Phytokarst is a phenomenon where speleothems or speleogens orient towards sunlight coming from a cave entrance. They may be depositional or may be pinnacles etched in bedrock that orient towards the sunlight. In the case of depositional speleothems (top 2 photos), green moss or algae are often seen growing on the formations. The bedrock type is shown in the 3 lower images from Hang Son Doong in Vietnam. These examples had red patches of bacterial growth that cause them to dissolve the bedrock in a manner that leaves small fingers pointing toward sunlight.
AUTHOR: Dave Bunnell