﻿The chapter embodies the authors' findings, and the 	 

logical conclusions they drew from them, on the mud cones 	 

(or 'mud volcanoes') they found In the intertidal zone and 	 

on the beach of the Alleppey mudbank region in 1972. Their 	 

experiment with regard to these mud cones confirm beyond 	 

doubt the viscous nature of the mud that underlies at 	 

Allepey, and its being, for all probability, the source of 	 

Alleppey mudbank. 	 

Similar mud cones observed earlier by some workers 	 

are also discussed briefly

Gopinathan, C P

Mathew, K J

Murty, A V S

Rao, D S

Regunathan, A

CMFRI Digital Repository

FOUR SOURCE OF M U D OF ALLEPPEY M U D B A N K : M U D CONE A N D THE MESSAGE IT CONVEYS C. p. GOPI NATHAN, A. REGUNATHAN, D. S. RAO, K. J . MATHEW and A. V. S. MURTHY ABSTRACT The chapter embodies the authors' findings, and the logical conclusions they drew from them, on the mud cones (or 'mud volcanoes') they found In the intertidal zone and on the beach of the Alleppey mudbank region in 1972. Their experiment with regard to these mud cones confirm beyond doubt the viscous nature of the mud that underlies at Allepey, and its being, for all probability, the source of Alleppey mudbank. Similar mud cones observed earlier by some workers are also discussed briefly. INTRODUCTION Crawford (1855) was the f irst to report on the mud cones, or 'mud volcanoes,' at Al leppey. He has inferred f rom this pheno-menon that there exists a subterranean mud at Al leppey that may be the source of mud for the Alleppey mudbank. Subsequently, Phi l ip Lake (1889) and Davey (1903), t o o , observed mud cones at Al leppey. However, after 1903 there had been no further records of mud cones in this region and, therefore, their role in the format ion of mudbanks was not taken seriously. But, in the course of our intensive invest igat ion on the mudbanks of the Kerala coast we came across active mud cones in the vic ini ty of the mudbank, that formed at Ambalapuzha, in July 1972. The fo l l ow ing account describes in detai l these mud cones and the insight they give into the nature of the underlying mud at Al leppey region, wh ich in all probabi l i ty contr ibutes the mud for the format ion of mudbank at Al leppey, as wel l as into the mechanism by which the mudbank is brought about. OBSERVATIONS Six active mud cones, in dif ferent stages of format ion, were seen at Kakkazham, a place about a kilometer from Ambalapuzha, about 18 MUDBANKS the northern l imit of the mudbank then in existence (See, Fig. 1), of wh ich three were on the beach, a few meters away from the h i gh -7«'^0 VALANJAVAZHI ,•••.••' / • * KAKKAZHAM 3 « \ AMBALAPUZHA N A KAROOR ' \ PURAKKAD 7sSo «^ Fig. 1. Diagram showing the places of mud cones at the beach and at the inter-tidal zone, and the cracl<s observed on the beach. water mark, and three in the water at the i n -tert idal zone (see Table 1). One of the cones that were in the intert idai zone, measuring 7.5 meters across, was found feeding the waves TABLE 1. Mud cone In water 1 2 3 On shore 4 5 6 Details of the mud cones at Kakkazham, observed in 1972. Mean Heig diameter cone ht of from (cm) ground level (en-at centre 425 — 535 -750 271 40 128 17 106 20 ') at peri Dhery — — — 27 15 15 Distance between cones (m) 2 45 25 34 w i th loose mud as wel l as lumps of i t . wh i l e in others fresh mud was oozing out adding to the cones. There were also ' c racks ' found to have developed in three places on the surface of the beach more or less parallel to the shore, about 29 m away from the mud cone that was feeding the waves. Each crack was about 2 cm wide,10 to 15 m long and separated from each other by about 3 to 5 m (Plate l ,A& B). During the high t ide the sea water covered this area, obl i terat ing the cracks, but they reappeared at the t ime of low t ide. Attempting t o gauge the depth of mud beneath the cones, we found that a ha i f - inch-thick Gl pipe fa i led to touch any hard bo t tom even when inserted to its fu l l length of 6 meters; but when t i l ted the hard sides could be fel t all round, showing that the cones were mounts, crusted by exposure, of loose mud emerging out of what appeared to be deep wel ls , fu l l of sof t and unconsol idated mud. In the t idal zone Qnes, on the other hand, this emerging mud, as and when it d id , was carried away by the waves, and what remained was only open mud wel ls, wh ich at t imes could be like quagmire, very dangerous to f ishermen. This is borne out by a sad incident fo ld us by the f ishermen when we enquired why a part i -cular spot on the tidal zone was marked out by a partly buried coconut trunk (see: Plate IV, C). A few days earlier to our v is i t , we were to ld , a boy, jumping into the water f rom a home-bound canoe, to haul it ashore, had, instead, jumpedunnot ic ingly into one of these gaping holes and sank down to its depth,in such a way that even his body was not able to be re-covered. It was this mud w e l l , wh ich was later covered by sand brought by the oncoming waves, that was thus marked, to ward off any further accidents. The mud cones, which were active when the S. W. monsoon was intense, became inac-tive or subsided w i t h the subsidence of the latter, obviously because the forces then res-ponsible for bringing the mud out from bene-ath had now languished. Wi th in a f ew days the upper crust of the beach cones became hard and broken d o w n to pel lets, due to sun l ight (Plate I I , A-C); but those in the intertidai zone gradually subsided and covered over by sand deposited by the onshore waves (Plate I I I , A) . CMFRI BULLETIN 19 Table 2 gives the successive changes the mud cones undergo during a period of t ime. TABLE 2. Observations on the behaviour of cones at Kal<l<azham IVIudcone Date of No. forma-tion At the inter-tidal zone 1 19-7-72 2 197-72 3 27-7-72 On the beach 4 18 7-72 5 14-7-72 6 15-7-72 Active phase (days) 12 9 10 9 10 12 Dormant Date of phase (days) 6 9 3 10 9 11 complete subsid-ence 6-8-72 6-8-72 9-8-72 6-8-75 2-8-72 5-8-72 DISCUSSION Toward the close of the last century and the beginning of the present, the subterranean mud was held to be the source of mud for the Aileppey mudbank by those authors who had chances to observe mud cones. However, the laterinvestigators, who never had any oppor-tuni ty of seeing the phenomenon in operat ion, were reluctant to accept th is v iew and they, instead, suggested alternate views about the source of mud for the Aileppey mudbank (see Chapter 3). Crawford (1855), on seeing the mud cones in operation on the beach and on the roads of Ai leppey, wrote that " the beach and roads presented then a singular appearance, nothing to be seen but these miniature volcaneso, some si lent, others act ive" . He also noticed subsidence of shore, after or during the rains, causing long fissures, varying f rom 120 to 360 f t in length. Phil ip Lake (1899) also had the experience of seeing mud cones and land subsidence in the v ic in i ty of the Ai leppey mudbank. He found subsidence of land to a depth of 2-3 f t ; the strip of shore subsided being to 60 ft in breadth and 900 ft in length. Further north of this he found the shore sunk in l i t t le steps so that there were a number of " l i t t l e terraces" each a few inches high, rising one above the other f rom the sea towards the shore. At the northern end, w i th in the inter-t idal zone, a heap of mud rose to a height of 2 or 3 ft above the level of the sand. A l l along the seaward edge of the subsided areas there were a number of "bas in-shaped ho les" in the sand having a diameter of 4 to 5 ft and a depth of 3 to 4 f t . In 1903, Davey had observed mud ooz ing out, as f rom l i t t le vo lcanoes, a l l around the o ld pier (Ai leppey pier) and br inging w i t h it decayed stems of trees. Our observat ions wel l conf irm these earlier observations and conclusions. The occurrence of cracks on the beaches, suggesting the sink-ing of the coast l ine, and eject ion of mud in the form of mud cones (and the cont inuing ooz ing of mud through i t ) show beyond doubt that the source of mud for the Aileppey mud-bank is of subterranean or ig in , the mec-hanism of bringing it out being the same as indicated by the format ion o f the mud cones. 20 MUDBANKS MUD CONE i" '^*' issr..i,.-Piate-I-A: The mud, in pellet form, scattered all over the beach- Also seen is a long crack along the beach as a result of subsidence. B: A close>up of the crack showing the subsidence of the seaward portion of tha land. C: An active mud cone. Plate-II.A: Thedry crust of a dormant cane; B: The mud cone starts suosiding. C; A fu'ly subsided mud cone. MUD CONE I . » Plate-Ill. A: Asubsided intertldal mud cone covered cverby sand. B&C: Measuring the depth of the mud cone with a 6-m G. I. pipe. /.r-?=* by Plate-I7.A: Tha windward limit of the mudbank marked the breaking of the waves, B: An active mud cone seen fesding the waves with subterranean mud. C: The spot, marked by a coconut trunk, where the mud well had been, in which a boy was reported to have sunk' 

Source of mud at Alleppey mudbanks: Its distribution and physical and chemical characteristics

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Source of mud at Alleppey mudbanks: Its distribution and physical and chemical characteristics

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