainage, base level, rock and time.
Real examples to use
Guilin and the Li River, China
Steep limestone towers rise from flat plains along the Li River near Guilin. Guilin was added in 2014 to the South China Karst World Heritage Site, which UNESCO first listed in 2007, and its towers are a classic example of tower karst.
Worked example: Libo and Guilin, South China
UNESCO describes cone karst and enclosed hollows at Libo, and both tower and cone karst at Guilin. So one region can have different karst forms. Guilin's rivers also bring water from outside the limestone area.
Watch out for this
Every cockpit must become a tower at a set age.
Karst depends on local rock, drainage and base level. Similar shapes can have different histories.
Check your understanding
Which description matches cockpit karst?
- Stalactites hanging from the roof inside a cave.
- A river split into channels around moving sandbars.
- Cone-shaped hills around star-shaped hollows.
Show the answer
Cone-shaped hills around star-shaped hollows.
Yes. That is cockpit karst.