2020 Top Ten of Polemic for Nature

Divergent boundary

In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts, which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands, which occur when the plates move apart to produce gaps that magma rises to fill

Spring scale

A spring scale, spring balance or newton meter is a type of mechanical force gauge or weighing scale. It consists of a spring fixed at one end with a hook to attach an object at the other. It works in accordance with Hooke's Law, which states that the force needed to extend or compress a spring by some distance scales linearly with respect to that distance. Therefore, the scale markings on the spring balance are equally spaced

Law of superposition

The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields pertaining to geological stratigraphy. In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface to form new deposits over time. This is paramount to stratigraphic dating, which requires a set of assumptions, including that the law of superposition holds true and

Palisade cell

Palisade cells are plant cells located on the leaves, right below the epidermis and cuticle. In simpler terms, they are known as leaf cells. They are vertically elongated, a different shape from the spongy mesophyll cells beneath them. The chloroplasts in these cells absorb a major portion of the light energy used by the leaf. Palisade cells occur in dicotyledonous plants, and also in the net-veined Monocots, the Araceae and Dioscoreaceae

Organ system

An organ system is a biological system consisting of a group of organs that work together to perform one or more functions. Each organ has a specialized role in a plant or animal body, and is made up of distinct tissues

Dry water

Dry water or empty water, a form of "powdered liquid", is an air–water emulsion in which water droplets are surrounded by a silica coating. Dry water consists of 95% liquid water, but the silica coating prevents the water droplets from combining and turning back into a bulk liquid. The result is a white powder

Oranda

An oranda is a breed of goldfish characterized by a prominent bubble-like "hood" on the head. The headgrowth or hood may be a prominent growth on the top of the head or may encase the entire face except the mouth

Maui ʻakepa

The Maui ʻakepa is a species of ʻakepa native to Maui in the Hawaiian Islands, and which was common throughout the island. Introduced mosquitoes and other animals to Maui contributed to the declining population, and the bird is considered Critically Endangered or possibly extinct by the IUCN Red List of Threatened Species. The latest reported sighting of this bird was in 1988, and in 2021 the United States Fish and Wildlife Service declared it extinct

Fractional distillation

Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to fractionate. Generally the component parts have boiling points that differ by less than 25 °C (45 °F) from each other under a pressure of one atmosphere. If the difference in boiling points is greater than 25 °C, a simple distillation is typically used. It is

Hamada

A hamada is a type of desert landscape consisting of high, largely barren, hard rocky plateaus, where most of the sand has been removed by deflation