Sunday, May 24, 2015
A remote galaxy shining brightly with infrared light equal to more than 300 trillion suns has been discovered using data from NASA's Wide-field Infrared Survey Explorer, or WISE. The galaxy, which belongs to a new class of objects recently discovered by WISE -- nicknamed extremely luminous infrared galaxies, or ELIRGs -- is the most luminous galaxy found to date.
Hidden among Earth's vast oceans are some of the tiniest and most vital organisms to the health of delicate ecosystems. Ocean microbes produce half of the oxygen we breathe, and are important drivers in chemical reactions and energy transfers that fuel critical ecological processes.
Using measurements of the elevation of the Antarctic ice sheet made by a suite of satellites, the researchers found that the Southern Antarctic Peninsula showed no signs of change up to 2009. Around 2009, multiple glaciers along a vast coastal expanse, measuring some 750km in length,
Tropical rainforests have long been considered Earth's lungs, sequestering large amounts of carbon dioxide from the atmosphere and thereby slowing down the increasing greenhouse effect and associated human made climate change. Scientists in a global research project now show that the vast extensions of semi-arid landscapes occupying the transition zone between rainforest and desert dominate the ongoing increase in carbon sequestration by ecosystems globally, as well as large fluctuations between wet and dry years.
Tuesday, May 13, 2014
Sunday, May 11, 2014
Mountains make up a large proportion of the earth's surface. Based on their mode of formation, four main types of mountains can be distinguished.
1. Fold mountains. These mountains are by far the most widespread and also the most important. They are caused by large-scale earth's movements, when stresses may be due to the increased load of the underlying rocks, flow movements in the mantle, magnetic intrusions into the crust, or the expansion or contraction of some part of the earth. When such stresses are initiated, the rocks are subjected to compressive forces that produce wrinkling or folding along the lines of weakness. Folding effectively shortens the earth's crust, creating from the original level surface a series of waves. The upfolded waves are called anticlines and the troughs or downfolds are synclines.
Rocks are very important economically. The thin surface layer of the earth, formed by the break-down of the rocks in various ways and by various processes, is known as soil. The geographer is, among other things, interested in the soil as the medium in which plants grow, hence the scene of production of most of man's food and most of his raw materials.
Man's vital water supply is connected with the nature of the rocks. Part of our drinking water is got by sinking wells to tap the sub-surface water which is filtered naturally during its passage through the rocks. The amount of surface run-off in the form of rivers and springs affects the siting of
The appearance and characteristic features of landforms are greatly influenced by the underlying rock type. Softer rocks like clay and shale are worn down much faster than harder rocks like granite.
The ancient rocks which dominate a great part of West Africa have been so greatly worn down by erosion that they now appear as peneplains. Granite domes for inselbergs have been formed where the old rocks resist erosion: and in some cases, such resistant high rocks produce high relief, such as the Jos Plateau of Nigeria, the Akwapim-Togo-Atacora ridges and the Birrimian uplands of Ghana, and the interior plateaux and mountains of Sierra Leone, Shales, schists and sandstones, being less resistant, form the much lower, rounded hills. Recent river sediments form flat plains.
Saturday, May 10, 2014
Sedimentary rocks are formed from sediment accumulated over long periods, usually under water. They are distinguished from the other rock types by their characteristic layer formation and are termed stratified rocks. The strata may vary in thickness from a few centimetres to many metres. The rocks may be coarse or fine-grained, soft or hard. The materials that form sedimentary rocks may be brought by streams, glaciers, winds or even animals. They are non-crystalline and often contain fossils of animals, plants and other micro-organisms. Sedimentary rocks are thus the most varied in their formation of all rocks. Sedimentary rocks are classified according to their age and different kinds of rocks formed during the same period are grouped together. It is
Igneous rocks are formed by the cooling and solidification of molten rock (magma) from beneath the earth's crust. They are normally crystalline in structure. They do not occur in strata (layers) nor do they contain fossils. Igneous rocks may be subdivided on the basis of mineral composition. When they contain a high proportion of silica they are said to be acid. Acid igneous rocks, such as granite, are less dense and are lighter in colour than basic rocks. These contain a greater proportion of basic of basic oxides, e.g. of iron, aluminum or magnesium, and are thus denser and darker in colour.
In terms of origin there are two main classes of
Friday, May 9, 2014
Rock Texture, Structure and Colour
Rock texture refers to the sizes of the mineral grains, that is, whether the rock is fine grained or coarse grained, dense glass or frothy glass. The texture of an igneous rock varies according to the environment in which solidification took place. Very rapid cooling of lava at the earth's surface results in a glassy texture. Moderately rapid cooling produces fine texture, while coarse textures are as a result of slow or gradual cooling of molten rock deep down in the crust. Textures of sedimentary rocks are recognizable on the basis of the size of the constituent grains and the minerals contained. Shale is a sedimentary rock formed from mud or clay and it is made up of particles of sand size 0.02mm - 2.00mm.
The colours of rocks are essentially a consequence of the minerals which make up the roc