Tons Of Rock Research Articles

An integrated shipboard ocean floor research system using a SeaBeam 210 ocean survey system installed on the R/V Ka'imikai‐o‐Kanaloa

An integrated shipboard research system capable of operating in waters of up to2,000 m has been designed and implemented by the Hawai'i Undersea Research Laboratory (HURL), University of Hawai'i. It uses a remotely operated ocean‐bottom survey camera system, a remotely operated vehicle (ROV), the Pisces V submersible, and a multibeam mapping system aboard the 225‐ft RIV Ka'imikai‐o‐Kanaloa. These systems are operated from the stern of Ka'imikai. The Pisces V submersible is deployed and recovered with a mounted Caley telearm and articulated A‐frame system. The integrated shipboard system was designed for a multipurpose use of the R/V Ka'imikai‐o‐Kanaloa for Pisces V daytime operations or nighttime operations with an electro‐optical cable using either the HURL ocean‐floor sidescan or photo and video systems operated at 10 m above the ocean floor. The 1.14‐in. diameter cable is also used to operate the RCV‐150 ROV. In order to obtain a reliable bathymetric database for potential dive sites, a SeaBeam system was installed on the vessel. The installation consists of a hybrid system with classic shipboard electronics and ceramic SeaBeam 210 underhull arrays. The first test results with the ship's bow thruster tunnel closed showed that the SeaBeam 210 system peformed continuously with a normal central beam‐crossing error of less than 10 m. The first field study with the system was conducted during September 1996 over the submarine volcano Loihi, Hawai'i. to resurvey the edifice after an unprecedented collapse of the summit had taken place. The use of both SeaBeam surveys and visual observations with the submersible Pisces V allowed the accurate mapping of newly formed features, such as the 300‐m‐deep. 1,000‐m‐side summit crater, to take place. Almost 300 million tons of rock collapsed into the summit during this event. Magma withdrawal within the magmatic plumbing of Loihi is probably the mechanism by which the summit collapse took place.

Blast from the past

Forget dynamite or hydraulic and mechanical drills. Industrial and federal researchers have started boring holes with rocket fuel.In a cooperative arrangement between Sandia National Laboratory, Global Environmental Solutions, and Universal Tech Corp., scientists and engineers extracted fuel from 200 rocket motors and used it as a mining explosive. In a demonstration completed last fall, researchers used 4950 kg of solid rocket propellant to move more than 22,500 metric tons of rock from the Lone Star Quarry in Prairie, Oklahoma. They found that the fuel improved blast energy and detonation velocity over traditional explosives, and it required fewer drill holes.

Optimization Of Overall Excavation Costs In A Coal Strip Mine

AbstractCoal strip mines are usually large scale operations that excavate millions of tons of rock per year; thus optimization of the overall excavation costs can bring quite significant savings.The Operations Research problem involved is explained, and a method of optimization is proposed. This method depends on the creation of a ‘diggability function”, which is obtained by correlating the shovel digging rate to the average displacement velocity of the rock broken by blasting with explosives. The correlation is made possible by the use of the blasting model BLASPA to simulate the rock velocity; it is converted into a mathematical relationship by means of a least square approach.The “diggability function”, together with simulated values of the percentage of rock cast far enough to require no handling by the shovel, are combined to calculate the average shovel costs per cubic yard of rock moved. These costs are added to the drill and explosives costs to arrive at a prediction of overall unit excavation cos...

Structure and bulk composition of the Tin Mountain Pegmatite, Black Hills, South Dakota

The Tin Mountain rare element pegmatite of the Black Hills, South Dakota, has become an important source of geochemical data and interpretations, but its structure and bulk chemical composition have been unclear because of irregularities in the shape of the pegmatite and because most of it is concealed beneath the surface. Construction of structure contour and isopach maps based on surface and underground maps, three drill holes, and revised versions of previous cross sections has yielded a rather simple and orderly interpretation of the structure and has led to calculations of the tonnage of each of the internal units and of the bulk composition of the pegmatite.The outcropping part of the pegmatite trends S 75 degrees E for 90 m and then connects with an arm of the pegmatite that plunges gently north-northwest for approximately another 90 m. An albite-quartz-muscovite wall zone completely surrounds four inner units. Though these four inner units are termed zones, in accordance with standard practice, differentiation is more in a vertical direction than in a concentric arrangement. The upper two of these units are perthite rich: the uppermost is a perthite-quartz-albite hood, and beneath it is a body consisting almost entirely of perthite. Both perthite units are chiefly in the easterly trending arm of the pegmatite. These are succeeded by a quartz-spodumene-lithian muscovite core and an underlying body of albite-quartz-spodumene pegmatite, which are almost entirely in the north-northwest-trending arm of the pegmatite.The pegmatite has about 250,000 metric tons of rock. The wall zone makes up about 37 percent of this tonnage. The percentages of the other four units are, from the top down, about 22, 13, 21, and 7, respectively. The normative bulk composition is quartz, 34.5 percent; albite, 34.1 percent; orthoclase, 22.3 percent; spodumene, 6.3 percent, and corundum, 2.8 percent.

Barricaded

The earsplitting vibrations, the hurricane force, the monstrous, pulsating shock waves had finally dissipated, although the men could still hear and feel the echoes through their ringing eardrums and the soles of their booted feet. The five of them were finally back on their feet, rising from the cowering, fetal position which they had assumed for the previous few eons. They had all expected death from the very first rumble of the distant explosion . None of them had ever been in a mine explosion before, but all of them had enough imagination to conjure up the images of a runaway tornado ripping through the confined, narrow entries. They saw bodies and pieces of bodies flying the entries as if they had a logical destination, as if the subway would spew forth their bodies on Central Avenue. They left horrible red streaks as they glanced along the ribs of the entries on their final trip. Some of their cap lights 27 were still working, and it appeared as if gigantic white tracers were shooting down the entries until they crashed sickeningly into a face or a post or whatever they happened to explode upon. There were several of these shooting stars, dying in their blaze of glory. These things had happened so quickly that there had been no time to think, to panic, to do anything. The force of the explosion was past, but every microsecond was etched indelibly into the brains of the five quivering men as they crawled from the crosscut which had somehow managed to take less force than the rest of the entries. The dust was so thick it seemed solid. The men fumbled for their self-rescuers and managed to get them in place. There was no smoke, only dust, but the men's senses were too numb to even attempt to make such distinctions. The self-rescuers were meant to stave off carbon monoxide poisoning and were definitely to be used in case of an explosion . In the case of these five men, the self-rescuers helped filter the dust so that they could at least take gasping breaths of air until the dust began to settle like the dust in a gray, underground tomb. Even the men appeared as gray ghosts to each other as they stumbled down the escapeway together. The dust settled on their bodies and rose again in dreamy clouds as their bodies moved in silence. The whole thing would have seemed part of a strange dream to an observer: five gray men walking through a spacious tomb. Complete silence reigned now that the explosion was done. Only the rustling of the men's clothes and their strange, raspy, self-rescuer muted breathing broke that silence. They sounded like men already dead instead of merely dying men. A gray cloud followed each of the five men, as if an evil aura emanated from these gray ghosts. There had been no words exchanged among them since the first vibrations of the distant explosion had fallen on their bodies. One of them had exclaimed in a half-whisper, "Damn!" That was all the time there had been. Now that they were moving hurriedly down the escapeway , the self-rescuers forbade their talking, so they heard only each other's breaths and grunts. They came to a wall of rubble, tons and tons of rock stretching they knew not how far. They crossed through a blown-out stopping to the return. The same wall of impenetrable chaos greeted their anxious eyes. There were only four entries on the section, so when they discovered the belt in the fourth entry covered by that same wall of death, they sat among the tangled wreckage of belt, stands and bed rails, their heads hanging, each saying a silent prayer to whatever he conceived his deity to be. Zeke Smith was the first to raise his head and remove his self-rescuer. He took a deep breath and looked around him at the huddled men and the twisted steel. It felt good to take an unhampered breath. The thought that he was perhaps shortening his life had of course occurred to him. Even though the air seemed fresh...

Rock-Eval Data Relating to Oil-Source Potential of Shales of New Albany Group (Devonian-Mississippian) in Illinois Basin: ABSTRACT

Only limited data on petroleum source rock potential of New Albany Group (Devonian-Mississippian) shales have been reported, with the exception of vitrinite reflectance and some petrographic analyses. The New Albany Group contains the thickest and most widespread continuous black shale beds in the Illinois basin. The New Albany extends from northwestern Illinois to southwestern Indiana and western Kentucky and is thought to have played a major role in petroleum generation throughout the basin. In this study, Rock-Eval pyrolysis was used to measure the petroleum-generative potential and production index of the shale. Seven geochemical logs, based on 143 core samples from across the basin, and a production index map, based on a total of 252 samples (cuttings and cores) in Illinois, were generated. Systematic variations of petroleum-generative potential of the shale were observed. The variations are related to the differences in shale lithofacies, depth, and geographic location. The upper portion of the New Albany - the Hannibal and Saverton Shales - has the lowest oil-generative potential. The Grassy Creek, Sweetland Creek, and other stratigraphically lower shales of the New Albany Group generally have good oil-generative potential. However, samples from the Hicks dome area of extreme southern Illinois are overmature and havemore » no oil-generative potential. Source rocks that have both good oil-generative potential (> 6 kg hydrocarbons per ton of rock) and a higher production index (> 0.09) are generally located at depths of 2,500-5,300 ft.« less

Glass produced by underground nuclear explosions

Detonation of an underground nuclear explosive deposits a large amount of energy in what can be considered to be a point source in space and time. The strong shock wave produced propagates spherically outward, initially vaporizing the explosive and nearby rock and subsequently melting, then heating the surrounding rock as the energy density decreases. The vaporized material expands adiabatically forming a cavity. As the energy in the vaporized material is dissipated during the cavity formation process, the explosive and rock debris condense and mix with the melted rock. The melt flows to the bottom of the cavity where it is cooled and quenched by fractured rock fragments falling from above as the cavity collapses. Measurements on a large number of underground nuclear explosions indicate that approximately 740 tons of rock and/or soil are melted for every kiloton (1012 cal) of explosive energy, or approximately 25% of the explosive energy goes to melting rock. The resulting glass composition reflects the composition of the unaltered rock with debris from the explosive added. A wide range of physical appearances has been observed, ranging from white pumice to dense, dark lava. In general, bulk composition and color vary with the amount of explosive iron incorporated into the glass. By inference, all the refractory explosion products are mixed with the solidified melt, although the degree of mixing inferred is highly variable. Recent electron microprobe studies of glasses produced by the low yield Rainier event in welded tuff have produced the following results: (1) glasses are dehydrated relative to the host media, (2) glasses are extremely heterogeneous with respect to major element chemistry on a 20 μm scale, (3) a ubiquitous feature is the presence of dark “marble-cake” regions in the glass; these are locally enriched in iron and may be related to the nuclear device debris, (4) optically amorphous regions with chemistries of the crystalline phases are found in the glasses and provide evidence of shock melting, (5) only limited major element redistribution and homogenization occur within the cavity. The short duration of the thermal pulse and the high viscosity of the melts produced by the Rainier event precluded re-homogenization by diffusion or convection, respectively.

A review of regional mineral resource assessment methods

Over 100 papers on regional mineral resource assessment of nonfuels are classified according to method(s) used and form(s) of product in order to help identify possible methods for future assessments. Types of products that have been used include: tons of metal; tons of rock and associated grade; gross value; potential; number of deposits; probability of one or more deposits; tons of rock, grade, and number of deposits by type; potential supply; and net value. Assessment methods considered are: time-rate, crustal abundance, cumulative tonnage versus grade, simple subjective, complex subjective, Bayesian, frequency, trend, geometric probability, multiple regression, discriminant analysis, modified component, multivariate logistic, cluster analysis or pattern recognition, and simulation.Selection of a method to be employed in an assessment should be based on: (1) appropriateness of the product to the problem, (2) limitations in resources, such as information or time available for the assessment, (3) the level of uncertainty and acceptability of biases in the assessment, and (4) the need for verification of results and acceptance of the method.

Geological Assessment of Petroleum Potential of Tertiary Basin, Western Oregon and Washington: ABSTRACT

Recent drilling and the subsequent discovery of gas near Mist, Oregon, have stirred new interest in the large Tertiary basin of western Oregon and Washington. Developments in the understanding of the regional tectonic framework of the western North America continental margin over the last 10 years has clarified some aspects of the geology of this area. Our new-found insight into the mobile nature of the crust provides little new indication, however, of the possible volumes of hydrocarbons in the basin. Our current work in the area indicates little that is End_Page 448------------------------------ dramatically new or different from other evaluations of this basin, and limitations due to vegetative cover, volcanic rocks, and scarce subsurface control still handicap any appraisal. Potential structural traps and many potentially good reservoir intervals are present. The upper Eocene section contains abundant coal, which provides a potential source for dry gas, either by bacterial or thermal generation. A good source for oil, however, has not been documented. Some fine-grained units within the Oligocene and Miocene section do indicate areas of abundant organic productivity and some approach to the conditions necessary to generate at least 2 to 3 gallons of oil per ton of rock. Also, analogy with the Eocene-Oligocene section of the Gulf of Alaska suggests that a Poul Creek-type oil shale could well exist in this basin, with perhaps 100 to 300 million bbl of undiscovered reserves a reasonable, although highly speculative, forecast. Assuming that a kerogen-rich, pot ntial oil source rock is present, it remains difficult to document areas where burial depths in this relatively low heat-flow basin have been sufficient for thermal maturation, especially for rocks younger than Eocene. We have little doubt, however, that areas of sufficient burial depth do exist and hope to document that in our current work. The abundant shows of gas in wells, including Mist, and active seeps, over the entire basin, and a corresponding scarcity of significant oil shows, active seeps, tar deposits, or kerogen-rich shales, suggest that coal-derived gas may well be the primary hydrocarbon resource. Based on a thermal maturation model and the potential volumes of coal buried below about 15,000 ft (4,572 m), this resource could total a trillion cubic ft of gas. Low temperature, bacterial generation of methane from the low-rank coals could double that total, although the probability of retaining this gas within the system is less than for the thermally derived gas. End_of_Article - Last_Page 449------------

Oil and Metals in Ordovician and Devonian Kerogenous Marine Strata of Central Nevada: ABSTRACT

Kerogen-rich mudstone, siltstone, dolomite, and chert units as much as 50 m thick in the Vinini (Ordovician) and Woodruff (Devonian) formations contain potential resources of syncrude oil, V, Zn, Mo, Se, Ag, and Cr. Most kerogenous rocks originally consisted of organic-rich siliceous muds, slimes, and oozes. Organic matter is mostly amorphous, flaky, and stringy sapropel composed of planktonic organisms. The strata are within strongly deformed eugeosynclinal Paleozoic marine rocks of the Roberts Mountains allochthon. Many fresh black rocks are low-grade oil shales which, upon pyrolysis, yield < 40 l of oil per metric ton of rock; some thin layers yield as much as 125 l per metric ton. In these rocks, solid bitumen and liquid oil commonly fill voids and microfractures. Such early-phase hydrocarbons probably were released during diagenesis and formed without any major thermal degradation of the kerogen. Geochemical data suggest that the organic matter is thermochemically immature to mature and has not been subjected to temperatures above 60°C since deposition. Hydrocarbon contents (< 100 to 5,400 ppm) and organic carbon contents (< 1 to 25 weight %) vary widely. V, Mo, Se, Ag, and Cr in fresh black rocks occur chiefly in organic matter; Zn occurs as sphalerite and Ni in iron sulfides. Concentrations are as much as 5,000 ppm V, 18,000 ppm Zn, 1,000 ppm Mo, 100 ppm Se, 20 ppm Ag, 150 ppm Ni, and 600 ppm Cr in unoxidized rocks. Enrichment of V and Se and depletion of Zn, Mo, Ni, and organic matter occur in oxidized rocks. End_of_Article - Last_Page 767------------

Exploitation of Very Low-Grade Uranium Deposits: ABSTRACT

Where once there was great optimism about the economic exploitation of very low-grade uranium deposits (0.002 to 0.010% U3O8) such as occur in the Chattanooga Shale and the Conway Granite, there now is almost equivalent pessimism. A 1978 National Research Council report rules out shales and granites as future uranium sources, because of the enormous mining and processing costs required and because the environmental impacts of the many huge operations that would be needed are not likely to be acceptable. Such a conclusion appears premature. Gold is won at an after-tax profit from deep-mined refractory ores in which it is found in concentrations as low as 3 ppm (0.0003%), much lower than the low end of the range cited for uranium in shales and gr nites; the price-grade relations for gold suggest that 0.006% U3O8 rock could become ore at a price well below $150/lb. The energy balance appears positive even for once-through LWR burning; with breeders, it would be strongly positive. To meet the projected 1980 United States annual requirement of 19,000 short tons of U3O8 from a single mine in rock containing 0.006% U3O8 at 70% recovery would require moving a minimum of 1.24 million short tons of rock a day--a large amount, but easily within the ability of present technology (5 or 6 large copper pits would be the equivalent), and possibly not unacceptable in a time of energy scarcity. The major constraint on potential uranium supply remains political, rather than geologi al or technological. End_of_Article - Last_Page 435------------

Lithium resources in the Yellowknife area, Northwest Territories, Canada

Lithium resources of the Yellowknife area are well documented in the published literature and in the records on file with the Mineral Resources Division, Canadian Department of Energy, Mines and Resources, Ottawa. The significant deposits occur as steeply dipping tabular, unzoned pegmatite dikes of Pre-Cambrian age dated at 2200 million years. The principal lithium mineral is spodumene. The numerous pegmatites are localized in metamorphic aureoles of knotted schists associated with granitic intrusions. Detailed mapping and surface sampling of fourteen properties within the district has demonstrated the presence of 49,000,000 tons of rock to a depth of 152m (500ft) having an average grade of 1.40% Li2O. These resources could be developed if and when market conditions place a strain on available supplies. Numerous other smaller or lower grade pegmatites exist throughout the district.

The emission of occluded gas from rocks as a function of stress: Its possible use as a tool for predicting earthquakes

Occluded gases were studied from fifteen types of rock, including igneous, metamorphic and sedimentary. The specimens were stressed to a crushing failure at room temperature under a vacuum of about 10−9 torr. The more abundant gases were H2, CH4, H2O, N2 CO, O2 and CO2. However, each rock released gas with a characteristic composition. The volume of gas released was a variable function of stress above a threshold value. The greatest rate of emission occurred over the latter 20% of the rock's ability to withstand stress. Analyses of stress‐released occluded gases (excluding water), released as a function of stress, are given for a granodiorite and a gneiss. Volumes (STP)of most gases observed prior to and upon failure of the rocks are equivalent to several hundred liters each per ton of rock. Stress‐induced emission of a widely distributed, highly mobile gas such as H2 could serve as an useful indicator of a critical stress build‐up in the earth's crust.

Respuestas de las mujeres shuar al conflicto socioambiental en el área del Proyecto Mirador (Ecuador)

El Proyecto Mirador es un proyecto de minería a gran escala situado en la Cordillera del Cóndor que planea iniciar aproximadamente en 2018 la extracción de unas 60.000 toneladas de roca al día. La magnitud del impacto socio-ambiental que produce esta actividad se debe a su vez a que se da en un área habitada en parte por la nacionalidad indígena shuar, que disfruta del derecho constitucional a conservar sus territorios ancestrales. En este texto analizo cuáles son los impactos que tiene la minería a gran escala sobre la población femenina shuar y cuál es su percepción en torno al conflicto que plantea. Los datos que manejo mantienen coherencia con el discurso ecofeminista centrado en la particularidad de las mujeres rurales de los países del “Sur” en relación con la naturaleza y el desarrollo.

A Prehistoric Quarry Near Ray, Arizona

ABSTRACTA prehistoric chrysocolla quarry was discovered near the Kennecott open pit copper mine at Ray, Arizona. Chrysocolla, a blue copper silicate, was sought by aboriginal miners, who moved over one hundred and eighty tons of rock in the quarry to obtain the mineral. Stone tools were recovered at the site, but no pottery was found. Prehistoric ruins in the area indicate that the miners may have been Hohokam.

SEDIMENTARY BRECCIAS IN THE SOUTHEAST MISSOURI LEAD DISTRICT

Research Article| July 01, 1958 SEDIMENTARY BRECCIAS IN THE SOUTHEAST MISSOURI LEAD DISTRICT F. G SNYDER; F. G SNYDER ST. JOSEPH LEAD COMPANY, BONNE TERRE, MISSOURI Search for other works by this author on: GSW Google Scholar J. W ODELL J. W ODELL ST. JOSEPH LEAD COMPANY, BONNE TERRE, MISSOURI Search for other works by this author on: GSW Google Scholar GSA Bulletin (1958) 69 (7): 899–926. https://doi.org/10.1130/0016-7606(1958)69[899:SBITSM]2.0.CO;2 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation F. G SNYDER, J. W ODELL; SEDIMENTARY BRECCIAS IN THE SOUTHEAST MISSOURI LEAD DISTRICT. GSA Bulletin 1958;; 69 (7): 899–926. doi: https://doi.org/10.1130/0016-7606(1958)69[899:SBITSM]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Sedimentary breccias are important ore-controlling structures in the lower half of the Bonneterre Formation in the southeast Missouri lead district. Four major breccia zones, each embracing over 60,000,000 tons of rock, have been delineated. Individual ore bodies in the breccia zones range from over 6000 feet long and containing several million tons to a few hundred feet with several thousand tons.The breccias formed along the flanks of calcarenite ridges by submarine slides into near-by depositional basins. Extensive mine workings and closely spaced diamond drilling in the breccia bodies permit reconstruction of entire slides and determination of facies relationships leading to their development.Lithofacies studies indicate that the four basic types of material composing the lower part of the Bonneterre Formation—argillaceous mud, sand-size sediment, recognizable algal deposits, and carbonate mud—may be referred to environments of deposition which are dominated by two elements, depositional ridges and basins. The ridges are composed for the most part of calcarenite and reef deposits, the basin sediments of fine-grained carbonate and argillaceous muds. Differential compaction led to oversteepening of slopes in the gradational zone between the ridge and basin deposits and initiated movement of unconsolidated and partially lithified sediments. Repeated slides at fairly close stratigraphic intervals account for great thicknesses of breccia in the lower part of the formation. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Fort Peck Dam on the Missouri River

The dam is located on the Missouri River approximately twenty miles from the town of Glasgow, Montana. It will be constructed of earth by the hydraulic process. The total length of the dam will be approximately 20,000 feet with the principal portion approximately 9,000 feet in length, and a maximum height of 230 feet above the bed of the river; the smaller portion being about 11,000 feet in length on the left bank. This latter portion is more in the nature of a dike and will vary in height from zero to sixty feet; it is planned to build this portion by the roll-fill method rather than hydraulically. The entire dam will require about 90,000,000 cubic yards of earth. For the upstream and downstream toes and facing on the upstream slope, a total of 5,000,000 tons of gravel and 3,000,000 tons of rock will be used. A steel sheet piling cut-off wall or diaphragm will be driven to firm shale along the center line of the dam. A roadway will be constructed on top of the dam. The reservoir created will have a maximum depth of 230 feet and an area of approximately 250,000 acres; a maximum length of 175 miles; and approximately 2500 miles of shore line. The maximum capacity of the reservoir will be approximately 20,000,000 acre feet. The required time to fill the reservoir after completion is problematical since it depends upon the flow of the river, but based on discharge records over the past 40 years, four years will be necessary.

LONDON

<h3>Is the Cost of Radium Justified? The Secret of the Chinkolobwe Mine</h3> The<i>Daily Herald</i>, the organ of the labor party, recently sent Dr. Haden Guest, a physician and socialist member of parliament, to the Belgian Congo "to probe the secrecy and mystery that surrounded the Chinkolobwe Mine—the richest radium deposit in the world." Dr. Guest asks, "Is the fabulous price of radium, $50,000 a gram, justified? Is it the result of curtailing supplies in the face of an ever growing demand of the civilized world?" Shortly after its discovery by Madame Curie, radium could be bought for $2,500 a gram. In 1910, small quantities were obtained from ore deposits at Joachimstal in Bohemia and four years later carnotite deposits in the United States yielded radium, which was sold at $120,000 a gram. From 200 to 400 tons of rock had to be crushed to yield a single gram of

Description of the Section of the Upper Green-Sand at the Undercliff, in the Isle of Wight

The next division, 8th, consists of a bed of fawn-coloured sandstone of about ten feet in thickness, containing nodules of rag, with Pectines, Terebratulæ, Rhynchonellæ, &amp;c., in the lower portion, which, owing to its softness and looseness of texture, the weather wears away, leaving the shells finely exposed. It is chiefly owing to such excavation of this bed, by the combined influence of the elements, that those great falls of the superincumbent masses have taken place at intervals along the line of the Undercliff, many such “founders” having happened within the memory of residents, and others being likely to occur constantly from this hard and solid mass of strata resting on an insecure foundation, the effects of which are still further increased by the presence of the Gault below.But a few years back a large mass near Blackgang thus assumed such a dangerous and threatening attitude, by the lower part of it being so much worn away, that the authorities blew it down with gunpowder. Many thousand tons of rock and debris were thus thrown down, completely blocking up and destroying the original road; one huge mass still stands close to the road, as large and as high as a good-sized cottage.A layer of rag-stone, called the “Big Rag-bed,” containing fossils, terminates what is termed the “sandstone-group.”