National Geographic: The Diamond Journey

When someone asks you to name a rare, precious gemstone, what springs to mind? If you're like most people, the answer is probably diamonds. But what makes diamonds so special? It may be because of all gemstones, diamonds take the longest to form, and travel the farthest to get to us. This inherently natural wonder has an incredible journey, far longer and more arduous than any other gemstone.

The Water Cycle - Animation

This animation shows the entire process of the water cycle throughout the course of a day.

The Mid-Atlantic Ridge

The mid ocean ridge systems are the largest geological features on the planet. The Mid-Atlantic Ridge (MAR) is a mostly underwater mountain range in the Atlantic Ocean that runs from 87°N -about 333km south of the North Pole- to subantarctic Bourvet island at 54°S.

The MAR is about 3 km in height above the ocean floor and 1000 to 1500 km wide, has numerous transform faults and an axial rift valley along its length.

Making North America: Origins

Experience the colossal geologic forces that shaped our continent over 3 billion years.

Map of El Salvador

Map of El Salvador.

Map of Egypt

Map of Egypt.

Map of Ecuador

Map of Ecuador.

Why is the sky blue?

To understand why the sky is blue, we first need to understand a little bit about light. Although light from the sun looks white it is really made up of a spectrum of many different colours, as we can see when they are spread out in a rainbow.

We can think of light as being a wave of energy, and different colours all have a different wavelength. At one end of the spectrum is red light which has the longest wavelength and at the other is blue and violet lights which have a much shorter wavelength.



Why is the sky blue?
When the sun's light reaches the Earth's atmosphere it is scattered, or deflected, by the tiny molecules of gas (mostly nitrogen and oxygen) in the air. Because these molecules are much smaller than the wavelength of visible light, the amount of scattering depends on the wavelength. This effect is called Rayleigh scattering, named after Lord Rayleigh who first discovered it.

Shorter wavelengths (violet and blue) are scattered the most strongly, so more of the blue light is scattered towards our eyes than the other colours. You might wonder why the sky doesn't actually look purple, since violet light is scattered even more strongly than blue. This is because there isn't as much violet in sunlight to start with, and our eyes are much more sensitive to blue.

The blue light that gives the sky its colour, is sufficiently bright to make all the stars that we see at night disappear since the light they emit is much dimmer.


Why does the blue fade towards the horizon?

You might also notice that the sky tends to be most vibrant overhead and fades to pale as its reaches the horizon.This is because the light from the horizon has had further to travel through the air and so has been scattered and rescattered. The Earth's surface also plays a role scattering and reflecting this light.

As a result of this increased amount of scattering, the dominance of blue light is decreased and so we see an increased amount of white light.

Map of East Timor

Map of East Timor.

Map of Dominican Republic

Map of Dominican Republic.

Map of Dominica

Map of Dominica.

Map of Djibouti

Map of Djibouti

Map of Denmark

Map of Denmark.

Map of Democratic Republic of Congo

Map of Democratic Republic of Congo.

Map of Czech Republic

Map of Czech Republic.

Map of Cyprus

Map of Cyprus.

Map of Cuba

Map of Cuba.

Map of Croatia

Map of Croatia.

Map of Cote d'Ivoire

Map of Cote d'Ivoire.

Map of Costa Rica

Map of Costa Rica.

Map of Comoros

Map of Comoros.

Map of Colombia

Map of Colombia

Map of China

Map of China

Map of Chile

Map of Chile

Map of Chad

Map of Chad

Map of Central African Republic

Map of Central African Republic

Map of Canada

Map of Canada

Map of Cameroon

Map of Cameroon.

Map of Cape Verde

Map of Cape Verde

Map of Cambodia

Map of Cambodia

Map of Burundi

Map of Burundi

Map of Burkina Faso

Map of Burkina Faso.

Map of Bulgaria

Map of Bulgaria.

Map of Brunei Darussalam

Map of Brunei Darussalam.

Map of Brazil

Map of Brazil.

Map of Botswana

Map of Botswana.

Map of Bosnia and Herzegovina

Map of Bosnia and Herzegovina.

Map of Bolivia

Map of Bolivia

Map of Bhutan

Map of Bhutan

Map of Benin

Map of Benin

Map of Belize

Map of Belize

Map of Belgium

Map of Belgium

Map of Belarus

Map of Belarus

What is ecological succession?

Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction.

The community begins with relatively few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The ╩║engine╩║ of succession, the cause of ecosystem change, is the impact of established species upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment.

It is a phenomenon or process by which an ecological community undergoes more or less orderly and predictable changes following a disturbance or the initial colonization of a new habitat. Succession may be initiated either by formation of new, unoccupied habitat, such as from a lava flow or a severe landslide, or by some form of disturbance of a community, such as from a fire, severe windthrow, or logging. Succession that begins in new habitats, uninfluenced by pre-existing communities is called primary succession, whereas succession that follows disruption of a pre-existing community is called secondary succession.

Succession was among the first theories advanced in ecology. The study of succession remains at the core of ecological science. Ecological succession was first documented in the Indiana Dunes of Northwest Indiana which led to efforts to preserve the Indiana Dunes. Exhibits on ecological succession are displayed in the Hour Glass, a museum in Ogden Dunes.

Map of Barbados

Map of Barbados

Zambia Flag Coloring Page

Zambia Flag Coloring Page

Map of Bangladesh

Map of Bangladesh

Tanzania Flag Coloring Page

Tanzania Flag Coloring Page

Map of Bahrain

Map of Bahrain

Swaziland Flag Colouring Page

Swaziland Flag Colouring Page

Map of Bahamas

Map of Bahamas

South Africa Flag Coloring Page

South Africa Flag Coloring Page