An overview of the Aurora Borealis or Northern Lights - learn how they're formed, where to see them, and how they're predicted.

Megadiversity is extreme biodiversity found in a small number of countries worldwide. Most megadiversity is found in tropical regions of the world.

Learn about the development and history of plate tectonics, from its innovation by Alfred Wegener to how scientists today understand how the plates of the Earth's lithosphere move.

An overview of the supercontinent of Pangea, which covered one-third of the planet and began to break up about 200 million years ago to form the modern continents of today.

An overview of mountain building and how geomorphologic processes contribute to the building and breaking of mountains.

An overview of biomes and how they differ. Learn all about biomes from this overview.

Learn all about the development of valleys through this great overview article on valley formation from the expert About.com Geography site.

Learn about the formation and creation of sand dunes around the world, from the About.com Geography GuideSite.

Learn about all types of solar eclipse - from total solar eclipse to partial solar eclipse. A solar eclipse is caused by the moon blocking the sun as viewed from the earth.

An overview of the subject of physical geography and its various aspects from your About.com Guide to Geography.

The Atacama Desert of northern Chile is the world's second driest region (icy Antarctica is first). Although the Tropic of Capricorn passes through the region, the Atacama lies in the rain shadow of Chile's Coast Range, which squeezes out the moisture from the atmosphere.

A listing of the composition of the atmosphere of the earth, from your About.com Guide to Geography.

Learn about the four spheres of the earth - the lithosphere, hydrosphere, biosphere, and atmosphere.

The prominent topography of the Basin and Range Province in the Western United States is due to a very specific geologic feature, which is only found in a few other basins and ranges around the world.

An overview of biogeography, the geographic distribution of plants and animals over the surface of the earth. This article is part of the expert Geography site at About.com

Learn about the Coriolis effect, which appears to deflect items moving on or above the earth's surface based on the rotation of the earth.

An overview of the December solstice.

Learn about the deserts of the world and other arid lands, from your About.com Guide to Geography.

Learn about water, wind, ice, and waves - the agents of erosion that wear away at the surface of the earth, from your About.com Guide to Geography.

Learn all about the size of the earth, the shape of the earth, and how its size and shape are measured in the science known as geodesy, from the About.com expert Geography GuideSite.

A great overview of geomorphology, which is the science of landforms with an emphasis on their origin, evolution, form, and distribution across the physical landscape. This overview of geomorphology is part of the About.com Geography site.

The rock and soil picked up and transported by glaciers creates new landscapes as it is eventually deposited by melting and retreating glaciers. Learn about deposition and moraines of glaciers.

Dangerous sinkholes and beautiful caverns are two results of landscapes known as karst topography. Learn about these features from your About.com Guide to Geography.

An overview of the field of study known as landscape ecology, discipline that explores the spatial aspects of ecology and the biosphere.

An overview of the atmospheric phenomenon known as lapse rate. Lapse rate explains the decrease or increase in temperature of a parcel of air that rises or lowers.

Discover all about the magnetic reversal of the earth's poles throughout the planet's history. The poles have reversed 170 times in the past 100 million years. Find out when it will happen next!

In the tradition of ancient geography, this feature describes a far-away and unfamiliar place, the planet Mars.

Find out more about the arc of volcanoes which circles the Pacific Ocean.

From clay to gravel, each soil partical fits into its own category.

An overview of the soil of the lithosphere, from your About.com Guide to Geography.

An overview of the energy and heat, known as radiation, that is received on earth from the sun. Learn about solar radiation and albedo, the reflection of the sun's energy from the About.com geography site.

Learn about the terminator line on the earth that separates light from darkness.

An overview of the earth's orbit around the sun, including the times when it is closest to the sun and farthest from the sun, known as perihelion and aphelion, respectively.

The facts about the key lines of latitude that relate to the position of the sun and the angle of the earth.

Learn about the start dates for each of the four seasons in the Northern and Southern Hemispheres. Find out about the earth-sun interaction on the June Solstice, December Solstice, March Equinox, and September Equinox, from your About.com Guide to Geography.

An overview of topographic prominence, the concept of looking at the local relief of a location based on the local terrain.

The summer solstice is the longest day in the year but it's not the day of earliest sunrise or sunset - learn more about this intriguing occurrence, from your About.com Guide to Geography.

This online physical geography textbook is an amazing resource. Its images and graphics really help to provide detailed information about the basics of physical geography.

Discover how igneous, metamorphic, and sedimentary rocks are created and how they can be recycled as part of the rock cycle of the earth's crust.

James Hutton, known as the father of geology, suggested that the earth was much older and that processes occurring in the present were the same processes that had operated in the past, and would be the processes that operate in the future. This concept became known as uniformitarianism and can be summarized by the phrase 'the present is the key to the past.'

June 21 is the summer solstice in the Northern Hemisphere and marks the beginning of summer for the earth north of the equator.

Learn about the benefit of trees in a community, from the About.com Geography GuideSite.

According to most experts, all modern dog breeds are posited to have originated from Southeast Asia. There, thousands of years ago, humans interacted with local grey wolf populations and eventually domesticated them.