GeologyRocks

What is A Mass-Extinction?

What Is A Mass-Extinction?

An extinction event is defined as a sharp decrease in the number of species over a short period of time. A mass extinction is further defined based on four points, pattern, duration, breadth and magnitude, and the event must:

• be confined to a short period of geological time
• Affect a wide variety of clades, that occupy a wide range of Habitats
• And eradicate a high proportion of species.

Foraminiferans As Palaeoenvironmental Indicators.

Foraminiferans (hereafter referred to as Forams) are unicellular protists that inhabit the world’s oceans and range from 20µm to a few centimetres in size. They tolerate a wide range of salinities from esturine to fully oceanic (~ 35‰) but are NOT found in freshwater. They can be either planktonic or benthic, do not photosynthesise so inhabit various depths, and are active predators.

Precambrian History of England and Wales

This is the companion tutorial to the Precambrian History of the Scotland.

This tutorial looks at the Precambrian of England and Wales which by the end of the Precambrian were on a completely different continent and separated from what is now Scotland by the Iapetus Ocean.

The Use Of Diatoms As Palaeoenvironmental Indicators

Diatoms are microscopic, photosynthetic algae (which due to the yellow-brown chloroplasts they contain are sometimes referred to as golden algae). Comprising one of the most common types of phytoplankton, they are found in a diverse range of environments from freshwater to saline oceanic waters. It is estimated that 20-25% of all the organic carbon fixation on Earth; via photosynthesis, is attributable to diatoms - in large due to their great abundance.

Submarine Mass Movement

Submarine mass movement processes, driven by gravitational forces, represent an important mechanism whereby vast amounts of sediment are rapidly transported downslope and redistributed into deep-water from an originally shallow-water setting, and their deposits are widely recognised in continental margins. Although there is a tendency to consider these processes independently, there is an increasing awareness that in many cases these processes need to be integrated to produce a model of margin development. The mass movement processes display large temporal and spatial variations and have different importance, but their interrelationship needs to be understood and background sedimentation processes must be considered. Increasing knowledge of mass movement processes on the continental slope also has interest for natural hazard assessment.

Geological Time

How do we know the age of the Earth? How do we know the age of rocks we find? There are two main ways to date rocks - absolute dating and relative dating. After the rocks have a date assigned to it, they can be put in some sort of order, and the relative dates worked out. This is the geological timescale.

The Ageing Earth

Plate Tectonics: The Evidence

The evidence for plate tectonics comes many fields, such as palaeontology, geophysics and climate study. The first evidence was the matching of continents and their rock types across oceans. This had been realised since the 17th Century. Theories of how continents moved were ad hoc at best. Alfred Wagner, an early 1900's German Meteorologist proposed that the continents of South America, Africa, India and Australia had been one continent in the past due to their similarity of fossils and palaeoclimate.

VMS Deposits on Cyprus

Ophiolite-hosted VHMS (Volcanic-Hosted Massive Sulphide) deposits, also known as Cyprus-type VHMS deposits, are seen in at least 25 of the worlds more than 200 known ophiolite terranes. The term Cyprus-type should now be considered a bit of a misnomer, as the Troodos ophiolite - to which the Cyprus-type name refers - is not a typical Mid-ocean ridge ophiolite - indeed it is considered to be a supra-subduction zone ophiolite, similar to the present day Mariana-Bonin arc.

The Geology of Cyprus

Cyprus is situated in the easternmost part of the Mediterranean, around 80 miles from Turkey in the north, around 100 miles from the coasts of Syria and Lebanon to the east and, to the south, around 300 miles from Egypt and Israel.

The Origin and Early Evolution of Birds

Birds are phylogenetically considered to be members of the theropod dinosaurs; their closest non-avian relatives are the dromaeosaurid theropods. The first known fossil bird is Archaeopteryx, from the late Jurassic of Bavaria, Germany, which is represented by seven skeletons and a feather. There is no fossil evidence from before this time that has been proven to be of avian origin. The fossil record of modern birds began in the early Tertiary (Padian et al., 1998).