Monday, January 31, 2011

Natural resources on Earth

Natural resource or natural capital is the planet’s air, water, soil,wildlife, mineral and natural purification , recycling, and pest controlprocesses. Solar capital is the energy from the sun.

Natural resources are:

   * Air, water and soil
   * Biological resources - plants and animals
   * Raw materials (like minerals)
   * Space and land
   * Wind, geothermal, tidal and solar energy

Natural resources are often classified into renewable, flow, and non-renewable resources.

Ecological resource- is anything required by organisms like you for normal maintenance,growth and reproduction.Examples are water,shelter, food, and habitat.Ecological resources include fish and wildlife populations, habitats, and their relationships to each other and the environment/ecosystem.

Economic resource- is anything obtained fromthe environment to meet your needs and wants. Examplesare food, water, shelter,manufactured goods,transportation,communication and recreation.

We have a lot of resources to meet our needs. Some of these resources are finite.Other resources are renewable but it takes time to replace or replenish them. Unfortunately,the rapid consumption of these raw materials by our expanding population has led to the exploitation of the natural resources. Exploitative attitudes of humans rapidly reduce theavailability of natural resources.

Sunday, January 30, 2011

How do tectonic plates move

Plate tectonic theory has developed slowly and progressively since it was developed in the 1960s. It is a theory that truly has the entire world as its experiment.According to the theory of plate tectonics, the Earth's crust and upper mantle are broken into moving plates of "lithosphere." The lithospheric plates are solid rock. There are several very large plates, each consisting of both oceanic and continental portions.There are a dozen or more smaller plates. The plates average about 80 kilometers (50 miles) in thickness.All of the plates are moving. They are slow, moving at speeds of centimeters to tens of centimeters per year. They slide along on top of an underlying mantle layer called the asthenosphere, which contains a little magma (molten rock). Many types of evidence indicate that the plates move.All objects on and in the Earth are pulled towards its center by the force of gravity. This may affect the plates at converging plate boundaries in areas called subduction zones, where one plate sinks into the mantle.At the midocean ridges, the plates are separating, pulled apart by the motion of convections cells beneath the plates. Lava then comes up to fill in the resulting gap and cools into solid rock when it comes into contact with cold ocean water,becoming new, young ocean floor. The ocean floor cools more as it ages (making it contract) and more and more sediments pile on top of it, so it becomes more and more dense with time. As the ocean floor moves away from the mid-ocean ridge (“sea-floor spreading”), it either pushes a continent (“continental drift”) or runs intoanother plate, leading to earthquakes.The movements of plates over millions of years resulted in the opening and closure of oceans and the formation and disassembly of continents.There are three principal types of plate boundary (divergent, convergent, and transform).


Plates move apart at divergent plate boundaries such as the oceanic ridge system that separates the North American and Eurasian plates in the north Atlantic Ocean. Plates crash into each other along convergent plate boundaries marked by volcanoes and mountain belts. Finally, plates slide past each other along a transform plate boundary such as the San
Andreas Fault, California, that separates the North American and Pacific plates.

Saturday, January 29, 2011

Magnetic field of the Earth

Earth's magnetic field is slightly tilted with respect to the planet's spin axis; there is currently a difference of about 11° between the two. Earth's magnetic field extends thousands of kilometers (miles) outward into space. The field forms a gigantic magnetic "bubble" in space around Earth. This magnetic bubble is called the magnetosphere.In addition to sources in Earth’s core, the magnetic field observable at the planet’s surface has sources in the crust and in the ionosphere and magnetosphere.Today the north magnetic pole is located about 700 miles(1,200 km) south-southeast of the north (spin) pole of the Earth (see red star on globe to left). Many times in the history of the Earth the core’s electrical currents have reversed direction, causing the north and south magnetic poles to switch positions!

The strength of the field at the Earth's surface ranges from less than 30 microteslas (0.3 gauss) in an area including most of South America and South Africa to over 60 microteslas (0.6 gauss) around the magnetic poles in northern Canada and south of Australia, and in part of Siberia.The field is similar to that of a bar magnet, but this similarity is superficial. The magnetic field of a bar magnet, or any other type of permanent magnet, is created by the coordinated spins of electrons and nuclei within iron atoms. The Earth's core, however, is hotter than 1043 K, the Curie point temperature at which the orientations of spins within iron become randomized. Such randomization causes the substance to lose its magnetic field. Therefore the Earth's magnetic field is caused not by magnetized iron deposits, but mostly by electric currents in the liquid outer core.

The ozone layer

Ozone is a triatomic molecule, consisting of three oxygen atoms.Ozone in the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and will burn sensitive plants; however, the ozone layer in the upper atmosphere is beneficial, preventing potentially damaging ultraviolet light from reaching the Earth's surface.Ozone is a pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution. At –112 °C, it condenses to form a dark blue liquid. It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below –193 °C, it forms a violet-black solid.


Ozone layer

The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer. Ozone used in industry is measured in ppm(OSHAexposure limits for example), and percent by mass or weight.This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is damaging to life on Earth.[1] It is mainly located in the lower portion of the stratosphere from approximately 13 to 40 kilometres (8.1 to 25 mi) above Earth, though the thickness varies seasonally and geographically

Ozone was discovered by Christian Friedrich Schönbeinin 1840, who named it after the Greekword for smell (ozein), from the peculiar odor in lightning storms.The odor from a lightning strike is from electrons freed during the rapid chemical changes, not the ozone itself.