Chalk in the context of "Headland"

A blackboard or a chalkboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, better known as chalk.

Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.

In geography and geology, a cliff or rock face is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.

An escarpment (or scarp) is a type of cliff formed by the movement of a geologic fault, a landslide, or sometimes by rock slides or falling rocks which change the differential erosion of the rock layers.

Deposition is the geological process in which sediments, soil and rocks are added to a landform or landmass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.

This occurs when the forces responsible for sediment transportation are no longer sufficient to overcome the forces of gravity and friction, creating a resistance to motion; this is known as the null-point hypothesis. Deposition can also refer to the buildup of sediment from organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which induced chemical processes (diagenesis) to deposit further calcium carbonate. Similarly, the formation of coal begins with the deposition of organic material, mainly from plants, in anaerobic conditions.

Calcium carbonate is a chemical compound with the chemical formula CaCO₃. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

Chalk mining is the extraction of chalk from underground and above ground deposits by mining. Mined chalk is used mostly to make cement and bricks.

Chalk mining was widespread in Britain in the 19th century because of the large amount of construction underway (and the Industrial Revolution). Some chalk mines were extensively large, with passages up to 25 feet (7.6 m) high and 15 feet (4.6 m) wide, their passages taking the form of a Norman arch. Because of chalk's softness, picks and shovels were used to excavate tunnels. Stepped slabs were dug into the chalk, allowing many miners to dig at the same time. Care had to be taken to avoid collapse, and places in which the chalk was soft were simply abandoned.

Coated paper (also known as enamel paper, gloss paper, and thin paper) is paper that has been coated with a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absorbency. Various materials, including kaolinite, calcium carbonate, bentonite, and talc, can be used to coat paper for high-quality printing, such as that used in the packaging industry and in magazines.

The chalk or china clay is bound to the paper with synthetic viscosifiers, such as styrene-butadiene latexes and natural organic binders such as starch. The coating formulation may also contain chemical additives as dispersants, resins, or polyethylene to give water resistance and wet strength to the paper, or to protect against ultraviolet radiation.

The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period.

Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. The primary objective of biostratigraphy is correlation, demonstrating that a particular horizon in one geological section represents the same period of time as another horizon at a different section. Fossils within these strata are useful because sediments of the same age can look completely different, due to local variations in the sedimentary environment. For example, one section might have been made up of clays and marls, while another has more chalky limestones. However, if the fossil species recorded are similar, the two sediments are likely to have been laid down around the same time. Ideally these fossils are used to help identify biozones, as they make up the basic biostratigraphy units, and define geological time periods based upon the fossil species found within each section.

Basic concepts of biostratigraphic principles were introduced in the early 1800s. A Danish scientist and bishop by the name of Nicolas Steno was one of the first geologists to recognize that rock layers correlate to the Law of Superposition. With advancements in science and technology, by the 18th century it began to be accepted that fossils were remains left by species that had become extinct, but were then preserved within the rock record. The method was well-established before Charles Darwin explained the mechanism behind it—evolution. Scientists William Smith, George Cuvier, and Alexandre Brongniart came to the conclusion that fossils then indicated a series of chronological events, establishing layers of rock strata as some type of unit, later termed biozone. From here on, scientists began relating the changes in strata and biozones to different geological eras, establishing boundaries and time periods within major faunal changes. By the late 18th century the Cambrian and Carboniferous periods were internationally recognized due to these findings. During the early 20th century, advancements in technology gave scientists the ability to study radioactive decay. Using this methodology, scientists were able to establish geological time, the boundaries of the different eras (Paleozoic, Mesozoic, Cenozoic), as well as Periods (Cambrian, Ordovician, Silurian) through the isotopes found within fossils via radioactive decay. Current 21st century uses of biostratigraphy involve interpretations of age for rock layers, which are primarily used by oil and gas industries for drilling workflows and resource allocations.