Clouds generally form when rising air is cooled to its dew point, the temperature at which the air becomes saturated. Water vapour normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds.
Deserts take up about one fifth of the Earth’s land surface.
The highest mountain on Earth based from sea level is Mount Everest (8,848 m) in the Himalayas of Asia. The highest known mountain in the Solar System is Olympus Mons on the planet Mars at 21,171 m
Rivers have been used for navigation for thousands of years. The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern Pakistan around 3300 BC.
Sedimentary rocks are the only type of rock that can contain fossils, the remains or imprints of dead organisms. The chance of fossilisation is higher when the sedimentation rate is high (so that a carcass is quickly buried).
The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only 5 percent of the total volume of the crust.
At sunrise and sunset when the path through the atmosphere is longer, the blue and green components are removed almost completely leaving the longer wavelength orange and red hues we see at those times.
Waterfalls are most commonly formed when a river is young.
Volcanoes are generally found where tectonic plates are diverging or converging.
The Sonoran Desert includes over 1000 native bee species.
The tropics include all the areas on the Earth where the Sun reaches a point directly overhead at least once during the solar year.
Greenland is, by area, the world's largest island that is not a continent. With a population of 56,452 (January 2010 estimate) it is the least densely populated dependency or country in the world.
