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Porosity and Permeability of Chalk
At a microscopic level, there can be a lot of space between the fossil particles that make up chalk. Land underlain by chalk directly below the soil is often well drained. In these areas, water that infiltrates into the soil encounters the top of the chalk and easily flows into the chalk’s pore spaces. It…
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Identifying Chalk
The keys to identifying chalk are its hardness, its fossil content, and its acid reaction. At a glance, diatomite and gypsum rock have a similar appearance. An examination with a hand lens will often reveal the fossil content, separating it from gypsum. Its reaction with dilute (5%) hydrochloric acid will separate it from both gypsum and diatomite. The acid reaction will surprise…
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Cretaceous: A Time of Chalk
Much chalk was deposited during the Cretaceous Period of geologic time. It was a time of global high sea levels that began at the end of the Jurassic Period about 145 million years ago and the beginning of the Paleogene Period about 66 million years ago. During the Cretaceous, warm waters of epeiric seas, seas that…
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How Does Chalk Form?
Chalk forms from a fine-grained marine sediment known as ooze. When foraminifera, marine algae, or other organisms living on the bottom or in the waters above die, their remains sink to the bottom and accumulate as ooze. If most of the accumulating organic debris consists of calcium carbonate, then chalk will be the type of rock that…
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What Is Chalk?
Chalk is a variety of limestone composed mainly of calcium carbonate derived from the shells of tiny marine animals known as foraminifera and from the calcareous remains of marine algae known as coccoliths. Chalk is usually white or light gray in color. It is extremely porous, permeable, soft and friable.
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Caliche Problems and Uses
The presence of caliche in a soil or sediment has many practical implications. These might include:
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How Does Caliche Form?
Caliche has a diversity of origins. The major process of forming caliche begins when calcium carbonate is leached from upper soil horizons by downward-percolating solutions. Dissolved calcium carbonate might also be delivered to the site in runoff and then percolate into the soil. The calcium carbonate then precipitates in a deeper soil horizon to form…
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What Does Caliche Look Like?
Typical caliche colors are white, gray, brown and reddish-brown. Well-developed caliche can have an appearance that resembles conglomerate, breccia, coquina, or sandstone if the cemented particles are of the proper type and size. Caliche can be a very hard, dense, heavy, and durable material if it is firmly bound by a cement that completely fills the interstitial voids between the…
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What Is Caliche?
“Caliche” is a shallow layer of soil or sediment in which the particles have been cemented together by the precipitation of mineral matter in their interstitial spaces. The cement is usually calcium carbonate; however, cements of magnesium carbonate, gypsum, silica, iron oxide, and a combination of these materials are known. Caliche is a common feature of…
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What are the Uses of Breccia?
The rock, breccia, has very few uses. It can be used as fill or road base where the technical requirements are minimal. It is rarely used in important projects because its composition, degree of cementation and competence are highly variable. The word “breccia” is used as a trade name for a group of dimension stone…