Caves are also formed by selective erosion by the sea of cliff bases. Very occasionally they occur in lava, either where lave has solidified over a mass of ice that has later melted, or where the surface of a mass of lave has solidified, molten lava beneath bursting through and flowing on (see lava tube).
PotholeThe distinguishing feature of a pothole is that it is more or less vertical. Potholes generally occur in limestone rocks where water has enlarged a joint by solution. Potholes often provide the entrances to cave systems.
Related categories GEOGRAPHY
• GEOLOGY AND PLANETARY SCIENCE
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