National Geographic

Encyclopedic Entries

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A divide is the elevated boundary between areas that are drained by different river systems.


A cove is a small, sheltered recess in the shoreline of a sea, lake, or river


Drought is an extended period of unusually dry weather when there is not enough rain.

La Niña

La Nina is a climate pattern that describes the cooling of surface ocean water along the tropical west coast of South America.


A village is a small settlement usually found in a rural setting.

alluvial fan

An alluvial fan is a triangle-shaped deposit of gravel, sand, and smaller materials called alluvium.


Dew is the moisture that forms at night when objects or the ground outside cool down by radiating, or emitting, their heat


A cape is a high point of land that extends into a river, lake, or ocean.


Buttes are tall, steep-sided towers of rock.


Bioluminescence is light emitted by living things through chemical reactions in their bodies.


Bedrock is the relatively hard, solid rock beneath surface materials such as soil and gravel


Blubber is the thick layer of fat under the skin of marine mammals, such as seals, whales, and walruses.


A tributary is a freshwater stream that feeds into a larger stream, river or other body of water. The larger, or parent, river is called the mainstem....


A waypoint is a reference point that helps us know where we are and where we're going. Whether we’re driving, sailing, or flying, waypoints help...


A waterspout is a column of rotating, cloud-filled wind. A waterspout descends from a cumulus cloud to an ocean or a lake.


A waterfall is a steep descent of a river or other body of water over a rocky ledge.

water table

The water table is a line beneath the surface of the Earth.

water cycle

The water cycle describes how water is exchanged (cycled) through Earth's land, ocean, and atmosphere.

oil shale

Oil shale is a type of rock that can be burned for energy or fuel.


A cliff is a mass of rock that rises very high and is almost vertical, like a wall


Fossils are the preserved remains, or traces of remains, of ancient animals and plants

renewable energy

Renewable energy comes from sources that will not be used up in our lifetimes, such as the sun and wind.

non-renewable energy

Non-renewable energy comes from sources that will eventually run out, such as oil and coal. 

great circle

Encyclopedic entry. A great circle is the largest possible circle that can be drawn around a sphere. All spheres have great circles.


Petroleum, or crude oil, is a fossil fuel and non-renewable source of energy.