GeologyRocks

What kinds of isolation can lead to the formation of a new species?

According to the biological species concept, populations are different species if gene flow between them is prevented by biological differences, known as reproductive barriers. If populations exchange genes they are conspecific, i.e. belong to the species, even if they differ greatly in morphology. If they are reproductively isolated, they are different species even if they are indistinguishable phenotypically. Therefore speciation arises from the evolution of biological barriers to gene flow (Futuyma, 1998).

Cubic Zirconia

This manufactured gemstone, more often referred to just as "C.Z.", first appeared on the market in 1978, and like all new things the price was quite high initially. It was marketed under the name of "Djevalite". Advances in the technology of laboratory producing has brought the price right down.

Meteor Craters

A meteorite is defined as any extraterrestrial solid mass that reaches the Earth's surface (Farris Lapidus, 1990). The term strictly extends from the nano scale e.g. dust particles, through to the macro scale e.g. 100s of metres in diameter (Zanda and Rotaru, 2001). However, the term meteorite is generally reserved for the larger particles that reach the Earth's surface.

Palaeozoic History of the UK - Part 1: Cambrian to Silurian

During the early Palaeozoic Scotland and England were still on separate continents, Laurentia and Avalonia respectively. Cambrian, Ordovician and Silurian rocks are found mainly in Scotland and Wales. This article covers the time period 550Ma to around 410Ma.

Precambrian History of Scotland

The Precambrian of the UK is mainly located in northern Scotland, however there are outcrops in England and Wales also. The oldest rock constituents found there date to around 3450Ma and belong to the Lewisian complex. The Precambrian formations are (youngest to oldest):

• Dalradian
• Moine
• Torridonian
• Lewisian

The location of these formations is shown in Figure 1a and a sketch cross section is shown in Figure 1b.

Programming Fortran 2

This is a continuation of Fortran 1. This tutorial might not make much sense unless you have read that first.

Writing and Reading from Files, Screens and Keyboards

Fortran is capable of reading data from files and from the keyboard. It can also write data to files and to the screen. The I/O (Input-Output) in Fortran is a little cumbersome and is not very flexible, but is easy to get the hang of.

Programming Fortran 1

This tutorial is designed for those who have to learn Fortran. Not that Fortran is a bad language to learn and it is used extensively throughout the scientific community. However, it is often the first programming language scientists encounter, so this tutorial designed to give you the basics of the language, without (hopefully) the use of complicated paradigms or ideas.

Gravity Surveying

Gravity surveying involves looking at the subsurface structure based on the differences in densities of the subsurface rocks. The idea is based around a causative body - one which produces a gravity anomaly. Assessment of gravity anomalies can give ideas about depth, size and shape of the causing body. Gravity anomalies are measured in ms^-2. As the anomalies are very small compared to the Earth's field (9.81ms^-2), they are commonly expressed in gravity units (g.u.), where 1 gu = 1μms^-2.

Introduction to the Geological Features of the Moon

The Moon is the only natural satellite of the Earth and formed at about the same time, over four and a half billion years ago, but has not evolved in the same way. Lacking an atmosphere, water and life, and having cooled more rapidly due to its smaller size, much of the surface has not been changed significantly for billions of years.

Introduction to Carbonates

Carbonates are rocks composed mainly of calcium carbonate, CaCO₃. Some examples of common carbonate rocks are limestones and chalk. Carbonates form by precipitation from water; either straight from the water, or induced by organisms, to make their shells or skeletons, and they form in many environments (Figure 1).