Trans.Inst.Indian Geographers ISSN 0970-9851 Excavation Features on Rock Coasts: A Study of Honeycombs, Taffoni and Caves from North Konkan

Ajay Kamble and S.R. Jog, -

Abstract Excavation of Geo-materials on a rocky coast, causes formation of geomorphic features like Honeycombs, Taffoni and Caves. These features mainly account for the consumption of cliff and platform surfaces. These differ not only in their size, but also as per their processes of formation. The North Konkan region has several patches of rocky coasts where these landforms are observed at many locations. These locations were surveyed to obtain morphometric variables such as size, length, width, depth, height etc. Apart from visual interpretation, the rocks and material characteristics were analyzed using microscopic observation of thin sections. Field survey, morphometric analysis and material analysis show that honeycombs are primarily a result of erosion by salt spray on a relatively resistant, fresh rock surface. Taffonis, which are similar features, are formed by excavation of severely weathered material. Notches and caves are larger in size, and are associated with differential weathering and erosion of different Basalt flows. Keywords : Rocky Coasts, Honeycombs, Taffoni, Notches, Basalt, Konkan

Introduction rock-mass, and hence, can be grouped On rocky coasts, the disintegration together. Honeycombs, taffonis, notches of rocks by mechanical or chemical and caves are such excavation features, processes would ultimately alter a rock- observed on most of the rocky shores. mass to become physically weak and Honeycombs and taffonis are micro- chemically unstable. The weathered and features, while notches and caves are loosened material is removed by various of much larger size, in increasing order. agents of erosion. Removal of rock- Among these, honeycombs and taffonis, mass, if it is site-specific, shall leave taffonis and caves and notches and behind its imprints in form of small and caves have a close association, and at large excavation features. Though being times, may share a cause-consequence varied in their size and morphology, relationship; i.e. honeycombs may give these features owe their origin to rise to taffonis and notches may be a common process, i.e. removal of enlarged to form caves.

Transactions | Vol. 41, No. 2, 2019 | 185 The present paper attempts to rather convenient to accept, since many describe the characteristics of these workers define them in a genetic context, features and discuss the various resulting due to a certain process. processes involved in their formation, Honeycombs have been observed in along North Konkan Coast of all climatic regions; from equatorial Maharashtra. to mid-latitudes (Palmer and Powers 1935, McGreevy 1985), and even in Study Area Antarctica (Nichols 1960). However, The area under consideration for the honeycombing contributes significantly study is a 40 km stretch in to the consumption of rocks and may of North Konkan. Extending from Dighi be considered as one of the primary in the north to Velas in the south, the area mechanisms of rock-disintegration lies between 17°55’ to 18°19’ latitude in coastal areas. The occurrence and and confined between 72°55’ and 73°E characteristics of honeycomb structures long (fig.1 See page 197). in the study area can be described as follows: The area for the present study is a part of North Konkan coast, in Raigad 1. Not all parts in the study area show District of Maharashtra. It is a strip of a developed honeycomb pattern. about 35-40km, extending from Murud Honeycombs are more commonly in the north, to Velas in the south. found in the southern part of the study area, at Hareshwar platforms, The coastal area is underlain by Shriwardhan point headland, and Deccan trap formation made up of Velas platform. Towards north, Basaltic flows. These rocks were platform does not formed due to outpouring of lava during exhibit a developed honeycomb the Cretaceous and Eocene period pattern. The platform rock rather (Krishnan 1982). has small pittings of 1-2mm, Rocky shores are observed at occupied by mollusks. Small sized, several locations in the study area. poorly developed honeycombs Some of these were selected for a may be observed at Adgaon detailed study. Bharadkhol Headland platform, though they are larger near Shekhadi, Headland at and pronounced on the Adgaon point, and Velas have stack surface. The sheltered sites occurrence of honeycombs. taffoni, of Dighi are more or less devoid caves and notches. of honeycombs. However, between Sarva and Nanvel headland to the Honeycombs north of Velas Agar, they show an Also called as “Stone lattice” or excellent development on platform “Stone lace”, honeycombs are small, surface. The following table closely-spaced depressions, up to a provides a summary of location few centimeters in diameter and depth and general characteristics of the (Trenhaile 1987). This definition is honeycombs in the study area.

186 | Transactions | Vol. 41, No. 2, 2019 Table 1 : Description and characteristics of honeycombs Location Description of honeycomb characteristics Size and depth Found over platforms and cliff face. Regular 2-2.5 cm in spacing, dark gray colour, sometimes reddish-brown diameter. Up to Velas with luster. Hard sidewalls. Found up to 4.5m above 2cm deep. the platform on the cliff face. Found mainly on cliff face, along with taffonis. 2-4 cm in Hareshwar Larger range of size. Dark colour, hard sidewalls, diameter, up to luster. Not much on platform surface. 4 cm deep Shrivardhan Mainly of cliff faces, very intricate, regular, deep. 3-5 cm in Point Max. depth observed at this site. Larger and irregular diameter, up to Headland near joints. No luster. Dark brown colour. 6 cm deep. Formed in reddish brown altered basalt, poorly Up to 2mm in Bharadkhol developed, not uniform lattice, in form of small diameter and Headland pitting. depth. 1.5-2cm on Small, irregular honeycombs on platform surface. Adgaon platform, 1cm Larger and deep on stack surface (3cm) deep. Very well developed lattice, spread over entire Between platform surface, and insitu boulders. Absent Up to 3 cm in Sarva and between inter-boulder spaces. Hard sidewalls, diameter, 2-2.5 Nanvel collapse of sidewalls and fusing of honeycombs, cm deep. Headland sharp pinnacles seen. Luster on sidewalls. Almost absent, small and irregular, only on platform Up to 1cm Dighi surface, formed in reddish altered basalt. diameter

2. It may be observed that development 3. Honeycombs do not show any of honeycombs falls more or less in affiliation to slope. Vertical, sloping, line with the exposure to the sea. as well as horizontal surfaces have Velas, Hareshwar and Shrivardhan developed honeycomb lattice, point headlands have larger, hence it is difficult to associate their regular and deeper honeycombs, presence with surfaces having a than Adgaon or Dighi, which are certain degree of slope. sheltered sites. Bharadkhol platform A strong relationship, however, may be cited as an exception to may be identified between this pattern, where honeycombs honeycomb development and show a poor development despite the type of rock. The best occupying a headland location. developed honeycombs were

Transactions | Vol. 41, No. 2, 2019 | 187 observed at Velas, Hareshwar of honeycombs does not seem and Shrivardhan Point headland, to be guided by joints. They are sites which have a massive, present on surfaces with, or without compact basalt (Plate 1a See joints, with almost equal frequency. page 198). This material is However, honeycombs tend to be cohesive, fine grained, and has larger and irregular in shape, near little amygdales, vesicles and the joints. The ones, occupying secondary minerals. The thin homogenous, joint-free areas, are section of these rocks show that more circular in shape and smaller. the basalt has not been altered 6. The maximum depth of an individual much (Plate1b See page 198). honeycomb structure observed is On the other hand, coarser and about 6cm. Beyond these depths, the altered basalt in the northern honeycomb walls either collapse, parts, i.e. Bharadkhol and Dighi, leaving behind sharp pinnacles. do not exhibit appreciable Fusing of honeycombs forms larger, honeycomb development. irregular shapes, but does not cause Bharadkhol headland does have any increase in depth. harder, compact, vertically jointed basalt forming cliff and 7. A close observation of an individual stack-top, but no honeycombs honeycomb reveals that the are observed on these rocks. depression has vertical walls, and the mouth of honeycomb does not 4. Neither the host rock, nor show any overhang or lip (Fig.2). honeycombs exhibit presence of any weaker material. The honeycomb Taffonis surface is smooth, sidewalls are hard and have a metallic luster of Taffonis and honeycombs may often reddish-brown colour. No rock- be confused with one another, due to debris is found in the honeycomb similarity in form. Since there is no depressions, except precipitation of precise criterion for differentiation salt. between the two, taffonis may be taken as large honeycombs. Some authors 5. Within a given cliff-platform have also considered honeycombing as complex, honeycombs have taffonis developed under unfavourable certain preferred locations. They conditions, so that their full size could are rarely observed near the low- not be attained (Martini 1978). It seems tide cliff or at platform margin. It to be an accepted fact that the taffonis is rather the central and landward are hollows carved in the rocks, which portions of platforms which have a are larger than honeycombs. Occurrence concentration of honeycombs. The of taffonis is not restricted to coastal cliff face also has honeycombs up environments alone. They have been to a height of 3-4m. The existence reported even from deserts (Mabutt

188 | Transactions | Vol. 41, No. 2, 2019 1977) and over a variety of rock-types, 3. The sidewall taffonis and the ranging from Granites (Bradley Et ones occupying the cave ceilings, al 1978, 1979), Sandstones (Mustoe are markedly different in their 1983), Limestones (Kelletat 1980) and shapes. The sidewall taffonis are Ash flow tuffs. (Mc Bride et al., 2000) comparatively smaller in size Taffonis observed in the study area (<20cm diameter) and generally, have a restricted occurrence, but their are circular. On the other hand, the peculiar characteristics differentiate cave ceiling taffonis are larger but them from honeycombs, and also offer elongated, elliptical or irregular in a clue in understanding their origin. shape (Plate 2). These observations are as follows: 4. The material in which the taffonis 1. Fully developed taffonis are are carved, is severely weathered. observed only at one site in the study Taffoni walls are weak, and can be area, i.e. at Hareshwar platform. broken by hand. The thin section of Restricted occurrence and relatively this material shows a highly altered immature taffonis are also found basalt (Plate 4b See page 199) which on velas platform. Overall, it may is comparatively coarser and appears be said that taffonis are confined to like a sedimentary formation in hand the southern portion of the study specimen (Plate 4a See page 199). area. Velas area has simple Aa 5. Orientation and shape of taffonis is basalt flows, while Hareshwar has influenced by plains of separation, like simple and some compound basalt joints. Joints seem to be the favoured flows exposed in the shore zone locations for developing taffonis. (Parthasarathy et al, 1984). The In case of longitudinal taffonis, highly altered coarse basalt does not ledges of dark coloured resistant support much taffoni development. material can be observed within 2. Though taffonis have been formed the taffonis (Plate 3 See page 199). over bare cliff faces, their best 6. Cross-section of a singular taffoni development can be seen on the (fig.2) shows the difference between cave walls and ceilings (Plate 2 the taffoni and honeycomb shape. See page 199) It may be noted that While honeycombs have wider almost all these are the “sidewall opening and vertical walls, taffonis taffonis”. No taffonis are observed preserve a pot-like shape, having on the platform surfaces. Intricate enlarged, hollow interior and pattern of taffonis exist on the cave comparatively smaller opening. The ceiling. The interior of the caves taffoni mouth generally has a lip or receive sunlight only in the late an overhang. Interior of taffonis can afternoon, and for rest of the day, be as deep as 1m and are cool and the cave interiors are shady. shady.

Transactions | Vol. 41, No. 2, 2019 | 189 7. Taffoni interiors have an 1. Caves and notches in the study area accumulation of rock-debris can be differentiated on the basis obtained from the sidewalls and of their shape and sizes. Caves are roofs. This material is essentially in generally elongated, wide openings, form of thin flakes of less than 1mm more than 3m in height and depth. thickness (Plate 4a) The flakes are Notches are comparatively smaller, fragile and have small holes on not exceeding 1.5m in height and their surface. These holes in fact, depth. The shapes of caves are mark the positions of secondary semicircular or irregular, while the mineral particles, which did not fall notches are generally parabolic. off along with the flake. The taffoni Despite these differences, caves and walls and roofs show presence of notches are much associated with secondary minerals, but they are each other, with respect to their hardly found among the deposited location. flakes at the taffoni-base. No salt 2. Developed cave structures are found was found in the taffoni deposits. only along Hareshwar platforms, though some smaller caves are seen Notches and caves a Velas. Caves are not observed Notches and caves, otherwise, are on Bharadkhol, Adgaon and Dighi prominent features of limestone coasts, platform. where the process of solution of the 3. There is a little variation in the rocks forms these features. A typical occurrence pattern of notches and notch would be in form of a narrow, caves. Notches are generally found deep undercut at the cliff base. Notches along with caves, but caves may are commonly found in warm, tropical not be essentially associated with limestone coasts. Caves are larger notches. On Bharadkhol platforms, and deeper, caused by solution and notches have developed, but caves are excavation of the cliff. not found. Neither caves, nor notches These definitions, however, cannot are found at Adgaon and Dighi. be applied to the study area. Features 4. Notches located at the cliff-base, are referred to as ‘caves’ in the study area, formed in homogenous, cohesive are much smaller in dimension. They material. Velas, Hareshwar and occupy the cliff base in form of wide some parts of Bharadkhol platforms semicircular or parabolic openings, have such basal notches. Their cut due to wave action. Since solution shape is generally parabolic. notches have a little scope of formation in basaltic areas, notches in the study 5. Caves are of variable heights. On area basically reflect the imprints of Hareshwar platforms, cave heights tidal fluctuations. The surveys and between 3-11m were observed observations confirm the following (Plate 6 See page 200). The characteristics of notches and caves. shapes of caves are semicircular,

190 | Transactions | Vol. 41, No. 2, 2019 or irregular, with overhangs at the the observation that vigorous wave cave mouth. environments on headlands and exposed 6. The interiors of the caves invariably coasts have the best development of have taffoni development. Not a honeycombs. Bruthans (2018) also single cave could be located at concluded that the hydraulic process, Hareshwar, without taffonis on its and alternate wetting and drying was sidewalls. Notches, however, are an important process in honeycomb free of taffonis, and are carved in formation. fresh or honeycombed rocks. Honeycomb development is least 7. In case of larger caves, rocks above affected by slope of the surface on the cave top are visibly different which it develops, suggesting that it than the ones, which host the cave. must essentially be a physical process, Cave formation generally coincides proceeding from exterior of the rock with the margins of two different towards the interior. If honeycombs were basalt flows. a result of chemical weathering, their occurrence would have shown some 8. Formation of caves at the low- affiliation to surfaces having a particular tide level could not be confirmed. slope value, where degree of moisture However, some tunneling action can accumulation was higher. Contrary to be inferred, as one can observe air this, the material in which honeycombs bubbles escaping through platform are formed, are more or less unaltered, joints, as a wave approaches the fresh rock faces. The thin sections as platform margin. well as rebound values confirm that the honeycomb-hosting material has not Discussion undergone much chemical alteration. As mentioned at the outset, honeycombs, Since chemical weathering does not taffonis, notches and caves are different seem to be the controlling factor for geomorphic features with respect to honeycombing, one may attempt to their origin, form and size. However, explain their origin due to mechanical since all of these are residuals of wave erosion or salt spray. Of the two, rock-mass excavation process, a the mechanical wave erosion cannot combined discussion of their genesis be assumed to operate so uniformly may lead to a better understanding. If so as to produce a regular, equispaced the characteristics of honeycombs and honeycomb lattice. Moreover, the taffonis are analyzed, it suggests that areas which are close to the platform honeycombing is a result of salt spray termination at the seaward side, and on un-weathered rocks, while taffonis which receive maximum wave impact, originate due to mechanical excavation are surprisingly devoid of honeycombs. of a severely weathered rock. Therefore, the only process which Association of honeycombs can account for their occurrence and with wave-splash, is reflected in characteristics, is the salt spray and

Transactions | Vol. 41, No. 2, 2019 | 191 related mechanisms. This also explains Altered basalts with coarser grains, the absence of honeycombs near do not possess the required granular platform margins. Since these parts are structure for honeycomb development. always kept wet by waves and splash, As the grains are larger and the secondary an alternating wetting and drying does minerals form bigger crystals, salt not take place, which is essential for precipitation may not be able to dislodge salt crystallization and precipitation. them. Even if some grains are removed, Platforms portions near the cliff base their effect is masked by the overall frequently undergo wetting and drying, coarse texture. Moreover, accumulation and hence, honeycombs are located in and crystallization of salts does not these zones. As observed by McGreevy remain uniform on rough surfaces. As (1985), salt crystallization is capable of a result, unequal distribution of grain dislodging mineral grains like quartz, dislodgement cannot produce a regular causing microscopic cavities in the honeycomb structures. It would rather rock surface. produce a rough, pitted surface, which Exploring salt spray as a probable is observed at sites like Bharadkhol and reason for honeycomb formation, Adgaon. Bharadkhol headland does answers most of the queries. It not have a compact, vertically jointed rock, only accounts for the salt precipitation but it overlies the altered basalt and observed in the honeycomb depressions, falls much away from the spray zone. but also explains why honeycombing On the Dolerite dykelets of Dighi, is poorly developed in coarse-grained honeycombs fail to develop because of rocks of Bharadkhol or Dighi. Since the dense jointing. Before honeycombs salt crystallization causes granular can develop, these rocks may get eroded disintegration, and proceeds grain by by waves. grain, the process shall work much Once developed, a honeycomb uniformly in fine-grained, homogenous structure can be stabilized by rocks. Thus, the honeycomb lattice precipitation of iron oxides, which shall be uniform in terms of size and can harden the sidewalls. The smooth depth. Shapes shall be circular, as surfaces and metallic reddish-brown the grain-dislodgement shall happen luster suggests that case-hardening of uniformly in all directions. If a patch honeycomb structures has occurred of comparatively weaker or weathered due to precipitation of iron oxides. material is encountered, the grain However, the fact that honeycombs do dislodgement shall not act uniformly, not penetrate much in depth, supports causing a change in honeycomb size the assumption that they are a result of and distortion in shapes. It has already salt spray. As a honeycomb deepens, been mentioned that honeycombs are its interiors shall he protected from salt larger but irregular near the joints, as spray and precipitation. Eventually, joints have a weathered material in the their deepening shall cease. Honeycomb vicinity, due to moisture accumulation. walls being harder, may resist erosion

192 | Transactions | Vol. 41, No. 2, 2019 for some time and remain as pinnacles. water-seepage from the cave top. This Finally, they shall collapse, exhuming a seepage may follow the existing joints fresh surface for honeycomb formation. or root penetrations, thereby causing Thus, it may be said with a fair degree a concentrated weathering along the of confidence that honeycombing paths of seepage. Thus, longitudinal is essentially a physical process, taffonis shall originate, when these associated with splash and salt spray on weathered tunnels are excavated. The a relatively fresh, fine grained rock. It material resistant to the weathering is a multi-nuclii, uniform process and shall remain as residual ledges within hence, produces a regular pattern of in taffoni structures (Plate 3). excavation holes, i.e. honeycombs. Taffonis are a much different structure, larger and deeper than honeycombs. An important characteristic of taffonis is that they are always associated with a weak and weathered material. The thin sections (plate 4b) of taffoni-host material and the taffoni wall, shows that the basalt is altered to such an extent that it resembles a sedimentary formation in hand specimen. Thus, Fig. 2: Difference between Honeycomb process of chemical weathering seems and Taffoni formation processes to be an essential condition for taffoni development. The best development of taffonis in cave interiors, must be If a homogenous, but weathered rock related to the accumulation of moisture, is exposed to spray action, it would at these locations. The typical taffoni start carving small pitting on the rock- shape, having smaller openings and surface. Thus, in coastal areas, the comparatively larger interiors also initial stage of taffoni development suggest that the deepening and widening may be similar to, or same as that of of the taffoni-interior is related to the honeycombs. Paradise (2013) has weathering of the rock-mass. It has also attributed an important role to been observed that the taffonis on the salt weathering in Tafoni formation. walls of the caves, are more or less However, the grain-dislodgement and regular in shape, while on the ceiling, excavation may proceed at a much they are larger but irregular (Plate faster rate, in all directions, imparting 2). On the cave walls, the moisture a spherical interior to the depression. obtained is by spray action, which has As the structure enlarged, and deepens, a uniform distribution. However, on the granular disintegration may slow down cave ceilings, the spray is aided by a or cease. Since the taffoni depressions

Transactions | Vol. 41, No. 2, 2019 | 193 occupy cool, shady areas, they shall are a result of salt spray and consequent experience alternate warm and cool thermal flaking in severely weathered, micro-climatic conditions during sunny homogenous rocks. days and nights. As compared to taffoni The caves and notches in the openings which are always warm, the study area are found in proximity. taffoni interiors shall experience a Comparatively smaller size of the larger range of temperature variations. notches, leads to an assumption that The severely weathered rock, having they are formed in comparatively a higher swelling and insolation resistant material. This assumption coefficient (Parthasarathy and Shah is strengthened by the observation 1984, Joshi 1980) shall readily respond that notches are developed in bare or to these micro-climatic variations. The honeycombed rocks, which are less alternate expansion and contractions weathered. The erosion and removal of of this material shall cause flaking rock-mass, therefore, shall be restricted of the material from taffoni-roof and within the tidal range. Notches, therefore, sidewalls. Flaking process shall be preserve the imprints of tidal inundation more effective in the interior of the zone, in a roughly parabolic shape. taffonis, as compared to its mouth. A compact, un-weathered material is Thus, widening of the mouth does not more suitable for the formation of a take place as much as excavation of typical notch. If the rock is weathered, the interior. Formation of the typical the notch-roof may become irregular, taffoni-shape with narrow mouth, and widening the notch opening and forming large, hollow interior, can be explained a feature similar to a small cave. Caves by the above-mentioned process. The on Velas platform, appear to be a result resistant secondary mineral particles of deformation of existing notches. In do not expand and contract, and hence, that respect, notches formation in the remain embedded in the rock-mass. study area, may represent an initial The surrounding layer of weathered stage in cave formation, where massive, material falls off as a flake, having homogeneous rocks are found (Plate 5 perforations or holes, where secondary See page 200). minerals were once located (plate 4a). Larger caves may seldom form in Coarse-grained rocks, therefore, are an un-weathered material. All large less suitable for taffoni development. caves in the study area essentially have The coarse texture, with a larger grain- taffoni development. Caves and taffonis size, shall restrict the formation of the appear to share a cause-consequence flakes. Thus, the coarser rock continues relationship, with one favouring the to weather in a non-uniform pattern, development of the other; i.e. formation thereby producing rough surfaces and fusing of large taffonis may form a and irregular depressions, rather than cave, while caves provide a cool, shady producing taffonis. Therefore, it can be place for further taffoni development. said that unlike honeycombs, taffonis Occurrence of largest caves coinciding

194 | Transactions | Vol. 41, No. 2, 2019 the margins of basalt flows, shows that References flow margins are the potential sites • Bradley, W.C., Hutton, J.T., and Twidale, for cave formation. Weathering and C.R. (1978): Role of salts in development excavation of a comparatively weaker of granitic taffoni, South Australia, J. Geol. flow between two resistant flows, can 86, pp 647-64. initiate cave formation. As the cave • Bruthans, J. et al. (2018): Origin of deepens, weathering penetrates into the Honeycombs: Testing the hydraulic resistant flows as well. Large boulders and case hardening hypotheses, are loosened from the cave roof and Geomophology, 303. pp. 68-83 collapse, forming overhangs at the cave • Karlekar, S.N. (1990) : The significance mouth(Plate 6). Thus, while notches of Harihareshwar shore platform in develop in a homogeneous rock interpretation of sea level changes along exposed to tidal oscillations, caves are Maharashtra coast, Trans. Inst. Ind. Geog. a result of a varying rock strata exposed Vol 12, no 2, Pune. to a tidal impact. • Kelletat, D. (1980): Studies on the age of honeycombs and tafoni features, Catena, 7, Conclusions pp 317-25. 1. Honeycombs develop on exposed • Mabutt, J.A. (1977): Desert Landforms, parts of rocky shores and are a MIT Press, Cambridge. result of erosion and salt spray on • Martini, I.P. (1978): Tafoni Weathering, un-weathered rocks. with examples from Tuscany, Italy, Z. Geomorph. 22, pp 44-67. 2. Taffoni develop in sheltered locations. These are formed due • McBride, E.F. and Picard, M.D. (2000) : to mechanical erosion of highly Origin and Development of Tafoni in tunnel weathered rock. spring tuff, Crystal Peak, Utah, USA, Earth Surface Processes and Landforms, 25(8), 3. Notches are formed at exposed 869-879. locations on relatively un-weathered • McGreevy, J.P. (1985): A preliminary rocks and are formed due to tidal scanning electron microscope study of oscillations. honeycomb weathering of sandstone in 4. Cave formation in the study area a coastal environment, Earth Surface is primarily due to differential Processes and Landforms, 10, pp 509-18. weathering on the margins of • Mustoe, G.E. (1983) : Cavernous varying lava flows. weathering in the Capitol Reef Desert, Utah, Earth Surface Processes and Landforms, 8, pp 517-26.

Transactions | Vol. 41, No. 2, 2019 | 195 • Nichols, R.L. (1960) : Geomorphology of • Trenhaile, A.S. (1987) : Geomorphology Marguerite Bay area, Palmer Peninsula, of Rock Coasts, Clarandon Press, Oxford, Antarctica, Geol. Soc. Am. Bull. 71, pp 384 p. 1421-50. • Palmer, H.S. and Powers, H.A. (1935) : Dr. Ajay Kamble Pits in coastal pahoehoe lavas controlled Associate Professor in Geography by gas bubbles, J. Geol. 43, pp 639-43. Bhavan’s College, Andheri, • Paradise, T.R. (2013) : Tafoni and other [email protected] rock basins, Treatise on Geomophology, Ed. Shroder, J., Pope, G.A., Academic Dr. S.R. Jog Press, San Diago, CA., Vol 4. pp 111-126 Professor of Geography (Retired), Dept. of Geography, • Parthasarathy, A. and Shah, S.D. (1984) : Savitribai Phule University of Pune.jog. Deccan volcanics-Rock material and Rock [email protected] mass characteristics and their significance in Engineering Geology, Deccan volcanism, Ed. Sukheshwala R.N., St. Xavier’s College, Mumbai, pp 233-244.

196 | Transactions | Vol. 41, No. 2, 2019 Fig. 1. The Study Area (See page 186 for the text).

Transactions | Vol. 41, No. 2, 2019 | 197 Plate 1a: Well-developed Honeycomb structure on cliff face, Velas (see page 188 for the text)

Plate 1b : Thin section of Honeycomb rock material showing almost unaltered Basalt with groundmass of pyroxine and feldspar (X40 CP) (see page 188 for the text)

198 | Transactions | Vol. 41, No. 2, 2019 Plate 2: Variation in Taffoni Shapes on Plate 3: Irregular-shaped, medium sized Cave wall and Cave ceiling, Hareshwar (15-20 cm) Taffonis, Hareshwar (Plate 2 & 3 - See page 190 for the text)

Plate 4a: Weathered flaky debris found in Taffoni interior (Plate 4 a&b See page 190 for the text)

Plate 4b: Thin section of Taffoni-debris showing highly altered Basalt (X40 CP)

Transactions | Vol. 41, No. 2, 2019 | 199 Plate 5: Notches coinciding High-Tide level in un-weathered basalt, Velas Platform (See page 190 for the text)

Plate 6: Cave formation in weathered Basalt, Hareshwar Platform (See page 190 for the text)

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