The process of erosion of rocks is continuous and eternal. The erosion is of three major types: Physical Weathering, Chemical Weathering and Biological Weathering.
Nighoj is the name of Village and Khale or Kund (a noun in local Marathi language) means pothole. These potholes are also called ‘Ranjan Khalage’; Ranjan means a huge earthen pot. A river Kukdi flows here and in the riverbed you see these potholes. Part of this river here is called ‘Malganga’ and a temple of Malganga Goddess (Kund Mauli) is on the river bank. Nighoj Kund
The riverbed here is Basalt Rock which is eroded over thousands of year. Wind (Aeolian), Ice, Waves and Water are the erosive agents; Water among them is most powerful. Water in all its forms is erosive; may it be by raindrops (splash erosion), or by water flowing on plane surface and collecting soft soil forming small rivulets and streams (sheet erosion) or by Strong Stream of water which causes ultimate erosion. Major erosion on our planet Earth is caused by Water.
The stream collects sand particles on the way, if more powerful it collects pebbles and if it is huge like flood it can collect rocks and even boulders; this causes the banks and the bed of the stream to erode. Again the velocity of the stream plays an important role. More the velocity more the erosion, the contents are rubbing the surface with momentum which is proportional to the velocity. Furthermore the sand particles and small pebbles if trapped in the gaps or holes keep on moving and rotating in circles causing continuous erosion until they find their way out.
Now this erosion is a direct impact (head ward collision) of both Water and the contents of water. I would like to give an example here of a method ‘Water Jet Cutting’ used in the Metal Parts Manufacturing Industries to Cut and Shape the Metal sheets and components by a ‘small in diameter but very powerful Water Jet stream containing fine silica sand ’ with tremendous force acting like a sharp piercing needle. Now you can imagine the power of water Stream. Water jet cutter .
Here in Nighoj these potholes are formed by the Stream of Water (River). The river brings sand and pebbles along with it. They are trapped in the small and big gaps between the stones and the cavities. Then they once trapped keep on moving with the motion of water and the grinding starts; This process of grinding goes on and on creating holes in the rocks until either they worn out totally or get escaped by water current or bore a hole through the rock and finally come out to flow with the water flow again. These pebbles and the sand is harder than the riverbed rock and hence the erosion resulting in to potholes. The size of the potholes being determined by the force of the whirlpool of water and pebbles trapped in the cavity and the time required for it to find an escape route.
Water is also a dissolving agent; it dissolves the sediments in the rocks and erodes it. Again the chemical composition of the water of stream will also decide the rate and type of erosion but here in Nighoh-Kund it is irrelevant being not really a major cause to create the potholes in the riverbed rocks.
They say that some potholes here are so big that you can walk through them, some so deep 100ft or so and don’t know where they lead to. If something falls in to water it disappears and don’t know where it goes. The water flow disappears in many holes and gushes out from some holes. Riverbed here is not really big, about 100 feet in width and some 3km long.
In monsoon there is lot of water and is thrilling to look at it from above, in summer you see these holes very clearly and some local fishermen know their way to walk through these potholes.
Don’t even think of going into the water but the fish sure do swim in there. You have seen this wonder now just relax and observe.
And now time for the questions! (Try answering any three).
You have witnessed this beautiful Earth-cache and sure you have observed it well to tell us:
1. How is the surface of the rock in general here? (Smooth/rough/porous/scratchy/edgy/or...)
2. Why are the potholes here round or roundish and not other shapes?
3. Look at the depths of the potholes at the edges and in the middle. Why do you think those in the middle are deeper?
4. What type of erosion is this?
5. There are many cracks in the rocks, which makes it more prone to erosion. Why?
You have found this odd place, you have seen it closely, learned something new and different about our Earth so why not have photo here and add it to your log (optional).
